HIV-1 Trans-infection Research Articles

HIV-1 Induced Cell-to-Cell Fusion orSyncytium Formation.

HIV-1 cell-free infection has been thoroughly investigated; however, its relevance and importance in vitro are questionable. Cell-cell transmission is now thought to be the dominant mode of transmission within the host; however precise molecular details remain elusive. The considerable potency of cell-cell transmission hinges upon its ability to hijack and manipulate host immunological function to target uninfected cells, along with overcoming restriction factors and increasing the speed of latent pool formation. Another question of relevance is virus induced cell-cell fusion and how this process is regulated. How often HIV-1 induces the formation of syncytia? Is cell-cell function a potential process for HIV-1 transmission? These questions are discussed and reviewed together with a description of the most common ways of HIV-1 entry and transinfection.

Macrophage Migration Inhibitory Factor Restriction of HIV-1 Transinfection from Dendritic Cells to CD4+ T Cells through the Regulation of Autophagy

At mucosal surfaces, immature resident Dendritic Cells (DC) and Langerhans Cells (LC) are among the first cell types to encounter and to be infected by HIV-1 virus (Ahmed et al., 2015, Pena-Cruz et al., 2018). LC and myeloid DCs can restrict early HIV-1 infection through active mechanisms of viral entry restriction due to their primary autophagic functions (Blanchet et al., 2010). During early-stage infection, the recognition of virus by DCs results in the release of cytokines: Interferon-stimulated genes and TGF-β have shown their contribution in the control of HIV-1 infection (Czubala et al., 2016, Soper et al., 2017).

134 Macrophage migration inhibitory factor restriction of HIV-1 trans-infection from dendritic cells to CD4+ T-cells via regulation of autophagy

At mucosal surfaces, immature resident Dendritic Cells, Langerhans Cells and their subsets are the first cell types to encounter HIV-1 virus. During the early stages of infection, dendritic cells sense the virus through innate immune mechanisms inducing maturation and activating adaptive immune responses. HIV-1 subverts the immune system by hijacking dendritic cells, impairing cellular function to promote survival and propagation by trans-infection to target CD4 T-cells across the virological synapse. In a well-established model of cell-to-cell HIV-1 transfer from monocyte-derived DCs to CD4 T-cells, we have evaluated the molecular contribution of cytokines and cytokine receptors during the transfer of HIV-1 virus from DCs to CD4 T cells using a high-throughput siRNA library. Here we show that when macrophage migration inhibitory factor (MIF) is disrupted, the dynamics of HIV-1 trans-infection from DCs to T cells are greatly affected, making it a restrictive cytokine. We report a critical link between MIF expression in dendritic cells and autophagy. We show that the formation of LC3+ autophagosomes is a MIF-dependent process, required for the clearance of intracellular virus by selective degradation. Thus, the regulation of MIF expression in dendritic cells is critical in the induction of autophagy during HIV-1 infection, thereby reducing HIV-1 transmission from DC to CD4+ T cells, one of its earliest steps of entry in the host.

HIV-1 Trans Infection via TNTs Is Impeded by Targeting C5aR.

Nonadjacent immune cells communicate through a complex network of tunneling nanotubes (TNTs). TNTs can be hijacked by HIV-1, allowing it to spread between connected cells. Dendritic cells (DCs) are among the first cells to encounter HIV-1 at mucosal sites, but they are usually efficiently infected only at low levels. However, HIV-1 was demonstrated to productively infect DCs when the virus was complement-opsonized (HIV-C). Such HIV-C-exposed DCs mediated an improved antiviral and T-cell stimulatory capacity. The role of TNTs in combination with complement in enhancing DC infection with HIV-C remains to be addressed. To this aim, we evaluated TNT formation on the surface of DCs or DC/CD4+ T-cell co-cultures incubated with non- or complement-opsonized HIV-1 (HIV, HIV-C) and the role of TNTs or locally produced complement in the infection process using either two different TNT or anaphylatoxin receptor antagonists. We found that HIV-C significantly increased the formation of TNTs between DCs or DC/CD4+ T-cell co-cultures compared to HIV-exposed DCs or co-cultures. While augmented TNT formation in DCs promoted productive infection, as was previously observed, a significant reduction in productive infection was observed in DC/CD4+ T-cell co-cultures, indicating antiviral activity in this setting. As expected, TNT inhibitors significantly decreased infection of HIV-C-loaded-DCs as well as HIV- and HIV-C-infected-DC/CD4+ T-cell co-cultures. Moreover, antagonizing C5aR significantly inhibited TNT formation in DCs as well as DC/CD4+ T-cell co-cultures and lowered the already decreased productive infection in co-cultures. Thus, local complement mobilization via DC stimulation of complement receptors plays a pivotal role in TNT formation, and our findings herein might offer an exciting opportunity for novel therapeutic approaches to inhibit trans infection via C5aR targeting.

