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pubmed:abstractText |
The fimbrial colonization factor antigen I (CFA/I) and coli surface antigen 4 (CS4) of enterotoxigenic Escherichia coli (ETEC) are antigenically different, but have closely related N-terminal amino acid sequences. We have studied the capacity of purified CFA/I and CS4 fimbriae respectively to prime and boost immune responses against the homologous and heterologous CFAs in parenterally immunized mice. Based on initial characterization of the kinetics of the primary and secondary CFA/l immune responses in serum as well as antibody-secreting cell (ASC) responses in spleen, two doses with different combinations of the purified CFAs were given 7 weeks apart. It was shown, using either assay, that CFA/l could both prime and boost immune responses against CS4, and, conversely, that CS4 could prime and boost immune responses against CFA/l. These findings suggest the presence of immunorecessive epitopes, or epitopes that are not surface-exposed on whole fimbriae, that are shared between CFA/l and CS4 and which can expand B-cell clones with specificity for heterologous fimbriae.
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