Biochemical and immunological characterization of an ETEC CFA/I adhesin cholera toxin B subunit chimera
PublisherPublic Library of Science
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AbstractSurface-expressed colonization factors and their subunits are promising candidates for inclusion into a multivalent vaccine targeting enterotoxigenic Escherichia coli (ETEC), a leading cause of acute bacterial diarrhea in developing regions. However, soluble antigens are often poorly immunogenic in the absence of an adjuvant. We show here that the serum immune response to CfaE, the adhesin of the ETEC colonization factor CFA/I, can be enhanced in BALB/c mice by immunization with a chimeric antigen containing CfaE and pentameric cholera toxin B subunit (CTB) of cholera toxin from Vibrio cholerae. We constructed this antigen by replacing the coding sequence for the A1 domain of the cholera toxin A subunit (CTA) with the sequence of donor strand complemented CfaE (dscCfaE) within the cholera toxin operon, resulting in a dscCfaE-CTA2 fusion. After expression, via non-covalent interactions between CTA2 and CTB, the fusion and CTB polypeptides assemble into a complex containing a single dscCfaE-CTA2 protein bound to pentameric CTB (dscCfaE-CTA2/CTB). This holotoxin-like chimera retained the GM1 ganglioside binding activity of CTB, as well as the ability of CfaE to mediate the agglutination of bovine red blood cells when adsorbed to polystyrene beads. When administered intranasally to mice, the presence of CTB in the chimera significantly increased the serum immune response to CfaE compared to dscCfaE alone, stimulating a response similar to that obtained with a matched admixture of dscCfaE and CTB. However, by the orogastric route, immunization with the chimera elicited a superior functional immune response compared to an equivalent admixture of dscCfaE and CTB, supporting further investigation of the chimera as an ETEC vaccine candidate.
SponsorsThis research was supported by the U.S. Army Military Infectious Diseases Research Program Work Unit Number 6000.RAD1.DA2. A0307 and NIH Grant UO1 AI070638 to SJS, NIH Grant R01 AI031940 to the University of Colorado School of Medicine for RKH as Principal Investigator, and by the Henry M. Jackson Foundation for the Advancement of Military Medicine.
Keywordcolonization factor CFA/I
cholera toxin B
Enterotoxigenic Escherichia coli
Identifier to cite or link to this itemhttps://www.scopus.com/inward/record.uri?eid=2-s2.0-85081966563&doi=10.1371%2fjournal.pone.0230138&partnerID=40&md5=7606bf3cba65117ee0f969cd13f12e75; http://hdl.handle.net/10713/12473