Experimental infection of calves with a gI, gE, US9 negative bovine herpesvirus type 5

In this work, a role for the genes encoding glycoproteins I (gI) and E (gE) and the US9 protein of bovine herpesvirus type 5 (BHV-5) in neuropathogenicity and reactivation of latent infections was examined. Calves infected intranasally with a gI/gE/US9 deleted recombinant shed up to 10^2.85 TCID₅₀/ml infectious virus in nasal secretions. Calves infected with the wild type BHV-5 parental virus shed up to 10⁵ TCID₅₀/ml virus. No signs of disease were observed in calves infected with the recombinant virus, whereas those infected with wild type virus displayed respiratory and neurological signs. The recombinant was only able to reach the basal portions of the central nervous system. In contrast, wild type virus was found widespread within the brain. Reactivation with dexamethasone 60 days post-infection resulted in reactivation of wild type virus, whereas the recombinant virus could not be reactivated. These studies demonstrate that genes gI, gE and US9 of BHV-5 are important for its neuropathogenicity and its ability to reactive from latency.