Antigenic variations among calf diarrhea coronaviruses by immunodiffusion and counterimmunoelectrophoresis.

The antigenic relationship among five bovine coronavirus isolates was studied using the counterimmunoelectrophoresis (CIE) and immunodiffusion (ID) techniques. By CIE, two precipitating antigens were observed for each coronavirus isolate. One antigen identified as the "M" coronaviral antigen was found to be common to the five isolates while the second antigen identified as the "m" coronaviral antigen differed between the isolates. Considering the later antigen, the isolates studied were placed in two antigenic groups, members of the same group being indistinguishable for the two antigens. By ID, reactions of partial identity were noted between viruses of the different groups.