 This is a phase 1, randomized, placebo-controlled, dose-escalation study of CCR5mAb004 in HIV-1 seropositive individuals who are not receiving concurrent antiretroviral therapy. Subjects will be randomly assigned to receive a single intravenous IV infusion of one of four dose levels of CCR5mAb004 or matching placebo. A minimum of 10 subjects will be randomized to each cohort at a ratio of 4:1 active:placebo. A minimum of 40 and maximum of 60 subjects will be enrolled. This study will be conducted at up to 10 sites in the United States. 