Polymorphonuclear neutrophils (PMNs) are innate immune cells with properties that include rapid infiltration into sites of inflammation, intrinsic phagocytic and other antibacterial activity, and expression of Fc receptors (FcRs) allowing mediation of Ab-mediated effector mechanisms [11]

Polymorphonuclear neutrophils (PMNs) are innate immune cells with properties that include rapid infiltration into sites of inflammation, intrinsic phagocytic and other antibacterial activity, and expression of Fc receptors (FcRs) allowing mediation of Ab-mediated effector mechanisms [11]. also Setrobuvir (ANA-598) account for up to 90% of the infected cell burden [1]. Control of established HIV-1 infection is mediated predominantly by CD8+ cytotoxic T cells [2], but there is also evidence that natural killer cells (NKs) play a role [3C5]. NKs can effect HIV-1 infected cell killing either directly, or via antibody-dependent cellular cytotoxicity (ADCC [6,7]). Although the role of ADCC in the control of HIV-1 infection is unclear, it does appear to contribute to the protective effect of antibodies (Abs) [8]. The role of monocytes (MCs) is less well established. Recent reports have demonstrated MC killing of an HIV-1-infected T cell line via an ADCC mechanism [9,10]. However, the target cells used in these assays were a recombinant antigen-coated immortalized cell line rather than infected autologous primary cells, and the relative efficiency of killing compared to NKs was not revealed. Polymorphonuclear neutrophils (PMNs) are innate immune cells with properties that include rapid infiltration into sites of inflammation, Rabbit Polyclonal to Collagen III intrinsic phagocytic and other antibacterial activity, and expression of Fc receptors (FcRs) allowing mediation of Ab-mediated effector mechanisms [11]. Although PMNs are classically described as cells with activity against extracellular pathogens [12,13], they have antiviral activity and can reduce influenza virus infection in cell culture by ADCC-type effector mechanisms [14,15]. In addition, their function against HIV-1-infected cells has been proposed in the presence and absence of HIV-1-specific Abs [16,17]. The rapid recruitment of PMNs, and with somewhat delayed kinetics, MCs, to sites of inflammation mean that if these cells have antiviral activity then they may influence HIV-1 transmission and/or established viral replication [18]. Here we show that MCs have killing activity equivalent to NKs Setrobuvir (ANA-598) both in the absence and presence of HIV-1 specific Abs, and that PMNs can also kill HIV-1-infected T cells via an Ab-dependent mechanism. These results have important implications for the role of innate immune effector cells in the establishment and control of HIV-1 infection. Results Primary target and effector cells were isolated from PBMCs freshly obtained from seven normal healthy subjects and immediately prepared for the killing assay. Different cell subsets were isolated using magnetic bead-based negative selection, and purity assessed using flow cytometry and markers specific for the individual cell types: CD4+ T cell (CD3); NK (CD56); MC (CD14) and PMN (CD66b). Mean purity across seven experiments was as follows: CD3+CD4+ T cells = 99.4%, NKs = 98.7%, MCs = 92.5% and PMNs = 100% (Figure 1). Open in a separate window Figure 1 Purity of isolated target and effector cells.Isolated cells were stained with an appropriate single cell marker for identification. The percent positive populations (B) were assessed on live-gated cells (A): CD4+ T cell = CD3hi, NK = CD56dim, MC = CD14hi, PMN = CD66bhi. The killing assay was based upon that previously described [19]. Briefly, CD4+ T cells were stimulated for 72 h and subsequently magnetofected? with HIV-1BaL for 48 h, yielding an average infection across seven experiments of 54.8%. Non-viable infected CD4+ T cell targets were excluded from analysis by selective labeling with a dead cell stain. Autologous effectors were isolated and combined at an effector:target ratio of 10:1 in the presence or absence of heat-inactivated human serum for 1 h at 37oC, fixed, permeabilized, and stained for intracellular viral Gag. Target cell killing (HIV-1 infected CD4+ T cell elimination – ICE), was evaluated by quantifying the loss of Gag+ CD3+ T cells from the live cell gate compared Setrobuvir (ANA-598) to Gag+ T cell loss in the absence of effector cells (Figure 2). Open in a separate window Figure 2 Gating strategy for ICE, Assay.(A) Effector cells were labeled with the phenotypic marker mAbs shown and targets labeled with LIVE/DEAD? stain and mixed. Live CD4+ T cells (targets) were identified by gating on live cells negative for the effector label (NK, MC, or PMN-FITC). Cells were fixed and stained for p24 to determine the frequency of infected targets. (B) Elimination of HIV-1-infected cells. Representative data show % p24 positive cells for uninfected CD4+ T cells, infected CD4+ T cells, infected CD4+ T cells + PMN + HIV- (control) serum, and infected CD4+.