Abstract

Immunization of Mice with Lactobacillus casei Expressing a Beta-Intimin Fragment Reduces Intestinal Colonization by Citrobacter rodentium ▿ † P. C. D. Ferreira 1 , J. B. da Silva 1 , R. M. F. Piazza 3 , L. Eckmann 2 , P. L. Ho 1 and M. L. S. Oliveira 1 , * 1 Centro de Biotecnologia, Instituto Butantan, São Paulo, Brazil, and Programa de Pós-Graduação Interunidades em Biotecnologia USP/IPT/I, Butantan, ICB-USP, São Paulo, Brazil 2 Department of Medicine, University of California—San Diego, La Jolla, California 3 Laboratório de Bacteriologia, Instituto Butantan, São Paulo, Brazil ABSTRACT Enteropathogenic Escherichia coli (EPEC) is a common cause of diarrhea in children from developing countries. Intimate adhesion of the bacteria to intestinal cells occurs via binding of the adhesin intimin to the TIR receptor exposed on cell surfaces. Here, Lactobacillus casei expressing a fragment of β-intimin ( L. casei -Int cv ) was tested as mucosal vaccines in mice against intestinal colonization with the murine pathogen Citrobacter rodentium . Oral or sublingual immunization of C57BL/6 mice with L. casei -Int cv induced anti-Int cv IgA in feces but no IgG in sera. Conversely, anti-Int cv IgG was induced in the sera of mice after sublingual immunization with purified Int cv . All vaccines were able to decrease C. rodentium recovery from feces. However, this reduction was more evident and sustained over time in mice immunized with L. casei -Int cv by the sublingual route. These mice also displayed an increase in interleukin 6 (IL-6) and gamma interferon (IFN-γ) secretion by spleen cells 10 days after infection. Additionally, oral or sublingual immunization of C3H/HePas mice, which are highly susceptible to C. rodentium infection, with L. casei -Int cv induced anti-Int cv antibodies and significantly increased survival after challenge. Immunohistological analysis of colon sections revealed that C. rodentium was located in deep fractions of the tissue from C3H/HePas mice immunized with L. casei whereas superficial staining was observed in colon sections from mice immunized with L. casei -Int cv. The results indicate that vaccines composed of L. casei expressing intimin may represent a promising approach and that the C3H/HePas infection model with C. rodentium can be used to evaluate potential vaccines against EPEC.