Immunogenicity of Vibrio cholerae O1 Fimbriae in Animal and Human Cholera

Abstract

Parenteral immunization with either formalin-fixed whole cells of the fimbriate Bgdl7 strain or purified fimbriae protected against Vibrio cholerae 01 infection in rabbits, independent of biotype and serotype. Parenteral immunization of adult rabbits with purified fimbriae prior to V. cholerae 01 challenge resulted in a reduction of 2 to 3 orders of magnitude in the number of bacteria recovered from the small intestines of immunized rabbits in comparison to non-immunized controls. IgG and IgA antibodies against fimbrillin of V. cholerae 01 were detected in the convalescent sera of patients with cholera; however, little fimbrial antigen was detected in the commercially available cholera vaccines when examined by polyclonal and monoclonal antibodies against fimbriae. These data suggest that fimbrial hemagglutinin is a major adhesin of V. cholerae 01 and that parenteral immunization with fimbriae generates a specific immune response in the gut that may serve as one means of mitigating subsequent V. cholerae 01 gut infection.Key words: Cholera, Fimbriae, Vaccine Cholera is an acute diarrheal disease that is caused by the Gram-negative bacillus Vibrio cholerae 01. V. cholerae 01 infects via uptake of contaminated water and foods and preferentially colonizes the upper small intestine.Fimbriae of V. cholerae 01 consist of cell-associated hemagglutinin that is proposed to be one of the major adhesins mediating the interaction of V. cholerae 01 and human epithelial cells in the small intestine (1). Passive protection tests with anti-mannose-binding hemagglutinin pili antibodies (polyclonal and monoclonal) have been proven effective in protection against experimental cholera caused by El Tor vibrios in infant mouse and in rabbit intestinal loop models (7): but to date, there has been no correlation between serum antibody titers to known antigens purified from V. cholerae 01 and clinical protection. Naturally occurring V. cholerae 01 infection confers longlasting protection against reinfection, but such effective V. cholerae 01 antigens remain to be elucidated.Experimentally infecting rabbits with V. cholerae 01 using the ligated ileal loop test has shown that the bacteria are associated with small intestinal epithelial cells (4,5,8). Therefore, small intestinal infection of rabbits may be used to analyze parameters of immunity that interfere with the persistence of V. cholerae 01 at the intestinal epithelium. As previously reported (2, 3), fimbriate V. cholerae 01 strain of Bgd17 (classical biotype, Inaba serotype) was selectively induced and hydrophobic fimbriae were purified from the fimbriate strain.

The ABCs (Antibody, B Cells, and Carbohydrate Epitopes) of Cholera Immunity: Considerations for an Improved Vaccine

“…The mouse model does however provide information about the potential protective efficacy of antibodies to a particular V. cholerae antigen. Antibodies from several species (mouse, rabbit, and human) of multiple isotypes (IgM, IgA, IgG1, IgG3) specific for multiple V. cholerae antigens (LPS, TcpA, TcpF, fimbriae) are protective in animal models of cholera (43,64,123,230). If protective antigens can be identified, it is clearly possible to manipulate the form of the antigen, the adjuvant, or the route of inoculation to induce the antibody isotype required for protection of humans.…”

Development of Hyperfimbriated Strains of Vibrio cholerne O1

“…Vaccines prepared either from purified fimbriae or fimbriated whole cells offer protection against challenge irrespective of biotype and serotype under experimental conditions when given orally or parenterally (9,14). The number of reports addressing the role of fimbriae of V cholerae O1 in adherence is negligible.…”

“…2b). Anti-pili monoclonal antiserum was developed against purified pili from strain BgdI7 by Dr. S. Nakamura (9). The prepilin hand is shown at 18.1 kDa.…”

“…These peptides are removed by prepilin peptidase between an invariant glycine residue and a phenylalanine (or methionine) residue prior to assembly of the fimbrillin to fimbriae (24). The fimbriae of V cholerae O1 were shown to be immunogenic and protective in animal and human cholera (1,9,14,18). When given orally, the fimbrial vaccine elicited a specific antibody not only in the small intesine, but also in the peripheral blood serum (1,14).…”

Immunogenicity and protective role of an IgA reactive 31-kDa antigen of Vibrio cholerae O139

“…Although most of these are directed against the LPS, antibodies against protein antigens also exist and have been the subject of investigation. IgA antibodies to MSHA and OMPs have been reported to appear in the sera of volunteers and cholera patients [14,17,18].…”