Vaccination of cats for feline rhinotracheitis results in a quantitative reduction of virulent feline herpesvirus-1 latency load after challenge.

We recently described the construction of a feline herpesvirus-1 (FHV-1) recombinant vaccine strain, FHV beta-galgLgE delta, containing a deletion in both the gI and the gE genes. We also reported comparative tests of its safety and efficacy in cats. These cats were unvaccinated or subcutaneously vaccinated with FHV beta-galgLgE delta, its isotypic parent strain (FHV-1SA), or a commercial FHV-1 vaccine strain (FHV-1CV) and subsequently challenged with a virulent field strain of FHV-1. Here we report the determination of FHV-1 field virus latency load after challenge in the same experimental animals. FHV-1 specific quantitative PCR was carried out on feline genomic DNA isolated from trigeminal ganglia, olfactory bulbs, and brain stems. We have determined that a reduction in field virus latency load in cats vaccinated subcutaneously with wild-type FHV-1 strains prior to challenge is dependent upon glycoproteins gL and gE deleted in FHV beta-galgLgE delta.