184-P: WEST NILE VIRUS PEPTIDE PRESENTATION BY HLA CLASS I

Aim Class I human leukocyte antigen molecules (A, B and C) reveal intracellular viruses by presenting viral peptide epitopes at the cell surface. At this point the number of viral ligands that decorate the HLA of an infected cell and biases in the targeting of these viral/HLA complexes by cytotoxic T lymphocytes is not understood. Our goal is to determine the number of viral ligands presented by the HLA of infected cells and to assess T cell decisions in responding to available targets. Methods A human epithelial cell line was transfected with three different soluble class I HLA-A and three HLA-B constructs. HLA-producing clones were expanded and grown in bioreactors and infected with West Nile virus (WNV) or were left uninfected. HLA/peptide complexes were purified from WNV-infected and uninfected cells. To identify WNV derived HLA ligands, peptides were isolated, comparatively mapped by mass spectroscopy and sequenced by MSMS. Results Of the 19 ligands identified in this study, 15 were eluted from HLA-A complexes and 4 were eluted from HLA-B. HLA-A ∗ 02:01 and A ∗ 11:01 each presented 6 viral peptides. Viral epitopes sampled by class I HLA were dispersed fairly evenly throughout different viral proteins (C, M, E, NS2b, NS3, NS4b and NS5). T cells from infected individuals tended to respond strongly to 1-2 particular viral ligands with minimal T cell activity to other viral epitopes. Conclusions These data indicate that HLA-A molecules tend to present the majority of WNV-derived ligands to CTL, suggesting that HLA-A and HLA-B may play different roles in the development of viral immunity. Class I HLA was unbiased, sampling peptides from various locations throughout the virus. While T cell activity was detected to most viral ligands, a clear hierarchy demonstrates that particular viral epitopes are key determinants of immune protection. These data will guide the development of vaccines, diagnostics, and therapeutics. Buchli: Pure Protein L.L.C.: Employee.