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Zehner M, Alt M, Ashurov A, Goldsmith JA, Spies R, Weiler N, Lerma J, Gieselmann L, Stöhr D, Gruell H, Schultz EP, Kreer C, Schlachter L, Janicki H, Laib Sampaio K, Stegmann C, Nemetchek MD, Dähling S, Ullrich L, Dittmer U, Witzke O, Koch M, Ryckman BJ, Lotfi R, McLellan JS, Krawczyk A, Sinzger C, Klein F. Single-cell analysis of memory B cells from top neutralizers reveals multiple sites of vulnerability within HCMV Trimer and Pentamer. Immunity 2023; 56:2602-2620.e10. [PMID: 37967532 DOI: 10.1016/j.immuni.2023.10.009] [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: 03/23/2023] [Revised: 07/02/2023] [Accepted: 10/18/2023] [Indexed: 11/17/2023]
Abstract
Human cytomegalovirus (HCMV) can cause severe diseases in fetuses, newborns, and immunocompromised individuals. Currently, no vaccines are approved, and treatment options are limited. Here, we analyzed the human B cell response of four HCMV top neutralizers from a cohort of 9,000 individuals. By single-cell analyses of memory B cells targeting the pentameric and trimeric HCMV surface complexes, we identified vulnerable sites on the shared gH/gL subunits as well as complex-specific subunits UL128/130/131A and gO. Using high-resolution cryogenic electron microscopy, we revealed the structural basis of the neutralization mechanisms of antibodies targeting various binding sites. Moreover, we identified highly potent antibodies that neutralized a broad spectrum of HCMV strains, including primary clinical isolates, that outperform known antibodies used in clinical trials. Our study provides a deep understanding of the mechanisms of HCMV neutralization and identifies promising antibody candidates to prevent and treat HCMV infection.
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Affiliation(s)
- Matthias Zehner
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany.
| | - Mira Alt
- Department of Infectious Diseases, West German Centre of Infectious Diseases, University Hospital Essen, University Duisburg-Essen, 45147 Essen, Germany
| | - Artem Ashurov
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Jory A Goldsmith
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Rebecca Spies
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Nina Weiler
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Justin Lerma
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Lutz Gieselmann
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany; German Center for Infection Research, Partner Site Bonn-Cologne, 50931 Cologne, Germany
| | - Dagmar Stöhr
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Henning Gruell
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Eric P Schultz
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA; Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Christoph Kreer
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Linda Schlachter
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Hanna Janicki
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | | | - Cora Stegmann
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA; Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Michelle D Nemetchek
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA; Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Sabrina Dähling
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Leon Ullrich
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Ulf Dittmer
- Institute for Virology, University Hospital Essen, University of Duisburg-Essen, 45147 Essen, Germany
| | - Oliver Witzke
- Department of Infectious Diseases, West German Centre of Infectious Diseases, University Hospital Essen, University Duisburg-Essen, 45147 Essen, Germany
| | - Manuel Koch
- Institute for Dental Research and Oral Musculoskeletal Biology, Center for Biochemistry, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany
| | - Brent J Ryckman
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA; Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, MT 59812, USA
| | - Ramin Lotfi
- Institute for Transfusion Medicine, Ulm University Medical Center, 89081 Ulm, Germany
| | - Jason S McLellan
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX 78712, USA
| | - Adalbert Krawczyk
- Department of Infectious Diseases, West German Centre of Infectious Diseases, University Hospital Essen, University Duisburg-Essen, 45147 Essen, Germany; Institute for Virology, University Hospital Essen, University of Duisburg-Essen, 45147 Essen, Germany
| | - Christian Sinzger
- Institute for Virology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Florian Klein
- Laboratory of Experimental Immunology, Institute of Virology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 50931 Cologne, Germany; German Center for Infection Research, Partner Site Bonn-Cologne, 50931 Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), University Hospital of Cologne, 50931 Cologne, Germany.
