Abstract
Recent data provide evidence that co-infection with human immunodeficiency virus type 1 (HIV-1) and human T lymphotropic virus type 2 (HTLV-2) delays progression to AIDS compared to isolated HIV-1 infection. These results were linked to expression of the HTLV-2 transcriptional activating gene known as Tax2. Preliminary studies in lymphocytic systems suggest that Tax2 is responsible for induction of CC-chemokines, which play a major role in innate immune responses against HIV-1. In this study, the effect of Tax2 on CC-chemokines (MIP-1α/CCL3, MIP-1β/CCL4, and RANTES/CCL5) in monocyte-derived macrophages (MDMs) was evaluated. An immortalized human monocytic cell line (U937) and donor-derived MDMs were used to evaluate these interactions. These cells were cultured in vitro, allowed to mature into macrophages for 14 d, and treated with Tax2 or Tax1 (the transcriptional activator of HTLV-1) at three concentrations (1, 10, and 100 pM) daily thereafter. Extracellular bacterial extract (EBE) lacking the vector and untreated samples served as controls. An additional group of donor-derived MDMs were transduced with an adenovirus vector that expressed either Tax2 or green fluorescent protein (GFP). Liposomal transfection agents alone were used as controls. Supernatants were collected from each sample on multiple days post-maturation and evaluated for MIP-1α, MIP-1β, and RANTES, by enzyme-linked immunosorbent assay. Analysis of variance and Tukey's Honestly Significant Difference tests were used to analyze the results. In all systems, cells exposed to either Tax2 or Tax1 expressed significantly (p<0.01) higher concentrations of CC-chemokines than controls. There was no significant difference in chemokine expression between Tax1-treated and Tax2-treated samples, between EBE-treated and EBE-untreated samples, or between GFP-transduced MDMs and controls. This suggests that HTLV-2 could alter innate immune responses in macrophagic reservoirs of HIV-1 in HIV-1/HTLV-2 co-infected individuals, and could guide the development of HIV-1 treatments.