Mucosal and systemic immunity to bovine herpesvirus-1 glycoprotein D confer resistance to viral replication and latency in cattle.

Mucosal immunity in the respiratory tract directed against bovine herpesvirus-1 (BHV-1) glycoprotein B forms an effective barrier against BHV-1 replication in cattle. Here we investigated the ability of a second BHV-1 glycoprotein, gD, to engender specific antibodies in nasal secretion and serum and protect against infection. We expected gD to give greater protection than gB because anti-gD antibodies prevent viral penetration into cells at much lower concentrations than anti-gB antibodies. Calves vaccinated once subcutaneously and thrice intranasally with affinity-purified BHV-1 gD had mucosal antibodies and three of five were protected against intranasal challenge by 10(7) p.f.u. of BHV-1. Four of the five vaccinated calves were proven free of BHV-1 latency by the lack of viral shedding following immunosuppression. The putative mucosal adjuvant, cholera toxin B subunit (CTB), did not significantly enhance mucosal immunity or protection against challenge or latency (P0.5) since only 4 of 6 gD plus CTB immunized calves were completely protected. Taken together, these data suggest that BHV-1 gD may be useful in a mucosal vaccine against BHV-1 infection in cattle but is less than totally effective when used alone.