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Lucas CJ, Davenport BJ, Carpentier KS, Tinega AN, Morrison TE. Two Conserved Phenylalanine Residues in the E1 Fusion Loop of Alphaviruses Are Essential for Viral Infectivity. J Virol 2022; 96:e0006422. [PMID: 35416719 PMCID: PMC9093095 DOI: 10.1128/jvi.00064-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 03/13/2022] [Indexed: 11/20/2022] Open
Abstract
Alphaviruses infect cells by a low pH-dependent fusion reaction between viral and host cell membranes that is mediated by the viral E1 glycoprotein. Most reported alphavirus E1 sequences include two phenylalanines (F87 and F95) in the fusion loop, yet the role of these residues in viral infectivity remains to be defined. Following introduction of wild type (WT), E1-F87A, and E1-F95A chikungunya virus (CHIKV) RNA genomes into cells, viral particle production was similar in magnitude. However, CHIKV E1-F87A and E1-F95A virions displayed impaired infectivity compared with WT CHIKV particles. Although WT, E1-F87A, and E1-F95A particles bound cells with similar efficiencies, E1-F87A and E1-F95A particles were unable to undergo fusion and entry into cells. Introduction of an F95A mutation in the E1 fusion loop of Mayaro virus or Venezuelan equine encephalitis virus also resulted in poorly infectious virions. We further tested whether an E1-F87A or E1-F95A mutation could be incorporated into a live-attenuated vaccine strain, CHIKV 181/25, to enhance vaccine safety. Infection of immunocompromised Ifnar1-/- and Irf3-/-Irf5-/-Irf7-/- mice with 181/25E1-F87A or 181/25E1-F95A resulted in 0% mortality, compared with 100% mortality following 181/25 infection. Despite this enhanced attenuation, surviving Ifnar1-/- and Irf3-/-Irf5-/-Irf7-/- mice were protected against virulent virus re-challenge. Moreover, single-dose immunization of WT mice with either 181/25, 181/25E1-F87A, or 181/25E1-F95A elicited CHIKV-specific antibody responses and protected against pathogenic CHIKV challenge. These studies define a critical function for residues E1-F87 and E1-F95 in alphavirus fusion and entry into target cells and suggest that incorporation of these mutations could enhance the safety of live-attenuated alphavirus vaccine candidates. IMPORTANCE Alphaviruses are human pathogens that cause both debilitating acute and chronic musculoskeletal disease and potentially fatal encephalitis. In this study, we determined that two highly conserved phenylalanine residues in the alphavirus E1 glycoprotein are required for fusion of viral and host cell membranes and viral entry into target cells. We further demonstrated that mutation of these phenylalanines results in a substantial loss of viral virulence but not immunogenicity. These data enhance an understanding of the viral determinants of alphavirus entry into host cells and could contribute to the development of new antivirals targeting these conserved phenylalanines or new live-attenuated alphavirus vaccines.
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Affiliation(s)
- Cormac J. Lucas
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
- RNA Bioscience Initiative, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Bennett J. Davenport
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Kathryn S. Carpentier
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Alex N. Tinega
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
| | - Thomas E. Morrison
- Department of Immunology and Microbiology, University of Colorado School of Medicine, Aurora, Colorado, USA
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2
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Greaves SA, Ravindran A, Santos RG, Chen L, Falta MT, Wang Y, Mitchell AM, Atif SM, Mack DG, Tinega AN, Maier LA, Dai S, Pinilla C, Grunewald J, Fontenot AP. CD4+ T cells in the lungs of acute sarcoidosis patients recognize an Aspergillus nidulans epitope. J Exp Med 2021; 218:212583. [PMID: 34410304 PMCID: PMC8383815 DOI: 10.1084/jem.20210785] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 06/18/2021] [Accepted: 07/22/2021] [Indexed: 11/05/2022] Open
Abstract
Löfgren’s syndrome (LS) is an acute form of sarcoidosis characterized by a genetic association with HLA-DRB1*03 (HLA-DR3) and an accumulation of CD4+ T cells of unknown specificity in the bronchoalveolar lavage (BAL). Here, we screened related LS-specific TCRs for antigen specificity and identified a peptide derived from NAD-dependent histone deacetylase hst4 (NDPD) of Aspergillus nidulans that stimulated these CD4+ T cells in an HLA-DR3–restricted manner. Using ELISPOT analysis, a greater number of IFN-γ– and IL-2–secreting T cells in the BAL of DR3+ LS subjects compared with DR3+ control subjects was observed in response to the NDPD peptide. Finally, increased IgG antibody responses to A. nidulans NDPD were detected in the serum of DR3+ LS subjects. Thus, our findings identify a ligand for CD4+ T cells derived from the lungs of LS patients and suggest a role of A. nidulans in the etiology of LS.
