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Johnson DM, Khakhum N, Wang M, Warner NL, Jokinen JD, Comer JE, Lukashevich IS. Pathogenic and Apathogenic Strains of Lymphocytic Choriomeningitis Virus Have Distinct Entry and Innate Immune Activation Pathways. Viruses 2024; 16:635. [PMID: 38675975 PMCID: PMC11053560 DOI: 10.3390/v16040635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/08/2024] [Accepted: 04/18/2024] [Indexed: 04/28/2024] Open
Abstract
Lymphocytic choriomeningitis virus (LCMV) and Lassa virus (LASV) share many genetic and biological features including subtle differences between pathogenic and apathogenic strains. Despite remarkable genetic similarity, the viscerotropic WE strain of LCMV causes a fatal LASV fever-like hepatitis in non-human primates (NHPs) while the mouse-adapted Armstrong (ARM) strain of LCMV is deeply attenuated in NHPs and can vaccinate against LCMV-WE challenge. Here, we demonstrate that internalization of WE is more sensitive to the depletion of membrane cholesterol than ARM infection while ARM infection is more reliant on endosomal acidification. LCMV-ARM induces robust NF-κB and interferon response factor (IRF) activation while LCMV-WE seems to avoid early innate sensing and failed to induce strong NF-κB and IRF responses in dual-reporter monocyte and epithelial cells. Toll-like receptor 2 (TLR-2) signaling appears to play a critical role in NF-κB activation and the silencing of TLR-2 shuts down IL-6 production in ARM but not in WE-infected cells. Pathogenic LCMV-WE infection is poorly recognized in early endosomes and failed to induce TLR-2/Mal-dependent pro-inflammatory cytokines. Following infection, Interleukin-1 receptor-associated kinase 1 (IRAK-1) expression is diminished in LCMV-ARM- but not LCMV-WE-infected cells, which indicates it is likely involved in the LCMV-ARM NF-κB activation. By confocal microscopy, ARM and WE strains have similar intracellular trafficking although LCMV-ARM infection appears to coincide with greater co-localization of early endosome marker EEA1 with TLR-2. Both strains co-localize with Rab-7, a late endosome marker, but the interaction with LCMV-WE seems to be more prolonged. These findings suggest that LCMV-ARM's intracellular trafficking pathway may facilitate interaction with innate immune sensors, which promotes the induction of effective innate and adaptive immune responses.
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Affiliation(s)
- Dylan M. Johnson
- Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, Louisville, KY 94202, USA (I.S.L.)
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 94202, USA
- Galveston National Laboratory, Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77550, USA; (N.K.); (J.E.C.)
- Sandia National Laboratories, Department of Biotechnology & Bioengineering, Livermore, CA 94550, USA
| | - Nittaya Khakhum
- Galveston National Laboratory, Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77550, USA; (N.K.); (J.E.C.)
| | - Min Wang
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY 94202, USA;
| | - Nikole L. Warner
- Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, Louisville, KY 94202, USA (I.S.L.)
- Department of Microbiology and Immunology, University of Louisville Health Sciences Center, Louisville, KY 94202, USA
| | - Jenny D. Jokinen
- Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, Louisville, KY 94202, USA (I.S.L.)
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY 94202, USA;
| | - Jason E. Comer
- Galveston National Laboratory, Department of Microbiology & Immunology, University of Texas Medical Branch, Galveston, TX 77550, USA; (N.K.); (J.E.C.)
| | - Igor S. Lukashevich
- Center for Predictive Medicine for Biodefense and Emerging Infectious Diseases, Louisville, KY 94202, USA (I.S.L.)
- Department of Pharmacology and Toxicology, University of Louisville Health Sciences Center, Louisville, KY 94202, USA;
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Katz M, Diskin R. The underlying mechanisms of arenaviral entry through matriglycan. Front Mol Biosci 2024; 11:1371551. [PMID: 38516183 PMCID: PMC10955480 DOI: 10.3389/fmolb.2024.1371551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Accepted: 02/15/2024] [Indexed: 03/23/2024] Open
Abstract
Matriglycan, a recently characterized linear polysaccharide, is composed of alternating xylose and glucuronic acid subunits bound to the ubiquitously expressed protein α-dystroglycan (α-DG). Pathogenic arenaviruses, like the Lassa virus (LASV), hijack this long linear polysaccharide to gain cellular entry. Until recently, it was unclear through what mechanisms LASV engages its matriglycan receptor to initiate infection. Additionally, how matriglycan is synthesized onto α-DG by the Golgi-resident glycosyltransferase LARGE1 remained enigmatic. Recent structural data for LARGE1 and for the LASV spike complex informs us about the synthesis of matriglycan as well as its usage as an entry receptor by arenaviruses. In this review, we discuss structural insights into the system of matriglycan generation and eventual recognition by pathogenic viruses. We also highlight the unique usage of matriglycan as a high-affinity host receptor compared with other polysaccharides that decorate cells.
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Affiliation(s)
| | - Ron Diskin
- Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot, Israel
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3
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Silva JG, Pais Ferreira D, Dumez A, Wyss T, Veber R, Danilo M, Pinschewer DD, Charmoy M, Held W. Emergence and fate of stem cell-like Tcf7+ CD8 + T cells during a primary immune response to viral infection. Sci Immunol 2023; 8:eadh3113. [PMID: 37976346 DOI: 10.1126/sciimmunol.adh3113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 10/23/2023] [Indexed: 11/19/2023]
Abstract
In response to infection, naïve CD8+ T (TN) cells yield a large pool of short-lived terminal effector (TTE) cells that eliminate infected host cells. In parallel, a minor population of stem cell-like central memory (TCM) cells forms, which has the capacity to maintain immunity after pathogen clearance. It has remained uncertain whether stem-like TCM cells arise by dedifferentiation from a subset of cytolytic TTE cells or whether priming generates stem-like cells capable of seeding the TCM compartment and, if so, when cytolytic TTE cells branch off. Here, we show that CD8+ T cells with stem-like properties, which are identified by the expression of TCF1 (encoded by Tcf7), are present across the primary response to infection. Priming programs TN cells to undergo multiple cell divisions, over the course of which TCF1 expression is maintained. These TCF1+ cells further expand relatively independently of systemic inflammation, antigen dose, or affinity, and they quantitatively yield TCF1+ TCM cells after pathogen clearance. Inflammatory signals suppress TCF1 expression in early divided TCF1+ cells. TCF1 down-regulation is associated with the irreversible loss of self-renewal capacity and the silencing of stem/memory genes, which precedes the stable acquisition of a TTE state. TCF1 expression restrains cell cycling, explaining in part the limited expansion of TCF1+ relative to TCF1- cells during the primary response. Thus, our data are consistent with terminal differentiation of effector cells being a step-wise process that is initiated by inflammation in primed stem-like cells, which would otherwise become central memory cells by default.
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Affiliation(s)
- Joana Gomes Silva
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
| | | | - Alexandre Dumez
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
| | - Tania Wyss
- Translational Data Science Facility, Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Romain Veber
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
| | - Maxime Danilo
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
| | - Daniel D Pinschewer
- Department of Biomedicine, Division of Experimental Virology, University of Basel, Basel, Switzerland
| | - Mélanie Charmoy
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
| | - Werner Held
- Department of Oncology, University of Lausanne, Lausanne, Switzerland
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Tibbs TN, Donoghue LJ, Buzzelli AA, Misumi I, DeMonia M, Ferris MT, Kelada SN, Whitmire JK. Mice with FVB-derived sequence on chromosome 17 succumb to disseminated virus infection due to aberrant NK cell and T cell responses. iScience 2023; 26:108348. [PMID: 38026197 PMCID: PMC10665959 DOI: 10.1016/j.isci.2023.108348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 09/19/2023] [Accepted: 10/23/2023] [Indexed: 12/01/2023] Open
Abstract
Zoonotic arenavirus infections can result in viral hemorrhagic disease, characterized by platelet loss, petechia, and multi-organ injury. The mechanisms governing these outcomes are likely impacted by virus strain and infection dose, as well as an individual's genetic background and immune constitution. To better understand the processes leading to severe pathogenesis, we compared two strains of inbred mice, C57BL/6J (B6) and FVB/NJ (FVB), that have diametrically opposed outcomes during disseminated lymphocytic choriomeningitis virus (LCMV) infection. Infection caused minimal pathogenesis in B6 mice, whereas FVB mice developed acute hepatitis and perished due, in part, to aberrant NK cell and T cell responses. Susceptible mice showed an outgrowth of cytolytic CD4+ T cells and loss of Treg cells. B6 congenic mice with the FVB allele at a 25Mb locus on chromosome 17 recapitulated FVB pathogenesis upon infection. A locus containing a limited number of variants in immune-related genes greatly impacts survival during infection.
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Affiliation(s)
- Taylor N. Tibbs
- Department of Microbiology and Immunology, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Lauren J. Donoghue
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Ashlyn A. Buzzelli
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Ichiro Misumi
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Maggie DeMonia
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Martin T. Ferris
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Samir N.P. Kelada
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
| | - Jason K. Whitmire
- Department of Microbiology and Immunology, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
- Department of Genetics, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, UNC-Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA
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5
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Hogeboom C. Does multiple sclerosis have a zoonotic origin? Correlations with lymphocytic choriomeningitis virus infection. Front Immunol 2023; 14:1217176. [PMID: 37398653 PMCID: PMC10313729 DOI: 10.3389/fimmu.2023.1217176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 06/06/2023] [Indexed: 07/04/2023] Open
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Quezada LK, Jin W, Liu YC, Kim ES, He Z, Indralingam CS, Tysl T, Labarta-Bajo L, Wehrens EJ, Jo Y, Kazane KR, Hattori C, Zuniga EI, Yeo GW, Chang JT. Early transcriptional and epigenetic divergence of CD8+ T cells responding to acute versus chronic infection. PLoS Biol 2023; 21:e3001983. [PMID: 36716323 PMCID: PMC9886247 DOI: 10.1371/journal.pbio.3001983] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 01/03/2023] [Indexed: 02/01/2023] Open
Abstract
During a microbial infection, responding CD8+ T cells give rise to effector cells that provide acute host defense and memory cells that provide sustained protection. An alternative outcome is exhaustion, a state of T cell dysfunction that occurs in the context of chronic infections and cancer. Although it is evident that exhausted CD8+ T (TEX) cells are phenotypically and molecularly distinct from effector and memory CD8+ T cells, the factors regulating the earliest events in the differentiation process of TEX cells remain incompletely understood. Here, we performed single-cell RNA-sequencing and single-cell ATAC-sequencing of CD8+ T cells responding to LCMV-Armstrong (LCMV-Arm) or LCMV-Clone 13 (LCMV-Cl13), which result in acute or chronic infections, respectively. Compared to CD8+ T cells that had undergone their first division in response to LCMV-Arm (Div1ARM) cells, CD8+ T cells that had undergone their first division in response to LCMV-Cl13 (Div1CL13) expressed higher levels of genes encoding transcription factors previously associated with exhaustion, along with higher levels of Ezh2, the catalytic component of the Polycomb Repressive Complex 2 (PRC2) complex, which mediates epigenetic silencing. Modulation of Ezh2 resulted in altered expression of exhaustion-associated molecules by CD8+ T cells responding to LCMV-Cl13, though the specific cellular and infectious contexts, rather than simply the level of Ezh2 expression, likely determine the eventual outcome. Taken together, these findings suggest that the differentiation paths of CD8+ T cells responding to acute versus chronic infections may diverge earlier than previously appreciated.
