Influenza A virus disruption of dendritic cell-natural killer cell crosstalk impacts activation of naïve helper and cytotoxic T cell subsets.

Dendritic cells (DCs) and natural killer (NK) cells engage in reciprocal interactions to trigger an efficient innate immune response while governing downstream adaptive immunity. Here, we used an ex vivo autologous human primary immune cell coculture system of DCs and NK cells to examine their impact on naïve CD4+ and CD8+ T cell (CD3+CD45RA+CD197+) activation in response to influenza A viral (IAV) infection. Using multiparameter flow cytometry, we observed that culturing T cells with both DCs and NK cells enhanced CD69 expression on CD4+ and CD8+ T cells, increased CD25 on CD4+ T cells, and promoted CD8+ T cell proliferation, compared with cultures with only NK cells or DCs. When DCs were exposed to the pandemic A/California/07/2009 (H1N1) strain or the A/Victoria/361/2011 (H3N2) strain, subsequent coculture with NK cells reduced the frequency of CD4+CD69+ and CD8+CD69+ naïve T cells. Notably, H3N2, but not H1N1, exposure also reduced CD4+CD25+ T cell frequencies. The IAV-mediated curtailment of T cell activation was dependent on viral replication because exposure to DCs with irradiated the H1N1 strain followed increased the frequency of CD4+CD69+, CD8+CD69+, CD4+CD25+, and CD8+CD25+ T cells, while irradiation of H3N2 increased the frequency of CD4+CD69+, CD8+CD69+ and proliferation of CD4+ and CD8+ T cells. These findings demonstrate that IAV can partially subvert DC-NK cell crosstalk to impair naïve T cell activation in a strain-dependent manner. This knowledge may guide the design of next-generation influenza vaccines to elicit robust cellular immune responses.