Characterization of non-membrane-damaging cytotoxin of non-toxigenic Vibrio cholerae O1 and its relevance to disease

The non-membrane-damaging cytotoxin which causes dramatic cell rounding of cultured HeLa cells was purified to homogeneity from a clinical strain (WO5 ) of non-toxigenic Vibrio cholerae O1 Inaba belonging to the El Tor biotype . The purified protein has a denatured molecular weight of 35 kDa and a nat ive molecular weight of approximately 37 kDa indicating the monomeric natur e of the protein. The 15 N-terminal amino acid sequence of non-membrane-dam aging cytotoxin showed complete homology to the hemagglutinin protease prev iously purified and characterized from V. cholerae O1. Purified non membran e-damaging cytotoxin from V. choler ne O1 was immunologically and biochemic ally identical to that previously purified from V. cholerae O26. Non-membra ne-damaging cytotoxin was found to be enterotoxic in rabbit ileal loop assa y inducing accumulation of non-hemorrhagic fluid at 100 mu g and elicited a concentration dependent increase in short circuit current and tissue condu ctance of rabbit ileal mucosa mounted on Ussing chambers. A significant ser um immunoglobulin G response against non-membrane-damaging cytotoxin was el icited by patients infected with V. cholerae O139 but not with V. cholerae O1. These properties make non-membrane-damaging cytotoxin a potential virul ence factor of V. cholerae which should be taken into consideration while m aking live, attenuated recombinant vaccine strains against cholera. (C) 199 8 Federation of European Microbiological Societies. Published by Elsevier S cience B.V. All rights reserved.