Safety and Immunogenicity Study of an Intranasal Shigella Flexneri 2a Invaplex 50 Vaccine

This is an open-labeled dose escalating trial in which a total of 32 subjects (minimum of 24 allowable) will receive one of four intranasal Invaplex 50 vaccine doses according to the following chart: Test articles/dose Group / N\* / Invaplex 50 A / 8 / 10 micrograms B / 8 / 50 micrograms C / 8 / 240 micrograms D / 8 / 480 micrograms \*minimum of 6 volunteers/group An interval no less than 7 days following the third (and final) dose (total of 35 days between initial dose at the lower dose level and the next initial dose at the next higher dose level) will separate volunteer groups receiving different doses. All volunteers will receive three immunizations. The first dosing time point is Day 0, the second is Day 14 (+- one day), and the third is Day 28 (+- 2 days). Blood and stool specimens will be collected at intervals to examine systemic and mucosal vaccine antigen-specific immune responses. Vaccine safety will be actively monitored during vaccination and for 28 days following the third vaccination dose.