HIV-1 trans-Infection Mediated by DCs: The Tip of the Iceberg of Cell-to-Cell Viral Transmission

HIV-1 cell-to-cell transmission is key for an effective viral replication that evades immunity. This highly infectious mechanism is orchestrated by different cellular targets that utilize a wide variety of processes to efficiently transfer HIV-1 particles. Dendritic cells (DCs) are the most potent antigen presenting cells that initiate antiviral immune responses, but are also the cells with highest capacity to transfer HIV-1. This mechanism, known as trans-infection, relies on the capacity of DCs to capture HIV-1 particles via lectin receptors such as the sialic acid-binding I-type lectin Siglec-1/CD169. The discovery of the molecular interaction of Siglec-1 with sialylated lipids exposed on HIV-1 membranes has enlightened how this receptor can bind to several enveloped viruses. The outcome of these interactions can either mount effective immune responses, boost the productive infection of DCs and favour innate sensing, or fuel viral transmission via trans-infection. Here we review these scenarios focusing on HIV-1 and other enveloped viruses such as Ebola virus or SARS-CoV-2.

IL-17A reprograms intestinal epithelial cells to facilitate HIV-1 replication and outgrowth in CD4+ T cells

SummaryThe crosstalk between intestinal epithelial cells (IECs) and Th17-polarized CD4+ T cells is critical for mucosal homeostasis, with HIV-1 causing significant alterations in people living with HIV (PLWH) despite antiretroviral therapy (ART). In a model of IEC and T cell co-cultures, we investigated the effects of IL-17A, the Th17 hallmark cytokine, on IEC ability to promote de novo HIV infection and viral reservoir reactivation. Our results demonstrate that IL-17A acts in synergy with TNF to boost IEC production of CCL20, a Th17-attractant chemokine, and promote HIV trans-infection of CD4+ T cells and viral outgrowth from reservoir cells of ART-treated PLWH. Importantly, the Illumina RNA-sequencing revealed an IL-17A-mediated pro-inflammatory and pro-viral molecular signature, including a decreased expression of type I interferon (IFN-I)-induced HIV restriction factors. These findings point to the deleterious features of IL-17A and raise awareness for caution when designing therapies aimed at restoring the paucity of mucosal Th17 cells in ART-treated PLWH.

Cocaine augments neuro-inflammation via modulating extracellular vesicle release in HIV-1 infected immune cells

BackgroundExtracellular Vesicles (EV) recently have been implicated in the pathogenesis of HIV-1 syndromes, including neuroinflammation and HIV-1 associated neurological disorder (HAND). Cocaine, an illicit stimulant drug used worldwide is known to exacerbate these HIV-1 associated neurological syndromes. However, the effects of cocaine on EV biogenesis and roles of EVs in enhancing HIV-1 pathogenesis are not yet well defined.ResultsHere, we investigated the effects of cocaine on EV biogenesis and release in HIV-1 infected immune cells and explored their roles in elicitation of neuroinflammation. We found that cocaine significantly augmented the release of EVs from uninfected and HIV-1 infected T-cells, DCs and macrophages. Further analysis of the molecular components of EVs revealed enhanced expression of adhesion molecules integrin β1 and LFA-1 in those EVs derived from cocaine treated cells. Intriguingly, in EVs derived from HIV-1 infected cells, cocaine treatment significantly increased the levels of viral genes in EVs released from macrophages and DCs, but not in T-cells. Exploring the molecular mechanism to account for this, we found that DCs and macrophages showed enhanced expression of the cocaine receptor Sigma 1-Receptor compared to T-cells. In addition, we found that cocaine significantly altered the integrity of the RNA-induced silencing complex (RISC) in HIV-1 infected macrophages and DCs compared to untreated HIV-1 infected cells. Characterizing further the molecular mechanisms involved in how cocaine increased EV release, we found that cocaine decreased the expression of the interferon-inducible protein BST-2; this resulted in altered trafficking of intracellular virus containing vesicles and EV biogenesis and release. We also observed EVs released from cocaine treated HIV-1 infected macrophages and DCs enhanced HIV-1 trans-infection to T-cells compared to those from untreated and HIV-1 infected cells. These EVs triggered release of proinflammatory cytokines in human brain microvascular endothelial cells (HBMECs) and altered monolayer integrity.ConclusionsTaken together, our results provide a novel mechanism which helps to elucidate the enhanced prevalence of neurological disorders in cocaine using HIV-1 infected individuals and offers insights into developing novel therapeutic strategies against HAND in these hosts.