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Affiliation(s)
- Sarah A Greaves
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Avinash Ravindran
- Department of Medicine, Solna, Karolinska University Hospital, Stockholm, Sweden.,Centre for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Radleigh G Santos
- Department of Mathematics, Nova Southeastern University, Ft. Lauderdale, FL
| | - Lan Chen
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Michael T Falta
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Yang Wang
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Angela M Mitchell
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Shaikh M Atif
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Douglas G Mack
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Alex N Tinega
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Lisa A Maier
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO.,Department of Medicine, National Jewish Health, Denver, CO
| | - Shaodong Dai
- Department of Pharmaceutical Sciences, University of Colorado Anschutz Medical Campus, Aurora, CO
| | - Clemencia Pinilla
- Center for Translational Science, Florida International University, Port St. Lucie, FL
| | - Johan Grunewald
- Department of Medicine, Solna, Karolinska University Hospital, Stockholm, Sweden
| | - Andrew P Fontenot
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, CO
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Falta MT, Crawford JC, Tinega AN, Landry LG, Crawford F, Mack DG, Martin AK, Atif SM, Li L, Santos RG, Nakayama M, Kappler JW, Maier LA, Thomas PG, Pinilla C, Fontenot AP. Beryllium-specific CD4+ T cells induced by chemokine neoantigens perpetuate inflammation. J Clin Invest 2021; 131:144864. [PMID: 33630763 DOI: 10.1172/jci144864] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 02/23/2021] [Indexed: 12/12/2022] Open
Abstract
Discovering dominant epitopes for T cells, particularly CD4+ T cells, in human immune-mediated diseases remains a significant challenge. Here, we used bronchoalveolar lavage (BAL) cells from HLA-DP2-expressing patients with chronic beryllium disease (CBD), a debilitating granulomatous lung disorder characterized by accumulations of beryllium-specific (Be-specific) CD4+ T cells in the lung. We discovered lung-resident CD4+ T cells that expressed a disease-specific public CDR3β T cell receptor motif and were specific to Be-modified self-peptides derived from C-C motif ligand 4 (CCL4) and CCL3. HLA-DP2-CCL/Be tetramer staining confirmed that these chemokine-derived peptides represented major antigenic targets in CBD. Furthermore, Be induced CCL3 and CCL4 secretion in the lungs of mice and humans. In a murine model of CBD, the addition of LPS to Be oxide exposure enhanced CCL4 and CCL3 secretion in the lung and significantly increased the number and percentage of CD4+ T cells specific for the HLA-DP2-CCL/Be epitope. Thus, we demonstrate a direct link between Be-induced innate production of chemokines and the development of a robust adaptive immune response to those same chemokines presented as Be-modified self-peptides, creating a cycle of innate and adaptive immune activation.
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Affiliation(s)
- Michael T Falta
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Jeremy C Crawford
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Alex N Tinega
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Laurie G Landry
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | | | - Douglas G Mack
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Allison K Martin
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Shaikh M Atif
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Li Li
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.,Department of Medicine, National Jewish Health, Denver, Colorado, USA
| | - Radleigh G Santos
- Department of Mathematics, Nova Southeastern University, Ft. Lauderdale, Florida, USA
| | - Maki Nakayama
- Barbara Davis Center for Childhood Diabetes, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - John W Kappler
- Department of Biomedical Research and.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Lisa A Maier
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.,Department of Medicine, National Jewish Health, Denver, Colorado, USA
| | - Paul G Thomas
- Department of Immunology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | | | - Andrew P Fontenot
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.,Department of Immunology and Microbiology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
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Mitchell AM, Falta MT, Tinega AN, Grunewald J, Pinilla C, Fontenot AP. Identifying T cell antigens in sarcoidosis. The Journal of Immunology 2016. [DOI: 10.4049/jimmunol.196.supp.54.20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Abstract
Sarcoidosis is a multisystem disorder which most commonly affects the lungs and involves the accumulation of CD4+ T cells at the sites of disease. The etiology of the disease is unknown, and the lack of a known antigen has hindered the study of disease pathogenesis. However, there is considerable evidence that CD4+ T cells are involved in the initiation and perpetuation of sarcoidosis. Previous work by our lab and others has demonstrated that particular T cell clones within the bronchoalveolar lavage (BAL) have been preferentially expanded in patients with sarcoidosis. These oligoclonal T cell populations accumulate within the lung and disappear with disease resolution. Furthermore, correlations have been observed between the expansions of CD4+T cells expressing the T cell receptor (TCR) α-chain variable (V) region Vα2.3 and the presence of the HLA-DRB1*0301 (DR3) allele in certain patient populations. Preliminary data suggest that cells within the BAL expressing TCRs utilizing Vα2.3, Vβ5.1, and Vβ5.3 are preferentially expanded before and after ex-vivo stimulation with IL-2. We hypothesize that sarcoidosis-specific CD4+ T cells accumulate and expand in the lungs of sarcoidosis patients in response to a specific antigen. To determine whether these expanded CD4+T cell clones play a pathogenic role in disease progression, as well as to address their antigen specificity, the TCRs of these clones have been characterized, and a combinatorial peptide library has been screened to identify candidate antigens that stimulate these clones. These unbiased data will provide clues to the disease-initiating antigens that drive sarcoidosis in a subset of patients and will lead to an extension of our findings to a larger disease cohort.
