Serum Antibodies Protect against Intraperitoneal Challenge with Enterotoxigenic Escherichia coli

Abstract EN

To assess whether anticolonization factor antigen I (CFA/I) fimbriae antibodies (Abs) from enterotoxigenic Escherichia coli (ETEC) can protect against various routes of challenge, BALB/c mice were immunized with a live attenuated Salmonella vaccine vector expressing CFA/I fimbriae.

Vaccinated mice elicited elevated systemic IgG and mucosal IgA Abs, unlike mice immunized with the empty Salmonella vector.

Mice were challenged with wild-type ETEC by the oral, intranasal (i.n.), and intraperitoneal (i.p.) routes.

Naïve mice did not succumb to oral challenge, but did to i.n.

challenge, as did immunized mice; however, vaccinated mice were protected against i.p.

ETEC challenge.

Two intramuscular (i.m.) immunizations with CFA/I fimbriae without adjuvant conferred 100% protection against i.p.

ETEC challenge, while a single 30 μg dose conferred 88% protection.

Bactericidal assays showed that ETEC is highly sensitive to anti-CFA/I sera.

These results suggest that parenteral immunization with purified CFA/I fimbriae can induce protective Abs and may represent an alternative method to elicit protective Abs for passive immunity to ETEC.