094 Cytokine and chemokine factors regulate HIV-1 trans-infection from dendritic cells to CD4+ T-cells

Dendritic cells (DC) is one of the earliest immune cells to encounter HIV-1 during acute infection at mucosal surfaces. They act as a critical interface between the innate and adaptive immune systems through mechanisms of antigen-presentation. HIV-1 subverts the immune system by hijacking DCs, impairing cellular function to promote survival and propagation by trans-infection to target CD4 T-cells. DCs are capable of highly effective viral transfer to target CD4+ T-cells across the virological synapse, a specialised virus-induced cell junction, which enables highly efficient viral dissemination and accelerated disease progression almost exclusively driven by cell-to-cell transmission. Our previous findings have shown a major role for cytokines and chemokines in the infection and transmission of HIV-1 from DC subsets, though a global study of their molecular functions has yet to be completed. In our model of cell-cell HIV-1 transfer from primary monocyte-derived DCs (MDDC) to CD4 T-cells, we used high-throughput siRNA screening against known cytokines, chemokines, cytokine and chemokine receptors. Using the Human ON-TARGET plus SMARTpool cytokine & chemokine siRNA library, we screened 319 individual genes and investigated their differential effects on HIV-1 transfer from monocyte-derived DCs (MDDC) to a CD4+ T cells. Our data identified several cytokines restricting against HIV-1 cell-to-cell transfer in DC to T cell assays. These candidates were further analyzed using loss-of-function assays, genetic downregulation and neutralisation assays. Disruption of specific cytokine-driven mechanisms in MDDC results in dramatic changes in the capacity for cell-to-cell transfer to CD4+ T-cells. Taken altogether, these data continue to support DCs as a therapeutic target during early-stage HIV-1 infection linking the cytokine network and informing potential novel therapeutic strategies against early-stage HIV-1 infection and transmission.

Generation of Liposomes to Study the Effect of Mycobacterium Tuberculosis Lipids on HIV-1 cis- and trans-Infections.

Tuberculosis (TB) is the leading cause of death among HIV-1-infected individuals and Mycobacterium tuberculosis (Mtb) co-infection is an early precipitate to AIDS. We aimed to determine whether Mtb strains differentially modulate cellular susceptibility to HIV-1 infection (cis- and trans-infection), via surface receptor interaction by their cell envelope lipids. Total lipids from pathogenic (lineage 4 Mtb H37Rv, CDC1551 and lineage 2 Mtb HN878, EU127) and non-pathogenic (Mycobacterium bovis BCG and Mycobacterium smegmatis) Mycobacterium strains were integrated into liposomes mimicking the lipid distribution and antigen accessibility of the mycobacterial cell wall. The resulting liposomes were tested for modulating in vitro HIV-1 cis- and trans-infection of TZM-bl cells using single-cycle infectious virus particles. Mtb glycolipids did not affect HIV-1 direct infection however, trans-infection of both R5 and X4 tropic HIV-1 strains were impaired in the presence of glycolipids from M. bovis, Mtb H37Rv and Mtb EU127 strains when using Raji-DC-SIGN cells or immature and mature dendritic cells (DCs) to capture virus. SL1, PDIM and TDM lipids were identified to be involved in DC-SIGN recognition and impairment of HIV-1 trans-infection. These findings indicate that variant strains of Mtb have differential effect on HIV-1 trans-infection with the potential to influence HIV-1 disease course in co-infected individuals.

