Expression And Immunoprotection Of Outer Membrane Proteins Of Salmonella Paratyphi A

Typhoid is an acute systemic infection, leading to 22 million cases of infection (including Paratyphoid) and more than 200,000 deaths annually. Typhoid resulted from Salmonella serotype Typhi and Paratyphoid from Salmonella serotypes Paratyphi A, B and C. In last decade the incidence of paratyphoid presented a tendency of increase in China. Therefore, a safe, effective, convenient and low-cost vaccine is warranted for the prevention of paratyphoid A.Salmonella serotypes Paratyphi A was a group of Gram-negative bacilli without capsule, whose outer membrane proteins (OMPs) played an important role in pathogenesis and stimulation of immune response. Thus, OMPs became the focus for research and development of vaccine from pathogenic microorganisms.In this thesis the colonization, expression and immune protection of outer membrane proteins of Salmonella serotypes Paratyphi A were studied, with the aim to ascertain the probability of using the outer membrane proteins of Salmonella paratyphi A as protection antigens and even as* candidates for developing vaccine for prevention of paratyphoid.Salmonella paratyphi A CMCC 50973 was chosen as the model strain due to its stronger virulence. 11 OMPs including NmpC, MipA, OmpW, PagC, OmpX, PomP, OmpC, FadL, TolC, BtuB and Imp were used as target proteins. The gene sequences of those proteins were amplified by PCR and colonized into the expression plasmid of pET-32a. The recombinant plasmids were screened out from E. coli (DH5a) and thus the expression systems for OMPs were successfully constructed. Under the inducing of IPTG, large amount of 11 OMPs was all over expressed and used for purification. Those OMPs deposited into salt solution whereas dissolved into water, therefore we used the strategy of supersonic to realize the purification of target proteins. The immune protection of 11 OMPs was studied by the methods of injection of OMPs into abdominal cavity and then in vivo attacking with Salmonella paratyphi A CMCC 50503. Statistic results showed that the immune protection rate of PagC, OmpX, NmpC, FadL, TolC and BtuB were 100%, 100%, 95%, 75%, 75% and 70%, respectively.