Molecular characterization and virulence of an alphaherpesvirus isolated from a BoHV1 gB-seropositive and gE-seronegative Italian buffalo

Abstract

During a serological survey, 157 out of 681 unvaccinated buffaloes resulted seropositive for bovine alphaherpesvirus 1 (BoHV1) glycoprotein B (gB) and seronegative for BoHV1 glycoprotein E (gE). These serological results were generally expected in animals vaccinated with a BoHV1 gE-deleted vaccine but not in unvaccinated animals. Seroneutralization tests on 36 selected sera detected neutralizing antibody titers more than three times higher for BuHV1 than for BoHV1. In order to investigate the virus, one of these buffaloes was injected with dexamethasone, and from nasal and vaginal swabs collected at different time points, a ruminant herpesvirus was isolated, characterized and also detected by PCR. Restriction enzyme analysis, sequencing and phylogenic analysis of gB and gD genes showed that the virus was genetically similar but not identical to BuHV1 strain b6. Intranasal inoculation of the virus in a healthy seronegative buffalo resulted in a mild and transient upper respiratory disease; the virus was isolated from clinical specimens and DNA was detected by PCR in nasal and vaginal swabs up to 9 days after infection. Further investigations should be aimed at sequencing the whole viral genome and at evaluating the host-range of this virus. Specific tests are needed to discriminate infections by different ruminant herpesviruses and to improve eradication programs of infectious bovine rhinotracheitis/infectious pustular vulvovaginitis in cattle.