Phase 1 meCS6 + LT(R192G) Vaccine Study

The Phase 1 section of this study is a randomized double blind trial in which a total of 60 subjects (minimum of 52 allowable) will receive on of two oral vaccine doses according to the following chart: Group Subset N CS6(Encapsulated) LT(R192G) I A 15 0.95mg 2 micrograms II B 15 0.95mg -- III A 15 0.95mg 2 micrograms IV B 15 0.95mg -- \*minimum of 13 volunteers/group Volunteers in Group I will receive three immunizations (study days 0, 14, and 28) during the vaccine series. Volunteers in Group II will receive four immunizations (study days 0, 2, 4, and 6) during the vaccine series. The two groups will be vaccinated separately for logistical purposes. Blood and stool specimens will be collected at intervals to examine systemic and mucosal vaccine antigen-specific immune responses. Vaccine safety will be actively evaluated during vaccination and for 4 weeks following the final vaccine dose.