Vaccination with a gE-negative bovine herpesvirus type 1 vaccine confers insufficient protection to a bovine herpesvirus type 5 challenge

In the present study, cross-protection to bovine herpesvirus type 5 (BHV-5) induced by bovine herpesvirus type 1 (BHV-1) vaccination was examined following inoculation of rabbits and calves with a glycoprotein E (gE)-negative BHV-1 vaccine and subsequent challenge with BHV-5. Rabbits (n = 5) and calves (n = 8) were vaccinated [five rabbits intranasally (IN), four calves IN and four intramuscularly (IM)] with 7.1 log(10) median tissue culture infective dose (TCID50) of the BHV-1 vaccine. Rabbits and calves were challenged IN [rabbits 2 weeks post-vaccination (pv); calves 5 weeks pv] with 9.1 log(10) TCID50 of BHV-5. Two out of five vaccinated rabbits died after challenge with typical BHV-5 disease, as did 3/5 non-vaccinated controls. In calves, 4/8 vaccinated animals displayed mild signs of disease, whereas 6/6 non-vaccinated controls developed signs of disease, so severe that 2/6 had to be killed. Besides, nasal virus shedding post-challenge was not reduced by vaccination. At necropsy, on day 21 post-challenge, typical BHV-5 lesions were evident in brain tissues of both vaccinated and non-vaccinated calves. Dexametasone administration at 180 days post-infection did not reactivate clinical signs despite BHV-5 shedding in nasal secretions of both vaccinated and non-vaccinated calves. These results show that the BHV-1 vaccine evaluated here did not confer protection to BHV-5 in rabbits. In calves, BHV-1 vaccination did confer some protection to BHV-5 induced clinical disease, but it did not prevent infection and had no effect on nasal virus shedding or on the development of encephalitic lesions. (c) 2006 Elsevier Ltd. All rights reserved.