Characterization of caprine herpesvirus 1 glycoprotein D gene and its translation product

Deletion of the thymidine kinase gene attenuates Caprine alphaherpesvirus 1 in goats

Caprine alphaherpesvirus 1 (CpHV-1) is a pathogen associated with systemic infection and respiratory disease in kids and subclinical infection or reproductive failure and abortions in adult goats. The enzyme thymidine kinase (TK) is an important viral product involved in nucleotide synthesis. This property makes the tk gene a common target for herpesvirus attenuation. Here we deleted the tk gene of a CpHV-1 isolate and characterized the recombinant CpHV-1^ΔTKin vitro and in vivo. In vitro characterization revealed that the recombinant CpHV-1^ΔTK replicated to similar titers and produced plaques of similar size to the parental CpHV-1 strain in BT and CRIB cell lines. Upon intranasal inoculation of young goats, the parental virus replicated more efficiently and for a longer period than the recombinant virus. In addition, infection with the parental virus resulted in mild systemic and respiratory signs whereas the kids inoculated with the recombinant CpHV-1^ΔTK virus remained healthy. Goats inoculated with the parental virus also developed higher neutralizing antibody titers when compared to CpHV-1^ΔTK inoculated animals. Dexamethasone (Dx) administration on days 35-39 post-inoculation did not result in virus shedding in nasal secretions, indicating lack of reactivation from latency. However, viral DNA was detected in the trigeminal ganglia of animals euthanized at 14 days post-Dx, indicating that both viruses successfully established latent infection. Our results show that the recombinant CpHV-1^ΔTK presents an attenuated phenotype when compared to the parental virus, and hence may represent a promising vaccine candidate to prevent CpHV-1 disease in goats.

Clinical protection of goats against CpHV-1 induced genital disease with a BoHV-4-based vector expressing CpHV-1 gD

Caprine herpesvirus type 1 (CpHV-1) is an alphaherpesvirus causing genital disease leading to abortion in adult pregnant goats and a systemic disease with high morbility and mortality in kids. Further, Caprine herpesvirus 1 infection represents a valuable large animal model for human herpesvirus induced genital disease, exploitable for pathogenic studies, new vaccines and antiviral molecules testing. Here, the bovine herpesvirus 4 (BoHV-4) based vector derived from an apathogenic isolate of BoHV-4 and expressing the immunodominant CpHV-1 glycoprotein D (BoHV-4-A-gD(cp)gD(106)ΔTK) was constructed and its ability to protect goats against CpHV-1 induced genital disease evaluated. The subcutaneous route of recombinant BoHV-4 administration was first tested in vivo/ex vivo by in vivo image analysis and in vitro by goat skin primary cultures preparation and transduction. Next, an exploratory immunization and safety study in goats was performed with two recombinant BoHV4, BoHV-4-A-gD(cp)gD(106)ΔTK or BoHV-4-CMV-IgK-gE2gD-TM. In both cases no clinical signs were evident but a good titer of serum neutralizing antibodies was produced in all inoculated animals. When a challenge experiment was performed in a new group of animals using a highly pathogenic dose of CpHV-1, all the vaccinated goats with BoHV-4-A-gD(cp)gD(106)ΔTK were protected toward CpHV-1 induced genital disease respect to the unvaccinated control which showed typical vaginal lesions with a high grade of clinical score as well as a long lasting viral shedding. In summary, the data acquired in the present study validate BoHV-4-based vector as a safe and effective viral vector for goat vaccination against CpHV-1 induced genital disease and pave the way for further applications.