Immunological responses of swine to porcine reproductive and respiratory syndrome virus infection

PRRSV is a member of the genus Arterivirus, family Arteriviridae, order Nidovirales. PRRSV is the causative agent of the most important infectious disease that affects swine herds world-wide, producing great economic losses. Since its emergence over 25 years ago, much has been learned about the immunobiology of PRRSV. The immune response to PRRSV infection is weak and relatively late. This results in long-term persistence of viral load (4-5 weeks), and infectious virions are detected in lymphoid tissue up to 157 days post-infection. Although the organism's immune response to PRRSV infection and the mechanisms of resistance to infection have not been fully explored, commercial vaccines are available on the market. These vaccines do not provide full and universal protection against PRRSV infection. The present review discusses current knowledge on the virus immunobiology, including the innate and adaptive immune responses to the virus and the regulation of the immune response by PRRSV.