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Affiliation(s)
- Lauren K. Quezada
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Wenhao Jin
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Yi Chia Liu
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Eleanor S. Kim
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Zhaoren He
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Cynthia S. Indralingam
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Tiffani Tysl
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Lara Labarta-Bajo
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Ellen J. Wehrens
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Yeara Jo
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Katelynn R. Kazane
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Christopher Hattori
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Elina I. Zuniga
- Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Gene W. Yeo
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States of America
- Institute for Genomic Medicine, University of California San Diego, La Jolla, California, United States of America
| | - John T. Chang
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
- Department of Medicine, Jennifer Moreno Department of Veteran Affairs Medical Center, San Diego, California, United States of America
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7
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Mammarenavirus Genetic Diversity and Its Biological Implications. Curr Top Microbiol Immunol 2023; 439:265-303. [PMID: 36592249 DOI: 10.1007/978-3-031-15640-3_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Members of the family Arenaviridae are classified into four genera: Antennavirus, Hartmanivirus, Mammarenavirus, and Reptarenavirus. Reptarenaviruses and hartmaniviruses infect (captive) snakes and have been shown to cause boid inclusion body disease (BIBD). Antennaviruses have genomes consisting of 3, rather than 2, segments, and were discovered in actinopterygian fish by next-generation sequencing but no biological isolate has been reported yet. The hosts of mammarenaviruses are mainly rodents and infections are generally asymptomatic. Current knowledge about the biology of reptarenaviruses, hartmaniviruses, and antennaviruses is very limited and their zoonotic potential is unknown. In contrast, some mammarenaviruses are associated with zoonotic events that pose a threat to human health. This review will focus on mammarenavirus genetic diversity and its biological implications. Some mammarenaviruses including lymphocytic choriomeningitis virus (LCMV) are excellent experimental model systems for the investigation of acute and persistent viral infections, whereas others including Lassa (LASV) and Junin (JUNV) viruses, the causative agents of Lassa fever (LF) and Argentine hemorrhagic fever (AHF), respectively, are important human pathogens. Mammarenaviruses were thought to have high degree of intra-and inter-species amino acid sequence identities, but recent evidence has revealed a high degree of mammarenavirus genetic diversity in the field. Moreover, closely related mammarenavirus can display dramatic phenotypic differences in vivo. These findings support a role of genetic variability in mammarenavirus adaptability and pathogenesis. Here, we will review the molecular biology of mammarenaviruses, phylogeny, and evolution, as well as the quasispecies dynamics of mammarenavirus populations and their biological implications.
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Beura LK, Scott MC, Pierson MJ, Joag V, Wijeyesinghe S, Semler MR, Quarnstrom CF, Busman-Sahay K, Estes JD, Hamilton SE, Vezys V, O'Connor DH, Masopust D. Novel Lymphocytic Choriomeningitis Virus Strain Sustains Abundant Exhausted Progenitor CD8 T Cells without Systemic Viremia. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2022; 209:1691-1702. [PMID: 36122933 PMCID: PMC9588727 DOI: 10.4049/jimmunol.2200320] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/21/2022] [Indexed: 01/04/2023]
Abstract
Lymphocytic choriomeningitis virus (LCMV) is the prototypic arenavirus and a natural mouse pathogen. LCMV-Armstrong, an acutely resolved strain, and LCMV-clone 13, a mutant that establishes chronic infection, have provided contrasting infection models that continue to inform the fundamental biology of T cell differentiation, regulation of exhaustion, and response to checkpoint blockade. In this study, we report the isolation and characterization of LCMV-Minnesota (LCMV-MN), which was naturally transmitted to laboratory mice upon cohousing with pet shop mice and shares 80-95% amino acid homology with previously characterized LCMV strains. Infection of laboratory mice with purified LCMV-MN resulted in viral persistence that was intermediate between LCMV-Armstrong and -clone 13, with widely disseminated viral replication and viremia that was controlled within 15-30 d, unless CD4 T cells were depleted prior to infection. LCMV-MN-responding CD8+ T cells biased differentiation toward the recently described programmed death-1 (PD-1)+CXCR5+Tim-3lo stemlike CD8+ T cell population (also referred to as progenitor exhausted T cells) that effectuates responses to PD-1 blockade checkpoint inhibition, a therapy that rejuvenates responses against chronic infections and cancer. This subset resembled previously characterized PD-1+TCF1+ stemlike CD8+ T cells by transcriptional, phenotypic, and functional assays, yet was atypically abundant. LCMV-MN may provide a tool to better understand the breadth of immune responses in different settings of chronic Ag stimulation as well as the ontogeny of progenitor exhausted T cells and the regulation of responsiveness to PD-1 blockade.
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Affiliation(s)
- Lalit K Beura
- Department of Molecular Microbiology and Immunology, Brown University, Providence, RI;
| | - Milcah C Scott
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
| | - Mark J Pierson
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN
| | - Vineet Joag
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
| | - Sathi Wijeyesinghe
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
| | - Matthew R Semler
- Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI; and
| | - Clare F Quarnstrom
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
| | - Kathleen Busman-Sahay
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton, OR
| | - Jacob D Estes
- Vaccine and Gene Therapy Institute, Oregon Health & Science University, Beaverton, OR
| | - Sara E Hamilton
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN
| | - Vaiva Vezys
- Center for Immunology, University of Minnesota, Minneapolis, MN
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
| | - David H O'Connor
- Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison, WI; and
| | - David Masopust
- Center for Immunology, University of Minnesota, Minneapolis, MN;
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN
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A Morbillivirus Infection Shifts DC Maturation Toward a Tolerogenic Phenotype to Suppress T Cell Activation. J Virol 2022; 96:e0124022. [PMID: 36094317 PMCID: PMC9517701 DOI: 10.1128/jvi.01240-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Viruses have evolved numerous strategies to impair immunity so that they can replicate more efficiently. Among those, the immunosuppressive effects of morbillivirus infection can be particularly problematic, as they allow secondary infections to take hold in the host, worsening disease prognosis. In the present work, we hypothesized that the highly contagious morbillivirus peste des petits ruminants virus (PPRV) could target monocytes and dendritic cells (DC) to contribute to the immunosuppressive effects produced by the infection. Monocytes isolated from healthy sheep, a natural host of the disease, were able be infected by PPRV and this impaired the differentiation and phagocytic ability of immature monocyte-derived DC (MoDC). We also assessed PPRV capacity to infect differentiated MoDC. Ovine MoDC could be productively infected by PPRV, and this drastically reduced MoDC capacity to activate allogeneic T cell responses. Transcriptomic analysis of infected MoDC indicated that several tolerogenic DC signature genes were upregulated upon PPRV infection. Furthermore, PPRV-infected MoDC could impair the proliferative response of autologous CD4+ and CD8+ T cell to the mitogen concanavalin A (ConA), which indicated that DC targeting by the virus could promote immunosuppression. These results shed new light on the mechanisms employed by morbillivirus to suppress the host immune responses. IMPORTANCE Morbilliviruses pose a threat to global health given their high infectivity. The morbillivirus peste des petits ruminants virus (PPRV) severely affects small-ruminant-productivity and leads to important economic losses in communities that rely on these animals for subsistence. PPRV produces in the infected host a period of severe immunosuppression that opportunistic pathogens exploit, which worsens the course of the infection. The mechanisms of PPRV immunosuppression are not fully understood. In the present work, we demonstrate that PPRV can infect professional antigen-presenting cells called dendritic cells (DC) and disrupt their capacity to elicit an immune response. PPRV infection promoted a DC activation profile that favored the induction of tolerance instead of the activation of an antiviral immune response. These results shed new light on the mechanisms employed by morbilliviruses to suppress the immune responses.
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Lassa virus glycoprotein complex review: insights into its unique fusion machinery. Biosci Rep 2022; 42:230708. [PMID: 35088070 PMCID: PMC8844875 DOI: 10.1042/bsr20211930] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 01/24/2022] [Accepted: 01/26/2022] [Indexed: 11/17/2022] Open
Abstract
Lassa virus (LASV), an arenavirus endemic to West Africa, causes Lassa fever—a lethal hemorrhagic fever. Entry of LASV into the host cell is mediated by the glycoprotein complex (GPC), which is the only protein located on the viral surface and comprises three subunits: glycoprotein 1 (GP1), glycoprotein 2 (GP2), and a stable signal peptide (SSP). The LASV GPC is a class one viral fusion protein, akin to those found in viruses such as human immunodeficiency virus (HIV), influenza, Ebola virus (EBOV), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). These viruses are enveloped and utilize membrane fusion to deliver their genetic material to the host cell. Like other class one fusion proteins, LASV-mediated membrane fusion occurs through an orchestrated sequence of conformational changes in its GPC. The receptor-binding subunit, GP1, first engages with a host cell receptor then undergoes a unique receptor switch upon delivery to the late endosome. The acidic pH and change in receptor result in the dissociation of GP1, exposing the fusion subunit, GP2, such that fusion can occur. These events ultimately lead to the formation of a fusion pore so that the LASV genetic material is released into the host cell. Interestingly, the mature GPC retains its SSP as a third subunit—a feature that is unique to arenaviruses. Additionally, the fusion domain contains two separate fusion peptides, instead of a standard singular fusion peptide. Here, we give a comprehensive review of the LASV GPC components and their unusual features.
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Chronic LCMV Infection Is Fortified with Versatile Tactics to Suppress Host T Cell Immunity and Establish Viral Persistence. Viruses 2021; 13:v13101951. [PMID: 34696381 PMCID: PMC8537583 DOI: 10.3390/v13101951] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 09/15/2021] [Accepted: 09/22/2021] [Indexed: 12/19/2022] Open
Abstract
Ever since the immune regulatory strains of lymphocytic choriomeningitis virus (LCMV), such as Clone 13, were isolated, LCMV infection of mice has served as a valuable model for the mechanistic study of viral immune suppression and virus persistence. The exhaustion of virus-specific T cells was demonstrated during LCMV infection, and the underlying mechanisms have been extensively investigated using LCMV infection in mouse models. In particular, the mechanism for gradual CD8+ T cell exhaustion at molecular and transcriptional levels has been investigated. These studies revealed crucial roles for inhibitory receptors, surface markers, regulatory cytokines, and transcription factors, including PD-1, PSGL-1, CXCR5, and TOX in the regulation of T cells. However, the action mode for CD4+ T cell suppression is largely unknown. Recently, sphingosine kinase 2 was proven to specifically repress CD4+ T cell proliferation and lead to LCMV persistence. As CD4+ T cell regulation was also known to be important for viral persistence, research to uncover the mechanism for CD4+ T cell repression could help us better understand how viruses launch and prolong their persistence. This review summarizes discoveries derived from the study of LCMV in regard to the mechanisms for T cell suppression and approaches for the termination of viral persistence with special emphasis on CD8+ T cells.
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Pipperger L, Riepler L, Kimpel J, Siller A, Stoitzner P, Bánki Z, von Laer D. Differential infection of murine and human dendritic cell subsets by oncolytic vesicular stomatitis virus variants. Oncoimmunology 2021; 10:1959140. [PMID: 34484872 PMCID: PMC8409795 DOI: 10.1080/2162402x.2021.1959140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Oncolytic viruses (OVs) can eradicate tumor cells and elicit antitumor immunity. VSV-GP, a chimeric vesicular stomatitis virus (VSV) with the glycoprotein (GP) of the lymphocytic choriomeningitis virus, is a promising new OV candidate. However, the interaction of VSV-GP with host immune cells is not fully understood. Dendritic cells (DCs) are essential for inducing efficient antitumor immunity. Thus, we aimed to investigate the interaction of VSV-GP with different murine and human DCs subsets in direct comparison to the less cytopathic variant VSV-dM51-GP and wild type VSV. Immature murine bone marrow-derived DCs (BMDCs) were equally infected and killed by VSV and VSV-GP. Human monocyte-derived DCs (moDCs) were more permissive to VSV. Interestingly, VSV-dM51-GP induced maturation instead of killing in both BMDCs and moDCs as well as a pronounced release of pro-inflammatory cytokines. Importantly, matured BMDCs and moDCs were no longer susceptible to VSV-GP infection. Mouse splenic conventional DC type 1 (cDC1) could be infected ex vivo by VSV and VSV-GP to a higher extent than cDC2. Systemic infection of mice with VSV-GP and VSV-dM51-GP resulted in strong activation of cDCs despite low infection rates in spleen and tumor tissue. Human blood cDC1 were equally infected by VSV and VSV-GP, whereas cDC2 showed preferential infection with VSV. Our study demonstrated differential DC infection, activation, and cytokine production after the treatment with VSV and VSV-GP variants among species and subsets, which should be taken into account when investigating immunological mechanisms of oncolytic virotherapy in mouse models and human clinical trials.
