Antigenicity and immunogenicity of fused B-subunit of heat labile toxin of Escherichia coli and colonization factor antigen I polyepitopes

• Linear B-cell epitopes were fused to ltb-(gly)5-cfaB(1-25).
• Sera of immunized rabbits reacted with solid-phase bound bacteria bearing CFA/I
• Sera failed to agglutinate or inhibit hemagglutination promoted by CFA/I+ strain
• Conformational changes due to CfaB polymerization reduced accessibility of epitopes

Linear B-cell epitopes (93AKEFEAAAL101 and 66PQLTDVLN73) of CfaB were genetically fused to ltb-(gly)5-cfaB(1-25). Sera of rabbits immunized with fusion proteins reacted strongly with solid-phase bound ETEC bacteria bearing CFA/I fimbriae. Sera failed to agglutinate or inhibit hemagglutination promoted by CFA/I-positive strain which may be due to solvent inaccessibility of epitope residues on intact fimbriae.