PROTECTIVE IMMUNE RESPONSES TO ENTEROPATHOGENIC ESCHERICHIA COLI STRAIN WITH A NEW RECOMBINANT BACILLUS SUBTILIS VACCINE STRAINS

Wilson Barros Luiz (USP); Juliano Domiraci Paccez (USP); Luís Carlos de Souza Ferreira (USP)

Recombinant Bacillus subtilis strains have been successfully engineered to express heterologous antigens and elicit systemic and mucosal immune responses following oral administration of spores or vegetative cells to murine hosts as a potential vaccine delivery system. Intimins are outer membrane proteins expressed by enteric bacterial pathogens, such as enteropathogenic Escherichia coli (EPEC) and enteroheamorrhagic Escherichia coli (EHEC) strains, capable of inducing intestinal attachment-and-effacement (A/E) lesions of enterocytes. The intimin cell-binding domain is located within a 280-amino-acid (Int280) carboxy terminus. In this study we developed B. subtilis vaccine strains expressing beta intimin of some EPEC serotypes strains and evaluated their immunogenicity in mice following oral delivery of spores or vegetative cells. DBA/2 female mice immunized with the B. subtilis vaccine strains develop strong systemic (serum IgG) and secreted (fecal and milk sIgA) anti-intimin responses. Anti-intimin antibodies generated in vaccinated mice recognized the native protein expressed by different EPEC and EHEC strains. Anti-intimin antibodies detected in mice immunized with the recombinant B. subtilis strains interfered with tight binding and cytoskeletal organization changes and inhibited host cell binding of EPEC strains. Moreover, female mice immunized with the B. subtilis vaccine strains conferred passive protection to newborns challenged with a virulent Atypical EPEC strain and partial protection with Typical EPEC strain. The results further support the use of B. subtilis strains as a mucosal vaccine vehicle and add important knowledge regarding pathogenesis and vaccine development against EPEC and EHEC-associated diseases. Researsch supported by FAPESP and CNPq grants.