Induction of CC-Chemokines with Antiviral Function in Macrophages by the Human T Lymphotropic Virus Type 2 Transactivating Protein, Tax2

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 (MIP1a/CCL3, MIP-1b/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-1a, MIP-1b, 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.

Inhibition of HIV Type 1 Replication by Human T Lymphotropic Virus Types 1 and 2 Tax Proteinsin Vitro

“…10,11 Briefly, transformed BL21(DE3) strains of Escherichia coli with pET-Tax1 or pETTax2 were grown at 18°C under ampicillin selection and induced using isopropyl b-d-thiogalactopyranoside (IPTG, Sigma). Heat-inactivated Tax1 and Tax2 preparations or extracellular bacterial extract (ebe) without the Tax vectors were used as negative controls.…”

“…7 Recently we have shown that Tax2 has the potential to modify innate host immune responses through increasing lymphocyte viability, activating monocytes and PBMC production of CCchemokines (CCL3, CCL4, and CCL5), and downregulating the CCR5 receptor. 10,11 It is plausible that Tax2 could modify innate host responses during HIV-1/HTLV-2 coinfection, potentially by hampering the fusion and entry of the most commonly transmitted HIV-1 strains. In fact, in a study investigating whether HTLV-1 infection could modulate HIV-1 infection of surrounding cells, primary CD4…”

“…Recently, our group reported that Tax2 and Tax1 proteins induced the expression of three CC-chemokines with antiviral function MIP-1a/CCL3, MIP-1b/CCL4, and RANTES/CCL5 from peripheral blood mononuclear cells (PBMCs) and monocytes with the concomitant downregulation of CCR5, the HIV-1 entry coreceptor. 10,11 These results suggested that Tax2 and Tax1 could promote innate immunity in the extracellular environment during HTLV-2 and HTLV-1 infections via CC-chemokine ligands and receptors, and led us to hypothesize that Tax2 and Tax1 may directly or indirectly inhibit HIV-1 replication. In the present study, an in vitro cell culture system was established where HIV-1-infected PBMCs were treated with Tax2 or Tax1 proteins.…”

Human T cell leukaemia virus type 2 tax protein mediates CC-chemokine expression in peripheral blood mononuclear cells via the nuclear factor kappa B canonical pathway

“…Recently our group reported that extracellular Tax1 and Tax2 proteins induce the expression of macrophage inflammatory protein (MIP)-1α/CCL3, MIP-1β/CCL4 and regulated upon activation normal T cell expressed and secreted (RANTES)/CCL5 from peripheral blood mononuclear cells (PBMCs) and monocyte-derived macrophages (MDMs) [24,25] with the concomitant down-regulation of CCR5, the HIV-1 co-receptor [24]. Additionally Tax1 and Tax2 expressed via adenoviral vectors delivered into MDMs also induced the secretion of CC-chemokines [25].…”

“…Additionally Tax1 and Tax2 expressed via adenoviral vectors delivered into MDMs also induced the secretion of CC-chemokines [25]. CC-chemokines have been correlated with innate resistance to HIV-1 infection, decreased viral loads in individuals already infected and protection against disease progression to AIDS [26].…”