A universal polysaccharide conjugated vaccine against O111 E. coli.

E. coli O111 strains are responsible for outbreaks of blood diarrhea and hemolytic uremic syndrome throughout the world. Because of their phenotypic variability, the development of a vaccine against these strains which targets an antigen that is common to all of them is quite a challenge. Previous results have indicated, however, that O111 LPS is such a candidate, but its toxicity makes LPS forbidden for human use. To overcome this problem, O111 polysaccharides were conjugated either to cytochrome C or to EtxB (a recombinant B subunit of LT) as carrier proteins. The O111-cytochrome C conjugate was incorporated in silica SBA-15 nanoparticles and administered subcutaneously in rabbits, while the O111-EtxB conjugate was incorporated in Vaxcine(TM), an oil-based delivery system, and administered orally in mice. The results showed that one year post-vaccination, the conjugate incorporated in silica SBA-15 generated antibodies in rabbits able to inhibit the adhesion of all categories of O111 E. coli to epithelial cells. Importantly, mice immunized orally with the O111-EtxB conjugate in Vaxcine(TM) generated systemic and mucosal humoral responses against all categories of O111 E. coli as well as antibodies able to inhibit the toxic effect of LT in vitro. In summary, the results obtained by using 2 different approaches indicate that a vaccine that targets the O111 antigen has the potential to prevent diarrhea induced by O111 E. coli strains regardless their mechanism of virulence. They also suggest that a conjugated vaccine that uses EtxB as a carrier protein has potential to combat diarrhea induced by ETEC.

Lipopolysaccharide as an Antigen Target for the Formulation of a Universal Vaccine against Escherichia coli O111 Strains

A promising approach to developing a vaccine against O111 strains of diarrheagenic Escherichia coli thatexhibit different mechanisms of virulence is to target either the core or the polysaccharide chain (O antigen)of their lipopolysaccharide (LPS). However, due to structural variations found in both these LPS components,to use them as antigen targets for vaccination, it is necessary to formulate a vaccine able to induce a humoralimmune response that can recognize all different variants found in E. coli O111 strains. In this study, it was demonstrated that, despite differences in composition of oligosaccharide repeat units between O111ab and O111ac LPS subtypes, antibodies against one O111 subtype can recognize and inhibit the adhesion to human epithelial cells of all categories of O111 E. coli(enteropathogenic E. coli [EPEC], enterohemorrhagic E. coli [EHEC], and enteroaggregative E. coli [EAEC]) strains regardless of the nature of their flagellar antigens, mechanisms of virulence, or O111 polysaccharide subtypes. These antibodies were also able to increase the clearance of different strains of O111 E. coli by macrophages. PCR analyses of the pathways involved in O111 LPS core biosynthesis showed that all EAEC strains have core type R2, whereas typical EPEC and EHEC havecore type R3. In contrast, atypical EPEC strains have core types R2 and R3. In summary, the results presentedherein indicate that the O111 polysaccharide and LPS core types R2 and R3 are antigen targets for panspecific immunotherapy against all categories of O111 E. coli.

Lipopolysaccharide as an antigen target for the formulation of a universal vaccine against Escherichia coli O111 strains.

A promising approach to developing a vaccine against O111 strains of diarrheagenic Escherichia coli that exhibit different mechanisms of virulence is to target either the core or the polysaccharide chain (O antigen) of their lipopolysaccharide (LPS). However, due to structural variations found in both these LPS components, to use them as antigen targets for vaccination, it is necessary to formulate a vaccine able to induce a humoral immune response that can recognize all different variants found in E. coli O111 strains. In this study, it was demonstrated that, despite differences in composition of oligosaccharide repeat units between O111ab and O111ac LPS subtypes, antibodies against one O111 subtype can recognize and inhibit the adhesion to human epithelial cells of all categories of O111 E. coli (enteropathogenic E. coli [EPEC], enterohemorrhagic E. coli [EHEC], and enteroaggregative E. coli [EAEC]) strains regardless of the nature of their flagellar antigens, mechanisms of virulence, or O111 polysaccharide subtypes. These antibodies were also able to increase the clearance of different strains of O111 E. coli by macrophages. PCR analyses of the pathways involved in O111 LPS core biosynthesis showed that all EAEC strains have core type R2, whereas typical EPEC and EHEC have core type R3. In contrast, atypical EPEC strains have core types R2 and R3. In summary, the results presented herein indicate that the O111 polysaccharide and LPS core types R2 and R3 are antigen targets for panspecific immunotherapy against all categories of O111 E. coli.