Taming PRRSV: revisiting the control strategies and vaccine design.

Porcine reproductive and respiratory syndrome virus (PRRSV) continues to be a threat, causing economically significant impacts on the swine industry worldwide. In this article, we share the information related to the Thai PRRSV and review the available options for PRRS control strategies. Unfortunately, the traditional control strategies and conventional vaccines fail to provide sustainable disease control, as they suffer from both antigenic heterogeneity and various immune evasion strategies of PRRSV. Induction of interleukin (IL)-10 following PRRSV infection is believed to be a focal mechanism leading to the unique immunological outcomes and interference of PRRS vaccine efficacy. It is likely that the nucleocapsid protein plays an important role in induction of IL-10 following PRRSV infection. We propose that removal or reduction of the PRRSV-induced, negative immunomodulatory effects especially during the first 2 weeks following infection is essential to establish proper anti-PRRSV immunity. In other word, incorporation of the "taming strategy" will be needed to reduce PRRSV-induced immunomodulatory effects, and to ensure maximal vaccine-induced immunity in the face of viral exposure. Any PRRSV vaccine that can induce cross-protective immunity and simultaneously eliminate the immunoinhibitory effects of PRRSV would be ideal. In addition, tracking of the inhibitory parameters, following the PRRSV challenge should be included in the vaccine testing protocol. Therefore, the future of PRRSV vaccine development relies tremendously on the basic knowledge of host-virus interactions and the communication between the basic and clinical PRRSV research fields.