Recognition of influenza A virus nucleoprotein by human cytotoxic T lymphocytes

A recombinant vaccinia virus (NP-VAC) containing cDNA corresponding to segment 5, the nucleoprotein (NP) gene of influenza A/PR/8/34 virus was used to examine the specificity of human influenza virus immune cytotoxic T lymphocytes (CTL). Effector cell preparations from two donors recognized autologous lymphocytes that had been infected with NP-VAC. Lysis was specific because cells infected with vaccinia virus were not killed and recognition was HLA-restricted. In one donor, the influenza virus-specific CTL response changed with time so that his effector cells no longer recognized autologous lymphocytes infected with NP-VAC. However, a component that was NP-specific remained because these CTL lysed the more sensitive autologous B lymphoblastoid cells that had been infected with NP-VAC. In four other donors, no NP-specific CTL response could be detected using autologous lymphocyte targets. Thus NP, an internal virus protein, is one antigen that is recognized by human influenza A virus-specific CTL, but it is likely that other individual virus components contribute to the total CTL response.