Potencial do polissacarídeo O26 para ser utilizado como antígeno em formulações vacinais contra a-EPEC e STEC

Abstract

According to the World Health Organization, diarrheal diseases are the second leading cause of mortality in the world in children under 5 years of age, with diarrheagenic Escherichia coli being the main etiological agent of bacterial origin. This group of E. coli is also responsible for outbreaks of bloody diarrhea and hemolytic uremic syndrome (HUS) in developed countries. Among the main groups of diarrheagenic E. coli are the strains belonging to serogroup O26 that can be categorized as EPEC (enteropathogenic E. coli) and STEC (shiga toxin producing E. coli). Currently, the best way to combat these pathogens is to develop a vaccine that is effective against both categories belonging to serogroup O26. Faced with this problem, this study aimed to determine the potential of the O26 polysaccharide, present in EPEC and STEC strains, to be used as a target antigen in vaccine formulations against these pathogens. For this, we used two different strains of serotype O26:H11, one from the EPEC category and the other from the STEC category. Being EPEC, capsulated bacteria, we determined the ability of anti-O26 antibodies to recognize capsulated and non-encapsulated bacteria. We also verified the ability of these antibodies to recognize bacteria in the presence of biofilm. Finally, we determined the ability of anti-O26 antibodies to increase EPEC phagocytosis by macrophages and inhibit the adhesion of these pathogens to epithelial cells. The results obtained by the ELISA technique showed that the level of recognition of biofilm-forming EPEC by anti-O26 antibodies was equivalent to the recognition of non-biofilm-producing STEC. The results also showed that the antibodies helped macrophages (J774A.1) in the phagocytosis of EPEC and were able to inhibit the adhesion of these bacteria to epithelial cells. In summary, the results indicate that the O26 polysaccharide is a good antigen candidate to be used in vaccine formulations against all E. coli strains belonging to the O26 serogroup, regardless of their virulence mechanism.