Determination of equine serum inhibitors for poliovirus by the gel-adsorption technique

Inhibitors found in certain equine sera active against poliovirus type 1 have been determined by the gel-adsorption method using aluminiumhydroxide-gel in the absence of cells. The inhibitor belongs to the 19S-class of macroglobulins (IgM), as revealed by gel-filtration with Sephadex G 200, by DEAE-cellulose-chromatography, and by sucrose density centrifugation. It is bound to the viral surface in-vitro in the absence of tissue cells. The specific complex may be precipitated with anti-equine globulin from rabbits. The inhibitor is destroyed by papain and by 2-mercapto-ethanol. The “residual infectivity” (10–25%) has been found bound to the inhibitor in-vitro. Its behavior in the gel-adsorption system is not altered if the virus-inhibitor complexes have previously been diluted. — Nonsensitive mutants and double mutants have been selected. There must exist at least three different combining sites for equine inhibitors on the surface of poliovirus type 1, strain Mahoney. Equine sera may be grouped according to the specificity of their inhibitory activity. The specific binding capacity is lost if the virus is heated at 50° C for 30 min.