VACCINATION AGAINST BOVINE HERPES MAMMILLITIS VIRUS-INFECTIONS IN GUINEA-PIGS

Bovine herpes mammillitis virus or bovine herpesvirus type 2 (BHV-2) c auses ulcerative lesions on the teats and udders of infected cows. Sin ce no commercial vaccine is available for this disease, we investigate d certain experimental BHV-2 vaccines against this virus in infected g uinea pigs. Vaginally infected guinea pigs get severe, self-limiting v aginal infections characterized by erythema and swelling and the produ ction of measurable vaginal virus titers. Two vaccine approaches were investigated: vaccination with wild-type (WT) virus by the subcutaneou s route, and vaccination either subcutaneously or intravaginally with a thymidine kinase (TK) deficient (TK-) virus. The TK- strain was prep ared by passage of BHV-2 in the presence of the potent TK-dependent an tiviral agent -2'-fluoro-beta-D-arabinofuranosyl)-5-methyluracil (FMAU ). The antiviral activity of FMAU against the virus in plaque reductio n assays changed from 0.05 to 2 mu M at the same time that the TK acti vity of the mutant virus decrease to 7% of WT virus TK activity. Subcu taneous vaccination of guinea pigs with WT and TK- viruses did not ind uce vaginal infection. Primary vaginal infection (vaccination) with th e TK- virus led to greatly reduced lesion severity compared to vaginal infection with the WT virus. However, the amount of vaginal virus tit ers recovered during these primary infections was similar for both TK- and WT viruses, indicating that both viruses had equal infecting pote ntial. Thirty days after vaccination the animals were re-infected intr avaginally with WT virus. The vaccinated animals showed dramatically r educed lesion severity and low recoverable virus titers compared to ag e-matched nonvaccinated animals. These results indicate the potential of a TK- vaccine given by two different routes or a WT virus administe red by a nonvaginal route to protect BHV-2-infected guinea pigs. These approaches may have application to the vaccination of dairy cattle su sceptible to BHV-2 infection.