Antigenic variation among murine coronaviruses: evidence for polymorphism on the peplomer glycoprotein, E2.

A panel of 28 monoclonal antibodies (MAb) against the structural proteins of murine hepatitis virus-4, strain JHM (MHV-4) was used in three antigen binding assays to determine the extent of antigenic homology among six strains of murine coronaviruses. The antigenic determinants studied were highly conserved on the E1 glycoproteins and nucleocapsid (N) proteins of all strains tested. In contrast, antigenic polymorphism was observed among the E2 glycoproteins. Of three previously described antigenic determinants against which neutralizing antibodies are directed, only one, termed A(E2), was conserved on all strains. Antigenic site B(E2) was found only on the strongly neurotropic MHV-4 and site C(E2) was present on the virulent MHV-4 and MHV-3 (hepatotropic) strains, but absent on the weakly pathogenic MHV-A59, MHV-1 and MHV-S strains. Four non-neutralizing antibodies against at least one topographically distinct antigenic determinant, which we previously designated D(E2), gave binding patterns consistent with two distinct sites. One of these was present on all MHV strains tested and the other was present on all strains except MHV-S. These non-neutralizing antigenic sites were redesignated E(E2) and D(E2) respectively.