| Porcine Reproductive and Respiratory Syndrome(PRRS)is a highly contagious disease caused by porcine reproductive and respiratory syndrome virus(PRRSV),which is characterized by reproductive failure of sows and respiratory diseases of weaned piglets.Infectious diseases,suffering from anorexia pigs,fever and other symptoms,pregnant sows abortion,stillbirth or mummified birth,piglets respiratory disease,and showed high mortality.Since the emergence of the disease in China has always been a threat to the sustained and healthy development of the pig industry can not be ignored as an important infectious disease.In view of the prevalence of PRRS in C hina,vaccine immunization is the most important and effective measure to prevent and control the disease.Domestic vaccine market is generally divided into two kinds of attenuated vaccine and inactivated vaccine,attenuated vaccine because of its clinical effect is better and widely used.But in actual use,due to the attenuated vaccine in the immunization time,immunization dose and the number of immunization and other aspects of the time there is no corresponding specification,the immune effect of attenuated vaccine is not a complete evaluation system,resulting in the use of attenuated vaccine on the confusion and immunity The effect can not be scientific evaluation and a series of problems.In order to further study the safety and immune effect of attenuated live vaccine in PRRS,we evaluated the immune effect of a live PRRS attenuated vaccine(MLV),which is commonly used in the market.The results showed that the clinical symptoms of the animals showed no obvious clinical symptoms and histopathological changes after immunization with MLV,which indicated that the vaccines had better safety;some of the pigs showed minor clinical symptoms after challenge;The pathological changes of lung,lymph node,tonsil,spleen and kidney of MLV group were significantly lower than that of the control group(P <0.05),but no significant difference was found in the histopathological analysis of the organs..The results of antibody detection showed that the time of antibodies against N protein was relatively late after MLV vaccination,and the time of neutralizing antibody against GP5 protein was relatively normal.The MLV immunized group and the control group The level of CD4 + and CD8 + in the MLV group was not significantly different between the two groups before and after challenge,and the levels of IFN-γ The results of immunohistochemistry showed that PRRSV could be detected in the lung,lymph node,tonsil and spleen of the MLV group,especially in the tonsil body Virus content is higher.The actual use of the vaccine in the production,the p ig farm production data have steadily improved,indicating that the vaccine suitable for field applications.These results indicate that MLV has high safety and can induce specific neutralizing antibody in vivo,and can inhibit the proliferation of highly pathogenic PRRSV in pig,which is suitable for clinical application of swine. |
