 Participants in Groups 1, 2, or 5 may decline to be in the leukapheresis group at any time and will be given the option of continuing in the blood draw group or withdrawing completely from the study. If specimens are not obtained for any reason at any visit, participants in Groups 1, 2, or 5 will default to either Group 3 or Group 4. Antiretroviral medications will not be provided by this study. 