Recent progress in cholera vaccination.

Cholera disease remains an important cause of morbidity and mortality in the third world. The parenteral cholera vaccine actually used offers only a 50% protection during 6 months. As Vibrio cholerae and its toxin don't cross the gut wall, the aim of new vaccines is to prevent the colonization and growth of the vibrio in the jejuno-ileum and to inhibit the fixation of cholera toxin (CT) on its enterocyte membrane receptor. This can be afforded by stimulation of the gut local immune system mainly represented by secretory IgA antibodies (Abs). New vaccines should comprise both bacterial and CT antigens and must be given by the oral route to induce the production of specific secretory IgA Abs in the gut. Four different ways are actually under study to produce an oral cholera vaccine. 1. Combination of CT-B subunit and killed vibrios. 2. Live recombinant Vibrio cholerae in which the CT coding gene has been deleted. 3. Synthetic peptides reproducing some immunodominant CT-epitopes. 4. Manipulation of the idiotypic network to induce the production of Abs mimicking CT-epitopes. This paper reviews the actual developments and advantages of these four approaches.