Human Immunodeficiency Virus Binding Research Articles

Macrophage- and CD4+ T cell-derived SIV differ in glycosylation, infectivity and neutralization sensitivity.

The human immunodeficiency virus (HIV) envelope protein (Env) mediates viral entry into host cells and is the primary target for the humoral immune response. Env is extensively glycosylated, and these glycans shield underlying epitopes from neutralizing antibodies. The glycosylation of Env is influenced by the type of host cell in which the virus is produced. Thus, HIV is distinctly glycosylated by CD4+ T cells, the major target cells, and macrophages. However, the specific differences in glycosylation between viruses produced in these cell types have not been explored at the molecular level. Moreover, it remains unclear whether the production of HIV in CD4+ T cells or macrophages affects the efficiency of viral spread and resistance to neutralization. To address these questions, we employed the simian immunodeficiency virus (SIV) model. Glycan analysis implied higher relative levels of oligomannose-type N-glycans in SIV from CD4+ T cells (T-SIV) compared to SIV from macrophages (M-SIV), and the complex-type N-glycans profiles seem to differ between the two viruses. Notably, M-SIV demonstrated greater infectivity than T-SIV, even when accounting for Env incorporation, suggesting that host cell-dependent factors influence infectivity. Further, M-SIV was more efficiently disseminated by HIV binding cellular lectins. We also evaluated the influence of cell type-dependent differences on SIV's vulnerability to carbohydrate binding agents (CBAs) and neutralizing antibodies. T-SIV demonstrated greater susceptibility to mannose-specific CBAs, possibly due to its elevated expression of oligomannose-type N-glycans. In contrast, M-SIV exhibited higher susceptibility to neutralizing sera in comparison to T-SIV. These findings underscore the importance of host cell-dependent attributes of SIV, such as glycosylation, in shaping both infectivity and the potential effectiveness of intervention strategies.

COVID-19 and comorbidities: A role for dipeptidyl peptidase 4 (DPP4) in disease severity?

The coronavirus disease 2019 (COVID-19) pandemic is caused by a novel betacoronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), similar to SARS-CoV and Middle East respiratory syndrome (MERS-CoV), which cause acute respiratory distress syndrome and case fatalities. COVID-19 disease severity is worse in older obese patients with comorbidities such as diabetes, hypertension, cardiovascular disease, and chronic lung disease. Cell binding and entry of betacoronaviruses is via their surface spike glycoprotein; SARS-CoV binds to the metalloprotease angiotensin-converting enzyme 2 (ACE2), MERS-CoV utilizes dipeptidyl peptidase 4 (DPP4), and recent modeling of the structure of SARS-CoV-2 spike glycoprotein predicts that it can interact with human DPP4 in addition to ACE2. DPP4 is a ubiquitous membrane-bound aminopeptidase that circulates in plasma; it is multifunctional with roles in nutrition, metabolism, and immune and endocrine systems. DPP4 activity differentially regulates glucose homeostasis and inflammation via its enzymatic activity and nonenzymatic immunomodulatory effects. The importance of DPP4 for the medical community has been highlighted by the approval of DPP4 inhibitors, or gliptins, for the treatment of type 2 diabetes mellitus. This review discusses the dysregulation of DPP4 in COVID-19 comorbid conditions; DPP4 activity is higher in older individuals and increased plasma DPP4 is a predictor of the onset of metabolic syndrome. DPP4 upregulation may be a determinant of COVID-19 disease severity, which creates interest regarding the use of gliptins in management of COVID-19. Also, knowledge of the chemistry and biology of DPP4 could be utilized to develop novel therapies to block viral entry of some betacoronaviruses, potentially including SARS-CoV-2.

T-Cell-Mimicking Nanoparticles Can Neutralize HIV Infectivity.

To improve human immunodeficiency virus (HIV) treatment and prevention, therapeutic strategies that can provide effective and broad-spectrum neutralization against viral infection are highly desirable. Inspired by recent advances of cell-membrane coating technology, herein, plasma membranes of CD4+ T cells are collected and coated onto polymeric cores. The resulting T-cell-membrane-coated nanoparticles (denoted as "TNPs") inherit T cell surface antigens critical for HIV binding, such as CD4 receptor and CCR5 or CXCR4 coreceptors. The TNPs act as decoys for viral attack and neutralize HIV by diverting the viruses away from their intended host targets. This decoy strategy, which simulates host cell functions for viral neutralization rather than directly suppressing viral replication machinery, has the potential to overcome HIV genetic diversity while not eliciting high selective pressure. In this study, it is demonstrated that TNPs selectively bind with gp120, a key envelope glycoprotein of HIV, and inhibit gp120-induced killing of bystander CD4+ T cells. Furthermore, when added to HIV viruses, TNPs effectively neutralize the viral infection of peripheral mononuclear blood cells and human-monocyte-derived macrophages in a dose-dependent manner. Overall, by leveraging natural T cell functions, TNPs show great potential as a new therapeutic agent against HIV infection.

