Characterization of immune responses to baculovirus-expressed equine herpesvirus type 1 glycoproteins D and H in a murine model.

A murine intranasal infection model for equine herpesvirus type 1 (EHV-1) was used to evaluate immune responses following immunization with insect cells infected by baculoviruses that express EHV-1 glycoproteins. Baculovirus recombinant glycoprotein D (gD) and gH both induced serum antibodies to EHV-1 when measured by ELISA. The gD recombinant also produced a neutralizing antibody response. Protective immunity, determined by accelerated clearance of virus from the target organs in the respiratory tract, was demonstrated in mice immunized with a baculovirus recombinant expressing gD. In addition to the serological response, evidence is presented which shows that cell-mediated responses also play an important role in protection. Both recombinants induced delayed-type hypersensitivity and lymphoproliferation to EHV-1 antigen. The protective effects of T cells were confirmed by adoptive transfer of spleen cells from baculovirus gD-immunized donors to recipients that were challenged with live EHV-1. Depletion of either CD4- or CD8-bearing cells from the gD-immunized donors reduced the ability of the recipients to clear virus from the target organs, although depletion of CD4 cells had a more marked effect.