Identification of an H5‐specific CTL epitope restricted by HLA‐A*0201 from H5N1 influenza virus

Abstract

Avian influenza (AI) virus H5N1 has been continually spreading worldwide and resulted in a severe human disease with a high mortality rate. The viral hemagglutinin (HA) is closely associated with its high pathogenicity, and is the main antigen that initiates the hormonal immune response against infection. In order to understand cellular immune responses against the HA protein of H5N1 subtype virus and the HA's role in the pathogenesis, a panel of potential HLA-A*0201-restricted H5 protein-derived peptides were selected from an online database and screened for potential CTL epitopes by in vitro refolding and T2 cell-stabilization assays. The eight peptides that could refold with HLA-A*0201 heavy chain and beta2 microglobulin molecules were assessed with an IFN-γ ELISPOT assay and tetramer staining to determine their capacity to stimulate CTLs in HLA-A2.1/Kb transgenic mice. A HLA-A*0201-restricted decameric epitope, P6 was found to be able to induce strong CTL responses, which were more potent than influenza virus dominating CTL epitope GL-9 (GILGFVFTL). P6 was also found to induce CTL response in patients recovered from H5N1 virus infection, P6-specific CTLs were observed at a percentage of 1.5% in CD8+ T cells by tetramer staining after 2 weeks’ stimulation with P6 in vitro. Thus, P6 may be a novel H5-specific CTL epitope and a potential target for characterization of virus control mechanisms and evaluation of candidate H5N1 vaccines.