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2
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Weiler N, Sampaio KL, Scherer M, Sinzger C. Generation of UL128-shRNA transduced fibroblasts for the release of cell-free virus from clinical human cytomegalovirus isolates. Biotechniques 2023; 75:183-194. [PMID: 37846844 DOI: 10.2144/btn-2023-0046] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2023] Open
Abstract
Working with recent isolates of human cytomegalovirus (HCMV) is complicated by their strictly cell-associated growth with lack of infectivity in the supernatant. Adaptation to cell-free growth is associated with disruption of the viral UL128 gene locus. The authors transduced fibroblasts with a lentiviral vector encoding UL128-specific-shRNA to allow the release of cell-free infectivity without genetic alteration. Transduced cells were cocultured with fibroblasts containing cell-associated isolates, and knockdown of the UL128 protein was validated by immunoblotting. Cell-free infectivity increased 1000-fold in isolate cocultures with UL128-shRNA compared with controls, and virions could be purified by density gradients. Transduced fibroblasts also allowed direct isolation of HCMV from a clinical specimen and cell-free transfer to other cell types. In conclusion, UL128-shRNA-transduced fibroblasts allow applications previously unsuitable for recent isolates.
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Affiliation(s)
- Nina Weiler
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
| | | | - Myriam Scherer
- Institute of Virology, Ulm University Medical Center, Ulm, Germany
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3
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Flomm FJ, Soh TK, Schneider C, Wedemann L, Britt HM, Thalassinos K, Pfitzner S, Reimer R, Grünewald K, Bosse JB. Intermittent bulk release of human cytomegalovirus. PLoS Pathog 2022; 18:e1010575. [PMID: 35925870 PMCID: PMC9352052 DOI: 10.1371/journal.ppat.1010575] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 05/06/2022] [Indexed: 01/24/2023] Open
Abstract
Human Cytomegalovirus (HCMV) can infect a variety of cell types by using virions of varying glycoprotein compositions. It is still unclear how this diversity is generated, but spatio-temporally separated envelopment and egress pathways might play a role. So far, one egress pathway has been described in which HCMV particles are individually enveloped into small vesicles and are subsequently exocytosed continuously. However, some studies have also found enveloped virus particles inside multivesicular structures but could not link them to productive egress or degradation pathways. We used a novel 3D-CLEM workflow allowing us to investigate these structures in HCMV morphogenesis and egress at high spatio-temporal resolution. We found that multiple envelopment events occurred at individual vesicles leading to multiviral bodies (MViBs), which subsequently traversed the cytoplasm to release virions as intermittent bulk pulses at the plasma membrane to form extracellular virus accumulations (EVAs). Our data support the existence of a novel bona fide HCMV egress pathway, which opens the gate to evaluate divergent egress pathways in generating virion diversity.
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Affiliation(s)
- Felix J. Flomm
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | - Timothy K. Soh
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | | | - Linda Wedemann
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
| | - Hannah M. Britt
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, United Kingdom
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, London, United Kingdom
| | | | | | - Kay Grünewald
- Centre for Structural Systems Biology, Hamburg, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
- University of Hamburg, Department of Chemistry, Hamburg, Germany
| | - Jens B. Bosse
- Centre for Structural Systems Biology, Hamburg, Germany
- Hannover Medical School, Institute of Virology, Hannover, Germany
- Cluster of Excellence RESIST (EXC 2155), Hannover Medical School, Hannover, Germany
- Leibniz-Institute of Virology (LIV), Hamburg, Germany
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Braun B, Laib Sampaio K, Kuderna AK, Widmann M, Sinzger C. Viral and Cellular Factors Contributing to the Hematogenous Dissemination of Human Cytomegalovirus via Polymorphonuclear Leukocytes. Viruses 2022; 14:v14071561. [PMID: 35891541 PMCID: PMC9323586 DOI: 10.3390/v14071561] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 07/12/2022] [Accepted: 07/16/2022] [Indexed: 02/06/2023] Open
Abstract
Polymorphonuclear leukocytes (PMNs) presumably transmit human cytomegalovirus (HCMV) between endothelial cells in blood vessels and thereby facilitate spread to peripheral organs. We aimed to identify viral components that contribute to PMN-mediated transmission and test the hypothesis that cellular adhesion molecules shield transmission sites from entry inhibitors. Stop codons were introduced into the genome of HCMV strain Merlin to delete pUL74 of the trimeric and pUL128 of the pentameric glycoprotein complex and the tegument proteins pp65 and pp71. Mutants were analyzed regarding virus uptake by PMNs and transfer of infection to endothelial cells. Cellular adhesion molecules were evaluated for their contribution to virus transmission using function-blocking antibodies, and hits were further analyzed regarding shielding against inhibitors of virus entry. The viral proteins pUL128, pp65, and pp71 were required for efficient PMN-mediated transmission, whereas pUL74 was dispensable. On the cellular side, the blocking of the αLβ2-integrin LFA-1 reduced virus transfer by 50% and allowed entry inhibitors to reduce it further by 30%. In conclusion, these data show that PMN-mediated transmission depends on the pentameric complex and an intact tegument and supports the idea of a virological synapse that promotes this dissemination mode both directly and via immune evasion.
