This is a prospective, open-label, non-controlled, non-randomized, single center study of the effect of adding the antiretroviral Maraviroc to the antiretroviral treatment regimen (HAART)of patients who have achieved a sustained virologic response to HAART but have had a sub-adequate immunologic response to treatment. Patients who have had a full virologic response (as defined by HIV-1 viral loads of < 48 copies/mL) for 12 months or more are defined as having a sub-adequate immunologic response if their CD4 lymphocyte count has not gone above 500.