A SUBUNIT GIV VACCINE, PRODUCED BY TRANSFECTED MAMMALIAN-CELLS IN CULTURE, INDUCES MUCOSAL IMMUNITY AGAINST BOVINE HERPESVIRUS-1 IN CATTLE

A truncated version of bovine herpes virus-1 (BHV-1) glycoprotein IV (tgIV) was produced in a novel, non-destructive expression system based upon regulation of gene expression by the bovine heat-shock protein 70A (hsp70) gene promoter in Madin Darby bovine kidney (MDBK) cells. In this system, up to 20 mu g ml(-1) of secreted tgIV, which is equivalent to the yield from 4 x 10(6) cells, was produced daily over a period of up to 18 days. Different doses of tsIV were injected intramuscularly into seronegative calves. Virus-neutralizing antibodies were induced by all doses of tsIV, both in the serum and in the nasal superficial mucosa. However, the low dose (2.3 mu g) induced significantly (p < 0.05) lower antibody titres than the medium (7 mu g) and high (21 mu g) doses. The medium and high doses of tgIV conferred protection from BHV-1 infection, as demonstrated by a significant (p < 0.05) reduction in clinical signs of respiratory disease and virus shedding in the nasal secretions postchallenge. However, the 2.3 mu g group, although partially protected, was not significantly (p > 0.05) different from the placebo group. This study demonstrated the potential of an intramuscularly administered tgIV subunit vaccine to induce mucosal immunity to BHV-1 using an economic protein production system and an acceptable vaccine formulation. In addition, a strong correlation was observed between neutralizing antibodies in the serum and nasal superficial mucosa, virus shedding and clinical disease. prognosticator of protection from BHV-1 infection and disease.