Immunogenicity and protective efficacy of recombinant pseudorabies virus expressing the two major membrane-associated proteins of porcine reproductive and respiratory syndrome virus.

Porcine reproductive and respiratory syndrome virus (PRRSV) infection still remains today as the most significant health threat to swine and poses a challenge to current vaccination strategies. To develop a new generation of vaccine against PRRSV, a live attenuated pseudorabies virus (PRV) was used as vaccine vector to express the two major membrane-associated proteins (GP5 or M) of PRRSV in various forms. Four PRV recombinants, rPRV-GP5 (expressing native GP5), rPRV-GP5m (expressing GP5m, a modified GP5), rPRV-GP5-M (co-expressing GP5 and M proteins), rPRV-GP5m-M (co-expressing GP5m and M proteins) were generated. Mouse immunized with all these recombinants developed comparable PRV-specific humoral immune responses and provided complete protection against a lethal PRV challenge. However, the highest level of PRRSV-specific neutralizing antibodies and lymphocyte proliferative responses was observed in mice immunized with rPRV-GP5m-M. The immunogenicity and protective efficiency of rPRV-GP5m-M were further evaluated in the piglets. Compared to commercial PRRSV killed vaccine, detectable PRRSV-specific neutralizing antibody and higher lymphocyte proliferative responses could be developed in piglets immunized with rPRV-GP5m-M before virus challenge. Furthermore, more efficient protection against a PRRSV challenge was obtained in piglets immunized with rPRV-GP5m-M, as showed by the balanced body-temperature fluctuation, shorter-term viremia, lower proportion of virus load in nasal and oropharyngeal scrapings and tissues, and milder lung lesions. These data indicate that the recombinant rPRV-GP5m-M is a promising candidate bivalent vaccine against both PRV and PRRSV infection.