End-stage liver disease is a common cause of non-AIDS-related mortality in HIV patients, despite effective anti-retroviral therapies (ARTs). HIV-1 infection causes gut CD4 depletion and is thought to contribute to increased gut permeability, bacterial translocation, and immune activation. Microbial products drain from the gut into the liver via the portal vein where Kupffer cells (KCs), the resident liver macrophage, clear translocated microbial products. As bacterial translocation is implicated in fibrogenesis in HIV patients through unclear mechanisms, we tested the hypothesis that HIV infection of KCs alters their response to LPS in a TLR4-dependent manner. We showed that HIV-1 productively infected KCs, enhanced cell-surface TLR4 and CD14 expression, and increased IL-6 and TNF-α expression, which was blocked by a small molecule TLR4 inhibitor. Our study demonstrated that HIV infection sensitizes KCs to the proinflammatory effects of LPS in a TLR4-dependent manner. These findings suggest that HIV-1-infected KCs and their dysregulated innate immune response to LPS may play a role in hepatic inflammation and fibrosis and represent a novel target for therapy.

Simian immunodeficiency virus (SIV)-specific CD8؉ T cells kill SIV-infected CD4 ؉ T cells in an major histocompatibility complex class I (MHC-I)-dependent manner. However, they are reportedly less efficient at killing SIV-infected macrophages. Since the viral accessory protein Nef has been shown to downregulate MHC-I molecules and enhance cytotoxic T lymphocyte (CTL) evasion in human immunodeficiency virus type 1 (HIV-1)-infected CD4؉ T cells, we examined whether Nef played a role in protecting SIV-infected macrophages from killing by SIV-specific CD8 ؉ T cells. To explore the role of Nef in CD8 ؉ T cell evasion, we compared the ability of freshly sorted SIV-specific CD8 ؉ T cells to readily suppress viral replication or eliminate CD4 ؉ T cells or monocyte-derived macrophages infected with SIV variants containing wild-type (WT) or mutated nef genes. As expected, SIVspecific CD8؉ T cells suppressed viral replication and eliminated the majority of SIV-infected CD4 ؉ T cells, and this killing was enhanced in CD4؉ T cells infected with the nef variants. However, macrophages infected with nef variants that disrupt MHC-I downregulation did not promote rapid killing by freshly isolated CD8 ؉ T cells. These results suggest that mechanisms other than Nef-mediated MHC-I downregulation govern the resistance of SIV-infected macrophages to CD8؉ T cell-mediated killing. This study has implications for viral persistence and suggests that macrophages may afford primate lentiviruses some degree of protection from immune surveillance. Macrophages may play an important role in human immunodeficiency virus type 1/simian immunodeficiency virus (HIV-1/SIV) pathogenesis. Infection of microglia and perivascular macrophages actively mediates entry of HIV-1 into the central nervous system (CNS), resulting in HIV-associated dementia, encephalitis, cognitive disorder, and peripheral neuropathy (1). Accumulating data suggest that tissue macrophages are an important reservoir of virus. Infection of rhesus macaques with a highly pathogenic hybrid simian-human immunodeficiency virus (SHIV) resulted in the rapid depletion of CD4 ϩ T cells such that macrophages were the principal reservoir that sustained high viral loads in the SHIV-infected animals (2). In another study, rhesus macaques depleted of CD4 ϩ T cells exhibited higher viral loads than nondepleted animals, and in situ staining performed on gut tissue revealed that macrophages were the primary source of viral replication (3). It has also been suggested that the level of monocyte turnover is responsible for disease progression in the macaque model of AIDS (4).Macrophages present unique obstacles to infection by primate lentiviruses. The nondividing status of terminally differentiated macrophages and low deoxynucleoside triphosphate (dNTP) levels have to be accommodated in order for primate lentiviruses to establish a productive infection (5, 6). Additionally, macrophages are resistant to the cytopathic effects of viral replication in comparison to the sensitivity of activated ...

