Growth properties and vaccine efficacy of recombinant pseudorabies virus defective in glycoprotein E and thymidine kinase genes.

Pseudorabies virus (PRV) is an alphaherpesvirus that causes pseudorabies (PR), an economically important viral disease of pigs. Marker vaccines were widely used in PR prevention and eradication programs. The purpose of this study was to construct a novel recombinant virus with deletions at defined regions in the glycoprotein E (gE) and thymine kinase (TK) genes by homologous recombination. This study also evaluated the safety and efficacy of the virus for a live attenuated marker vaccine. No significant difference was observed in virus replication between gE gene-deleted (gE(-)), gE/TK double gene-deleted (gE(-)TK(-)), and wild-type PRV by growth curve analysis. However, gE(-)TK(-) PRV was completely attenuated in mice. To evaluate the immunogenicity of gE(-)TK(-) PRV, four 12-week-old specific-pathogen-free pigs per group were immunized intramuscularly with viral titers of 1×10(4), 1×10(5), or 1×10(6) TCID50, followed by intranasal challenge infection with virulent PRV (1×10(8) TCID50) at 3 weeks post vaccination. The gE(-)TK(-) PRV-vaccinated pigs displayed no general adverse effects after immunization and had protective immune responses after PRV challenge. Thus, gE(-)TK(-) PRV was safe and efficacious and might be a potential candidate for a live attenuated marker vaccine against PRV.