Research and development of a novel subunit vaccine for the currently circulating pseudorabies virus variant in China

Pseudorabies (PR) is a devastating viral disease which leads to fatal encephalitis and respiratory disorders in pigs. Commercial gE-deleted live pseudorabies virus (PRV) vaccine has been widely used to control this disease in China. However, the new-emerging variants of PRV compromises the protection provided by current vaccines and lead to the outbreak of PR in vaccinated pig herds. Several killed and live vaccine candidates based on current PRV variants have been reported to be effective to control the disease. A subunit vaccine based on gB protein, one major PRV glycoprotein which elicits strong humoral and cellular immune responses, however, was never evaluated for protection against the current circulating PRV variants. In this study, full-length PRV gB protein was successfully expressed in baculovirus/insect cells in the soluble format and was tested on 3-week-old piglets as a subunit vaccine. Compared with unvaccinated pigs, the gB-vaccinated pigs developed specific antibody-mediated responses and were protected from the virulent PRV HN1201 challenge. All vaccinated pigs survived without showing any PRV-specific respiratory and neurological signs, but all unvaccinated pigs died within 7 days after HN1201 challenge. Hence, this novel gB-based vaccine could be applied as an effective subunit vaccine to control PRV variant in China