077 RNA interference screening for novel cytokine and chemokine factors regulating HIV-1 trans-infection from dendritic cells to CD4+ T-cells

The propagation of HIV-1 is driven in part by cell-to-cell transmission most frequently observed in dendritic cells (DC) and their subsets - one of the earliest immune cells likely to encounter HIV-1 during acute infection at mucosal surfaces. DCs are capable of highly effective viral transfer to target CD4+ T-cells across the virological synapse, a specialised virus-induced cell junction, which enables wide-spread viral dissemination and accelerated disease progression. Our previous findings have implicated a major role for cytokines and chemokines in the infection and transmission of HIV-1 from DC subsets, though a global study of their molecular functions has yet to be completed. In this study, we screened 319 individual genes using the Human ON-TARGET plus SMARTpool cytokine & chemokine siRNA library to investigate the differential effects on HIV-1 transfer from monocyte-derived DCs (MDDC) to a CD4+ SupT1 T-lymphoblastic cell line. Using integrative, data-driven approaches we successfully identified several cytokine superfamilies with potent restrictive properties against HIV-1 trans-infection from MDDC to SupT1. The activities of these candidates were validated using three key loss-of-function assays including genetic downregulation, neutralisation by biologics and pharmacological inhibition in trans- to both SupT1 and autologous CD4+ T-cells. Disruption of specific cytokine-driven mechanisms in MDDC results in dramatic changes in the capacity for cell-to-cell transfer to CD4+ T-cells. These findings add to a growing body of evidence linking the cytokine network which will inform novel therapeutic strategies against early-stage HIV-1 infection and transmission

The potential role of HLA-I associated adaptation in elevated risk of infection among HIV-1 STEP study vaccine recipients

Abstract The biological mechanism(s) underlying the elevated risk of HIV-1 acquisition among vaccine recipients in Merck STEP study remain unclear. HIV-1 frequently adapts to CD8 T cell responses, leading to the accumulation of adapted epitopes (AE). Recently, we demonstrated that in chronic HIV infection, CD8 T responses skewed by HLA-I associated adaptation enhanced HIV trans-infection of CD4 T cells by dendritic cells (DCs). However, whether adaptation in HIV vaccines induces a pro-inflammatory status and aids in potentiating infection is unknown. Using in-vitro studies, we evaluated whether an enhanced CD4 T cell trans-infection mediated by AE-specific CD8 T cells could be a potential biological mechanism for the observed increased risk of HIV acquisition in the Step Study. We found that CD8 T cells responding to AE demonstrated a higher capacity in promoting DCs maturation than non-adapted epitope (NAE) (p=0.007). Additionally, DCs matured by AE-specific CD8 T cells, showed a higher trend in inducing HIV trans-infection of CD4 T cells in each of the four vaccinee samples tested. We also analyzed the potential in-vivo impact of adaptation on the rate of infection among vaccine recipients in the STEP study. Our data showed that vaccine recipients with high adaptation to the vaccine immunogen were at an increased risk of HIV acquisition compared to recipients with medium/low adaptation or placebos (HR=2.98, p=0.02, high (n=21), medium (n=639), low (n=192) and placebo (n=865)). Taken together, our results show that in STEP study, AE-specific CD8 T cells may have contributed to an enhanced risk of HIV-1 acquisition by promoting viral trans-infection of CD4 T cells by DC. These findings have important implications for future HIV vaccine design.

Identification of Host Trafficking Genes Required for HIV-1 Virological Synapse Formation in Dendritic Cells.

