4. Have a medical condition that, in the study physician's judgment, may interfere with safe study participation for the individual study candidate. Because medical conditions may differ in terms of safe participation on an individual basis, this criterion must be based on a physician's determination after a medical history, exam, and lab tests and may also involve consultation with a study candidate's primacy care physician. Some examples of medical conditions that may be exclusionary for a particular individual, however include active tuberculosis, unstable and/or significant cardiovascular or liver disease, unstable diabetes (i.e., glycosylated hemoglobin A1C of 12%), uncontrolled HIV infection, altered renal function (serum creatinine males and females:>3x upper limit of normal) or clinically significant elevated liver enzymes (ALT or AST greater than 3x the upper limit of normal)