Effect of Influenza Virus Infection on Phagocytic and Cytopeptic Capacities of Guinea Pig Macrophages

Guinea pigs were exposed to influenza Al virus by aerosol. Peritoneal and alveolar macrophages were harvested three days after virus exposure and allowed to attach overnight to Leighton tubes. These macrophages were then challenged with a suspension of Klebsiella pneumoniae for two hours. The macrophages were washed free of extracellular bacteria and antibiotics were added to prevent extracellular multiplication. Plate counts were made at various time intervals on disrupted macrophages to determine the number of viable intracellular bacteria remaining. Alveolar macrophages that had been exposed to virus in vivo ingested the bacteria at a rate significantly greater (p <.05) than that of non-virus exposed control macrophages. However, virus exposed macrophages exhibited significantly reduced intracellular killing (cytopepsis) (p <.01) as compared to controls. In vitro virus exposed macrophages exhibited no significant difference in the rate of phagocytosis or cytopepsis. The data support the hypothesis that virus infection reduces host resistance to bacterial infection by interfering in vivo with cytopepsis of the ingested bacteria.