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Expression of cholera toxin epitopes inserted in flagellin by attenuated Salmonella strains

Julia Raquel Acero-Reyes; Salete M.C. Newton

Laboratório de Genética, Departamento de Microbiologia, Instituto de Ciências Biomédicas II, USP. Avenida Lineu Prestes 1374, Cidade Universitária, 05508-900 São Paulo, SP, Brasil. Send correspondence to J.R.A.-R.

ABSTRACT

A novel antigen expression system has recently been developed by means of bacterial flagella, which are potent immunogens (Newton et al., Science 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 well as to address some practical questions concerning the flagellar antigen expression system. The resulting constructs were non-motile although expression of chimeric flagellin was detected by immunoblotting and electron microscopy. Orné of the constructs (CTP-1 + CTP-3) severely affected flagellin expression.

Keywords: cholera toxin; epitopes; flagellin;Salmonella.

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