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Affiliation(s)
- Lisa Pipperger
- Institute of Virology, Medical University of Innsbruck, Innsbruck, Austria
| | - Lydia Riepler
- Institute of Virology, Medical University of Innsbruck, Innsbruck, Austria
| | - Janine Kimpel
- Institute of Virology, Medical University of Innsbruck, Innsbruck, Austria
| | - Anita Siller
- Central Institute of Blood Transfusion and Immunology, University Hospital Innsbruck, Innsbruck, Austria
| | - Patrizia Stoitzner
- Department of Dermatology, Venereology & Allergology, Medical University of Innsbruck, Innsbruck, Austria
| | - Zoltán Bánki
- Institute of Virology, Medical University of Innsbruck, Innsbruck, Austria
| | - Dorothee von Laer
- Institute of Virology, Medical University of Innsbruck, Innsbruck, Austria
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13
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Kaseke C, Tano-Menka R, Senjobe F, Gaiha GD. The Emerging Role for CTL Epitope Specificity in HIV Cure Efforts. J Infect Dis 2021; 223:32-37. [PMID: 33586771 PMCID: PMC7883022 DOI: 10.1093/infdis/jiaa333] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The development of an effective human immunodeficiency virus (HIV) cure is a critical global health priority. A major obstacle to this effort is the establishment of a latent reservoir of HIV infected cells, which necessitates lifelong therapy, causing both logistical and adherence burdens for infected individuals. However, in a subset of these individuals, cytotoxic T lymphocytes (CTLs) can durably suppress viral outgrowth in the absence of therapy, providing a path towards a viable HIV cure. In this review, we discuss the emerging role that CTLs have in HIV cure efforts, with particular emphasis on epitope specificity. Recent studies have demonstrated that successful in vivo containment of the virus is rooted in the specific targeting of fitness-constrained, mutation-resistant regions of the HIV proteome. We highlight these new insights, providing context with previous observations in HIV and other models of viral control, and delineate their translation into a therapeutic vaccine.
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Affiliation(s)
- Clarety Kaseke
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard, Cambridge, Massachusetts, USA
| | - Rhoda Tano-Menka
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard, Cambridge, Massachusetts, USA
| | - Fernando Senjobe
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard, Cambridge, Massachusetts, USA.,Virology Program, Harvard Medical School, Boston, Massachusetts, USA
| | - Gaurav D Gaiha
- Ragon Institute of Massachusetts General Hospital, Massachusetts Institute of Technology, and Harvard, Cambridge, Massachusetts, USA.,Gastrointestinal Unit, Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
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14
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Joseph S, Campbell KP. Lassa Fever Virus Binds Matriglycan-A Polymer of Alternating Xylose and Glucuronate-On α-Dystroglycan. Viruses 2021; 13:1679. [PMID: 34578260 PMCID: PMC8473316 DOI: 10.3390/v13091679] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 08/18/2021] [Accepted: 08/20/2021] [Indexed: 11/18/2022] Open
Abstract
Lassa fever virus (LASV) can cause life-threatening hemorrhagic fevers for which there are currently no vaccines or targeted treatments. The late Prof. Stefan Kunz, along with others, showed that the high-affinity host receptor for LASV, and other Old World and clade-C New World mammarenaviruses, is matriglycan-a linear repeating disaccharide of alternating xylose and glucuronic acid that is polymerized uniquely on α-dystroglycan by like-acetylglucosaminyltransferase-1 (LARGE1). Although α-dystroglycan is ubiquitously expressed, LASV preferentially infects vascular endothelia and professional phagocytic cells, which suggests that viral entry requires additional cell-specific factors. In this review, we highlight the work of Stefan Kunz detailing the molecular mechanism of LASV binding and discuss the requirements of receptors, such as tyrosine kinases, for internalization through apoptotic mimicry.
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Affiliation(s)
| | - Kevin P. Campbell
- Howard Hughes Medical Institute, Senator Paul D. Wellstone Muscular Dystrophy Specialized Research Center, Department of Molecular Physiology and Biophysics and Department of Neurology, Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA 52242, USA;
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15
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Coffin CS, Mulrooney-Cousins PM, Michalak TI. Hepadnaviral Lymphotropism and Its Relevance to HBV Persistence and Pathogenesis. Front Microbiol 2021; 12:695384. [PMID: 34421849 PMCID: PMC8377760 DOI: 10.3389/fmicb.2021.695384] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 07/19/2021] [Indexed: 12/20/2022] Open
Abstract
Since the discovery of hepatitis B virus (HBV) over five decades ago, there have been many independent studies showing presence of HBV genomes in cells of the immune system. However, the nature of HBV lymphotropism and its significance with respect to HBV biology, persistence and the pathogenesis of liver and extrahepatic disorders remains underappreciated. This is in contrast to studies of other viral pathogens in which the capability to infect immune cells is an area of active investigation. Indeed, in some viral infections, lymphotropism may be essential, and even a primary mechanism of viral persistence, and a major contributor to disease pathogenesis. Nevertheless, there are advances in understanding of HBV lymphotropism in recent years due to cumulative evidence showing that: (i) lymphoid cells are a reservoir of replicating HBV, (ii) are a site of HBV-host DNA integration and (iii) virus genomic diversification leading to pathogenic variants, and (iv) they play a role in HBV resistance to antiviral therapy and (v) likely contribute to reactivation of hepatitis B. Further support for HBV lymphotropic nature is provided by studies in a model infection with the closely related woodchuck hepatitis virus (WHV) naturally infecting susceptible marmots. This animal model faithfully reproduces many aspects of HBV biology, including its replication scheme, tissue tropism, and induction of both symptomatic and silent infections, immunological processes accompanying infection, and progressing liver disease culminating in hepatocellular carcinoma. The most robust evidence came from the ability of WHV to establish persistent infection of the immune system that may not engage the liver when small quantities of virus are experimentally administered or naturally transmitted into virus-naïve animals. Although the concept of HBV lymphotropism is not new, it remains controversial and not accepted by conventional HBV researchers. This review summarizes research advances on HBV and hepadnaviral lymphotropism including the role of immune cells infection in viral persistence and the pathogenesis of HBV-induced liver and extrahepatic diseases. Finally, we discuss the role of immune cells in HBV diagnosis and assessment of antiviral therapy efficacy.
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Affiliation(s)
- Carla S Coffin
- Liver Unit, Department of Gastroenterology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Patricia M Mulrooney-Cousins
- Molecular Virology and Hepatology Research Group, Division of Basic Medical Sciences, Faculty of Medicine, Health Sciences Centre, Memorial University of Newfoundland, St. John's, NL, Canada
| | - Tomasz I Michalak
- Molecular Virology and Hepatology Research Group, Division of Basic Medical Sciences, Faculty of Medicine, Health Sciences Centre, Memorial University of Newfoundland, St. John's, NL, Canada
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16
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Ring SS, Cupovic J, Onder L, Lütge M, Perez-Shibayama C, Gil-Cruz C, Scandella E, De Martin A, Mörbe U, Hartmann F, Wenger R, Spiegl M, Besse A, Bonilla WV, Stemeseder F, Schmidt S, Orlinger KK, Krebs P, Ludewig B, Flatz L. Viral vector-mediated reprogramming of the fibroblastic tumor stroma sustains curative melanoma treatment. Nat Commun 2021; 12:4734. [PMID: 34354077 PMCID: PMC8342618 DOI: 10.1038/s41467-021-25057-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 07/19/2021] [Indexed: 11/13/2022] Open
Abstract
The tumor microenvironment (TME) is a complex amalgam of tumor cells, immune cells, endothelial cells and fibroblastic stromal cells (FSC). Cancer-associated fibroblasts are generally seen as tumor-promoting entity. However, it is conceivable that particular FSC populations within the TME contribute to immune-mediated tumor control. Here, we show that intratumoral treatment of mice with a recombinant lymphocytic choriomeningitis virus-based vaccine vector expressing a melanocyte differentiation antigen resulted in T cell-dependent long-term control of melanomas. Using single-cell RNA-seq analysis, we demonstrate that viral vector-mediated transduction reprogrammed and activated a Cxcl13-expressing FSC subset that show a pronounced immunostimulatory signature and increased expression of the inflammatory cytokine IL-33. Ablation of Il33 gene expression in Cxcl13-Cre-positive FSCs reduces the functionality of intratumoral T cells and unleashes tumor growth. Thus, reprogramming of FSCs by a self-antigen-expressing viral vector in the TME is critical for curative melanoma treatment by locally sustaining the activity of tumor-specific T cells. Lymphocytic choriomeningitis virus (LCMV)-based viral vectors have been shown to induce potent antitumor immune responses. Here the authors show that a LCMV-based vaccine vector remodels the tumor-associated fibroblastic stroma, sustaining CD8+ T cell activation and reducing tumor growth in a preclinical model of melanoma.
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Affiliation(s)
- Sandra S Ring
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Jovana Cupovic
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland.,Max Planck Institute of Immunology and Epigenetics, Freiburg, Germany
| | - Lucas Onder
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Mechthild Lütge
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | | | - Cristina Gil-Cruz
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Elke Scandella
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Angelina De Martin
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Urs Mörbe
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Fabienne Hartmann
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Robert Wenger
- Department of Plastic Reconstructive Surgery, Kantonsspital St. Gallen, St. Gallen, Switzerland
| | - Matthias Spiegl
- Department of Plastic Reconstructive Surgery, Kantonsspital St. Gallen, St. Gallen, Switzerland
| | - Andrej Besse
- Department of Medical Oncology and Hematology, Kantonsspital St.Gallen, St.Gallen, Switzerland
| | - Weldy V Bonilla
- Division of Experimental Virology, Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | | | | | - Philippe Krebs
- Institute of Pathology, University of Berne, Berne, Switzerland
| | - Burkhard Ludewig
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland. .,Institute of Experimental Immunology, University of Zurich, Zurich, Switzerland.
| | - Lukas Flatz
- Institute of Immunobiology, Kantonsspital St.Gallen, St.Gallen, Switzerland. .,Department of Dermatology, Kantonsspital St. Gallen, St. Gallen, Switzerland. .,Department of Dermatology, University Hospital Zurich, Zurich, Switzerland.
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17
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The Interplay between Bluetongue Virus Infections and Adaptive Immunity. Viruses 2021; 13:v13081511. [PMID: 34452376 PMCID: PMC8402766 DOI: 10.3390/v13081511] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 07/19/2021] [Accepted: 07/28/2021] [Indexed: 12/18/2022] Open
Abstract
Viral infections have long provided a platform to understand the workings of immunity. For instance, great strides towards defining basic immunology concepts, such as MHC restriction of antigen presentation or T-cell memory development and maintenance, have been achieved thanks to the study of lymphocytic choriomeningitis virus (LCMV) infections. These studies have also shaped our understanding of antiviral immunity, and in particular T-cell responses. In the present review, we discuss how bluetongue virus (BTV), an economically important arbovirus from the Reoviridae family that affects ruminants, affects adaptive immunity in the natural hosts. During the initial stages of infection, BTV triggers leucopenia in the hosts. The host then mounts an adaptive immune response that controls the disease. In this work, we discuss how BTV triggers CD8+ T-cell expansion and neutralizing antibody responses, yet in some individuals viremia remains detectable after these adaptive immune mechanisms are active. We present some unpublished data showing that BTV infection also affects other T cell populations such as CD4+ T-cells or γδ T-cells, as well as B-cell numbers in the periphery. This review also discusses how BTV evades these adaptive immune mechanisms so that it can be transmitted back to the arthropod host. Understanding the interaction of BTV with immunity could ultimately define the correlates of protection with immune mechanisms that would improve our knowledge of ruminant immunology.
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18
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Slow viral propagation during initial phase of infection leads to viral persistence in mice. Commun Biol 2021; 4:508. [PMID: 33927339 PMCID: PMC8084999 DOI: 10.1038/s42003-021-02028-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/12/2021] [Indexed: 11/13/2022] Open
Abstract
Immune evasion of pathogens can modify the course of infection and impact viral persistence and pathology. Here, using different strains of the lymphocytic choriomeningitis virus (LCMV) model system, we show that slower propagation results in limited type I interferon (IFN-I) production and viral persistence. Specifically, cells infected with LCMV-Docile exhibited reduced viral replication when compared to LCMV-WE and as a consequence, infection with LCMV-Docile resulted in reduced activation of bone marrow derived dendritic cells (BMDCs) and IFN-I production in vitro in comparison with LCMV-WE. In vivo, we observed a reduction of IFN-I, T cell exhaustion and viral persistence following infection of LCMV-Docile but not LCMV-WE. Mechanistically, block of intracellular protein transport uncovered reduced propagation of LCMV-Docile when compared to LCMV-WE. This reduced propagation was critical in blunting the activation of the innate and adaptive immune system. When mice were simultaneously infected with LCMV-Docile and LCMV-WE, immune function was restored and IFN-I production, T cell effector functions as well as viral loads were similar to that of mice infected with LCMV-WE alone. Taken together, this study suggests that reduced viral propagation can result in immune evasion and viral persistence. Using different strains of the lymphocytic choriomeningitis virus (LCMV), Xu, Wang et al. show that a slow viral propagation limits type I interferon (IFN-I) production and viral persistence in mice. This study suggests a reduced viral propagation as a mechanism for immune evasion and viral persistence.
