Studies on the soluble antigen of influenza virus: I. The release of S antigen from elementary bodies by treatment with ether

Abstract

Soluble (S) antigen is readily released from influenza virus particles by exposure to ether. In order to obtain reproducible results with maximal yields of S and minimal damage to or loss of hemagglutinating and virus (V) antigen activities the technique described by Hoyle was modified and standardized. Elementary body suspensions which contained at least 5120 HA units per milliliter, and which failed to react per se with anti-S, were exposed to 1 2 volume of anesthetic ether at room temperature for periods up to 2 hours under constant agitation by a magnetic stirrer. Under these conditions, the hemagglutinating activity, as measured with guinea pig red cells, increased up to sixteenfold with all four influenza A strains tested; agglutination of chicken red cells was slightly enhanced with one of the strains and reduced twofold or more with the other three. The V antigen levels remained essentially unaltered. On the average, about 40 HA units of standard elementary bodies were required to yield one unit of S. Release of S became apparent within a few minutes of treatment. This was accompanied by nearly complete loss of infectivity and the sedimentation of the HA activity by high-speed centrifugation was markedly reduced. These results do not necessarily imply that the virus particles are disintegrated, as has been discussed.