Influenza in ferrets and guinea pigs: effect on cell-mediated immunity.

Two different animal models were studied to determine whether localized upper respiratory tract viral infection was associated with suppression of systemic cell-mediated immunity. During influenza infection in ferrets, there was no significant decrease in lymphocyte responsiveness to phytohemagglutinin (PHA). Guinea pigs given influenza showed no significant change in their response to PHA or to picryl human serum albumin (picHSA), to which they had been immunized previously. Delayed hypersensitivity skin test responses to picHSA in guinea pigs remained intact during infection. No change in the percentage of circulating T lymphocytes was detected during influenza infection. Transfer of immunity to nonsensitized recipient guinea pigs from picHSA-sensitized guinea pigs was accomplished during influenza infection. Lack of a suppressive effect on systemic cell-mediated immunity after influenza challenge in these two animal models of mild influenza confirmed previous findings in humans with mild influenza infection.