II. To assess the effect of MK-3475 (pembrolizumab) on circulating HIV and the HIV viral reservoir in patients on effective combination anti-retroviral therapy (cART), as measured by plasma HIV single copy ribonucleic acid (RNA), cluster of differentiation (CD)4+ T-cell associated HIV unspliced RNA, CD4+ T-cell associated integrated HIV deoxyribonucleic acid (DNA) provirus, ratio of HIV unspliced RNA/DNA, "Tat/Rev induced limiting dilution assay" (TILDA), and phylogenetic analysis of HIV-1 molecular evolution.