Dendritic cells (DCs) are one of the earliest targets of HIV-1 infection acting as a "Trojan horse," concealing the virus from the innate immune system and delivering it to T cells via virological synapses (VS). To explicate how the virus is trafficked through the cell to the VS and evades degradation, a high-throughput small interfering RNA screen targeting membrane trafficking proteins was performed in monocyte-derived DCs. We identified several proteins including BIN-1 and RAB7L1 that share common roles in transport from endosomal compartments. Depletion of target proteins resulted in an accumulation of virus in intracellular compartments and significantly reduced viral trans-infection via the VS. By targeting endocytic trafficking and retromer recycling to the plasma membrane, we were able to reduce the virus's ability to accumulate at budding microdomains and the VS. Thus, we identify key genes involved in a pathway within DCs that is exploited by HIV-1 to traffic to the VS.IMPORTANCE The lentivirus human immunodeficiency virus (HIV) targets and destroys CD4+ T cells, leaving the host vulnerable to life-threatening opportunistic infections associated with AIDS. Dendritic cells (DCs) form a virological synapse (VS) with CD4+ T cells, enabling the efficient transfer of virus between the two cells. We have identified cellular factors that are critical in the induction of the VS. We show that ADP-ribosylation factor 1 (ARF1), bridging integrator 1 (BIN1), and Rab GTPases RAB7L1 and RAB8A are important regulators of HIV-1 trafficking to the VS and therefore the infection of CD4+ T cells. We found these cellular factors were essential for endosomal protein trafficking and formation of the VS and that depletion of target proteins prevented virus trafficking to the plasma membrane by retaining virus in intracellular vesicles. Identification of key regulators in HIV-1 trans-infection between DC and CD4+ T cells has the potential for the development of targeted therapy to reduce trans-infection of HIV-1 in vivo.

Virion-incorporated PSGL-1 and CD43 inhibit both cell-free infection and transinfection of HIV-1 by preventing virus–cell binding

HIV-1 particles incorporate various host transmembrane proteins in addition to viral Env glycoprotein during assembly at the plasma membrane. In polarized T cells, HIV-1 structural protein Gag localizes to the plasma membrane of uropod, a rear-end protrusion. Notably, uropod transmembrane proteins PSGL-1 and CD43 cocluster specifically with Gag assembling at the plasma membrane even in cells that do not form uropods. Recent reports have shown that expression of either PSGL-1 or CD43 in virus-producing cells reduces the infectivity of progeny virions and that HIV-1 infection reduces the cell surface expression of these proteins. However, the mechanisms for both processes remain to be determined. In this study, we found that virion incorporation of PSGL-1 and CD43 closely correlates with diminished virion infectivity. PSGL-1 and CD43 inhibited virus attachment to CD4+ cells irrespective of the presence of Env. These proteins also inhibited virion attachment to CD4- lymphoid organ fibroblastic reticular cells that mediate transinfection of CD4+ T cells. Consistent with the possibility that highly extended extracellular domains of these proteins physically block virus-cell attachment, the inhibitory effect of PSGL-1 required its full-length ectodomain. HIV-1 encoding Gag mutants that are defective in either coclustering with these host proteins or ESCRT-dependent particle release failed to reduce PSGL-1 on surface of infected cells. This study reveals an anti-HIV-1 mechanism that suppresses virus-cell attachment and a previously unappreciated process of HIV-1-mediated down-regulation of host antiviral proteins, both of which likely require virion incorporation of these proteins.

Dendritic Cell Maturation Regulates TSPAN7 Function in HIV-1 Transfer to CD4+ T Lymphocytes.

Dendritic cells (DCs) serve a key function in host defense, linking innate detection of microbes to activation of pathogen-specific adaptive immune responses. DCs express cell surface receptors for HIV-1 entry, but are relatively resistant to productive viral replication. They do, however, facilitate infection of co-cultured T-helper cells through a process referred to as trans-infection. We previously showed that tetraspanin 7 (TSPAN7), a transmembrane protein, is involved, through positive regulation of actin nucleation, in the transfer of HIV-1 from the dendrites of immature monocyte-derived DCs (iMDDCs) to activated CD4+ T lymphocytes. Various molecular mechanisms have been described regarding HIV-1 trans-infection and seem to depend on DC maturation status. We sought to investigate the crosstalk between DC maturation status, TSPAN7 expression and trans-infection. We followed trans-infection through co-culture of iMDDCs with CD4+ T lymphocytes, in the presence of CXCR4-tropic replicative-competent HIV-1 expressing GFP. T cell infection, DC maturation status and dendrite morphogenesis were assessed through time both by flow cytometry and confocal microscopy. Our previously described TSPAN7/actin nucleation-dependent mechanism of HIV-1 transfer appeared to be mostly observed during the first 20 h of co-culture experiments and to be independent of HIV replication. In the course of co-culture experiments, we observed a progressive maturation of MDDCs, correlated with a decrease in TSPAN7 expression, a drastic loss of dendrites and a change in the shape of DCs. A TSPAN7 and actin nucleation-independent mechanism of trans-infection, relying on HIV-1 replication, was then at play. We discovered that TSPAN7 expression is downregulated in response to different innate immune stimuli driving DC maturation, explaining the requirement for a TSPAN7/actin nucleation-independent mechanism of HIV transfer from mature MDDCs (mMDDCs) to T lymphocytes. As previously described, this mechanism relies on the capture of HIV-1 by the I-type lectin CD169/Siglec-1 on mMDDCs and the formation of a “big invaginated pocket” at the surface of DCs, both events being tightly regulated by DC maturation. Interestingly, in iMDDCs, although CD169/Siglec-1 can capture HIV-1, this capture does not lead to HIV-1 transfer to T lymphocytes.

