The goal of this proposal is to determine the effect of maraviroc when it has been a part of the antiretroviral (ART) regimen given immediately after allogeneic hematopoietic cell transplant (allo-HCT) for HIV-1 infected participants who have a hematopoietic malignancy or other underlying disorder requiring an allogeneic transplant. Maraviroc has been given in practice to alleviate symptoms of graft vs. host disease (GvHD). Given its mechanism of action, it may also have an effect on the reservoir size of HIV-1 in infected patients. This study will inform potential future studies, evaluating the effect of this approach on the incidence and severity of GvHD, and determining its effect on HIV-1 reservoir.