EXPRESSION OF CHOLERA-TOXIN EPITOPES INSERTED IN FLAGELLIN BY ATTENUATED SALMONELLA STRAINS

A novel antigen expression system has recently been developed by means of bacterial flagella, which are potent immunogens (Newton etal., Sci ence 244:70-72, 1989). Here we show the insertion of two epitopes from the cholera toxin B-subunit in Salmonella flagelin, CTP-1 (residues 8 -20) and CTP-3 (residues 50-64) (Jacob et al., Proc. Natl. Acad. Sci. USA 81:7893-7896, 1984). First, we inserted CTP-1 for expression as a flagellar fusion; a hybrid flagellin expressing CTP-1 and CTP-3 in the hypervariable region of the flagellin gene was also constructed in an attempt to increase the cholera toxin neutralization potential, as we ll as to address some practical questions concerning the flagellar ant igen expression system. The resulting constructs were non-motile altho ugh expression of chimeric flagellin was detected by immunoblotting an d electron microscopy. One of the constructs (CTP-1 + CTP-3) severely affected flagellin expression.