Comparative studies of the structural proteins and glycoproteins of equine herpesviruses 2 and 5

The structural proteins of equine herpesvirus 2 (EHV-2) and EHV-5, recently shown to be gammaherpesviruses, were identified and compared. Labelled proteins and glycoproteins were separated by SDS-PAGE and although EHV-2 and EHV-5 had similar protein profiles, bands in some positions were virus-specific. Six glycoproteins, with distinct profiles, were identified for both EHV-2 and EHV-5. Rabbit antisera to EHV-2 and EHV-5 and horse antiserum to EHV-2 were used in radioimmunoprecipitations, Western blot analysis and ELISA to investigate the immunogenicity and cross-reactivity of virus proteins. These analyses revealed that while EHV-2 and EHV-5 proteins share many common epitopes, they also possess type-specific epitopes. A 0.71 kb region of the EHV-2 glycoprotein B (gB) gene was expressed as a fusion protein in Escherichia coli. Antiserum raised in a rabbit to the EHV-2 fusion protein was used to identify a 64K EHV-2 protein as EHV-2 gB. Antiserum to EHV-2 gB was used to identify a 66K EHV-5 protein as EHV-5 gB. These proteins, which may represent subunits of gB rather than the entire molecule, appear the most immunodominant of the structural virion proteins as identified by Western blot.