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Deciphering the Potential Coding of Human Cytomegalovirus: New Predicted Transmembrane Proteome. Int J Mol Sci 2022; 23:ijms23052768. [PMID: 35269907 PMCID: PMC8911422 DOI: 10.3390/ijms23052768] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 02/18/2022] [Accepted: 02/26/2022] [Indexed: 02/06/2023] Open
Abstract
CMV is a major cause of morbidity and mortality in immunocompromised individuals that will benefit from the availability of a vaccine. Despite the efforts made during the last decade, no CMV vaccine is available. An ideal CMV vaccine should elicit a broad immune response against multiple viral antigens including proteins involved in virus-cell interaction and entry. However, the therapeutic use of neutralizing antibodies targeting glycoproteins involved in viral entry achieved only partial protection against infection. In this scenario, a better understanding of the CMV proteome potentially involved in viral entry may provide novel candidates to include in new potential vaccine design. In this study, we aimed to explore the CMV genome to identify proteins with putative transmembrane domains to identify new potential viral envelope proteins. We have performed in silico analysis using the genome sequences of nine different CMV strains to predict the transmembrane domains of the encoded proteins. We have identified 77 proteins with transmembrane domains, 39 of which were present in all the strains and were highly conserved. Among the core proteins, 17 of them such as UL10, UL139 or US33A have no ascribed function and may be good candidates for further mechanistic studies.
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Schleiss MR, Fernández-Alarcón C, Hernandez-Alvarado N, Wang JB, Geballe AP, McVoy MA. Inclusion of the Guinea Pig Cytomegalovirus Pentameric Complex in a Live Virus Vaccine Aids Efficacy against Congenital Infection but Is Not Essential for Improving Maternal and Neonatal Outcomes. Viruses 2021; 13:v13122370. [PMID: 34960639 PMCID: PMC8706200 DOI: 10.3390/v13122370] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Revised: 11/19/2021] [Accepted: 11/20/2021] [Indexed: 01/17/2023] Open
Abstract
The development of a vaccine against congenital human cytomegalovirus (HCMV) infection is a major priority. The pentameric complex (PC) of virion envelope proteins gH, gL, UL128, UL130, and UL131A is a key vaccine target. To determine the importance of immunity to the homologous PC encoded by guinea pig cytomegalovirus (GPCMV) in preventing congenital CMV, PC-intact and PC-deficient live-attenuated vaccines were generated and directly compared for immunogenicity and efficacy against vertical transmission in a vertical transmission model. A virulent PC-intact GPCMV (PC/intact) was modified by galK mutagenesis either to abrogate PC expression (PC/null; containing a frame-shift mutation in GP129, homolog of UL128) or to delete genes encoding three MHC Class I homologs and a protein kinase R (PKR) evasin while retaining the PC (3DX/Δ145). Attenuated vaccines were compared to sham immunization in a two-dose preconception subcutaneous inoculation regimen in GPCMV seronegative Hartley guinea pigs. Vaccines induced transient, low-grade viremia in 5/12 PC/intact-, 2/12 PC/null-, and 1/11 3DX/Δ145-vaccinated animals. Upon completion of the two-dose vaccine series, ELISA titers for the PC/intact group (geometic mean titer (GMT) 13,669) were not significantly different from PC/null (GMT 8127) but were significantly higher than for the 3DX/Δ145 group (GMT 6185; p < 0.01). Dams were challenged with salivary gland-adapted GPCMV in the second trimester. All vaccines conferred protection against maternal viremia. Newborn weights were significantly lower in sham-immunized controls (84.5 ± 2.4 g) compared to PC/intact (96 ± 2.3 g), PC/null (97.6 ± 1.9 g), or 3DX/Δ145 (93 ± 1.7) pups (p < 0.01). Pup mortality in sham-immunized controls was 29/40 (73%) and decreased to 1/44 (2.3%), 2/46 (4.3%), or 4/40 (10%) in PC/intact, PC/null, or 3DX/Δ145 groups, respectively (all p < 0.001 compared to control). Congenital GPCMV transmission occurred in 5/44 (11%), 16/46 (35%), or 29/38 (76%) of pups in PC/intact, PC/null, or 3DX/Δ145 groups, versus 36/40 (90%) in controls. For infected pups, viral loads were lower in pups born to vaccinated dams compared to controls. Sequence analysis demonstrated that infected pups in the vaccine groups had salivary gland-adapted GPCMV and not vaccine strain-specific sequences, indicating that congenital transmission was due to the challenge virus and not vaccine virus. We conclude that inclusion of the PC in a live, attenuated preconception vaccine improves immunogenicity and reduces vertical transmission, but PC-null vaccines are equal to PC-intact vaccines in reducing maternal viremia and protecting against GPCMV-related pup mortality.
