- Participants MUST receive appropriate care and treatment for HIV infection, including antiretroviral medications, when clinically indicated and should be under the care of a physician experienced in HIV management; participants will be eligible regardless of antiretroviral medication (including no antiretroviral medication) provided there is no intention to initiate therapy or the regimen has been stable for at least 4 weeks with no intention to change the regimen within 8 weeks following study entry; as study-specific (antiretroviral-based) strata fill, however, only participants who are receiving the therapies eligible for the remaining open strata will be accrued