Schistosoma mansoni soluble egg antigen (SEA) and recombinant Omega-1 modulate induced CD4+ T-lymphocyte responses and HIV-1 infection in vitro

Parasitic helminths evade, skew and dampen human immune responses through numerous mechanisms. Such effects will likely have consequences for HIV-1 transmission and disease progression. Here we analyzed the effects that soluble egg antigen (SEA) from Schistosoma mansoni had on modulating HIV-1 infection and cytokine/chemokine production in vitro. We determined that SEA, specifically through kappa-5, can potently bind to DC-SIGN and thereby blocks DC-SIGN mediated HIV-1 trans-infection (p<0.05) whilst not interfering with cis-infection. DCs exposed to SEA whilst maturing under Th2 promoting conditions, will upon co-culture with naïve T-cells induce a T-cell population that was less susceptible to HIV-1 R5 infection (p<0.05) compared to DCs unexposed to SEA, whereas HIV-1 X4 virus infection was unaffected. This was not observed for DCs exposed to SEA while maturing under Th1 or Th1/Th2 (Tmix) promoting conditions. All T-cell populations induced by SEA exposed DCs demonstrate a reduced capacity to produce IFN-γ and MIP-1β. The infection profile of T-cells infected with HIV-1 R5 was not associated with down-modulation of CCR5 cell surface expression. We further show that DCs maturing under Tmix conditions exposed to plant recombinant omega-1 protein (rω-1), which demonstrates similar functions to natural ω-1, induced T-cell populations that were less sensitive for HIV-1 R5 infection (p<0.05), but not for X4 virus infection. This inhibition associated again with a reduction in IFN-γ and MIP-1β expression, but additionally correlated with reduced CCR5 expression. We have shown that SEA parasite antigens and more specifically rω-1 can modulate HIV-1 infectivity with the potential to influence disease course in co-infected individuals.

Efficient HIV-1 Trans Infection of CD4+ T Cells Occurs in the Presence of Antiretroviral Therapy

BackgroundAntiretroviral therapy (ART) has dramatically improved the quality of life of people with HIV-1 infection (PWH). However, it is not curative, and interruption of ART results in rapid viral rebound. Cell-to-cell transfer of HIV-1, or trans infection, is a highly efficient mechanism of virus infection of CD4+ T cells by professional antigen-presenting cells (APCs), that is, dendritic cells (DCs), macrophages, and B lymphocytes.MethodsAPC from HIV seronegative donors treated with ART in vitro (CCR5 agonist, NRTI, PI and NNRTI, alone or in combination), were loaded with HIV R5-tropic HIVBal and mixed with autologous or heterologous CD4+ T lymphocytes to assess trans infection. Ex vivo APC from chronic HIV-infected MACS participants before and after initiation of ART, were also loaded with HIV R5-tropic HIVBal and tested for trans infection against autologous or heterologous CD4+ T lymphocytes. Virus replication was measured by p24 ELISA.ResultsHere we show in vitro that antiretroviral drugs did not block the ability of DCs and B cells to trans-infect CD4+ T cells, although they were effective in blocking direct cis infection of CD4+ T cells. Moreover, ex vivo DCs and B cells from ART-suppressed PWH mediated efficient HIV-1 trans infection of CD4+ T cells, which were resistant to direct cis infection.ConclusionsOur study supports a role for HIV-1 trans infection in maintenance of the HIV-1 reservoir during ART.