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Affiliation(s)
- Mark R. Schleiss
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN 55455, USA; (C.F.-A.); (N.H.-A.)
- Correspondence: ; Tel.: +1-612-626-9913
| | - Claudia Fernández-Alarcón
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN 55455, USA; (C.F.-A.); (N.H.-A.)
| | - Nelmary Hernandez-Alvarado
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN 55455, USA; (C.F.-A.); (N.H.-A.)
| | - Jian Ben Wang
- Department of Pediatrics, Virginia Commonwealth University, Richmond, VA 23298, USA; (J.B.W.); (M.A.M.)
| | - Adam P. Geballe
- Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA;
| | - Michael A. McVoy
- Department of Pediatrics, Virginia Commonwealth University, Richmond, VA 23298, USA; (J.B.W.); (M.A.M.)
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Tang J, Frascaroli G, Zhou X, Knickmann J, Brune W. Cell Fusion and Syncytium Formation in Betaherpesvirus Infection. Viruses 2021; 13:v13101973. [PMID: 34696402 PMCID: PMC8537622 DOI: 10.3390/v13101973] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/22/2021] [Accepted: 09/28/2021] [Indexed: 12/14/2022] Open
Abstract
Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.
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Affiliation(s)
- Jiajia Tang
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Center for Single-Cell Omics, School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China
| | - Giada Frascaroli
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Xuan Zhou
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Jan Knickmann
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
| | - Wolfram Brune
- Leibniz Institute for Experimental Virology (HPI), 20251 Hamburg, Germany; (J.T.); (G.F.); (X.Z.); (J.K.)
- Correspondence:
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8
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Peptide Derivatives of Platelet-Derived Growth Factor Receptor Alpha Inhibit Cell-Associated Spread of Human Cytomegalovirus. Viruses 2021; 13:v13091780. [PMID: 34578361 PMCID: PMC8473290 DOI: 10.3390/v13091780] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 08/26/2021] [Accepted: 09/01/2021] [Indexed: 12/27/2022] Open
Abstract
Cell-free human cytomegalovirus (HCMV) can be inhibited by a soluble form of the cellular HCMV-receptor PDGFRα, resembling neutralization by antibodies. The cell-associated growth of recent HCMV isolates, however, is resistant against antibodies. We investigated whether PDGFRα-derivatives can inhibit this transmission mode. A protein containing the extracellular PDGFRα-domain and 40-mer peptides derived therefrom were tested regarding the inhibition of the cell-associated HCMV strain Merlin-pAL1502, hits were validated with recent isolates, and the most effective peptide was modified to increase its potency. The modified peptide was further analyzed regarding its mode of action on the virion level. While full-length PDGFRα failed to inhibit HCMV isolates, three peptides significantly reduced virus growth. A 30-mer version of the lead peptide (GD30) proved even more effective against the cell-free virus, and this effect was HCMV-specific and depended on the viral glycoprotein O. In cell-associated spread, GD30 reduced both the number of transferred particles and their penetration. This effect was reversible after peptide removal, which allowed the synchronized analysis of particle transfer, showing that two virions per hour were transferred to neighboring cells and one virion was sufficient for infection. In conclusion, PDGFRα-derived peptides are novel inhibitors of the cell-associated spread of HCMV and facilitate the investigation of this transmission mode.
