Viral neuraminidase treatment of dendritic cells enhances antigen-specific CD8⁺ T cell proliferation, but does not account for the CD4⁺ T cell independence of the CD8⁺ T cell response during influenza virus infection

In vitro studies demonstrate that the increased alloreactive T cell response to dendritic cells (DC) that are treated with either live or inactivated influenza virus A/PR/8/34 is due to viral neuraminidase (NA) activity. Since virus-specific cytotoxic T lymphocytes (CTL) play an important role in immunity to heterologous influenza strains, we compared the activation of CD8⁺ T cells by untreated and NA-treated DC. Increased CTL activity was induced by NA-treated DC both in vitro and in vivo. Since the generation of CTL in response to influenza virus infection does not require prior "activation" of DC by CD4⁺ T cells (as is the case for many antigens), we asked whether NA activity contributed to this unconditional CD8⁺ T cell response. This was not the case. Future studies will determine the factors that are responsible for the CD4⁺ T-cell-independent influenza virus-specific CTL response.