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, FHVβ-galgIgEΔ, 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 FHVβ-galgIgEΔ, 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 gI and gE deleted in FHVβ-galgIgEΔ.