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Brenner S, Braun B, Read C, Weil T, Walther P, Schrader T, Münch J, von Einem J. The Molecular Tweezer CLR01 Inhibits Antibody-Resistant Cell-to-Cell Spread of Human Cytomegalovirus. Viruses 2021; 13:v13091685. [PMID: 34578265 PMCID: PMC8472163 DOI: 10.3390/v13091685] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 08/20/2021] [Accepted: 08/23/2021] [Indexed: 02/06/2023] Open
Abstract
Human cytomegalovirus (HCMV) uses two major ways for virus dissemination: infection by cell-free virus and direct cell-to-cell spread. Neutralizing antibodies can efficiently inhibit infection by cell-free virus but mostly fail to prevent cell-to-cell transmission. Here, we show that the ‘molecular tweezer’ CLR01, a broad-spectrum antiviral agent, is not only highly active against infection with cell-free virus but most remarkably inhibits antibody-resistant direct cell-to-cell spread of HCMV. The inhibition of cell-to-cell spread by CLR01 was not limited to HCMV but was also shown for the alphaherpesviruses herpes simplex viruses 1 and 2 (HSV-1, -2). CLR01 is a rapid acting small molecule that inhibits HCMV entry at the attachment and penetration steps. Electron microscopy of extracellular virus particles indicated damage of the viral envelope by CLR01, which likely impairs the infectivity of virus particles. The rapid inactivation of viral particles by CLR01, the viral envelope as the main target, and the inhibition of virus entry at different stages are presumably the key to inhibition of cell-free virus infection and cell-to-cell spread by CLR01. Importance: While cell-free spread enables the human cytomegalovirus (HCMV) and other herpesviruses to transmit between hosts, direct cell-to-cell spread is thought to be more relevant for in vivo dissemination within infected tissues. Cell-to-cell spread is resistant to neutralizing antibodies, thus contributing to the maintenance of virus infection and virus dissemination in the presence of an intact immune system. Therefore, it would be therapeutically interesting to target this mode of spread in order to treat severe HCMV infections and to prevent dissemination of virus within the infected host. The molecular tweezer CLR01 exhibits broad-spectrum antiviral activity against a number of enveloped viruses and efficiently blocks antibody-resistant cell-to-cell spread of HCMV, thus representing a novel class of small molecules with promising antiviral activity.
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Affiliation(s)
- Sina Brenner
- Institute of Virology, Ulm University Medical Center, 89081 Ulm, Germany; (S.B.); (B.B.); (C.R.)
| | - Berenike Braun
- Institute of Virology, Ulm University Medical Center, 89081 Ulm, Germany; (S.B.); (B.B.); (C.R.)
| | - Clarissa Read
- Institute of Virology, Ulm University Medical Center, 89081 Ulm, Germany; (S.B.); (B.B.); (C.R.)
- Central Facility for Electron Microscopy, Ulm University, 89081 Ulm, Germany;
| | - Tatjana Weil
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany; (T.W.); (J.M.)
| | - Paul Walther
- Central Facility for Electron Microscopy, Ulm University, 89081 Ulm, Germany;
| | - Thomas Schrader
- Faculty of Chemistry, University of Duisburg-Essen, 45117 Essen, Germany;
| | - Jan Münch
- Institute of Molecular Virology, Ulm University Medical Center, 89081 Ulm, Germany; (T.W.); (J.M.)
- Core Facility Functional Peptidomics, Ulm University Medical Center, 89081 Ulm, Germany
| | - Jens von Einem
- Institute of Virology, Ulm University Medical Center, 89081 Ulm, Germany; (S.B.); (B.B.); (C.R.)
- Correspondence: ; Tel.: +49-(0)731-500-65104; Fax: +49-(0)731-500-65102
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10
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Schultz EP, Yu Q, Stegmann C, Day LZ, Lanchy JM, Ryckman BJ. Mutagenesis of Human Cytomegalovirus Glycoprotein L Disproportionately Disrupts gH/gL/gO over gH/gL/pUL128-131. J Virol 2021; 95:e0061221. [PMID: 34132577 PMCID: PMC8354327 DOI: 10.1128/jvi.00612-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Accepted: 06/04/2021] [Indexed: 01/14/2023] Open
Abstract
Cell-free and cell-to-cell spread of herpesviruses involves a core fusion apparatus comprised of the fusion protein glycoprotein B (gB) and the regulatory factor gH/gL. The human cytomegalovirus (HCMV) gH/gL/gO and gH/gL/pUL128-131 facilitate spread in different cell types. The gO and pUL128-131 components bind distinct receptors, but how the gH/gL portions of the complexes functionally compare is not understood. We previously characterized a panel of gL mutants by transient expression and showed that many were impaired for gH/gL-gB-dependent cell-cell fusion but were still able to form gH/gL/pUL128-131 and induce receptor interference. Here, the gL mutants were engineered into the HCMV BAC clones TB40/e-BAC4 (TB), TR, and Merlin (ME), which differ in their utilization of the two complexes for entry and spread. Several of the gL mutations disproportionately impacted gH/gL/gO-dependent entry and spread over