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Falta MT, Tinega AN, Mack DG, Bowerman NA, Crawford F, Kappler JW, Pinilla C, Fontenot AP. Metal-specific CD4+ T-cell responses induced by beryllium exposure in HLA-DP2 transgenic mice. Mucosal Immunol 2016; 9:218-28. [PMID: 26129650 PMCID: PMC4698108 DOI: 10.1038/mi.2015.54] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 05/16/2015] [Indexed: 02/04/2023]
Abstract
Chronic beryllium disease (CBD) is a granulomatous lung disorder that is associated with the accumulation of beryllium (Be)-specific CD4(+) T cells into the lung. Genetic susceptibility is linked to HLA-DPB1 alleles that possess a glutamic acid at position 69 (βGlu69), and HLA-DPB1*02:01 is the most prevalent βGlu69-containing allele. Using HLA-DP2 transgenic (Tg) mice, we developed a model of CBD that replicates the major features of the human disease. Here we characterized the T-cell receptor (TCR) repertoire of Be-responsive CD4(+) T cells derived from the lungs of Be oxide-exposed HLA-DP2 Tg mice. The majority of Be-specific T-cell hybridomas expressed TCR Vβ6, and a subset of these hybridomas expressed identical or nearly identical β-chains that were paired with different α-chains. We delineated mimotopes that bind to HLA-DP2 and form a complex recognized by Be-specific CD4(+) T cells in the absence of Be. These Be-independent peptides possess an arginine at p5 and a tryptophan at p7 that surround the Be-binding site within the HLA-DP2 acidic pocket and likely induce charge and conformational changes that mimic those induced by the Be(2+) cation. Collectively, these data highlight the interplay between peptides and Be in the generation of an adaptive immune response in metal-induced hypersensitivity.
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Affiliation(s)
- Michael T. Falta
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
| | - Alex N. Tinega
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
| | - Douglas G. Mack
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
| | - Natalie A. Bowerman
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
| | - Frances Crawford
- Department of Immunology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
,Howard Hughes Medical Institute, National Jewish Health, Denver, CO 80206 USA
| | - John W. Kappler
- Department of Immunology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
,Howard Hughes Medical Institute, National Jewish Health, Denver, CO 80206 USA
| | - Clemencia Pinilla
- Torrey Pines Institute for Molecular Studies, San Diego, CA 92121 USA
| | - Andrew P. Fontenot
- Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
,Department of Immunology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045 USA
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6
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Wehrmann F, Lavelle JC, Collins CB, Tinega AN, Thurman JM, Burnham EL, Simonian PL. γδ T cells protect against LPS-induced lung injury. J Leukoc Biol 2015; 99:373-86. [PMID: 26428678 DOI: 10.1189/jlb.4a0115-017rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 09/01/2015] [Indexed: 12/23/2022] Open
Abstract
γδ T lymphocytes are a unique T cell population with important anti-inflammatory capabilities. Their role in acute lung injury, however, is poorly understood but may provide significant insight into lung-protective mechanisms occurring after injury. In a murine model of lung injury, wild-type C57BL/6 and TCRδ(-/-) mice were exposed to Escherichia coli LPS, followed by analysis of γδ T cell and macrophage subsets. In the absence of γδ T cells, TCRδ(-/-) mice developed increased inflammation and alveolar-capillary leak compared with wild-type C57BL/6 mice after LPS exposure that correlated with expansion of distinct macrophage populations. Classically activated M1 macrophages were increased in the lung of TCRδ(-/-) mice at d 1, 4, and 7 after LPS exposure that peaked at d 4 and persisted at d 7 compared with wild-type animals. In response to LPS, Vγ1 and Vγ7 γδ T cells were expanded in the lung and expressed IL-4. Coculture experiments showed decreased expression of TNF-α by resident alveolar macrophages in the presence of γδ T cells that was reversed in the presence of an anti-IL-4-blocking antibody. Treatment of mice with rIL4 resulted in reduced numbers of M1 macrophages, inflammation, and alveolar-capillary leak. Therefore, one mechanism by which Vγ1 and Vγ7 γδ T cells protect against LPS-induced lung injury is through IL-4 expression, which decreases TNF-α production by resident alveolar macrophages, thus reducing accumulation of M1 macrophages, inflammation, and alveolar-capillary leak.
