Preparation of two Novel Staphylococcus- aureus Capsular Polysaccharide 5 and 8-Recombinant Protein Immunoconjugates

Background and Obgectives: Staphylococcus aureus (S. aureus) is one of the most common pathogens in the hospital and the community. The emergence of broad-spectrum antibiotic resistance in S. aureus has made the treatment process more difficult. Therefore, there is an urgent need for a vaccine to reduce susceptibility to the infection.Materials and Methods In this report, we describe a simple approach to conjugate S.aureus capsular polysaccharide 5 (CP5) and 8 (CP8) to a fusion protein (Hla-MntCSACOL0723) and investigation of its bioactivity. The conjugation was done by using adipic acid dihydrazide (ADH) and (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide) (EDAC). The groups of mice were immunized with conjugate vaccines, capsular polysaccharides and PBS. The functional activity of the vaccine candidates was evaluated by enzyme-linked immunosorbent assay (ELISA), opsonophagocytosis tests and determination of bacterial load Result: The results showed that the specific antisera raised against conjugate molecules were higher than those of the purified capsular polysaccharides during the study. The opsonic activity of the conjugate vaccines antisera was significantly higher than polysaccharides alone (58% vs. 16.3% at 1:2 dilution, P ˂ 0.05), so that the number of S. aureus COL strain cells decreased in both in vitro and in vivo conditions. Conclusion: In conclusion, the immunoconjugates could elicit high specific antibodies titer against capsular polysaccharides by improving its immunogenicity.