P1.031 CD4 Independent Binding of HIV to Human Mannose Receptor on Vaginal Epithelial Cells and Sperm

Human Immunodeficiency Virus (HIV) is known to bind CD4 receptor and subsequently to CXCR4 or CCR5 coreceptors and further transmits the infection. However sperm and vaginal epithelial cells which are...

R5 human immunodeficiency virus type 1 with efficient DC-SIGN use is not selected for early after birth in vertically infected children

The binding of human immunodeficiency virus (HIV) to C-type lectin receptors may result in either enhanced trans-infection of T-cells or virus degradation. We have investigated the efficacy of HIV-1 utilization of DC-SIGN, a C-type lectin receptor, in the setting of intrauterine or intrapartum mother-to-child transmission (MTCT). Viruses isolated from HIV-1-infected mothers at delivery and from their vertically infected children both shortly after birth and later during the progression of the disease were analysed for their use of DC-SIGN, binding and ability to trans-infect. DC-SIGN use of a child's earlier virus isolate tended to be reduced as compared with that of the corresponding maternal isolate. Furthermore, the children's later isolate displayed enhanced DC-SIGN utilization compared with that of the corresponding earlier virus. These results were also supported in head-to-head competition assays and suggest that HIV-1 variants displaying efficient DC-SIGN use are not selected for during intrauterine or intrapartum MTCT. However, viruses with increased DC-SIGN use may evolve later in paediatric HIV-1 infections.

Plasmacytoid Dendritic Cells (pDCs) From HIV Controllers Produce Interferon-α and Differentiate Into Functional Killer pDCs Under HIV Activation

Human immunodeficiency virus (HIV) controllers spontaneously control viremia and CD4 T-cell depletion in contrast to viremic patients. After HIV exposure, plasmacytoid dendritic cells (pDCs) produce high levels of interferon alpha (IFN-α) and express the apoptotic ligand TRAIL (tumor necrosis factor-related apoptosis inducing ligand). Simian models have shown that prolonged high levels of IFN-α production could be responsible for AIDS progression. We studied pDC activation in response to human immunodeficiency virus (HIV) using flow cytometry and 3D microscopy. We show here that pDCs from controller patients produced higher levels of IFN-α in response to HIV than pDCs from viremic patients but similar levels to pDCs from healthy donors. Because binding of HIV to CD4 is essential for pDC activation, the low CD4 expression by pDCs from viremic patients may explain the weak IFN-α response to HIV. Three-dimensional microscopy revealed that pDCs from controllers and healthy donors expressed intracellular TRAIL that is relocalized to the membrane after HIV exposure. In contrast, pDCs from viremic patients expressed membrane TRAIL without any stimulation. We demonstrate that, in response to HIV, pDCs from controller patients produce IFN-α, express membrane TRAIL, and induce apoptosis of T-cell lines.

Analytical features of particle counting sensor based on plasmon assisted microscopy of nano objects

We present a new analytical method for concentration measurements of nano objects of different nature such as polystyrene nanoparticles or viruses. The method is based on counting single particles of interest bound to a functionalized sensor surface. The counting rate was used for concentration measurements. For polystyrene particles, the counting rate was found to be in good agreement with the theoretically predicted one. Binding of human immunodeficiency virus (HIV) virus-like particles (VLPs) to the sensor surface functionalized with antibodies was observed. The concentration of HIV–VLP was estimated by means of well-characterized solutions of artificial nanoparticles as a reference material. The results are in a good agreement with standard enzyme-linked immunosorbent assay (ELISA) analysis. Factors are discussed which determine the detection power of the method.