Strategies aimed at eliminating persistent viral reservoirs from HIV-1-infected individuals have focused on CD4؉ T-cell reservoirs. However, very little attention has been given to approaches that could promote elimination of tissue macrophage reservoirs. HIV-1 infection of macrophages induces phosphorylation of colony-stimulating factor 1 receptor (CSF-1R), which confers resistance to apoptotic pathways driven by tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), thereby promoting viral persistence. In this study, we assessed whether CSF-1R antagonists (PLX647, PLX3397, and PLX5622) restored apoptotic sensitivity of HIV-1-infected macrophages in vitro. PLX647, PLX3397, and PLX5622 at clinically relevant concentrations blocked the activation of CSF-1R and reduced the viability of infected macrophages, as well as the extent of viral replication. Our data show that strategies targeting monocyte colony-stimulating factor (MCSF) signaling could be used to promote elimination of HIV-1-infected myeloid cells and to contribute to the elimination of persistent viral reservoirs. IMPORTANCEAs the HIV/AIDS research field explores approaches to eliminate HIV-1 in individuals on suppressive antiviral therapy, those approaches will need to eliminate both CD4 ؉ T-cell and myeloid cell reservoirs. Most of the attention has focused on CD4 ؉ Tcell reservoirs, and scant attention has been paid to myeloid cell reservoirs. The distinct nature of the infection in myeloid cells versus CD4؉ T cells will likely dictate different approaches in order to achieve their elimination. For CD4 ؉ T cells, most strategies focus on promoting virus reactivation to promote immune-mediated clearance and/or elimination by viral cytopathicity. Macrophages resist viral cytopathic effects and CD8؉ T-cell killing. Therefore, we have explored clearance strategies that render macrophages sensitive to viral cytopathicity. This research helps inform the design of strategies to promote clearance of the macrophage reservoir in infected individuals on suppressive antiviral therapy. Macrophages are permissive to infection by primate lentiviruses, including human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV) (1-3); have a prolonged life span (4, 5); and are widely distributed throughout the body in tissues like the lymph nodes (6), gut (7-9), central nervous system (10), and lung (11). Because macrophages are resistant to viral cytopathic effects, they have the potential to act as a viral reservoir in HIV-1-infected individuals on suppressive antiretroviral therapy (ART) (1, 12-17). Furthermore, infected macrophages harbor infectious HIV-1 particles in stable intracellular virus-containing compartments (VCCs) that are connected to the plasma membrane (18). These VCCs protect the archived virions from antibody-mediated neutralization (19) while enabling infection in trans at virological synapses with nearby T cells (13,20). These synapses promote cell-to-cell transmission and a high multiplicity of infect...

BackgroundResistance to the fusion inhibitor enfuvirtide (ENF) is achieved by changes in the gp41 subunit of the HIV envelope glycoprotein (Env). Specific ENF-associated mutational pathways correlate with immunological recovery, even after virological failure, suggesting that the acquisition of ENF resistance alters gp41 pathogenicity. To test this hypothesis, we have characterized the expression, fusion capability, induction of CD4+ T cell loss and single CD4+ T cell death of 48 gp41 proteins derived from three patients displaying different amino acids (N, T or I) at position 140 that developed a V38A mutation after ENF-based treatment.ResultsIn all cases, intra-patient comparison of Env isolated pre- or post-treatment showed comparable values of expression and fusogenic capacity. Furthermore, Env with either N or T at position 140 induced comparable losses of CD4+ T-cells, irrespective of the residue present at position 38. Conversely, Env acquiring the V38A mutation in a 140I background induced a significantly reduced loss of CD4+ T cells and lower single-cell death than did their baseline controls. No altered ability to induce single-cell death was observed in the other clones.ConclusionsOverall, primary gp41 proteins with both V38A and N140I changes showed a reduced ability to induce single cell death and deplete CD4+ T cells, despite maintaining fusion activity. The specificity of this phenotype highlights the relevance of the genetic context to the cytopathic capacity of Env and the role of ENF-resistance mutations in modulating viral pathogenicity in vivo, further supporting the hypothesis that gp41 is a critical mediator of HIV pathogenesis.