Study On Purification And Immunologic Effect Of 42KD Protein From GBS

Group B Streptococcus (GBS) have emerged as a major cause of infections including pneumonia, meningitis and sepsis in the newborn. Not only polysaccharide vaccine usually bring inferior immunocompetence but also polysaccharide is prone to be degraded, which limited the extensive application of polysaccharide vaccine. Though streptococcus polysaccharide-protein conjugates vaccine overcomes disadvantage of the polysaccharide vaccine, it did not solve the limit of serotype. At the same time, a single carrier protein in conjugate vaccine did not provide enough carrier effect. The toxicity and complication brought with the preparation are unavoidable if we increase the quantity of the carrier protein. Therefore, many scholar look for a vaccine on the base of surface protein which can elicit protetive immunity.In this experimentation, a one-step chromatography for purification of 42KD protein from Streptococcus serotype â…¢ was used, and resulted in a preparation with the recovery of 8%. The purification of the protein is 100%, and its point isoelectric (pI) is 6.6. Its property may be a glycoprotein. The findings from experimentation suggests this proteins locating on surface of bacteria and being released out as well.Antibody response was evaluated in mice immunizd by 42K.D protein with different immunization dose and by the different immunization procedure. The highest titer of antibody against 42KD protein was 1:24576. Which indicated that 42KD protein has good immunogenicity. After immunizing the mice in the optimum procedure, we challenge the mice in Intradermal with streptococcus to observe the active and passive protection The immunity exponent of NIH mice is 100 in test group and infant mice is 40,which indicates that the quantity of bacteria resisted in test groups is larger than those in negative control when they are infected. The survival ratio of adult mice achieve 100% with 1LD₅₀ and 10LD₅₀ ,the negativecontrol is 50% and 37.5%. In protective experimentation of passive immunity ,the survival ratio of infant mice achieve 100% with 1LD50, whereas the negative control is only 50% , indicating that the survival ratio of infant mice was larger than negative control . The data suggests that 42KD protein may elicit protective immunity to adult and infant mice. Through protecting test with different immunizing doses, the findings indicated that protecting capability is relation to the titer of IgG specific antibody .In experimentation of cross protection against pneumococcal, Pn6B: CMCC 31492 and Pnl9F: CMCC 31699 were used, It was found that 42KD protein can not elicit cross protective against pneumococcal.