Cholera toxin improves the F4(K88)-specific immune response following oral immunization of pigs with recombinant FaeG

• Published in: Veterinary immunology and immunopathology 2005-01, Vol.103 (1), p.21-29
• Main Authors: Verdonck, F., Snoeck, V., Goddeeris, B.M., Cox, E.
• Format: Article
• Language: English
• Subjects: Adhesins, Escherichia coli - immunology; Administration, Oral; Animals; Antibodies, Bacterial - blood; Antigens, Bacterial - immunology; Cholera toxin; Cholera Toxin - pharmacology; Enterotoxigenic Escherichia coli; Escherichia coli Proteins - immunology; Escherichia coli Vaccines - immunology; F4(K88) fimbriae; FaeG adhesin; Fimbriae Proteins - immunology; Immunization; Pig; Recombinant Proteins - immunology; Swine; Vaccines, Synthetic - immunology
• ISSN: 0165-2427; 1873-2534
• DOI: 10.1016/j.vetimm.2004.08.012

Oral immunization of both humans and animals with non-replicating soluble antigens often results in the induction of oral tolerance. However, receptor-dependent uptake of orally administered soluble antigens can lead to the induction of an antigen-specific immune response. Indeed, oral immunization of pigs with recombinant FaeG (rFaeG), the adhesin of the F4(K88) fimbriae of enterotoxigenic Escherichia coli (ETEC), induces an F4-specific humoral and cellular immune response. This response is accompanied with a reduction in the excretion of F4 + E. coli following challenge. To improve the immune response against F4, rFaeG was orally co-administered with the mucosal adjuvant cholera toxin (CT). Oral immunization of pigs with rFaeG and CT significantly improved the induction of an F4-specific humoral and cellular immune response and also significantly reduced the faecal F4 + E. coli excretion following F4 + ETEC challenge as compared to rFaeG-immunized pigs. Therefore, the present study demonstrates that CT can act in pigs as a mucosal adjuvant for antigens that bind to the intestinal epithelium by a CT-receptor-independent mechanism.