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19
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Labarta-Bajo L, Nilsen SP, Humphrey G, Schwartz T, Sanders K, Swafford A, Knight R, Turner JR, Zúñiga EI. Type I IFNs and CD8 T cells increase intestinal barrier permeability after chronic viral infection. J Exp Med 2021; 217:152069. [PMID: 32880630 PMCID: PMC7953738 DOI: 10.1084/jem.20192276] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 06/29/2020] [Accepted: 08/06/2020] [Indexed: 12/16/2022] Open
Abstract
Intestinal barrier leakage constitutes a potential therapeutic target for many inflammatory diseases and represents a disease progression marker during chronic viral infections. However, the causes of altered gut barrier remain mostly unknown. Using murine infection with lymphocytic choriomeningitis virus, we demonstrate that, in contrast to an acute viral strain, a persistent viral isolate leads to long-term viral replication in hematopoietic and mesenchymal cells, but not epithelial cells (IECs), in the intestine. Viral persistence drove sustained intestinal epithelial barrier leakage, which was characterized by increased paracellular flux of small molecules and was associated with enhanced colitis susceptibility. Type I IFN signaling caused tight junction dysregulation in IECs, promoted gut microbiome shifts and enhanced intestinal CD8 T cell responses. Notably, both type I IFN receptor blockade and CD8 T cell depletion prevented infection-induced barrier leakage. Our study demonstrates that infection with a virus that persistently replicates in the intestinal mucosa increases epithelial barrier permeability and reveals type I IFNs and CD8 T cells as causative factors of intestinal leakage during chronic infections.
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Affiliation(s)
- Lara Labarta-Bajo
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA
| | - Steven P Nilsen
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
| | - Gregory Humphrey
- Department of Pediatrics, University of California, San Diego, La Jolla, CA
| | - Tara Schwartz
- Department of Pediatrics, University of California, San Diego, La Jolla, CA
| | - Karenina Sanders
- Department of Pediatrics, University of California, San Diego, La Jolla, CA
| | - Austin Swafford
- Center for Microbiome Innovation, University of California, San Diego, La Jolla, CA
| | - Rob Knight
- Department of Pediatrics, University of California, San Diego, La Jolla, CA.,Center for Microbiome Innovation, University of California, San Diego, La Jolla, CA.,Department of Bioengineering, University of California, San Diego, La Jolla, CA.,Department of Computer Science and Engineering, University of California, San Diego, La Jolla, CA
| | - Jerrold R Turner
- Laboratory of Mucosal Barrier Pathobiology, Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA
| | - Elina I Zúñiga
- Division of Biological Sciences, University of California, San Diego, La Jolla, CA
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20
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Krolik M, Csepregi L, Hartmann F, Engetschwiler C, Flatz L. Recombinant lymphocytic choriomeningitis virus-based vaccine vector protects type I interferon receptor deficient mice from viral challenge. Vaccine 2021; 39:1257-1264. [PMID: 33518468 DOI: 10.1016/j.vaccine.2021.01.047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 12/07/2020] [Accepted: 01/16/2021] [Indexed: 01/20/2023]
Abstract
Reverse genetically engineered recombinant lymphocytic choriomeningitis virus (rLCMV) is a novel vaccine vector platform. Here, we investigate the safety and efficacy of rLCMV in mice lacking a functional type I interferon system with high susceptibility to viral infections. Propagation-deficient rLCMV vector expressing ovalbumin as a model antigen is cleared from type I interferon receptor-deficient mice (Ifnar-/-) within seven days post vaccination. In Ifnar-/-, induction of vaccine antigen specific T cells is delayed compared to wild type animals. However, immunization of Ifnar-/- results in potent memory formation and generates multifunctional cytotoxic CD8+ T cells. Most importantly, Ifnar-/- vaccinated with rLCMV are protected from a challenge with the aggressive LCMV Clone 13. Our data provide evidence for an excellent safety profile with maintained efficacy in immunocompromised animals.
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Affiliation(s)
- Michal Krolik
- Institute of Immunobiology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland
| | - Lucia Csepregi
- Institute of Immunobiology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland
| | - Fabienne Hartmann
- Institute of Immunobiology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland
| | - Céline Engetschwiler
- Institute of Immunobiology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland
| | - Lukas Flatz
- Institute of Immunobiology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland; Department of Dermatology, University Hospital Zurich, Gloriastrasse 31, 8091 Zurich, Switzerland; Department of Oncology and Hematology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland; Department of Dermatology, Kantonsspital St.Gallen, Rorschacher Strasse 95, 9007 St.Gallen, Switzerland.
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21
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Davenport B, Eberlein J, Nguyen TT, Victorino F, van der Heide V, Kuleshov M, Ma'ayan A, Kedl R, Homann D. Chemokine Signatures of Pathogen-Specific T Cells II: Memory T Cells in Acute and Chronic Infection. THE JOURNAL OF IMMUNOLOGY 2020; 205:2188-2206. [PMID: 32948682 DOI: 10.4049/jimmunol.2000254] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 08/07/2020] [Indexed: 12/20/2022]
Abstract
Pathogen-specific memory T cells (TM) contribute to enhanced immune protection under conditions of reinfection, and their effective recruitment into a recall response relies, in part, on cues imparted by chemokines that coordinate their spatiotemporal positioning. An integrated perspective, however, needs to consider TM as a potentially relevant chemokine source themselves. In this study, we employed a comprehensive transcriptional/translational profiling strategy to delineate the identities, expression patterns, and dynamic regulation of chemokines produced by murine pathogen-specific TM CD8+TM, and to a lesser extent CD4+TM, are a prodigious source for six select chemokines (CCL1/3/4/5, CCL9/10, and XCL1) that collectively constitute a prominent and largely invariant signature across acute and chronic infections. Notably, constitutive CCL5 expression by CD8+TM serves as a unique functional imprint of prior antigenic experience; induced CCL1 production identifies highly polyfunctional CD8+ and CD4+TM subsets; long-term CD8+TM maintenance is associated with a pronounced increase of XCL1 production capacity; chemokines dominate the earliest stages of the CD8+TM recall response because of expeditious synthesis/secretion kinetics (CCL3/4/5) and low activation thresholds (CCL1/3/4/5/XCL1); and TM chemokine profiles modulated by persisting viral Ags exhibit both discrete functional deficits and a notable surplus. Nevertheless, recall responses and partial virus control in chronic infection appear little affected by the absence of major TM chemokines. Although specific contributions of TM-derived chemokines to enhanced immune protection therefore remain to be elucidated in other experimental scenarios, the ready visualization of TM chemokine-expression patterns permits a detailed stratification of TM functionalities that may be correlated with differentiation status, protective capacities, and potential fates.
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Affiliation(s)
- Bennett Davenport
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029.,Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Jens Eberlein
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Tom T Nguyen
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Francisco Victorino
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Verena van der Heide
- Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029.,Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Maxim Kuleshov
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029; and.,Mount Sinai Center for Bioinformatics, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Avi Ma'ayan
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029; and.,Mount Sinai Center for Bioinformatics, Icahn School of Medicine at Mount Sinai, New York, NY 10029
| | - Ross Kedl
- Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045
| | - Dirk Homann
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, CO 80045; .,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045.,Diabetes, Obesity and Metabolism Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029.,Precision Immunology Institute, Icahn School of Medicine at Mount Sinai, New York, NY
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22
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Population structure of Lassa Mammarenavirus in West Africa. Viruses 2020; 12:v12040437. [PMID: 32294960 PMCID: PMC7232344 DOI: 10.3390/v12040437] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 04/07/2020] [Accepted: 04/10/2020] [Indexed: 01/01/2023] Open
Abstract
Lassa mammarenavirus (LASV) is the etiologic agent of Lassa fever. In endemic regions in West Africa, LASV genetic diversity tends to cluster by geographic area. Seven LASV lineages are recognized, but the role of viral genetic determinants on disease presentation in humans is uncertain. We investigated the geographic structure and distribution of LASV in West Africa. We found strong spatial clustering of LASV populations, with two major east–west and north–south diversity gradients. Analysis of ancestry components indicated that known LASV lineages diverged from an ancestral population that most likely circulated in Nigeria, although alternative locations, such as Togo, cannot be excluded. Extant sequences carrying the largest contribution of this ancestral population include the prototype Pinneo strain, the Togo isolates, and a few viruses isolated in Nigeria. The LASV populations that experienced the strongest drift circulate in Mali and the Ivory Coast. By focusing on sequences form a single LASV sublineage (IIg), we identified an ancestry component possibly associated with protection from a fatal disease outcome. Although the same ancestry component tends to associate with lower viral loads in plasma, the small sample size requires that these results are treated with extreme caution.
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23
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Alothaimeen T, Seaver K, Mulder R, Gee K, Basta S. Granulocyte/Macrophage Colony-Stimulating Factor-Derived Macrophages Exhibit Distinctive Early Immune Response to Lymphocytic Choriomeningitis Virus Infection. Viral Immunol 2020; 33:477-488. [PMID: 32255741 DOI: 10.1089/vim.2019.0178] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Granulocyte/macrophage colony-stimulating factor (GM-CSF) and macrophage CSF (M-CSF) modulate differentiation and immune functions of macrophages (MΦ). Our aim was to evaluate how different MΦ differentiation conditions influence the MΦ response to virus infection. To address this, we differentiated bone marrow-derived MΦ in either GM-CSF or M-CSF and measured the cytokine responses to two different strains of lymphocytic choriomeningitis virus (LCMV) (clone 13; Cl13 or Armstrong; ARM). GM-CSF MΦ infected with either LCMV-ARM or -Cl13 produced more IL-6 than M-CSF MΦ, whereas M-CSF MΦ generated more IL-10 than GM-CSF MΦ. Interestingly, in M-CSF MΦ, LCMV-ARM induced more IL-10 production than Cl13. However, we could not detect any IL-12p70 or IL-23 after infection from either cell types. We also observed that GM-CSF MΦ was more efficient than M-CSF MΦ in supporting antigen-specific CD8+ T cell proliferation. Taken together, our data demonstrate that GM-CSF and M-CSF MΦ differ in how they respond to viral infection by their production of different cytokines, and their support for CD8+ T cell proliferation.
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Affiliation(s)
- Torki Alothaimeen
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Kyle Seaver
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Rylend Mulder
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Katrina Gee
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
| | - Sameh Basta
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Canada
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The Utility of Human Immune System Mice for High-Containment Viral Hemorrhagic Fever Research. Vaccines (Basel) 2020; 8:vaccines8010098. [PMID: 32098330 PMCID: PMC7157695 DOI: 10.3390/vaccines8010098] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2019] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 12/18/2022] Open
Abstract
Human immune system (HIS) mice are a subset of humanized mice that are generated by xenoengraftment of human immune cells or tissues and/or their progenitors into immunodeficient mice. Viral hemorrhagic fevers (VHFs) cause severe disease in humans, typically with high case fatality rates. HIS mouse studies have been performed to investigate the pathogenesis and immune responses to VHFs that must be handled in high-containment laboratory facilities. Here, we summarize studies on filoviruses, nairoviruses, phenuiviruses, and hantaviruses, and discuss the knowledge gained from using various HIS mouse models. Furthermore, we discuss the complexities of designing and interpreting studies utilizing HIS mice while highlighting additional questions about VHFs that can still be addressed using HIS mouse models.
