Serum Immune Responses of Pigs after a Challenge with Porcine Reproductive and Respiratory Syndrome Virus (PRRSV)

Porcine Reproductive and Respiratory Syndrome (PRRS) is the most economically important infectious disease of swine. After PRRS virus (PRRSV) infection most pigs exhibit weak early innate immune response, and poor late adaptive cytokine responses; using PRRS Host Genetics Consortium (PHGC) samples we evaluated pig serum cytokine levels using FMIA (Fluorescent Microsphere Immunoassay). Samples were collected at 0, 4, 7, 11, 14, 21, 28, 35, 42 days post infection (dpi) with PRRSV from weaned PHGC pigs that had been categorized with high or low viremia. The FMIA detected simultaneously 7 cytokines, representing early innate [interleukin-1b (IL-1b), IL-8, interferon–alpha (IFNa)], T helper 1 (Th1) (IL-12), Th2 (IL-4), and regulatory (IL-10) immune responses and cell migration chemokine (CCL2). Only the serum levels of IL-4were unchanged (P>0.05) after the viral infection.The concentration of the remaining cytokines changed (P<0.05) during the progression of the viral desease. The concentration of IL-8 and CCL2 increased faster in high viremia pigs. Serum IFNa averaged 500 pg/ml at dpi 0, increased 5 fold at dpi 4 and decreased to basal levels from dpi 7 (P<0.05); however, this decrease was slower (P<0.05) in high viremia animals. By dpi 21 both groups were similar until the end of the sampling period . These results indicate that the serum concentrations of IL-8, IFNa and CCL2 are significantly altered after PRRSV infection. We are probing correlations of cytokine profiles with serum viral levels and for effects on growth performance. Support: CNPq postdoctoral fellowship (200602/2010-1) to KPCA and National Pork Board grant #09-244.