Enterotoxigenic Escherichia coli (ETEC) strains expressing only coli s
urface antigen 6 (CS6) have previously been isolated from patients wit
h diarrhea, but the immunogenicity of CS6 has not been established in
humans. We have detected CS6-specific immunoglobulin A responses in th
e feces and blood of patients convalescing from natural ETEC disease a
nd of volunteers given an oral ETEC vaccine.