<qa>  What is the main reason for the safety evaluation?A 2 arm study involving a series of 3 triweekly doses of PRO 542. One arm will involve patients on a stable dose of anti-retroviral therapy and the other arm will consist of patients not receiving anti-retroviral therapy. Three patients will be enrolled in each arm followed by a safety evaluation. Following the safety evaluation, 3 more patients may be enrolled in each arm. After the first 12 patients, an additional 12 patients may be enrolled pending safety data. 