Candidate live oral cholera vaccine strains produce a new cholera toxin

Abstract

When six candidate live oral cholera vaccine strains deleted for one or all known virulence factors are tested for enterotoxin production, two of them caused fluid accumulation in the initial rabbit ileal loop (RIL) test, the others did so after 1-3 serial passages through RIL. Culture filtrates also showed similar secretory response. Ten times concentrated culture filtrates of these strains gave precipitin band against anti-new cholera toxin showing reaction of identity. These observations clearly indicate that vaccine strains produce a secretogen antigenically similar to the new cholera toxin.