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Affiliation(s)
- Fabian Wehrmann
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - James C Lavelle
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Colm B Collins
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Alex N Tinega
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Joshua M Thurman
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Ellen L Burnham
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
| | - Philip L Simonian
- Departments of *Medicine and Pediatrics, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, Colorado, USA
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Falta MT, Pinilla C, Mack DG, Tinega AN, Crawford F, Giulianotti M, Santos R, Clayton GM, Wang Y, Zhang X, Maier LA, Marrack P, Kappler JW, Fontenot AP. Identification of beryllium-dependent peptides recognized by CD4+ T cells in chronic beryllium disease. ACTA ACUST UNITED AC 2013; 210:1403-18. [PMID: 23797096 PMCID: PMC3698527 DOI: 10.1084/jem.20122426] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Identification of peptides that form complexes with beryllium and class II HLA molecules and are recognized by CD4+ T cells from patients with chronic beryllium disease. Chronic beryllium disease (CBD) is a granulomatous disorder characterized by an influx of beryllium (Be)-specific CD4+ T cells into the lung. The vast majority of these T cells recognize Be in an HLA-DP–restricted manner, and peptide is required for T cell recognition. However, the peptides that stimulate Be-specific T cells are unknown. Using positional scanning libraries and fibroblasts expressing HLA-DP2, the most prevalent HLA-DP molecule linked to disease, we identified mimotopes and endogenous self-peptides that bind to MHCII and Be, forming a complex recognized by pathogenic CD4+ T cells in CBD. These peptides possess aspartic and glutamic acid residues at p4 and p7, respectively, that surround the putative Be-binding site and cooperate with HLA-DP2 in Be coordination. Endogenous plexin A peptides and proteins, which share the core motif and are expressed in lung, also stimulate these TCRs. Be-loaded HLA-DP2–mimotope and HLA-DP2–plexin A4 tetramers detected high frequencies of CD4+ T cells specific for these ligands in all HLA-DP2+ CBD patients tested. Thus, our findings identify the first ligand for a CD4+ T cell involved in metal-induced hypersensitivity and suggest a unique role of these peptides in metal ion coordination and the generation of a common antigen specificity in CBD.
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Affiliation(s)
- Michael T Falta
- Department of Medicine, University of Colorado, Denver, Aurora, CO 80045, USA
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Tinega AN, Pellé R, Kang'a S, Gicheru MM, Taracha ELN, Nene V, Graham SP. Fusion of a cell penetrating peptide from HIV-1 TAT to the Theileria parva antigen Tp2 enhances the stimulation of bovine CD8+ T cell responses. Vet Immunol Immunopathol 2009; 130:107-13. [PMID: 19249107 DOI: 10.1016/j.vetimm.2009.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 01/14/2009] [Accepted: 01/20/2009] [Indexed: 10/21/2022]
Abstract
Immunity to the bovine apicomplexan parasite Theileria parva is associated with MHC-I restricted CD8+ T cell responses directed against the intralymphocytic schizont stage of the parasite. A number of schizont-stage antigens that are targets of CD8+ T cell responses from immune animals have been identified but an effective delivery strategy that consistently induces protective CD8+ T cell responses remains to be developed. This study aimed to determine whether fusing Tat, a cell penetrating peptide (CPP) from HIV-1 TAT, to a CD8+ T cell target antigen from T. parva (Tp2) enhances the cytosolic delivery and subsequent stimulation of bovine CD8+ T cell responses in vitro. Using IFN-gamma ELISpot and cytotoxicity assays, it was demonstrated that recombinant Tat-Tp2 fusion protein possessed a superior ability to access MHC-I processing and presentation pathway and to stimulate CD8+ T cell responses compared to recombinant Tp2 protein. Exposure of APC to Tat-Tp2 protein for only 30 min was sufficient for protein uptake and stimulation of CD8+ T cells. This work describes for the first time the utility of a CPP to enhance MHC-I presentation in a veterinary species and supports the evaluation of CPP fusion proteins in the induction of CD8+ T cell responses in vivo.
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Affiliation(s)
- Alex N Tinega
- International Livestock Research Institute, P.O. Box 30709, Nairobi 00100, Kenya
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