Effect of staphylococcal protein A on complement-potentiated neutralization of herpes simplex virus and immune lysis of virus-infected cells.

Interaction of staphylococcal protein A (SPA) with human serum depressed the ability of such serum to neutralize herpes simpled virus (HSV)-antibody labialis. SPA-induced depression of serum-dependent virus neutralization appeared to be due to consumption of complement by SPA. In addition, SPA attached to antibody-treated, HSV-infected cells and inhibited complement mediated immune cytolysis. The amount of inhibition obtained depended upon the with the infected cells. The possible significance of SPA in the pathogenesis of viral disease complicated by secondary staphylococcal infection is discussed.