Construction Of BP26 Gene Marker Strain Brucella Abortus S19 Evaluation Of The Immunogenicity In Mice

Brucellosis, which is caused by Brucella, is one of the most important bacterial zoonosis endemic in many countries. Brucella spp.is the pathogen of brucellosis. Brucella are facultative intracellular, gram-negative coccobacilli without spore, flagella and capsule. One important characteristics of Brucellosis is that once infected, it is hard to cure completely. Therefore, prevention is the most important means to control it. Vaccination is most efficient means for brucella prevention.The vaccines widely used in our courty are live attenuated vaccine strains,such as Brucella abortus S19, Brucella melitensis M5 and Brucella suis S2. It is found that these vaccines have cross immunity. However, these vaccines also have some limitations or defects. For example, a important defect of these vaccines is that, they have very similar antigenicity to virulent strains, and therefore, it is very difficult to differentiate the immunization from infection. Therefore, how to resolve these problems of these vaccines is important for brucellosis prevention.BP26 is an important diagnostic antigen for Brucella. It is extensively used in Brucella diagnosis. BP26 is a periplasmic protein, and not only play no roles in virulence, but also it possess good antigenity. These characteristics make it a good candidate antigen for gene marker vaccine development. Deletion of this antigen can never affect the virulence, but provide a means for differentiation.So, in the present study, we planed to modify the live attenuated strain by deleting the bp26 gene, mutant of Brucella abortus named S19-â–³26 was successfully constructed by replacing the bp26 gene of attenuated S19 with kanamycin resistence gene. In infection experiment, Compared with S19, mutant S19-â–³26 maintains same safety and residual virulence in mice, at the same time mice infected with S19-â–³26 doesn't produced anti-bp26 antibodies, which would allow differentiation animals infected with S19-â–³26 from animals infected S19 and S544 by measuring the anti-bp26 antibodies by iELISA using rBP26 as antigen. In protection experiment, mutant S19-â–³26 possesses the same high protective ability compared with S19. Altogether these results indicate that Brucella abortus S19-â–³26 might be a promising vaccine strain in preventing, monitoring, cleaning brucellosis.