CD8A and viral infectious disease: In addition, we did not notice any noticeable change in the expression of granzyme A, suggesting that the IL-17A signaling may be more effective in inducing perforin expression than granzyme A. Consistent with our findings on the roles of perforin, previous studies have demonstrated that CD8+ T cells require perforin to clear viral infections, including WNV from infected neurons [82,94,95].