Associate Professor Midwestern Univ., Glendale Glendale, Arizona, United States
Introduction/Rationale: Crosstalk between innate dendritic cells (DC) and natural killer (NK) cells plays a key role in activating virus-specific T cells, yet the mechanisms by which influenza A viruses (IAV) govern this process remain incompletely understood.
Methods: Using an ex vivo autologous human primary immune cell culture system, we evaluated how DC–NK cell interactions affect naïve T cell activation under steady state conditions and following exposure to genetically distinct IAV strains—A/California/07/2009 (H1N1) (Cal/09) and A/Victoria/361/2011 (H3N2) (Vic/11).
Results: Using flow cytometry we found that exposure of DCs to IAV in co-culture with NK cells reduced the frequency of CD4+CD69+ and CD8+CD69+ naïve T cells and CD4+ and CD8+ naïve T cell IFN-γ and TNF production. Notably, Vic/11, but not Cal/09, exposure also reduced CD4+CD25+ T cell frequencies and elicited lower IFN-γ production by CD4+ and CD8+ T cells compared with Cal/09. To investigate the viral protein responsible for usurping DC-NK cell crosstalk and T cell activation, we have built DNA constructs encoding each of the 10 viral proteins from each virus to use as templates for in vitro transcription and subsequent delivery into DCs and have detected both hemagglutinin and nucleoprotein by Western blot in pilot experiments.
Conclusion: This question has direct implications for influenza messenger RNA–based vaccine design, as genetically separating the viral protein that elicits a protective immune response, including harboring conserved T cell epitopes, may be useful in the selection of the vaccine antigen candidate most effective at eliciting a robust T cell response.