477 Identification of host cell factors involved HIV-1 trans-infection in dendritic cells

477 Identification of host cell factors involved HIV-1 trans-infection in dendritic cells

Secondary lymphoid organ fibroblastic reticular cells mediate trans-infection of HIV-1 via CD44-hyaluronan interactions

Fibroblastic reticular cells (FRCs) are stromal cells in secondary lymphoid organs, the major sites for HIV-1 infection of CD4+ T cells. Although FRCs regulate T cell survival, proliferation, and migration, whether they play any role in HIV-1 spread has not been studied. Here, we show that FRCs enhance HIV-1 spread via trans-infection in which FRCs capture HIV-1 and facilitate infection of T cells that come into contact with FRCs. FRCs mediate trans-infection in both two- and three-dimensional culture systems and in a manner dependent on the virus producer cells. This producer cell dependence, which was also observed for virus spread in secondary lymphoid tissues ex vivo, is accounted for by CD44 incorporated into virus particles and hyaluronan bound to such CD44 molecules. This virus-associated hyaluronan interacts with CD44 expressed on FRCs, thereby promoting virus capture by FRCs. Overall, our results reveal a novel role for FRCs in promoting HIV-1 spread.

Inefficient HIV-1 trans Infection of CD4+ T Cells by Macrophages from HIV-1 Nonprogressors Is Associated with Altered Membrane Cholesterol and DC-SIGN.

ABSTRACTProfessional antigen-presenting cells (APC; myeloid dendritic cells [DC] and macrophages [MΦ]; B lymphocytes) mediate highly efficient HIV-1 infection of CD4+ T cells, termed trans infection, that could contribute to HIV-1 pathogenesis. We have previously shown that lower cholesterol content in DC and B lymphocytes is associated with a lack of HIV-1 trans infection in HIV-1-infected nonprogressors (NP). Here, we assessed whether HIV-1 trans infection mediated by another major APC, MΦ, is deficient in NP due to altered cholesterol metabolism. When comparing healthy HIV-1 seronegatives (SN), rapid progressors (PR), and NP, we found that monocyte-derived MΦ from NP did not mediate HIV-1 trans infection of autologous CD4+ T cells, in contrast to efficient trans infection mediated by SN and PR MΦ. MΦ trans infection efficiency was directly associated with the number of DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN)-expressing MΦ. Significantly fewer NP MΦ expressed DC-SIGN. Unesterified (free) cholesterol in MΦ cell membranes and lipid rafting was significantly lower in NP than PR, as was virus internalization in early endosomes. Furthermore, simvastatin (SIMV) decreased the subpopulation of DC-SIGN+ MΦ as well as cis and trans infection. Notably, SIMV decreased cell membrane cholesterol and led to lipid raft dissociation, effectively mimicking the incompetent APC trans infection environment characteristic of NP. Our data support that DC-SIGN and membrane cholesterol are central to MΦ trans infection, and a lack of these limits HIV-1 disease progression. Targeting the ability of MΦ to drive HIV-1 dissemination in trans could enhance HIV-1 therapeutic strategies.IMPORTANCE Despite the success of combination antiretroviral therapy, neither a vaccine nor a cure for HIV infection has been developed, demonstrating a need for novel prophylactic and therapeutic strategies. Here, we show that efficiency of MΦ-mediated HIV trans infection of CD4+ T cells is a unique characteristic associated with control of disease progression, and it is impaired in HIV-infected NP. In vitro treatment of MΦ from healthy donors with SIMV lowers their cholesterol content, which results in a strongly reduced trans infection ability, similar to the levels of MΦ from NP. Taken together, our data support the hypothesis that MΦ-mediated HIV-1 trans infection plays a role in HIV infection and disease progression and demonstrate that the use of SIMV to decrease this mechanism of virus transfer should be considered for future HIV therapeutic development.

922 HIV-1 trans-infection of T-cells via dendritic cells requires endosomal sorting and polarized trafficking to the virological synapse

922 HIV-1 trans-infection of T-cells via dendritic cells requires endosomal sorting and polarized trafficking to the virological synapse