Studies of the Complement Fixation Reaction in Virus Systems

Abstract

Summary Sera collected from horses, swine, and cattle before inoculation with either the New Jersey or Indiana types of vesicular stomatitis virus and at periodic intervals thereafter, were tested by complement-fixation methods with antigens prepared from chick embryo tissues infected with these respective viruses. Convalescent sera from the three species differed in their behaviour in these tests. In horses as in guinea pigs, complement-fixing activity with homologous VS antigen appeared in about six to eight days after infection, reached a maximum titer in ten days to two weeks, remained relatively constant for seven to ten days then began to decline. No cross fixation between types was recorded. None of the cattle sera at any time exhibited any fixation in direct complement-fixation tests with homologous antigen. To demonstrate non-complement-fixing antibody in these convalescent bovine sera it was necessary to employ an indirect complement-fixation method using hyperimmune guinea pig or convalescent horse serum to detect residual antigen. The time of antibody development as indicated by the appearance of inhibitory activity in these indirect tests coincided with that demonstrated in horses by direct complement-fixing tests. The convalescent pig sera showed marked prozones effects (increased hemolysis) in lower serum dilutions. This increased hemolysis was traceable to certain substances present in normal as well as in convalescent swine serum and not to non-complement-fixing antibodies corresponding to those in convalescent bovine sera. Natural hemolysins for sheep red cells, third component of complement, and possibly other constituents, notably lipids, apparently contribute to this augmented hemolysis or reduced fixation of complement.