Preparation And Preclinical Evaluation Of Experimental Group B Streptococcal Capsular Polysaccharide-protein Conjugate Vaccine

GBS are the prime cause of bacterial pneumononia and meningitis in newborns and peripartum maternal infections. In addition, recent reports have documented the importance of GBS as a cause of infection in adults with certain underlying medical condition. Vaccination with a capsular polysaccharide-protein conjugate might be an effective approach to the prevention of GBS infections.The type III strain GBS32325 was used for preparation of type III capsular polysaccharide. To investigate growth parameters that regulate expression of CPS by GBS type III, the type III strain GBS32325 was cultured in flasks with different fluid culture medium, searching for the optimum factors. Under such optimal factors, GBS was scaled up in 10L or 100L fermentor. The CPS concentration in fermentation was 652ug/mL, while the bacterial number was 2.4 X 109/mL after growth 5-6 hours in fermentor.Capsular polysaccharide was fractional concentrated from the fermentor culture supernatant by a concentration of 55% or 75% ethanol and purified. The purified type IIICPS contained <1% of protein, and <1% of nucleic acid. The recovery of these purified CPS were 0.021g/L and 0.042g/L, the Kav were 0.52, 0.68.The purified type IIICPS was conjugated to tetanus toxoid(TT) with EDAC, using ADH as a spacer. The yield rate as Kav<0.08 in conjugates were 20%and 70%.Mice were immunized with these conjugates or purified CPS by subcutaneous (s.c.) routes. Antibodies to type IIICPS were measured with ELISA. All of the CPS-protein conjugates were superior to unconjugated CPS in eliciting CPS-specific immune responses in serum. The findings indicates: TT as a carrier protein for GBS IIICPS could markedly improve the immune responses; the experimental GBS III CPS conjugates should be investigated to prevent GBS infections in human.