CHARACTERIZATION AND APPLICATION OF EXTRACELLULAR MOLECULES PRODUCED BY Salmonella typhi, ISOLATED FROM FISH Rastrelliger kanagurta

Aim: The research is aimed to isolate, characterize extracellular molecules from Salmonella typhi isolated from a fish, Rastrelliger kanagurta, to explore their potential to be used as vaccine candidates.

Methodology: Salmonella typhi strain isolated from marine fish, was grown in optimized medium for expression of Vi polysaccharide and Flagellin C protein. Expression of both the molecules is optimized and the molecules are characterized by NMR, SEM and HPLC.

Results: Salmonella typhi strain, isolated from a fish Rastrelliger kanagurta from Machilipatnam was observed to produce Polysaccharide (ViP) and Protein (Flagellin C). Polysaccharide (ViP) and FlagellinC were isolated and purified. The clean/refined polysaccharide from the current Salmonella isolate were put through analysis for the establishment of sugar moieties and also to understand rheology of extracellular molecules, SEM, NMR and HPLC analysis were performed. The HPLC profile confirms ~500 KD size of polysaccharide. The polysaccharide conforms to be virulence polysaccharide by NMR. The SDS PAGE results suggested the existence of the~50 kDa protein Flagellin C.

Conclusion: Different protein carriers (TT, CRM197 and DT) are used for producing conjugate vaccines, as a futuristic idea from the present work, ViP and FliC produced by the same organism can be used for preparation of a conjugate vaccine. This conjugate of ViP-FliC would elicit better immune response as both molecules will be originated from same organism, which would provide a homologous origin advantage.