title: Hypervariable region 1 variant acting as TCR antagonist affects hepatitis C virus-specific CD4+ T cell repertoire by favoring CD95-mediated apoptosis.
abstract: We have described previously that hypervariable region 1 (HVR1) variants of hepatitis C virus (HCV) frequently act as T cell receptor (TCR) antagonists for HVR1-specific helper T cells. These naturally occurring HVR1-antagonistic sequences interfered with the effects of HVR1-agonistic sequences such as TCR down-regulation and early activatory signals. By taking advantage of these findings, in this paper, we have analyzed the fate of these HVR1-specific antagonized CD4+ T cells. We present the evidence that TCR antagonism renders agonist-activated T cells susceptible to bystander CD95-mediated killing by suppressing the expression of cellular Fas-associated death domain-like interleukin-1beta-converting enzyme-like inhibitor proteins. To verify whether the TCR repertoire of a HVR1-specific T cell population could be modified consequently, we used a HVR1-agonistic sequence to induce in vitro CD4+ T cells and another HVR1 sequence with antagonistic property to mediate suppressive phenomena. HVR1-specific T cells were cultured with the agonist alone or with the agonist plus the antagonist. HVR1 specificity and T cell repertoires were followed over time by analyzing TCR beta-variable gene segment by "spectratyping". The results showed that the specificity for the agonist was rapidly spoiled after culture in the presence of the antagonist, and the TCR repertoire was strongly modified as a result of CD95-mediated apoptosis of agonist-specific clonal expansions. These data support the hypothesis that in HCV infection, the generation of TCR antagonists may reshape the T cell repertoire, representing an efficacious immune evasion strategy of a highly mutant pathogen.
authors.affiliation: Department of Cellular and Developmental Biology, La Sapienza University, Rome, 00185, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Scottà
authors.forename: Loretta
authors.initials: L
authors.lastname: Tuosto
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Masci
authors.forename: Luigi
authors.initials: L
authors.lastname: Racioppi
authors.forename: Enza
authors.initials: E
authors.lastname: Piccolella
authors.forename: Loredana
authors.initials: L
authors.lastname: Frasca
mesh_terms: D000956:Antigens, Viral / Q000276:immunology*; D017209:Apoptosis / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D015536:Down-Regulation / Q000276:immunology; D018984:Epitopes, T-Lymphocyte; D016174:Hepacivirus / Q000276:immunology* / Q000472:pathogenicity; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology; D015843:Serpins / Q000096:biosynthesis / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology*; D014764:Viral Proteins / Q000096:biosynthesis / Q000276:immunology*; D019014:fas Receptor / Q000276:immunology*
chemical_list: D000956:Antigens, Viral; D018984:Epitopes, T-Lymphocyte; C400562:HVR1 protein, Hepatitis C virus; D016693:Receptors, Antigen, T-Cell, alpha-beta; D015843:Serpins; D014764:Viral Proteins; D019014:fas Receptor; C074641:interleukin-1beta-converting enzyme inhibitor