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Abstract
Viral population numbers are extremely large compared with those of their host species. Population bottlenecks are frequent during the life cycle of viruses and can reduce viral populations transiently to very few individuals. Viruses have to confront several types of constraints that can be divided into basal, cell-dependent, and organism-dependent constraints. Viruses overcome them exploiting a number of molecular mechanisms, with an important contribution of population numbers and genome variation. The adaptive potential of viruses is reflected in modifications of cell tropism and host range, escape to components of the host immune response, and capacity to alternate among different host species, among other phenotypic changes. Despite a fitness cost of most mutations required to overcome a selective constraint, viruses can find evolutionary pathways that ensure their survival in equilibrium with their hosts.
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26
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A unique variant of lymphocytic choriomeningitis virus that induces pheromone binding protein MUP: Critical role for CTL. Proc Natl Acad Sci U S A 2019; 116:18001-18008. [PMID: 31427525 DOI: 10.1073/pnas.1907070116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Lymphocytic choriomeningitis virus (LCMV) WE variant 2.2 (v2.2) generated a high level of the major mouse urinary protein: MUP. Mice infected with LCMV WE v54, which differed from v2.2 by a single amino acid in the viral glycoprotein, failed to generate MUP above baseline levels found in uninfected controls. Variant 54 bound at 2.5 logs higher affinity to the LCMV receptor α-dystroglycan (α-DG) than v2.2 and entered α-DG-expressing but not α-DG-null cells. Variant 2.2 infected both α-DG-null or -expressing cells. Variant 54 infected more dendritic cells, generated a negligible CD8 T cell response, and caused a persistent infection, while v2.2 generated cytotoxic T lymphocytes (CTLs) and cleared virus within 10 days. By 20 days postinfection and through the 80-day observation period, significantly higher amounts of MUP were found in v2.2-infected mice. Production of MUP was dependent on virus-specific CTL as deletion of such cells aborted MUP production. Furthermore, MUP production was not elevated in v2.2 persistently infected mice unless virus was cleared following transfer of virus-specific CTL.
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27
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Plume JM, Todd D, Bonthius DJ. Viral Strain Determines Disease Symptoms, Pathology, and Immune Response in Neonatal Rats with Lymphocytic Choriomeningitis Virus Infection. Viruses 2019; 11:E552. [PMID: 31207945 PMCID: PMC6631398 DOI: 10.3390/v11060552] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 06/11/2019] [Accepted: 06/12/2019] [Indexed: 12/13/2022] Open
Abstract
When infection with lymphocytic choriomeningitis (LCMV) occurs during pregnancy, the virus can infect the fetus and injure the fetal brain. However, type, location, and severity of neuropathology differ among cases. One possible explanation for this diversity is that fetuses are infected with different viral strains. Using a rat model of congenital LCMV infection, we investigated how differences in LCMV strain (E350, WE2.2, and Clone 13) affect outcome. Rat pups received intracranial inoculations on postnatal day 4. E350 initially targeted glial cells, while WE2.2 and Clone 13 targeted neurons. The E350 strain induced focal destructive lesions, while the other strains induced global microencephaly. E350 attracted large numbers of CD8+ lymphocytes early in the disease course, while Clone 13 attracted CD4+ lymphocytes, and the infiltration occurred late. The E350 and WE2.2 strains induced large increases in expression of pro-inflammatory cytokines, while Clone 13 did not. The animals infected with E350 and WE2.2 became ataxic and performed poorly on the negative geotaxis assay, while the Clone 13 animals had profound growth failure. Thus, in the developing brain, different LCMV strains have different patterns of infection, neuropathology, immune responses and disease symptoms. In humans, different outcomes from congenital LCMV may reflect infection with different strains.
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Affiliation(s)
- Jeffrey M Plume
- Neuroscience Program, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
| | - Dylan Todd
- Neuroscience Program, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
| | - Daniel J Bonthius
- Neuroscience Program, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
- Department of Neurology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
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28
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Pedragosa M, Riera G, Casella V, Esteve-Codina A, Steuerman Y, Seth C, Bocharov G, Heath S, Gat-Viks I, Argilaguet J, Meyerhans A. Linking Cell Dynamics With Gene Coexpression Networks to Characterize Key Events in Chronic Virus Infections. Front Immunol 2019; 10:1002. [PMID: 31130969 PMCID: PMC6509617 DOI: 10.3389/fimmu.2019.01002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 04/18/2019] [Indexed: 01/29/2023] Open
Abstract
The host immune response against infection requires the coordinated action of many diverse cell subsets that dynamically adapt to a pathogen threat. Due to the complexity of such a response, most immunological studies have focused on a few genes, proteins, or cell types. With the development of “omic”-technologies and computational analysis methods, attempts to analyze and understand complex system dynamics are now feasible. However, the decomposition of transcriptomic data sets generated from complete organs remains a major challenge. Here, we combined Weighted Gene Coexpression Network Analysis (WGCNA) and Digital Cell Quantifier (DCQ) to analyze time-resolved mouse splenic transcriptomes in acute and chronic Lymphocytic Choriomeningitis Virus (LCMV) infections. This enabled us to generate hypotheses about complex immune functioning after a virus-induced perturbation. This strategy was validated by successfully predicting several known immune phenomena, such as effector cytotoxic T lymphocyte (CTL) expansion and exhaustion. Furthermore, we predicted and subsequently verified experimentally macrophage-CD8 T cell cooperativity and the participation of virus-specific CD8+ T cells with an early effector transcriptome profile in the host adaptation to chronic infection. Thus, the linking of gene expression changes with immune cell kinetics provides novel insights into the complex immune processes within infected tissues.
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Affiliation(s)
- Mireia Pedragosa
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain
| | - Graciela Riera
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain
| | - Valentina Casella
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain
| | - Anna Esteve-Codina
- CNAG-CRG, Center for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra, Barcelona, Spain
| | - Yael Steuerman
- Cell Research and Immunology Department, Tel Aviv University, Tel Aviv, Israel
| | - Celina Seth
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain
| | - Gennady Bocharov
- Marchuk Institute of Numerical Mathematics, Russian Academy of Sciences, Moscow, Russia.,Institute for Personalized Medicine, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Simon Heath
- CNAG-CRG, Center for Genomic Regulation (CRG), Barcelona Institute of Science and Technology, Barcelona, Spain.,Universitat Pompeu Fabra, Barcelona, Spain
| | - Irit Gat-Viks
- Cell Research and Immunology Department, Tel Aviv University, Tel Aviv, Israel
| | - Jordi Argilaguet
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain
| | - Andreas Meyerhans
- Infection Biology Laboratory, Department of Experimental and Health Sciences (DCEXS), Universitat Pompeu Fabra, Barcelona, Spain.,Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain
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Pallmer K, Barnstorf I, Baumann NS, Borsa M, Jonjic S, Oxenius A. NK cells negatively regulate CD8 T cells via natural cytotoxicity receptor (NCR) 1 during LCMV infection. PLoS Pathog 2019; 15:e1007725. [PMID: 30995287 PMCID: PMC6469806 DOI: 10.1371/journal.ppat.1007725] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Accepted: 03/21/2019] [Indexed: 11/23/2022] Open
Abstract
Besides their function in recognizing cancerous and virally infected cells, natural killer (NK) cells have the potential to shape adaptive immune responses. However, the mechanisms employed by NK cells to negatively regulate virus-specific CD8 T cell responses remain to be fully defined. Using activating receptor natural cytotoxicity receptor (NCR) 1 deficient (NCR1gfp/gfp) mice, we found increased numbers of virus-specific CD8 T cells, leading to enhanced virus control during acute LCMV infection. Furthermore, virus-specific CD8 T cells were more activated in the absence of NCR1, resulting in exacerbated immunopathology, documented by weight loss, and superior virus control early during chronic LCMV infection. Transfer experiments of virus-specific CD8 T cells into NCR1 deficient hosts revealed a direct cross talk between NK and CD8 T cells. Studies on the splenic microarchitecture revealed pronounced disorganization of T cells in infected NCR1gfp/gfp mice, resulting in enhanced immunopathology and disruption of the T cell niche upon chronic LCMV infection. Our data show a novel pathway employed by NK cells to regulate antiviral CD8 T cell responses, namely direct recognition and elimination of activated CD8 T cells via NCR1 early during infection to protect the host from an overshooting T cell response. LCMV, which is part of the Arenaviridae family, is a well-established mouse model for acute and chronic virus infections, and it has allowed the identification of many immunological principles that were subsequently confirmed in human infections, such as CTL escape or CD8 T cell exhaustion. NK cells belong to the first line defense, being activated early following infection or exposure to malignant cells, and mediate their antiviral or anti-tumoral effect by direct cytotoxicity and inflammatory cytokine secretion. While NK cells are dispensable for control of LCMV, NK cells have the potential to shape adaptive immunity by regulating T cell responses. The absence of NK cells leads to increased T cell immunity and thereby, to faster eradication of the virus. However, the detailed mechanisms of how NK cells control antiviral T cell responses is still poorly defined. Here, we identified the activating NK cell receptor NCR1 to be involved in the regulation of CD8 T cell responses during acute and chronic LCMV infection. The absence of NCR1 led to a more robust CD4 and CD8 T cell response and to superior viral control in acute and chronic LCMV infections. However, the increased CD8 T cell responses led to severe immunopathology in the setting of chronic infection. Hence, NK cells curtail CD8 T cell responses to protect the host from immunopathological damage in an NCR1 dependent manner.
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Affiliation(s)
| | | | | | - Mariana Borsa
- Institute of Microbiology, ETH Zürich, Zürich, Switzerland
| | - Stipan Jonjic
- Department of Histology and Embryology, Faculty of Medicine, Rijeka, Croatia
| | - Annette Oxenius
- Institute of Microbiology, ETH Zürich, Zürich, Switzerland
- * E-mail:
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30
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Brisse ME, Ly H. Hemorrhagic Fever-Causing Arenaviruses: Lethal Pathogens and Potent Immune Suppressors. Front Immunol 2019; 10:372. [PMID: 30918506 PMCID: PMC6424867 DOI: 10.3389/fimmu.2019.00372] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 02/14/2019] [Indexed: 12/22/2022] Open
Abstract
Hemorrhagic fevers (HF) resulting from pathogenic arenaviral infections have traditionally been neglected as tropical diseases primarily affecting African and South American regions. There are currently no FDA-approved vaccines for arenaviruses, and treatments have been limited to supportive therapy and use of non-specific nucleoside analogs, such as Ribavirin. Outbreaks of arenaviral infections have been limited to certain geographic areas that are endemic but known cases of exportation of arenaviruses from endemic regions and socioeconomic challenges for local control of rodent reservoirs raise serious concerns about the potential for larger outbreaks in the future. This review synthesizes current knowledge about arenaviral evolution, ecology, transmission patterns, life cycle, modulation of host immunity, disease pathogenesis, as well as discusses recent development of preventative and therapeutic pursuits against this group of deadly viral pathogens.
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Affiliation(s)
- Morgan E Brisse
- Biochemistry, Molecular Biology, and Biophysics Graduate Program, University of Minnesota, St. Paul, MN, United States.,Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
| | - Hinh Ly
- Department of Veterinary and Biomedical Sciences, University of Minnesota, St. Paul, MN, United States
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31
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Suprunenko T, Hofer MJ. Complexities of Type I Interferon Biology: Lessons from LCMV. Viruses 2019; 11:v11020172. [PMID: 30791575 PMCID: PMC6409748 DOI: 10.3390/v11020172] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/17/2019] [Accepted: 02/18/2019] [Indexed: 12/11/2022] Open
Abstract
Over the past decades, infection of mice with lymphocytic choriomeningitis virus (LCMV) has provided an invaluable insight into our understanding of immune responses to viruses. In particular, this model has clarified the central roles that type I interferons play in initiating and regulating host responses. The use of different strains of LCMV and routes of infection has allowed us to understand how type I interferons are critical in controlling virus replication and fostering effective antiviral immunity, but also how they promote virus persistence and functional exhaustion of the immune response. Accordingly, these discoveries have formed the foundation for the development of novel treatments for acute and chronic viral infections and even extend into the management of malignant tumors. Here we review the fundamental insights into type I interferon biology gained using LCMV as a model and how the diversity of LCMV strains, dose, and route of administration have been used to dissect the molecular mechanisms underpinning acute versus persistent infection. We also identify gaps in the knowledge regarding LCMV regulation of antiviral immunity. Due to its unique properties, LCMV will continue to remain a vital part of the immunologists' toolbox.
