Antibodies to human coronavirus OC43 measured by radial haemolysis in gel

An application of the haemolysis-in-gel (HIG) technique was developed to quantitate antibodies against the human coronavirus OC43. Preinfection and convalescent sera from two patients with verified OC43 infection showed a significant increase in antibody titres measured by HIG as well as by haemagglutination-inhibition (HI). 241 of the other 306 sera tested (80%) caused radial haemolysis in gels containing viral antigen-sensitized erythrocytes and complement. No haemolysis was seen in gels prepared with unifected material. Correlation of the diameter of the haemolysis ring to the respective HI titre was highly significant. However, 62 sera (20%) with HI titres between 8 and 320 were negative in the HIG. Attempts to show that these sera contained nonspecific inhibitors of haemagglutination were unsuccessful. OC43 HI and HIG probably measure different antibody ppulations.