ABSTRACT
The colonization factor antigen I (CFA/I) is one of the most epidemiologically relevant enterotoxigenic Escherichia coli (ETEC) fimbrial adhesins, which 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 the CFA/I protein in vitro, as revealed by Western blot and immunofluorescence microscopy. Administration of a single pRECFA 100-microg dose induced a long-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 subclass was IgG2a, suggesting a Th-1-type immune response. A second dose with the same amount of purified DNA, given 2 weeks later, caused a booster effect on the immunoglobulin levels, but did not qualitatively alter the isotypes and subclasses of the induced antibody response. Immunization with different amounts of purified DNA and/or number of doses showed that maximal transient CFA/I-specific antibody levels could be obtained after two 100-microg doses of pRECFA given 2 weeks apart, but long-term antibody levels were similar.
Subject(s)
Antibodies, Bacterial/immunology , Antigens, Bacterial/immunology , Bacterial Proteins/immunology , DNA, Bacterial/immunology , Escherichia coli/immunology , Fimbriae Proteins , Plasmids/immunology , Animals , Antigens, Bacterial/genetics , Bacterial Proteins/genetics , Bacterial Vaccines/immunology , Cell Line , Cricetinae , Escherichia coli/genetics , Immunoglobulin Isotypes , Male , Mice , Mice, Inbred BALB C , Peptide Biosynthesis , Vaccination/methods , Vaccines, DNA/immunologyABSTRACT
Mice vaccinated with CL-14, a non-infective and non-pathogenic clone isolated from Trypanosoma cruzi CL strain, become protected against lethal challenge by infective trypomastigotes. It has been shown that animals infected with T. cruzi show polyclonal activation of B lymphocytes with an early production of several non-specific immunoglobulins. Vaccinated mice, however, have an early production of antigen-specific IgG1 and IgG2b. Considering the lack of infectivity of CL-14, our data strongly suggest a role for IgG1 and IgG2b in protection to T. cruzi.
