A QUANTITATIVE STUDY OF THE EFFICACY OF A DELETION MUTANT BOVINE HERPESVIRUS-1 DIFFERENTIAL VACCINE IN REDUCING THE ESTABLISHMENT OF LATENCY BY WILDTYPE VIRUS

Using quantitive polymerase chain reaction (PCR) Ive have studied the latency established by wildtype ( WT) bovine herpesvirus-1 (BHV-1) aft er challenge of cattle that had been vaccinated with a double deletion (gC-lth-) mutant BHV-1 vaccine. Fourteen animals were vaccinated intr amuscularly with 2 ml containing 10(7.4) CCID50 (cell culture infectio us dose 50%) of IBRV(NG) dltkdlgC and challenged along with six unvacc inated control animals, 30 days later with 10(8.2) CCID50 of WT BHV-1 (Cooper). The ability of this vaccine to prevent acute clinical BHV-1 infection after this challenge has been previously reported(1). Sixty days after challenge, eight of the vaccinates and the six control anim als were euthanitized and the trigeminal ganglia (TG) examined for the amount of WT BHV-1 DNA by an internal standard quantitative PCR. The quantitative protocol that,ve used is based on co-amplification of BHV -1 gC specific sequences (present in WT BHV-1 but absent in the vaccin e strain) and sequences from the bovine growth hormone (BGH) gene, whi ch is used as an internal standard The TG of the eight vaccinates cont ained BHV-1 WT DNA, but in a statistically, significantly lower amount than the unvaccinated controls. These results are significant from th e standpoint that, to our knowledge, this is the first report of a sys tematic quantitative approach to the study of the effect of BHV-1 vacc ines on latency. This technique could be used to measure and compare t he efficiency of various BHV-1 vaccines in preventing or diminishing l atency, which is a significant factor for the perpetuation of BHV-1 in cattle populations. Copyright (C) 1997 Elsevier Science Ltd.