Vaccine-elicited immune responses prevent clinical AIDS in SHIV89.6P-infected rhesus monkeys

Accumulating evidence has demonstrated the importance of cytotoxic T lympho cytes (CTLs) and helper T lymphocytes in controlling HIV-1 replication. We have elicited immune responses in rhesus monkeys utilizing DNA vaccines aug mented by the administration of IL-2/Ig, a fusion protein consisting of int erleukin-2 and the Fc portion of IgG2. These vaccine-elicited immune respon ses did not prevent infection following a high-dose intravenous challenge w ith SHIV89.6P but did control viremia to nearly undetectable levels and pre vented immunodeficiency and clinical disease. In contrast, control monkeys developed high levels of viremia, and exhibited a rapid loss of CD4(+) T ce lls, significant clinical disease progression, and death in half of the ani mals by day 140 following challenge. Vaccine approaches that elicit immune responses capable of reducing plasma viral loads, but not capable of induci ng sterilizing immunity, may still provide substantial clinical benefits. ( C) 2001 Elsevier Science B.V. All rights reserved.