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Affiliation(s)
- Tamara Suprunenko
- School of Life and Environmental Sciences, the Marie Bashir Institute for Infectious Diseases and Biosecurity, Charles Perkins Centre, and the Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.
| | - Markus J Hofer
- School of Life and Environmental Sciences, the Marie Bashir Institute for Infectious Diseases and Biosecurity, Charles Perkins Centre, and the Bosch Institute, The University of Sydney, Sydney, NSW 2006, Australia.
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32
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Kahan SM, Zajac AJ. Immune Exhaustion: Past Lessons and New Insights from Lymphocytic Choriomeningitis Virus. Viruses 2019; 11:E156. [PMID: 30781904 PMCID: PMC6410286 DOI: 10.3390/v11020156] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 02/08/2019] [Accepted: 02/09/2019] [Indexed: 12/16/2022] Open
Abstract
Lymphocytic choriomeningitis virus (LCMV) is a paradigm-forming experimental system with a remarkable track record of contributing to the discovery of many of the fundamental concepts of modern immunology. The ability of LCMV to establish a chronic infection in immunocompetent adult mice was instrumental for identifying T cell exhaustion and this system has been invaluable for uncovering the complexity, regulators, and consequences of this state. These findings have been directly relevant for understanding why ineffective T cell responses commonly arise during many chronic infections including HIV and HCV, as well as during tumor outgrowth. The principal feature of exhausted T cells is the inability to elaborate the array of effector functions necessary to contain the underlying infection or tumor. Using LCMV to determine how to prevent and reverse T cell exhaustion has highlighted the potential of checkpoint blockade therapies, most notably PD-1 inhibition strategies, for improving cellular immunity under conditions of antigen persistence. Here, we discuss the discovery, properties, and regulators of exhausted T cells and highlight how LCMV has been at the forefront of advancing our understanding of these ineffective responses.
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Affiliation(s)
- Shannon M Kahan
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - Allan J Zajac
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
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33
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Pontremoli C, Forni D, Sironi M. Arenavirus genomics: novel insights into viral diversity, origin, and evolution. Curr Opin Virol 2019; 34:18-28. [DOI: 10.1016/j.coviro.2018.11.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/01/2018] [Accepted: 11/02/2018] [Indexed: 12/18/2022]
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34
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Effects of Friend Virus Infection and Regulatory T Cells on the Antigen Presentation Function of B Cells. mBio 2019; 10:mBio.02578-18. [PMID: 30670616 PMCID: PMC6343038 DOI: 10.1128/mbio.02578-18] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The primary role of B cells in immunity is considered the production of pathogen-specific antibodies, but another, less-well-studied, function of B cells is to present foreign antigens to T cells to stimulate their activation and proliferation. Dendritic cells (DCs) are considered the most important antigen-presenting cells (APCs) for CD8+ T cells, but DCs lose APC function when infected with Friend virus (FV), a model retrovirus of mice. Interestingly, B cells were better able to stimulate CD8+ T cell responses when they were infected with FV. We also found that the activation status of B cells under homeostatic conditions was potently modulated by regulatory T cells. This study illustrates an important link between B cell and T cell responses and illustrates an additional mechanism by which regulatory T cells suppress critical T cell responses during viral infections. Friend virus (FV) is a naturally occurring mouse retrovirus that infects dividing cells of the hematopoietic lineage, including antigen-presenting cells (APCs). The infection of APCs by viruses often induces their dysfunction, and it has been shown that FV infection reduces the ability of dendritic cells (DCs) to prime critical CD8+ T cell responses. Nonetheless, mice mount vigorous CD8+ T cell responses, so we investigated whether B cells might serve as alternative APCs during FV infection. Direct ex vivo analysis of B cells from FV-infected mice revealed that infected but not uninfected B cells upregulated expression of the costimulatory molecules CD80, CD86, and CD40, as well as major histocompatibility complex class II (MHC-II) molecules. Furthermore, in vitro studies showed that, compared to uninfected B cells from the same mice, the FV-infected B cells had significantly enhanced APC function, as measured by their capacity to prime CD8+ T cell activation and proliferation. Thus, in contrast to DCs, infection of B cells with FV enhanced their APC capacity and ability to stimulate the CD8+ T cell responses essential for virus control. FV infections also induce the activation and expansion of regulatory T cells (Tregs), so it was of interest to determine the impact of Tregs on B cell activation. The upregulation of costimulatory molecule expression and APC function of B cells was even more strongly enhanced by in vivo depletion of regulatory T cells than infection. Thus, Tregs exert potent homeostatic suppression of B cell activation that is partially overcome by FV infection.
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35
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Lymphocytic choriomeningitis virus Clone 13 infection causes either persistence or acute death dependent on IFN-1, cytotoxic T lymphocytes (CTLs), and host genetics. Proc Natl Acad Sci U S A 2018; 115:E7814-E7823. [PMID: 30061383 DOI: 10.1073/pnas.1804674115] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Understanding of T cell exhaustion and successful therapy to restore T cell function was first described using Clone (Cl) 13 variant selected from the lymphocytic choriomeningitis virus (LCMV) Armstrong (ARM) 53b parental strain. T cell exhaustion plays a pivotal role in both persistent infections and cancers of mice and humans. C57BL/6, BALB, SWR/J, A/J, 129, C3H, and all but one collaborative cross (CC) mouse strain following Cl 13 infection have immunosuppressed T cell responses, high PD-1, and viral titers leading to persistent infection and normal life spans. In contrast, the profile of FVB/N, NZB, PL/J, SL/J, and CC NZO mice challenged with Cl 13 is a robust T cell response, high titers of virus, PD-1, and Lag3 markers on T cells. These mice all die 7 to 9 d after Cl 13 infection. Death is due to enhanced pulmonary endothelial vascular permeability, pulmonary edema, collapse of alveolar air spaces, and respiratory failure. Pathogenesis involves abundant levels of Cl 13 receptor alpha-dystroglycan on endothelial cells, with high viral replication in such cells leading to immunopathologic injury. Death is aborted by blockade of interferon-1 (IFN-1) signaling or deletion of CD8 T cells.
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36
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Nice TJ, Robinson BA, Van Winkle JA. The Role of Interferon in Persistent Viral Infection: Insights from Murine Norovirus. Trends Microbiol 2018; 26:510-524. [PMID: 29157967 PMCID: PMC5957778 DOI: 10.1016/j.tim.2017.10.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/20/2017] [Accepted: 10/30/2017] [Indexed: 12/21/2022]
Abstract
Persistent viral infections result from evasion or avoidance of sterilizing immunity, extend the timeframe of virus transmission, and can trigger disease. Prior studies in mouse models of persistent infection have suggested that ineffective adaptive immune responses are necessary for persistent viral infection. However, recent work in the murine norovirus (MNV) model of persistent infection demonstrates that innate immunity can control both early and persistent viral replication independently of adaptive immune effector functions. Interferons (IFNs) are central to the innate control of persistent MNV, apart from a role in modulating adaptive immunity. Furthermore, subtypes of IFN play distinct tissue-specific roles in innate control of persistent MNV infection. Type I IFN (IFN-α/β) controls systemic replication, and type III IFN (IFN-λ) controls MNV persistence in the intestinal epithelium. In this article, we review recent findings in the MNV model, highlighting the role of IFNs and innate immunity in clearing persistent viral infection, and discussing the broader implications of these findings for control of persistent human infections.
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Affiliation(s)
- Timothy J Nice
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR, USA.
| | - Bridget A Robinson
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR, USA
| | - Jacob A Van Winkle
- Department of Molecular Microbiology and Immunology, Oregon Health and Science University, Portland, OR, USA
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37
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Hastie KM, Saphire EO. Lassa virus glycoprotein: stopping a moving target. Curr Opin Virol 2018; 31:52-58. [PMID: 29843991 PMCID: PMC6193841 DOI: 10.1016/j.coviro.2018.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 05/10/2018] [Accepted: 05/11/2018] [Indexed: 11/25/2022]
Abstract
The structure of a prefusion arenavirus GPC was enigmatic for many years, owing to the metastable and non-covalent nature of the association between the receptor binding and fusion subunits. Recent engineering efforts to stabilize the glycoprotein of the Old World arenavirus Lassa in a native, yet cleaved state, allowed the first structure of any arenavirus prefusion GPC trimer to be determined. Comparison of this structure with the structures of other arenavirus glycoprotein subunits reveals surprising findings: that the receptor binding subunit, GP1, of Lassa virus is conformationally labile, while the GP1 subunit of New World arenaviruses is not, and that the arenavirus GPC adopts a trimeric state unlike other glycoproteins with similar fusion machinery. Structural analysis, combined with recent biochemical data regarding antibody epitopes and receptor binding requirements, provides a basis for rational vaccine design.
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Affiliation(s)
- Kathryn M Hastie
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Erica Ollmann Saphire
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA; Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA, USA.
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38
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Fedeli C, Moreno H, Kunz S. Novel Insights into Cell Entry of Emerging Human Pathogenic Arenaviruses. J Mol Biol 2018; 430:1839-1852. [PMID: 29705070 DOI: 10.1016/j.jmb.2018.04.026] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/19/2018] [Accepted: 04/21/2018] [Indexed: 12/14/2022]
Abstract
Viral hemorrhagic fevers caused by emerging RNA viruses of the Arenavirus family are among the most devastating human diseases. Climate change, global trade, and increasing urbanization promote the emergence and re-emergence of these human pathogenic viruses. Emerging pathogenic arenaviruses are of zoonotic origin and reservoir-to-human transmission is crucial for spillover into human populations. Host cell attachment and entry are the first and most fundamental steps of every virus infection and represent major barriers for zoonotic transmission. During host cell invasion, viruses critically depend on cellular factors, including receptors, co-receptors, and regulatory proteins of endocytosis. An in-depth understanding of the complex interaction of a virus with cellular factors implicated in host cell entry is therefore crucial to predict the risk of zoonotic transmission, define the tissue tropism, and assess disease potential. Over the past years, investigation of the molecular and cellular mechanisms underlying host cell invasion of human pathogenic arenaviruses uncovered remarkable viral strategies and provided novel insights into viral adaptation and virus-host co-evolution that will be covered in the present review.
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Affiliation(s)
- Chiara Fedeli
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, Lausanne CH-1011, Switzerland
| | - Héctor Moreno
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, Lausanne CH-1011, Switzerland
| | - Stefan Kunz
- Institute of Microbiology, Lausanne University Hospital and University of Lausanne, Lausanne CH-1011, Switzerland.
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IRF9 Prevents CD8 + T Cell Exhaustion in an Extrinsic Manner during Acute Lymphocytic Choriomeningitis Virus Infection. J Virol 2017; 91:JVI.01219-17. [PMID: 28878077 DOI: 10.1128/jvi.01219-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 08/27/2017] [Indexed: 12/13/2022] Open
Abstract
Effective CD8+ T cell responses play an important role in determining the course of a viral infection. Overwhelming antigen exposure can result in suboptimal CD8+ T cell responses, leading to chronic infection. This altered CD8+ T cell differentiation state, termed exhaustion, is characterized by reduced effector function, upregulation of inhibitory receptors, and altered expression of transcription factors. Prevention of overwhelming antigen exposure to limit CD8+ T cell exhaustion is of significant interest for the control of chronic infection. The transcription factor interferon regulatory factor 9 (IRF9) is a component of type I interferon (IFN-I) signaling downstream of the IFN-I receptor (IFNAR). Using acute infection of mice with lymphocytic choriomeningitis virus (LCMV) strain Armstrong, we show here that IRF9 limited early LCMV replication by regulating expression of interferon-stimulated genes and IFN-I and by controlling levels of IRF7, a transcription factor essential for IFN-I production. Infection of IRF9- or IFNAR-deficient mice led to a loss of early restriction of viral replication and impaired antiviral responses in dendritic cells, resulting in CD8+ T cell exhaustion and chronic infection. Differences in the antiviral activities of IRF9- and IFNAR-deficient mice and dendritic cells provided further evidence of IRF9-independent IFN-I signaling. Thus, our findings illustrate a CD8+ T cell-extrinsic function for IRF9, as a signaling factor downstream of IFNAR, in preventing overwhelming antigen exposure resulting in CD8+ T cell exhaustion and, ultimately, chronic infection.IMPORTANCE During early viral infection, overwhelming antigen exposure can cause functional exhaustion of CD8+ T cells and lead to chronic infection. Here we show that the transcription factor interferon regulatory factor 9 (IRF9) plays a decisive role in preventing CD8+ T cell exhaustion. Using acute infection of mice with LCMV strain Armstrong, we found that IRF9 limited early LCMV replication by regulating expression of interferon-stimulated genes and Irf7, encoding a transcription factor crucial for type I interferon (IFN-I) production, as well as by controlling the levels of IFN-I. Infection of IRF9-deficient mice led to a chronic infection that was accompanied by CD8+ T cell exhaustion due to defects extrinsic to T cells. Our findings illustrate an essential role for IRF9, as a mediator downstream of IFNAR, in preventing overwhelming antigen exposure causing CD8+ T cell exhaustion and leading to chronic viral infection.