Modulation of HIV Binding to Epithelial Cells and HIV Transfer from Immature Dendritic Cells to CD4 T Lymphocytes by Human Lactoferrin and its Major Exposed LF-33 Peptide

Lactoferrin (LF), a multifunctional molecule present in human secretions, has potent inhibitory activities against human immunodeficiency virus (HIV). The aim of the study was to evaluate whether human LF (hLF) and its exposed domain LF-33 represented by the peptide (LF-33-GRRRRSVQWCAVSQPEATKCFQWQRNMRKVRGP) involved in LF-HIV gag binding and endotoxines neutralization, may inhibit early steps of HIV mucosal transmission. Human LF and the peptide LF-33 inhibited the attachment of primary X4-tropic HIV-1NDK and R5-tropic HIV-1JR-CSF strains to human endometrial (HEC-1) and colorectal (HT-29) CD4-negative epithelial cells, the purified hLF being more potent (up to 80%) than the LF-33 peptide. In addition, the hLF, but not the LF-33 peptide, inhibited up to 40% the transfer in trans of HIV-1JR-CSF and HIV-1NDK, from immature dendritic cells to CD4 T lymphocytes, likely in a DC-SIGN-dependent manner. Altogether, these findings demonstrate that hLF can interfere with HIV-1 mucosal transmission by blocking virus attachment to epithelial cells and by inhibiting virus transfer from dendritic cells to CD4 T cells, two crucial steps of HIV dissemination from mucosae to lymphoid tissue.

Assessing protein–RNA interactions using microfluidic capillary mobility shift assays

We describe a novel method of characterizing protein–RNA interactions using a fluorescence-based multiwell capillary electrophoresis platform based on microfluidic technology. As a proof of concept, we studied the binding of human immunodeficiency virus 1 (HIV-1) transactivator of transcription (Tat) to the transactivation-responsive RNA (TAR). We established conditions to quantify the binding of recombinant HIV-1 Tat to TAR RNA and validated the assay by demonstrating the dependence of this interaction on the presence of the UCU bulge in TAR. In addition, we showed that neomycin inhibited Tat–TAR binding in a dose-dependent manner (IC 50 = 1.6–3.0 μM). This microfluidic-based method is high-throughput screening compatible and may be applicable to targeting other nucleic acid–protein interactions.

Could CD4 Capture byCD8+T Cells Play a Role in HIV Spreading?

CD8+ T cells have been shown to capture plasma membrane fragments from target cells expressing their cognate antigen, a process termed “trogocytosis”. Here, we report that human CD4, the Human Immunodeficiency Virus (HIV) receptor, can be found among the proteins transferred by trogocytosis. CD4 is expressed in a correct orientation after its capture by CD8+ T cells as shown by its detection using conformational antibodies and its ability to allow HIV binding on recipient CD8+ T cells. Although we could not find direct evidence for infection of CD8+ T cells having captured CD4 by HIV, CD4 was virologically functional on these cells as it conferred on them the ability to undergo syncytia formation induced by HIV-infected MOLT-4 cells. Our results show that acquisition of CD4 by CD8+ T cells via trogocytosis could play a previously unappreciated role for CD8+ T cells in HIV spreading possibly without leading to their infection.

Oligomerization of the Macrophage Mannose Receptor Enhances gp120-mediated Binding of HIV-1

C-type lectin receptors expressed on the surface of dendritic cells and macrophages are able to bind glycoproteins of microbial pathogens via mannose, fucose, and N-acetylglucosamine. Langerin on Langerhans cells, dendritic cell-specific intercellular adhesion molecule 3-grabbing nonintegrin on dendritic cells, and mannose receptor (MR) on dendritic cells and macrophages bind the human immunodeficiency virus (HIV) envelope protein gp120 principally via high mannose oligosaccharides. These C-type lectin receptors can also oligomerize to facilitate enhanced ligand binding. This study examined the effect of oligomerization of MR on its ability to bind to mannan, monomeric gp120, native trimeric gp140, and HIV type 1 BaL. Mass spectrometry analysis of cross-linked MR showed homodimerization on the surface of primary monocyte-derived dendritic cells and macrophages. Both monomeric and dimeric MR were precipitated by mannan, but only the dimeric form was co-immunoprecipitated by gp120. These results were confirmed independently by flow cytometry analysis of soluble monomeric and trimeric HIV envelope and a cellular HIV virion capture assay. As expected, mannan bound to the carbohydrate recognition domains of MR dimers mostly in a calcium-dependent fashion. Unexpectedly, gp120-mediated binding of HIV to dimers on MR-transfected Rat-6 cells and macrophages was not calcium-dependent, was only partially blocked by mannan, and was also partially inhibited by N-acetylgalactosamine 4-sulfate. Thus gp120-mediated HIV binding occurs via the calcium-dependent, non-calcium-dependent carbohydrate recognition domains and the cysteine-rich domain at the C terminus of MR dimers, presenting a much broader target for potential inhibitors of gp120-MR binding.

