A quantitative theory of influenza virus hemagglutination-inhibition.

Viruses of the mumps-Newcastle-influenza group occupy a prominent position in current research on viruses because of their enzymatic activity against certain mucoproteins, which occur in nature as surface constituents of cells (e.g., red blood cells) and as dissolved components of biological fluids (so-called inhibitors of hemagglutination). Some aspects of the history of this development have been discussed in recent reviews (Svedmyr, 1949a; Briody, 1950; Burnet, 1951). In previous studies (Lanni et al., 1951a,b; Lanni and Lanni, 1951) we have been concerned with complex changes in the shape of the hemagglutinationinhibition curve which occur when egg white inhibitor is treated with active influenza viruses. As further experiments progressed, it became evident that no satisfactory interpretation could reasonably be expected in the absence of an adequate analysis of the basic phenomenon of hemagglutination-inhibition by unmodified inhibitor. Since the key to this analysis was not discovered until after the period of experimentation had terminated, the desirability of certain experiments, e.g., the direct measurement of the rate of adsorption of virus onto red blood cells, failed to be anticipated. In this paper there is developed and tested a quantitative theory of hemagglutination-inhibition phenomena observed with egg white inhibitor and heated (enzymatically inactive) swine influenza virus. The parameters of the theory are derived from experiments which constituted controls in the studies of the interaction of inhibitor with active (unheated) virus.