The C-terminal regions of the envelope glycoprotein gp2 of equine herpesviruses 1 and 4 are antigenically distinct.

The unusual mucin-like high molecular mass (Mr) glycoprotein 2 (gp2) has only been described in the equid alphaherpesviruses, among which there is considerable antigenic cross-reactivity. Equine herpesvirus 1 (EHV-1) gp2 is cleaved into a highly glycosylated N-terminal subunit and a 42 kDa C-terminal cleavage product. In order to investigate their antigenic recognition by horses naturally infected with EHV-1 and/or equine herpesvirus 4 (EHV-4), the C-terminal cleavage product and high Mr gp2 were affinity purified. Cross-reactivity between EHV-1 and EHV-4 was observed for the high Mr gp2 using Western blotting. In contrast only horses with antibodies to EHV-1 detected the 42 kDa EHV-1 gp2 C-terminal cleavage product. This phenomenon was evident in pooled sera from adult horses and also in foals that had demonstrated seroconversion due to EHV-1 infection. The results indicate that the C-terminal region of EHV-1 gp2 is antigenically distinct from that of EHV-4 gp2 and can be detected only after an EHV-1-specific immune response.