gH/gL/pUL128-131 processes. The effects of some mutants could be explained by impaired gH/gL/gO assembly, but other mutants impacted gH/gL/gO function. Soluble gH/gL/gO containing the L201 mutant failed to block HCMV infection despite unimpaired binding to PDGFRα, indicating the existence of other important gH/gL/gO receptors. Another mutant (L139) enhanced the gH/gL/gO-dependent cell-free spread of TR, suggesting a "hyperactive" gH/gL/gO. Recently published crystallography and cryo-electron microscopy studies suggest structural conservation of the gH/gL underlying gH/gL/gO and gH/gL/pUL128-131. However, our data suggest important differences in the gH/gL of the two complexes and support a model in which gH/gL/gO can provide an activation signal for gB. IMPORTANCE The endemic betaherpesvirus HCMV circulates in human populations as a complex mixture of genetically distinct variants, establishes lifelong persistent infections, and causes significant disease in neonates and immunocompromised adults. This study capitalizes on our recent characterizations of three genetically distinct HCMV BAC clones to discern the functions of the envelope glycoprotein complexes gH/gL/gO and gH/gL/pUL128-13, which are promising vaccine targets that share the herpesvirus core fusion apparatus component, gH/gL. Mutations in the shared gL subunit disproportionally affected gH/gL/gO, demonstrating mechanistic differences between the two complexes, and may provide a basis for more refined evaluations of neutralizing antibodies.
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Affiliation(s)
- Eric P. Schultz
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana, USA
| | - Qin Yu
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Cora Stegmann
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Le Zhang Day
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
- Biochemistry and Biophysics Program, University of Montana, Missoula, Montana, USA
| | - Jean-Marc Lanchy
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
| | - Brent J. Ryckman
- Division of Biological Sciences, University of Montana, Missoula, Montana, USA
- Center for Biomolecular Structure and Dynamics, University of Montana, Missoula, Montana, USA
- Biochemistry and Biophysics Program, University of Montana, Missoula, Montana, USA
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Murine Cytomegalovirus MCK-2 Facilitates In Vivo Infection Transfer from Dendritic Cells to Salivary Gland Acinar Cells. J Virol 2021; 95:e0069321. [PMID: 34132572 DOI: 10.1128/jvi.00693-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The cytomegaloviruses (CMVs) spread systemically via myeloid cells and demonstrate broad tissue tropism. Human CMV (HCMV) UL128 encodes a component of the virion pentameric complex (PC) that is important for entry into epithelial cells and cell-cell spread in vitro. It possesses N-terminal amino acid sequences similar to those of CC chemokines. While the species specificity of HCMV precludes confirmation of UL128 function in vivo, UL128-like counterparts in experimental animals have demonstrated a role in salivary gland infection. How they achieve this has not been defined, although effects on monocyte tropism and immune evasion have been proposed. By tracking infected cells following lung infection, we show that although the UL128-like protein in mouse CMV (MCMV) (designated MCK-2) facilitated entry into lung macrophages, it was dispensable for subsequent viremia mediated by CD11c+ dendritic cells (DCs) and extravasation to the salivary glands. Notably, MCK-2 was important for the transfer of MCMV infection from DCs to salivary gland acinar epithelial cells. Acinar cell infection of MCMVs deleted of MCK-2 was not rescued by T-cell depletion, arguing against an immune evasion mechanism for MCK-2 in the salivary glands. In contrast to lung infection, peritoneal MCMV inoculation yields mixed monocyte/DC viremia. In this setting, MCK-2 again promoted DC-dependent infection of salivary gland acinar cells, but it was not required for monocyte-dependent spread to the lung. Thus, the action of MCK-2 in MCMV spread was specific to DC-acinar cell interactions. IMPORTANCE Cytomegaloviruses (CMVs) establish myeloid cell-associated viremias and persistent shedding from the salivary glands. In vitro studies with human CMV (HCMV) have implicated HCMV UL128 in epithelial tropism, but its role in vivo is unknown. Here, we analyzed how a murine CMV (MCMV) protein with similar physical properties, designated MCK-2, contributes to host colonization. We demonstrate that MCK-2 is dispensable for initial systemic spread from primary infection sites but within the salivary gland facilitates the transfer of infection from dendritic cells (DCs) to epithelial acinar cells. Virus transfer from extravasated monocytes to the lungs did not require MCK-2, indicating a tissue-specific effect. These results provide new information about how persistent viral tropism determinants operate in vivo.
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