Establishment Of Mice Model Infected By Brucella And Application In Evaluation Of Efficacy Of Vaccine

As an infectious diseases,Brucellosis were caused by Brucella spp,which can infect people and animals.China called it a Class B infectious.However.Brucellosis was a global disease,not only disserviced human health,livestock development,but also effected life development and the international trade.People who infected showed acute febrile symptom like influenza, it was difficult to eliminate in a long time, which accompanied with serious complications and affected the normal function of muscles, bones and other tissues. Brucellosis could be spreaded through respiratory, digestive mucosa and broken skin.As an ancient disease,people had did lots of research,but the problems of prevention and treatment have not resolved on account of its species type complex,such as brucella transmission and pathogenesis,the structure and function of virulence gene,the functions of immunogenicity proteins and structural proteins.as well as research and development of vaccines safely.In this study,we cultured and purified B.abortus 2308 virulent strain,then counted bacteria quantity per millilitre,infected BALB/C mice artificially.In the way of intraperitoneal injection per 104CFU and intranasal approach per 106CFU bacterium.In next serveral weeks, we observed the mice clinical symptom and pathological change,the results showed that the infection groups took the similar clinical symptom like mammals:the mice was paroxysmal gloomy with clothing hair messy and cold chills.Liver and Spleen were damaged in the early time, after 4 weeks the liver and spleen index were increased in intraperitoneal injection groups. significant difference from the control group(P<0.05), intranasal infection groups compared the control.the spleen and lung index was significant difference at 6 weeks(P<0.05).The lung was lesion acutely, showed typical pneumonia in the late weeks.The antibodies in serum showed positive by RBT,SAT and IELISA.The study proved that BALB/C mice was impressionable to Brucella.and it could be a good animal model using Brucella research.Based on the above research,collecting kinds of organs in different groups to isolate bacteria and identified by PCR.made tissue sections in conventional methods for pathological examination and immunohistochemical detection for antigen distribution.The results showed that Brucella were principal presence in mouse liver. spleen and lung at different weeks.Histological observation in organs.the lymphocyte,neutrophil infiltration were diffuse disposition, venous dilatation and congestion.In microscope, liver sinus border cells and Kupffer cells hyperplasied,there were several epithelioid cell granulomas within the lobular;In the spleen medulla macrophages and plasma cells increased, a small number of visible fibrous tissues hyperplasied,and the splenic follicles became larger, also the germinal center increased; alveolar wall capillary hemorrhaged and oozed,alveolar septum widened. Immunohistochemistry results showed that positive signal was in the liver cytoplasm, near the capsule was positive strongly,and lymphocytes,neutrophil infiltrated.the liver nuclei stained shallow. In spleen, positive signals were mainly located in the splenic follicles and lymphocytes,histiocytes and macrophages.In the spleen.there was a small amount of hemosiderin, neutrophils and lymphocytes scattered,but not defined.So pathological observation was the foundation for Brucella pathogenesis research.This study used a mouse model of Brucella to evaluate vaccine protective effect of A19. The A19 vaccine strain was inoculated BALB/C mice through the groin injecting.The result showed that the immunized group of mice did not show obvious clinical symptoms, but its liver and spleen was intumesced.there was not characteristic granulomas by pathology observed.The vaccine strains could stimulate the body to produce high density of antibodies.Immunized mice were attacked on the B.abortus 2308 strains, the results showed the number of bacteria were not raise.the content of cytokine of IFN-γand IL-2 expressing increased, compared with control group were significant disparity.Experimental results showed that the A19 vaccine had an action to protect the body against Brucella attacked.and BALB/C mice infected Brucella as a model could also evaluate the vaccine protection effect.