Biotherapeutic Amelioration of Enteric Infection and Colon Cancer using Specific Probiotics and Prebiotics

Abstract

Enteric diseases such as colon cancer and enteric infections are a major threat to the society. Colon cancer accounts for the fourth most common cause of death and the third most common cancer affecting the people worldwide. In the present research, probiotic strains have been isolated from human gut and screened for its biosafety aspects and probiotic characteristics to prevent enteric infection by Salmonella enterica subsp. enterica serovar Typhimurium. The efficacy of the screened strains was determined by using simulated colonic model fermenting insoluble and non-digestible fibres from the food grains after oro-gastrointestinal digestion. The isolated strains could produce multiple bacteriocins, vitamins like folates and riboflavin and short chain fatty acids. Their efficacy was also tested in Drosophila model infected with Salmonella Typhimurium and was found to be effective in both prophylactic and therapeutic mode of treatment with the isolated probiotic strains. The probiotic strains enhanced the survival of adult Drosophila under oxidative stress and improved the total antioxidant status of the fly. The isolated probiotic strains thus showed prospectus to be used as live biotherapeutic product for the prevention and treatment of enteric infection by Salmonella Typhimurium. A prebiotic based drug delivery system was developed by conjugating ferulic acid (FA) to fructo-oligosaccharide (FOS) increasing the bioavailability of FA in the intestine. Two types ofconjugates were synthesized: FA FOS I water insoluble self-assembled microparticles and FA FOS II water soluble conjugate. Both showed anti-cancer activity, cell cycle arrest and apoptosis in-vitro with high selectivity towards cancer cells. The FA FOS II acted as a pro drug which carried FA to the intestine and released them by the action of microbiota. This phenomenon increased the bioavailability of FA in the large intestine and increased the t1/2 of FA in the rat plasma from 30 min to 240 min, which suggests that the free FA is slowly and persistently released by the microbial action in the large intestine enabling controlled and sustained release of the payload (FA) at the target site (colon) and persistence in the plasma. The anticancer efficacy of FA FOS conjugates was tested in both xenograft mice model of colon cancer and in colitis induced colon cancer mice model. There was improvement in the antioxidant profile in the mice plasma and reduction in the inflammation of the intestine treated with FA FOS II evident from immunohistochemistry (IHC) profile of the mouse colon tissue. The FA FOS conjugate also positively modulated the gut microbiota by enhancing the beneficial population of bacteria Lachnospiraceae, Ruminococcaceae and reducing the potentially harmful population of the microbiota Bacteriodes and Prevotella. Both FA FOS I and FA FOS II increased the immune mediated tumour surveillance by enhancing the presence of helper T-cells and cytotoxic-T cells in the tumour microenvironment in the AOM DSS mediated colon cancer model.