Antibody response in mice immunized with a plasmid DNA encoding the colonization factor antigen I of enterotoxigenic Escherichia coli

The colonization factor antigen I (CFA/I) is one of the most epidemiologica lly relevant enterotoxigenic Escherichia coli (ETEC) fimbrial adhesins, whi ch mediates the binding to human small intestine epithelium. A recombinant eukaryotic expression plasmid, pRECFA, encoding the CFA/I protein fused to the glycoprotein D of herpes simplex type 1 virus, was used to generate an antibody response in a murine model following intramuscular inoculation of purified DNA. Eukaryotic cells (BHK-21) transfected with pRECFA expressed t he CFA/I protein in vitro, as revealed by Western blot and immunofluorescen ce microscopy, Administration of a single pRECFA 100-mu g dose induced a lo ng-term CFA/I-specific antibody response in BALB/c mice composed mainly of IgG and, to a lesser extent, IgA isotypes. The major CFA/I-specific IgG sub class was IgG2a, suggesting a Th-l-type immune response. A second dose with the same amount of purified DNA, given 2 weeks later, caused a booster eff ect on the immunoglobulin levels, but did not qualitatively alter the isoty pes and subclasses of the induced antibody response. Immunization with diff erent amounts of purified DNA and/or number of doses showed that maximal tr ansient CFA/I-specific antibody levels could be obtained after two 100-mu g doses of pRECFA given 2 weeks apart, but long-term antibody levels were si milar. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B,V. All rights reserved.