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40
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Acciani M, Alston JT, Zhao G, Reynolds H, Ali AM, Xu B, Brindley MA. Mutational Analysis of Lassa Virus Glycoprotein Highlights Regions Required for Alpha-Dystroglycan Utilization. J Virol 2017; 91:e00574-17. [PMID: 28679759 PMCID: PMC5571257 DOI: 10.1128/jvi.00574-17] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/22/2017] [Indexed: 12/27/2022] Open
Abstract
Lassa virus (LASV) is an enveloped RNA virus endemic to West Africa and responsible for severe cases of hemorrhagic fever. Virus entry is mediated by the glycoprotein complex consisting of a stable-signal peptide, a receptor-binding subunit, GP1, and a viral-host membrane fusion subunit, GP2. Several cellular receptors can interact with the GP1 subunit and mediate viral entry, including alpha-dystroglycan (αDG) and lysosome-associated membrane protein 1 (LAMP1). In order to define the regions within GP1 that interact with the cellular receptors, we implemented insertional mutagenesis, carbohydrate shielding, and alanine scanning mutagenesis. Eighty GP constructs were engineered and evaluated for GP1-GP2 processing, surface expression, and the ability to mediate cell-to-cell fusion after low-pH exposure. To examine virus-to-cell entry, 49 constructs were incorporated onto vesicular stomatitis virus (VSV) pseudoparticles and transduction efficiencies were monitored in HAP1 and HAP1-ΔDAG1 cells that differentially produce the αDG cell surface receptor. Seven constructs retained efficient transduction in HAP1-ΔDAG1 cells yet poorly transduced HAP1 cells, suggesting that they are involved in αDG utilization. Residues H141, N146, F147, and Y150 cluster at the predicted central core of the trimeric interface and are important for GP-αDG interaction. Additionally, H92A-H93A, 150HA, 172HA, and 230HA displayed reduced transduction in both HAP1 and HAP1-ΔDAG1 cells, despite efficient cell-to-cell fusion activity. These mutations may interfere with interactions with the endosomal receptor LAMP1 or interfere at another stage in entry that is common to both cell lines. Insight gained from these data can aid in the development of more-effective entry inhibitors by blocking receptor interactions.IMPORTANCE Countries in which Lassa virus is endemic, such as Nigeria, Sierra Leone, Guinea, and Liberia, usually experience a seasonal outbreak of the virus from December to March. Currently, there is neither a preventative vaccine nor a therapeutic available to effectively treat severe Lassa fever. One way to thwart virus infection is to inhibit interaction with cellular receptors. It is known that the GP1 subunit of the Lassa glycoprotein complex plays a critical role in receptor recognition. Our results highlight a region within the Lassa virus GP1 protein that interacts with the cellular receptor alpha-dystroglycan. This information may be used for future development of new Lassa virus antivirals.
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Affiliation(s)
- Marissa Acciani
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Jacob T Alston
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Guohui Zhao
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Hayley Reynolds
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Afroze M Ali
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Brian Xu
- Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
| | - Melinda A Brindley
- Department of Infectious Diseases, Department of Population Health, Center for Vaccines and Immunology, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA
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Pontremoli C, Forni D, Cagliani R, Pozzoli U, Riva S, Bravo IG, Clerici M, Sironi M. Evolutionary analysis of Old World arenaviruses reveals a major adaptive contribution of the viral polymerase. Mol Ecol 2017; 26:5173-5188. [PMID: 28779541 DOI: 10.1111/mec.14282] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2017] [Revised: 07/25/2017] [Accepted: 07/31/2017] [Indexed: 12/17/2022]
Abstract
The Old World (OW) arenavirus complex includes several species of rodent-borne viruses, some of which (i.e., Lassa virus, LASV and Lymphocytic choriomeningitis virus, LCMV) cause human diseases. Most LCMV and LASV infections are caused by rodent-to-human transmissions. Thus, viral evolution is largely determined by events that occur in the wildlife reservoirs. We used a set of human- and rodent-derived viral sequences to investigate the evolutionary history underlying OW arenavirus speciation, as well as the more recent selective events that accompanied LASV spread in West Africa. We show that the viral RNA polymerase (L protein) was a major positive selection target in OW arenaviruses and during LASV out-of-Nigeria migration. No evidence of selection was observed for the glycoprotein, whereas positive selection acted on the nucleoprotein (NP) during LCMV speciation. Positively selected sites in L and NP are surrounded by highly conserved residues, and the bulk of the viral genome evolves under purifying selection. Several positively selected sites are likely to modulate viral replication/transcription. In both L and NP, structural features (solvent exposed surface area) are important determinants of site-wise evolutionary rate variation. By incorporating several rodent-derived sequences, we also performed an analysis of OW arenavirus codon adaptation to the human host. Results do not support a previously hypothesized role of codon adaptation in disease severity for non-Nigerian strains. In conclusion, L and NP represent the major selection targets and possible determinants of disease presentation; these results suggest that field surveys and experimental studies should primarily focus on these proteins.
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Affiliation(s)
- Chiara Pontremoli
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
| | - Diego Forni
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
| | - Rachele Cagliani
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
| | - Uberto Pozzoli
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
| | - Stefania Riva
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
| | - Ignacio G Bravo
- Laboratory MIVEGEC, UMR CNRS 5290, IRD 224, UM, Centre National de la Recherche Scientifique, Montpellier, France
| | - Mario Clerici
- Department of Physiopathology and Transplantation, University of Milan, Milan, Italy.,Don C. Gnocchi Foundation ONLUS, IRCCS, Milan, Italy
| | - Manuela Sironi
- Bioinformatics, Scientific Institute IRCCS E. MEDEA, Bosisio Parini, Italy
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Iwasaki M, Sharma SM, Marro BS, de la Torre JC. Resistance of human plasmacytoid dendritic CAL-1 cells to infection with lymphocytic choriomeningitis virus (LCMV) is caused by restricted virus cell entry, which is overcome by contact of CAL-1 cells with LCMV-infected cells. Virology 2017; 511:106-113. [PMID: 28843812 DOI: 10.1016/j.virol.2017.08.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Revised: 08/07/2017] [Accepted: 08/14/2017] [Indexed: 01/06/2023]
Abstract
Plasmacytoid dendritic cells (pDCs), a main source of type I interferon in response to viral infection, are an early cell target during lymphocytic choriomeningitis virus (LCMV) infection, which has been associated with the LCMV's ability to establish chronic infections. Human blood-derived pDCs have been reported to be refractory to ex vivo LCMV infection. In the present study we show that human pDC CAL-1 cells are refractory to infection with cell-free LCMV, but highly susceptible to infection with recombinant LCMVs carrying the surface glycoprotein of VSV, indicating that LCMV infection of CAL-1 cells is restricted at the cell entry step. Co-culture of uninfected CAL-1 cells with LCMV-infected HEK293 cells enabled LCMV to infect CAL-1 cells. This cell-to-cell spread required direct cell-cell contact and did not involve exosome pathway. Our findings indicate the presence of a novel entry pathway utilized by LCMV to infect pDC.
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Affiliation(s)
- Masaharu Iwasaki
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Siddhartha M Sharma
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Brett S Marro
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA
| | - Juan C de la Torre
- Department of Immunology and Microbiology, The Scripps Research Institute, La Jolla, CA, USA.
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43
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IL-10: A Multifunctional Cytokine in Viral Infections. J Immunol Res 2017; 2017:6104054. [PMID: 28316998 PMCID: PMC5337865 DOI: 10.1155/2017/6104054] [Citation(s) in RCA: 204] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/13/2017] [Accepted: 02/01/2017] [Indexed: 12/15/2022] Open
Abstract
The anti-inflammatory master regulator IL-10 is critical to protect the host from tissue damage during acute phases of immune responses. This regulatory mechanism, central to T cell homeostasis, can be hijacked by viruses to evade immunity. IL-10 can be produced by virtually all immune cells, and it can also modulate the function of these cells. Understanding the effects of this multifunctional cytokine is therefore a complex task. In the present review we discuss the factors driving IL-10 production and the cellular sources of the cytokine during antiviral immune responses. We particularly focus on the IL-10 regulatory mechanisms that impact antiviral immune responses and how viruses can use this central regulatory pathway to evade immunity and establish chronic/latent infections.
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Mbanwi AN, Wang C, Geddes K, Philpott DJ, Watts TH. Irreversible splenic atrophy following chronic LCMV infection is associated with compromised immunity in mice. Eur J Immunol 2016; 47:94-106. [PMID: 27730627 DOI: 10.1002/eji.201646666] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 09/25/2016] [Accepted: 10/07/2016] [Indexed: 01/16/2023]
Abstract
Lymphocytic choriomeningitis virus clone 13 (LCMV13) infection of mice is a widely used model for investigating the mechanisms driving persistent viral infection in humans. LCMV13 disrupts splenic architecture early during infection, but this returns to normal within a few weeks. However, the long-term effects of LCMV13 infection on splenic structure have not been reported. Here, we report that persistent infection with LCMV13 results in sustained splenic atrophy that persists for at least 500 days following infection, whereas infection with the acutely infecting LCMV Armstrong is associated with a return to preinfection spleen weights. Splenic atrophy is associated with loss of T, B, and non-B non-T cells, with B cells most significantly affected. These effects were partly ameliorated by anti-NK1.1 or anti-CD8 antibody treatment. Antigen presentation was detectable at the time of contraction of the spleen, but no longer detected at late time points, suggesting that continued antigen presentation is not required to maintain splenic atrophy. Immunity to Salmonella infection and influenza vaccination were decreased after the virus was no longer detected. Thus splenic atrophy following LCMV13 infection is irreversible and may contribute to impaired immunity following clearance of LCMV13.
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Affiliation(s)
- Achire N Mbanwi
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Chao Wang
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Kaoru Geddes
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Dana J Philpott
- Department of Immunology, University of Toronto, Toronto, ON, Canada
| | - Tania H Watts
- Department of Immunology, University of Toronto, Toronto, ON, Canada
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Residues K465 and G467 within the Cytoplasmic Domain of GP2 Play a Critical Role in the Persistence of Lymphocytic Choriomeningitis Virus in Mice. J Virol 2016; 90:10102-10112. [PMID: 27581982 DOI: 10.1128/jvi.01303-16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 08/22/2016] [Indexed: 11/20/2022] Open
Abstract
Several arenaviruses, chiefly Lassa virus (LASV), cause hemorrhagic fever disease in humans and pose serious public health concerns in their regions of endemicity. Moreover, mounting evidence indicates that the worldwide-distributed prototypic arenavirus, lymphocytic choriomeningitis virus (LCMV), is a neglected human pathogen of clinical significance. We have documented that a recombinant LCMV containing the glycoprotein (GPC) gene of LASV within the backbone of the immunosuppressive clone 13 (Cl-13) variant of the Armstrong strain of LCMV (rCl-13/LASV-GPC) exhibited Cl-13-like growth properties in cultured cells, but in contrast to Cl-13, rCl-13/LASV-GPC was unable to establish persistence in immunocompetent adult mice, which prevented its use for some in vivo experiments. Recently, V459K and K461G mutations within the GP2 cytoplasmic domain (CD) of rCl-13/LASV-GPC were shown to increase rCl-13/LASV-GPC infectivity in mice. Here, we generated rCl-13(GPC/VGKS) by introducing the corresponding revertant mutations K465V and G467K within GP2 of rCl-13 and we show that rCl-13(GPC/VGKS) was unable to persist in mice. K465V and G467K mutations did not affect GPC processing, virus RNA replication, or gene expression. In addition, rCl-13(GPC/VGKS) grew to high titers in cultured cell lines and in immunodeficient mice. Further analysis revealed that rCl-13(GPC/VGKS) infected fewer splenic plasmacytoid dendritic cells than rCl-13, yet the two viruses induced similar type I interferon responses in mice. Our findings have identified novel viral determinants of Cl-13 persistence and also revealed that virus GPC-host interactions yet to be elucidated critically contribute to Cl-13 persistence. IMPORTANCE The prototypic arenavirus, lymphocytic choriomeningitis virus (LCMV), provides investigators with a superb experimental model system to investigate virus-host interactions. The Armstrong strain (ARM) of LCMV causes an acute infection, whereas its derivative, clone 13 (Cl-13), causes a persistent infection. Mutations F260L and K1079Q within GP1 and L polymerase, respectively, have been shown to play critical roles in Cl-13's ability to persist in mice. However, there is an overall lack of knowledge about other viral determinants required for Cl-13's persistence. Here, we report that mutations K465V and G467K within the cytoplasmic domain of Cl-13 GP2 resulted in a virus, rCl-13(GPC/VGKS), that failed to persist in mice despite exhibiting Cl-13 wild-type-like fitness in cultured cells and immunocompromised mice. This finding has uncovered novel viral determinants of viral persistence, and a detailed characterization of rCl-13(GPC/VGKS) can provide novel insights into the mechanisms underlying persistent viral infection.
