title: Construction of a non-toxigenic Escherichia coli oral vaccine strain expressing large amounts of CS6 and inducing strong intestinal and serum anti-CS6 antibody responses in mice.
abstract: Coli surface antigen 6 (CS6) is one of the most prevalent non-fimbrial colonization factors (CFs) of enterotoxigenic Escherichia coli (ETEC) bacteria, which are the most common cause of diarrhea among infants and children in developing countries. Since immune protection against ETEC is mainly mediated by locally produced IgA antibodies in the gut, much effort is focused on the development of an oral CF-based vaccine. Previous work has described the preparation of candidate E. coli vaccine strains expressing immunogenic amounts of fimbrial CF antigens such as CFA/I and CS2, which are retained after formalin treatment. However, attempts to generate E. coli expressing immunogenic amounts of CS6 and to preserve the immunological activity of the CS6 protein in a killed whole-cell vaccine have failed until now. Here we describe the construction of a recombinant non-toxigenic E. coli strain, with thyA as a non-antibiotic-based selection, which expresses large amounts of CS6 antigen on the bacterial surface, and show that phenol inactivation of the bacteria does not destroy the CS6 antigen properties. Oral immunization of mice with such phenol-killed CS6 over-expressing E. coli bacteria induced strong fecal and intestinal IgA and serum IgG+IgM antibody responses to CS6 that exceeded the responses induced by an ETEC reference strain naturally expressing CS6 and previously used as a vaccine strain. Our data indicate that the described phenol-inactivated non-toxigenic and CS6 over-expressing E. coli strain may be a useful component in an oral ETEC vaccine.
authors: University of Gothenburg Vaccine Research Institute, and WHO Collaborating Center for Research on Enterotoxigenic Escherichia coli, Department of Microbiology and Immunology, The Sahlgrenska Academy of University of Gothenburg, S-40530 Gothenburg, Sweden. Joshua.Tobias@microbio.gu.se
authors: Joshua
authors: J
authors: Tobias
authors: Ann-Mari
authors: AM
authors: Svennerholm
authors: Nils I A
authors: NI
authors: Carlin
authors: Michael
authors: M
authors: Lebens
authors: Jan
authors: J
authors: Holmgren
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000917:Antibody Formation; D000942:Antigens, Bacterial / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D004927:Escherichia coli Infections / Q000276:immunology* / Q000517:prevention & control; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D022361:Escherichia coli Vaccines / Q000276:immunology*; D005260:Female; D005557:Formaldehyde; D005822:Genetic Vectors; D018928:Immunity, Mucosal; D007070:Immunoglobulin A / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D007422:Intestines / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019800:Phenol
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; C098406:CS6 antigen, E coli; D029968:Escherichia coli Proteins; D022361:Escherichia coli Vaccines; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D005557:Formaldehyde; D019800:Phenol