CS3 fimbriae of enterotoxigenic Escherichia coli as chimeric expression carriers of heterologous antigenic determinants

CS3 fimbriae, which are the strong immunogen, are produced by human enterot oxigenic Escherichia coli (ETEC). The possibility of using CS3 as a carrier of foreign antigenic determinants was investigated. A SacII site sequence was inserted into the structural gene of CS3 subunit by site-specific mutag enesis based on analyzing and predicting the properties of the proteins. A recombinant strain expressing CS3/CTP3 hybrid fimbriae was constructed by i nserting the sequence encoding CTP3 into the SacII site created by directed mutagenesis in the structural gene of CS3 subunit and transforming the rec ombinant plasmid into the host of DHS alpha. The result of SDS-PAGE showed that the hybrid CS3/CTP3 molecules were the fusion proteins with molecular masses of about 18.5 ku. Inoculating mice orally and intraperitoneally show ed that both antibodies against CS3 and CTP3 were elicited. These results i ndicate that CS3 pill could be an exposure vector for heterologous antigeni c determinants and become a powerful tool for the development of oral vacci nes directed against mucosal pathogens.