Randomized, controlled study of the safety and immunogenicity of Peru-15, a live attenuated oral vaccine candidate for cholera, in adult volunteers in Bangladesh
A live oral Vibrio cholerae O1 El Tor vaccine candidate, Peru-15, was studied for safety, immunogenicity, and excretion in phase 1 (inpatient) and phase 2 (outpatient) studies of Bangladeshi adults. A single dose of Peru-15 or placebo was given in standard bicarbonate and ascorbic acid buffer. Study treatment did not elicit any major adverse events in the volunteers, during either the inpatient or the outpatient phases, and there were no reports of diarrhoea. V. cholerae was isolated from the stool of only 1 volunteer and was found to be genetically identical to the vaccine strain. Vibriocidal antibody responses were seen in 30 (75%) of 40 vaccine recipients and in 3 (10%) of 30 placebo recipients. Peripheral blood immunoglobulin (Ig) A and IgM antibody-secreting cell responses to lipopolysaccharide were seen in the majority of vaccine recipients (response rate, 78%-88%). Seroconversion for lipopolysaccharide-specific IgA antibodies was seen in 88% of vaccine recipients. The response in vaccine recipients was significantly higher than that in placebo recipients, in all of the immunological assays. A lower immunological response against cholera toxin B subunit was detected. The safety and immunogenicity of this Peru-15 vaccine candidate indicates the usefulness of future studies in Bangladesh, where cholera is endemic.