Volunteers will be screened for eligibility within 60 days prior to enrollment. Screening will include obtaining informed consent prior to any study procedure. This will be followed by medical history, physical examination, review of current medications, blood samples for safety labs (WBC, Hct, Hgb, platelet count; chemistry panel; screening for HIV, HLA-B27, HBV, and HCV); urine pregnancy testing for females. Stool will be tested for infection.