The vaccine is given as a nose spray. Volunteers will receive a 3-dose vaccination with doses spaced two weeks apart. Volunteers will be assigned to a vaccination group based on their order of enrollment with consideration of their availability to complete the necessary vaccinations and follow-up visits.

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.

Inclusion Criteria:

• Be in very good health.

Exclusion Criteria:

• Smoker, or have stopped smoking less than one year ago
• Pregnant
• History of chronic illnesses, such as: asthma, chronic sinusitis, or chronic seasonal allergies (such as hay fever)
• Received a vaccination for Shigella or exposure to Shigella bacteria in a research study or through work in a laboratory
• Positive for HIV, hepatitis B, and hepatitis C by blood test
• Using anti-diarrheal, anti-constipation, or antacid medications on a regular basis