Monoclonal antibodies for study of antigenic variation in coxsackievirus type B4: association of antigenic determinants with myocarditic properties of the virus.

Monoclonal antibodies were produced to a field strain ( Mil ) of group B coxsackievirus type 4 (CBV-4), and to the prototype JVB strain. Nine were neutralizing antibodies and four were non-neutralizing antibodies with virus-specific activity in indirect immunofluorescence (IF) staining. On the basis of reactivity with the panel of monoclonal antibodies, nine different strains of CBV-4 were found to fall into five distinct antigenic groups. Antigenic variants were produced by using the neutralizing monoclonal antibodies to select variants from the Mil virus stock which were no longer susceptible to the selecting antibody. A high frequency of antigenic variation was seen. By using the variants in cross-neutralization and IF tests with the monoclonal antibodies, it was possible to identify five tentative antigenic sites functional in neutralization; one site appeared to be complex and possibly to consist of overlapping epitopes. Reactivity of the monoclonal antibodies was similar, but not necessarily identical, by neutralization and by IF staining. The antigenic variants were found to differ from the parent Mil strain, and from one another, in their myocarditic and cardiotropic properties in a murine model. Two of the variants produced more extensive cardiac pathology, and two produced higher virus titres in the heart than was produced by the parent strain. One variant was notable for extensive production of necrotic lesions in the myocardium. Four of the variants showed less histopathology and three produced less virus in the heart than was produced by the parent strain.