Production of antitoxic immunity by live oral cholera vaccine.

Present knowledge about the extent of antitoxic immunity produced by cholera vaccination is meagre. Kasai and Burrows (J. Infect. Diseases 116:606, 1966) reported that the parenteral injection of killed vaccine increases the antitoxin titer of rabbit sera. They also showed that patients recovering from cholera develop antitoxic activity in their sera. Bhattacharya and Mukerjee (unpublished data) observed that case strains of Vibrio eltor and V. cholerae multiplied more slowly in the ligated intestinal loop of adult rabbits immunized intraintestinally with live cultures of a challenged with graded doses of toxin. Toxin was prepared by a method similar to that described by J. P. Craig (J. Bacteriol. 92:793, 1966). Strain 569B, a known toxinogenic V. cholerae strain, was grown for 3 hr in papain broth. A 2-ml amount of the culture was then added to a 500-ml conical flask containing 100 ml of Syncase medium (Finkelstein, Norris, and Dutta, J. Infect. Diseases 114:203, 1964). The flask was incubated at 30 C for 48 hr with constant shaking on a rotary shaker to provide maximal aeration. The contents were then centrifuged at 23,000 x g for