Swine Protective Immune Responses To Porcine Reproductive And Respiratory Syndrome Virus Infection-Changes Of CD4, CD8 T Lymphocytes Subsets In Different Immune Status

Porcine reproductive and respiratory syndrome (PRRS) is a swine disease characterized by reproductive disorders and respiratory disease, and induces highly morbidity rates and mortality rates to the pig industry worldwide since 1987 the first reported by the USA. Studies have shown that both PRRSV infection could induce function of immune system suppression. Therefore, it is worthwhile to investigate the relationship of PRRSV and CSFV infection/immunity, and make clear of against to the PRRSV infection. Meanwhile, provide further basis for deigning more effective vaccine and controlling the prevalence of PRRSV.To clarify the whether there is protection for PRRSV after effective CSFV vaccination, finally, the test starting from cellular immunity, the proportion of T lymphocyte subset in PBL were to be examined in order to explore the mechanism of specific-immune function more deeply. In order to select the SPF swines to the study, 380 sows'serum samples were detected by ELISA and detected about the PRRSV, CSFV, PCV-2 and PRV. In the end,20 both CSFV and PRRSV antibody-negative pigs were found out. Based to the results of serum antibody test and the four virus detection (PRRV, CSFV, PCV-2 and PRV), randomly divided the pigs in 4 groups: group A, B, C and D, isolation rearing. The A and B groups were immunized with the normal dosage of PRRS vaccine (no adjuvant), the C and D groups were immunized with phosphate buffer saline (PBS).7 days later, B and D groups of pigs were inoculated with BJ-4 of PRRSV by intranasal instillation of 2mL 103.2 TCID50, groups A and C served as no-infection control pigs after 7days, and then collected the complete blood within heparin by venipuncture of jugular vein (pigs) using sterile equipment and procedures, respectively at the 1,7,14,21 and 28 days after the infection. The CD3, CD4 and CD8 T cells were analyzed by Flow Cytometry (FCM), the data were analyzed with SPSS13.0.The results showed that, CD3+ T cells were primary increased and then reduced of the infected pigs, whatever CSFV vaccinated or not, and had a significantly increased at 7th day (P<0.05); both CD4+ and CD8+ T cells proportion were significantly reduced in acute phase of PRRSV at the 7th day and 14th day (P<0.01), and the proportion of CD8+ T cells reduced more lately and slowly than CD4+ T cells; the proportion of CD4+ plus CD8+ T cells was significantly reduced in acute phase of PRRSV infection (P<0.05); CD4+/CD8+ T cells ratio play an important role in immune response, and it can protect the immune when the ratio reaches 1; it was significantly reduced in acute phase which couldn't protect the pigs in immune response, and had significantly reduced at 7th day and 14th day (P<0.01); these stata suggested that immune system was suppressed and the CD3+ T cells differentiation were blocked in acute phase of PRRSV infection, caused large concentration of it in PBL in short time.it is uncovered that proportion of CD4+ T cells reduced led to decline the function of clear the PRRSV, caused the pigs might be more susceptible to secondary-infection, and infection led to the T lymphocyte immune suppression compared with the active T lymphocytes in healthy pigs. Interestingly, the proportions of CD4+CD8+ double-positive T cells and CD4-CD8- T cells had some increased in the group of PRRSV infection which compared with the groups of the PRRSV infection but no CSFV vaccination, which suggested that the function of T cells immune is declined. Compared with both CSFV vaccination and PRRSV infection group, in the CSFV vaccination but no'infection of PRRSV the proportion of CD3+ T cells reduced more severe; and the proportions of CD4+ and CD8+ T cells had more significantly reduced (P<0.05); CD4+CD8+ double-positive and CD4-CD8-proportions had more significant increased; meanwhile, CD4+/CD8+ T cells ratio had more significantly lowly (P<0.01); the most important is that the immune suppression is advanced, and had stronger suppression. The results suggested that the pigs which had CSFV vaccination would provide protective effect to PRRSV infection. In other words, the pigs which had the specific-immune would against the secondary-infection.