| Porcine reproductive and respiratory syndrome (PRRS) was first reported in the United States in 1987 . The causal agent of PRRS was first isolated in The Netherlands in 1991. PRRSV is endemic in most swine-producing countries, and today it is associated with majore conomic losses.Clinicalsigns of PRRS in growing pigs include fever, anorexia, and respira-tory disease characterized by dyspnea and tachypnea. Reproductive failure associated with PRRSV is characterized bymid- to late-term abortions, increased numbers of mummified fetuses, decreased numbers of pigs born alive, increased numbers of weak-born pigs, and generally poor reproductive performance.PRRS has been reported in China and is associated with majore conomic losses. How to prevente PRRS and reduce conomic losses is the primary studying subject. The molecular biology, vaccine and vaccine adjuvant of PRRSV have been researched. Because of the antigen variation, it is very difficult to prevente PRRS. Due to the conomic losses and potential threat, the preventional method was needed to control the prevenlence of PRRS in China. The study of immunosuppression mechanism will provide theoretical basis for prevention of PRRS.13 health pigs of 46 days old were randomly divided into three groups and 5 pigs in group A and B each, 3 pigs in group C. 48 days old, the pigs from A group were injected 3 mL PRRSV LC (TCID50: l0-5.25 /0.1 mL) per pig, and the pigs from B group were inject 3 mL cells without PRRSV. Pigs in group A and B were injected hog cholera vaccine, group C were injected 4mL normal saline when 50 days old. Measure the body tempreture and record the clinical symptoms every day. Two precaval vein blood samples were collected when 1d, 7d, 14d, 21d, 28d, and 35d after hog cholera vaccine immunity. One blood sample was used to separate serum and detect the antibody titer of hog cholera, the other blood sample was used to separate lymphcyte and detect T lymphocyte transformation rate. ELISA and MTT methods were used to detect the hog cholera antibody titer and peripheral blood T lymphocyte transformation rate. Hog cholera antibody titer of pigs in group B was significant induced (P<0.01) when 7 days after immunity and in group A was not significant induced(P>0.05). Hog cholera antibody titer of pigs in group B is significantly greater than that of pigs in group A after immunity 14 days. It shows that PRRSV can inhibit humoral immunity. T lymphocyte transformation rate were no significant diferent in group A, B and C when 1 day after immunity. T lymphocyte transformation rate of pigs in group B is significantly higher than that of pigs in group A after immunity 7d, 21d, 28d, and 35d. The results show that PRRSV can deduce the cellular immunity.3 health pigs of 60 days old were randomly divided into two groups and 2 pigs in group A, 1 pig in group B. Pigs from A group were injected 3 mL PRRSV LC (TCID50: l0-5.25 /0.1 mL) per pig. Clinical syndrome was detected and pigs were slaughtered when 25 days after challenge. Lymph node, spleen, lung and liver were collected, fixed in the neutral formalin liquid and making paraffin sections. Histochemistry method was used to detect the pathological lesion of PRRSV to pigs. The major lesion is central vein dilation and full of red cells in liver, lymph sinus full of exudate in lymph node, imphoid nodule deduce and focal hemorrhage in spleen, alveolar wall edema and thickening, focal hemorrhage in lung. There are not abnormal changes in tissues of pigs in group B. |
PDF Full Text Request