Appearance of influenza A virus antigenic variants after treatment of infected MDCK cells with human leukocytes.

Exudation of polymorphonuclear leukocytes (PMN) from the infected mucosa is a characteristic feature of influenza virus infection. Since reactive oxygen species generated by PMN can be strong mutagens, the possibility of production of antigenic variants of the virus by virus-PMN interaction was investigated. Cloned influenza A NWS (H1N1) virus multiplying in Madin-Darby canine kidney cells was treated with human peripheral PMN. Assays in the presence and absence of monoclonal antibody to the cloned virus showed a seven- to ten-fold increase in the frequency of variants in the presence of PMN. The mutagenic effect was abolished by addition of superoxide dismutase to the culture.