CD40 ligand expressed in adenovirus can improve the immunogenicity of the GP3 and GP5 of porcine reproductive and respiratory syndrome virus in swine

Porcine reproductive and respiratory syndrome virus (PRRSV) has recently caused heavy economic losses in swine industry worldwide. Current vaccination strategies only provide a limited protective efficacy, thus immune modulators are being considered to enhance the effectiveness of PRRSV vaccines. In this study, the recombinant adenoviruses expressing porcine CD40 ligand (CD40L) and GP3/GP5 of PRRSV were constructed and the immune responses were examined in pigs. The results showed that rAd-CD40L-GP35 (co-expressing CD40L and GP3-GP5) or rAd-GP35 (expressing GP3-GP5) plus rAd-CD40L (expressing CD40L) could provide significant higher specific anti-PRRSV ELISA antibody and neutralizing antibody. And the levels of proliferative responses of peripheral blood mononuclear cells (PBMC), IFN-γ and IL-4 were markedly increased in rAd-CD40L-GP35 and rAd-CD40L plus rAd-GP35 groups than those in rAd-GP35 group. Following homologous challenge with Chinese isolate of the North-American genotype of PRRSV, pigs inoculated with recombinant rAd-CD40L-GP35 and rAd-CD40L plus rAd-GP35 showed lighter clinical signs and lower viremia, as compared to those in rAd-GP35 group. It indicated that porcine CD40L could effectively increase humoral and cell-mediated immune responses of GP3 and GP5 of PRRSV. Porcine CD40L might be used as an attractive adjuvant or immunotargeting strategies to enhance the PRRSV subunit vaccine responses in swine.