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Demethylation of the PD-1 Promoter Is Imprinted during the Effector Phase of CD8 T Cell Exhaustion. J Virol 2016; 90:8934-46. [PMID: 27466420 DOI: 10.1128/jvi.00798-16] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/19/2016] [Indexed: 01/22/2023] Open
Abstract
UNLABELLED PD-1 is an inhibitory receptor that has a major role in T cell dysfunction during chronic infections and cancer. While demethylation of the PD-1 promoter DNA is observed in exhausted T cells isolated from chronically infected individuals, little is known about when this stable demethylation of PD-1 promoter DNA is programmed during the course of a chronic infection. To assess if PD-1 promoter DNA demethylation is impacted by prolonged stimulation during effector phase of chronic infection, we adoptively transferred virus-specific day 8 effector CD8 T cells from mice infected with lymphocytic choriomeningitis virus (LCMV) clone 13 into recipient mice that had cleared an acute infection. We observed that LCMV-specific CD8 T cells from chronically infected mice maintained their surface expression of PD-1 even after transfer into acute immune mice until day 45 posttransfer. Interestingly, the PD-1 transcriptional regulatory region continued to remain unmethylated in these donor CD8 T cells generated from a chronic infection. The observed maintenance of PD-1 surface expression and the demethylated PD-1 promoter were not a result of residual antigen in the recipient mice, because similar results were seen when chronic infection-induced effector cells were transferred into mice infected with a variant strain of LCMV (LCMV V35A) bearing a mutation in the cognate major histocompatibility complex class I (MHC-I) epitope that is recognized by the donor CD8 T cells. Importantly, the maintenance of PD-1 promoter demethylation in memory CD8 T cells was coupled with impaired clonal expansion and higher PD-1 re-expression upon secondary challenge. These data show that the imprinting of the epigenetic program of the inhibitory receptor PD-1 occurs during the effector phase of chronic viral infection. IMPORTANCE Since PD-1 is a major inhibitory receptor regulating T cell dysfunction during chronic viral infection and cancers, a better understanding of the mechanisms that regulate PD-1 expression is important. In this work, we demonstrate that the PD-1 epigenetic program in antigen-specific CD8 T cells is fixed during the priming phase of chronic infection.
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47
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Simulundu E, Mweene AS, Changula K, Monze M, Chizema E, Mwaba P, Takada A, Ippolito G, Kasolo F, Zumla A, Bates M. Lujo viral hemorrhagic fever: considering diagnostic capacity and preparedness in the wake of recent Ebola and Zika virus outbreaks. Rev Med Virol 2016; 26:446-454. [PMID: 27593704 PMCID: PMC7169100 DOI: 10.1002/rmv.1903] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 08/03/2016] [Accepted: 08/04/2016] [Indexed: 12/18/2022]
Abstract
Lujo virus is a novel Old World arenavirus identified in Southern Africa in 2008 as the cause of a viral hemorrhagic fever (VHF) characterized by nosocomial transmission with a high case fatality rate of 80% (4/5 cases). Whereas this outbreak was limited, the unprecedented Ebola virus disease outbreak in West Africa, and recent Zika virus disease epidemic in the Americas, has brought into acute focus the need for preparedness to respond to rare but potentially highly pathogenic outbreaks of zoonotic or arthropod‐borne viral infections. A key determinant for effective control of a VHF outbreak is the time between primary infection and diagnosis of the index case. Here, we review the Lujo VHF outbreak of 2008 and discuss how preparatory measures with respect to developing diagnostic capacity might be effectively embedded into existing national disease control networks, such as those for human immunodeficiency virus, tuberculosis, and malaria.
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Affiliation(s)
- Edgar Simulundu
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Aaron S Mweene
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Katendi Changula
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia
| | - Mwaka Monze
- University Teaching Hospital & National Virology Reference Laboratory, Lusaka, Zambia
| | | | | | - Ayato Takada
- Department of Disease Control, School of Veterinary Medicine, University of Zambia, Lusaka, Zambia.,Division of Global Epidemiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.,Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan
| | - Guiseppe Ippolito
- Lazzaro Spallanzani National Institute for Infectious Diseases, IRCCS, Rome, Italy
| | - Francis Kasolo
- World Health Organization, WHO Africa, Brazzaville, Republic of Congo
| | - Alimuddin Zumla
- Department of Infection, Division of Infection and Immunity, University College London, UK.,University of Zambia - University College London Research & Training Programme (www.unza-uclms.org), University Teaching Hospital, Lusaka, Zambia
| | - Matthew Bates
- Department of Infection, Division of Infection and Immunity, University College London, UK.,University of Zambia - University College London Research & Training Programme (www.unza-uclms.org), University Teaching Hospital, Lusaka, Zambia.,HerpeZ (www.herpez.org), University Teaching Hospital, Lusaka, Zambia
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48
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Imai J, Otani M, Sakai T, Hatta S. Purification of the subcellular compartment in which exogenous antigens undergo endoplasmic reticulum-associated degradation from dendritic cells. Heliyon 2016; 2:e00151. [PMID: 27656684 PMCID: PMC5021789 DOI: 10.1016/j.heliyon.2016.e00151] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 08/26/2016] [Indexed: 12/20/2022] Open
Abstract
Dendritic cells (DCs) are capable of processing and presenting exogenous antigens using MHC class I molecules. This pathway is called antigen cross-presentation and plays an important role in the stimulation of naïve CD8(+) T cells for infectious and tumor immunity. Our previous studies in DC2.4 cells and bone marrow-derived DCs revealed that exogenously added ovalbumin (OVA) is processed through endoplasmic reticulum (ER)-associated degradation (ERAD) for cross-presentation. In this study, we aimed to further confirm these results by purification of the subcellular compartment in which exogenous antigens undergo ERAD from homogenates of DC2.4 cells pretreated with biotinylated OVA (bOVA). bOVA-containing vesicles were purified using streptavidin (SA)-magnetic beads from cell homogenates and were found to contain ER chaperones and ERAD components together with proteins for antigen presentation. In purified microsomes, bOVA was retained in membranous fractions and degraded by the ubiquitin proteasome system in presence reticulocyte lysates and ATP. These results strongly suggested that DCs processed and degraded exogenous antigens through ERAD for cross-presentation in this purified subcellular compartment.
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Affiliation(s)
- Jun Imai
- Laboratory of Physiological Chemistry, Faculty of Pharmacy, Tkasaki University of Health and Welfare, 60 Nakaorui-machi, Takasaki-shi, Gunma 370-0033, Japan
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Utzschneider DT, Alfei F, Roelli P, Barras D, Chennupati V, Darbre S, Delorenzi M, Pinschewer DD, Zehn D. High antigen levels induce an exhausted phenotype in a chronic infection without impairing T cell expansion and survival. J Exp Med 2016; 213:1819-34. [PMID: 27455951 PMCID: PMC4995073 DOI: 10.1084/jem.20150598] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 06/13/2016] [Indexed: 02/01/2023] Open
Abstract
Using recombinant antigen variant-expressing chronic LCMV strains, Zehn and colleagues showed that amount rather than antigen strength is a key determinant of inducing a chronic infection phenotype in T cells. Chronic infections induce T cells showing impaired cytokine secretion and up-regulated expression of inhibitory receptors such as PD-1. What determines the acquisition of this chronic phenotype and how it impacts T cell function remain vaguely understood. Using newly generated recombinant antigen variant-expressing chronic lymphocytic choriomeningitis virus (LCMV) strains, we uncovered that T cell differentiation and acquisition of a chronic or exhausted phenotype depend critically on the frequency of T cell receptor (TCR) engagement and less significantly on the strength of TCR stimulation. In fact, we noted that low-level antigen exposure promotes the formation of T cells with an acute phenotype in chronic infections. Unexpectedly, we found that T cell populations with an acute or chronic phenotype are maintained equally well in chronic infections and undergo comparable primary and secondary expansion. Thus, our observations contrast with the view that T cells with a typical chronic infection phenotype are severely functionally impaired and rapidly transition into a terminal stage of differentiation. Instead, our data unravel that T cells primarily undergo a form of phenotypic and functional differentiation in the early phase of a chronic LCMV infection without inheriting a net survival or expansion deficit, and we demonstrate that the acquired chronic phenotype transitions into the memory T cell compartment.
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Affiliation(s)
- Daniel T Utzschneider
- Swiss Vaccine Research Institute, 1066 Epalinges, Switzerland Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, 1011 Lausanne, Switzerland
| | - Francesca Alfei
- Swiss Vaccine Research Institute, 1066 Epalinges, Switzerland Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, 1011 Lausanne, Switzerland
| | - Patrick Roelli
- Swiss Vaccine Research Institute, 1066 Epalinges, Switzerland Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, 1011 Lausanne, Switzerland Bioinformatics Core Facility, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - David Barras
- Bioinformatics Core Facility, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Vijaykumar Chennupati
- Swiss Vaccine Research Institute, 1066 Epalinges, Switzerland Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, 1011 Lausanne, Switzerland Ludwig Center for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland
| | - Stephanie Darbre
- Department of Pathology and Immunology, University of Geneva, 1211 Geneva, Switzerland World Health Organization Collaborating Center for Vaccine Immunology, University of Geneva, 1211 Geneva, Switzerland
| | - Mauro Delorenzi
- Ludwig Center for Cancer Research, University of Lausanne, 1015 Lausanne, Switzerland Faculty of Biology and Medicine, Department of Oncology, University of Lausanne, 1015 Lausanne, Switzerland Bioinformatics Core Facility, SIB Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
| | - Daniel D Pinschewer
- Division of Experimental Virology, Department of Biomedicine, University of Basel, 4003 Basel, Switzerland
| | - Dietmar Zehn
- Swiss Vaccine Research Institute, 1066 Epalinges, Switzerland Division of Immunology and Allergy, Department of Medicine, Lausanne University Hospital, 1011 Lausanne, Switzerland
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Crystal structure of the prefusion surface glycoprotein of the prototypic arenavirus LCMV. Nat Struct Mol Biol 2016; 23:513-521. [PMID: 27111888 PMCID: PMC4945123 DOI: 10.1038/nsmb.3210] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 03/24/2016] [Indexed: 11/08/2022]
Abstract
Arenaviruses exist worldwide and can cause hemorrhagic fever and neurologic disease. A single glycoprotein expressed on the viral surface mediates entry into target cells. This glycoprotein, termed GPC, contains a membrane-associated signal peptide, a receptor-binding subunit termed GP1 and a fusion-mediating subunit termed GP2. Although GPC is a critical target of antibodies and vaccines, the structure of the metastable GP1-GP2 prefusion complex has remained elusive for all arenaviruses. Here we describe the crystal structure of the fully glycosylated prefusion GP1-GP2 complex of the prototypic arenavirus LCMV at 3.5 Å. This structure reveals the conformational changes that the arenavirus glycoprotein must undergo to cause fusion and illustrates the fusion regions and potential oligomeric states.
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