Quantitative Detection Of Porcine Cytokines And Viruses In Porcine Respiratory And Reproductive Syndrome Virus Infected Pigs

In this paper, dynamics of porcine cytokines and differentiation of lymphocytes in peripheral blood mononuclear cells (PBMCs), replication of viruses in porcine alveolar macrophages (PAMs), and pathological changes in infected tissues from pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV) strain CH-la were studied.Competitive PCR was developed and used to quantitatively detect mRNA expressions of porcine IL-12 p40, IFN-y, IL-4 and IL-10 in PBMCs and PAMs during the early infection. The expression of IFN-y, one of Thl type cytokines, in PRRSV-infected pigs was enhanced dramatically compared to that in the control pigs. While the mRNA of p40 of IL-12, an IFN-y-inducing cytokine, was decreased. IL-4 was hardly detectable in the PBMCs and PAMs, possibly due to too low expression or otherwise inhibition by the virus. The expression of IL-10, another Th2 type cytokine, was decreased slightly. The percentage of CD3+, CD4+ and CD8+ T cells in PBMCs firstly dropped markedly, then rose remarkably, while SWC6+ cells had a consistent increase, suggesting a compensatory proliferation in response to the loss of T cells caused by the virus infection.The infected pigs demonstrated serious interstitial pneumonia. The virus was shown to primarily replicate in the lung of the infected pigs, and then spread to lymph nodes, spleen and tonsil.We concluded that the cell-mediated immune response during the early period of PRRSV infection might play a dominant role, however, the virus replication was not effectively inhibited.This is the first report about quantitative study on the dynamics of porcine cytokines in the PBMCs and the replication of virus in tissues of PRRSV-infected pigs using a competitive PCR. Our research might provide some hints to the study of the pathogenesis ofPRRS.