Role of gp120 Trimerization on HIV Binding Elucidated with Brownian Adhesive Dynamics

We simulated the docking of human immunodeficiency virus (HIV) with a cell membrane using Brownian adhesive dynamics. The main advance in the current version of Brownian adhesive dynamics is that we use a simple bead-spring model to coarsely approximate the role of gp120 trimerization on HIV docking. We used our simulations to elucidate the effect of env spike density on the rate and probability of HIV binding, as well as the probability that each individual gp120 trimer is fully engaged. We found that for typical CD4 surface densities, viruses expressing as few as 8 env spikes will dock with binding rate constants comparable to viruses expressing 72 spikes. We investigated the role of cellular receptor diffusion on the degree of binding achieved by the virus on both short timescales (where binding has reached steady state but before substantial receptor accumulation in the viral-cell contact zone has occurred) and long timescales (where the system has reached steady state). On short timescales, viruses with 10–23 env trimers most efficiently form fully engaged trimers. On long timescales, all gp120 in the contact area will become bound to CD4. We found that it takes seconds for engaged trimers to cluster CD4 molecules in the contact zone, which partially explains the deleay in viral entry.

The HIV-1 Envelope Glycoprotein gp120 Features Four Heparan Sulfate Binding Domains, Including the Co-receptor Binding Site

It is well established that the human immunodeficiency virus-1 envelope glycoprotein surface unit, gp120, binds to cell-associated heparan sulfate (HS). Virus infectivity is increased by such interaction, and a variety of soluble polyanions efficiently neutralize immunodeficiency virus-1 in vitro. This interaction has been mainly attributed to the gp120 V3 loop. However, although evidence suggested that this particular domain does not fully recapitulate the binding activity of the protein, the ability of HS to bind to other regions of gp120 has not been completely addressed, and the exact localizations of the polysaccharide binding sites are not known. To investigate in more detail the structural basis of the HS-gp120 interaction, we used a mapping strategy and compared the heparin binding activity of wild type and mutant gp120 using surface plasmon resonance-based binding assays. Four heparin binding domains (1-4) were identified in the V2 and V3 loops, in the C-terminal domain, and within the CD4-induced bridging sheet. Interestingly, three of them were found in domains of the protein that undergo structural changes upon binding to CD4 and are involved in co-receptor recognition. In particular, Arg(419), Lys(421), and Lys(432), which directly interact with the co-receptor, are targeted by heparin. This study provides a complete account of the gp120 residues involved in heparin binding and identified several binding surfaces that constitute potential target for viral entry inhibition.

Inhibition of HIV‐1 transmission in trans from dendritic cells to CD4+ T lymphocytes by natural antibodies to the CRD domain of DC‐SIGN purified from breast milk and intravenous immunoglobulins

The present study demonstrates that human breast milk and normal human polyclonal immunoglobulins purified from plasma [intravenous immunoglobulins (IVIg)] contain functional natural immunoglobulin A (IgA) and IgG antibodies directed against the carbohydrate recognition domain (CRD) domain of the dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) molecule, which is involved in the binding of human immunodeficiency virus (HIV)-1 to dendritic cells (DCs). Antibodies to DC-SIGN CRD were affinity-purified on a matrix to which a synthetic peptide corresponding to the N-terminal CRD domain (amino-acid 342-amino-acid 371) had been coupled. The affinity-purified antibodies bound to the DC-SIGN peptide and to the native DC-SIGN molecule expressed by HeLa DC-SIGN+ cells and immature monocyte-derived dendritic cells (iMDDCs), in a specific and dose-dependent manner. At an optimal dose of 200 microg/ml, natural antibodies to DC-SIGN CRD peptide purified from breast milk and IVIg stained 25 and 20% of HeLa DC-SIGN+ cells and 32 and 12% of iMDDCs, respectively. Anti-DC-SIGN CRD peptide antibodies inhibited the attachment of virus to HeLa DC-SIGN by up to 78% and the attachment to iMDDCs by only 20%. Both breast milk- and IVIg-derived natural antibodies to the CRD peptide inhibited 60% of the transmission in trans of HIV-1(JRCSF), an R5-tropic strain, from iMDDCs to CD4+ T lymphocytes. Taken together, these observations suggest that the attachment of HIV to DCs and transmission in trans to autologous CD4+ T lymphocytes occur through two independent mechanisms. Our data support a role of natural antibodies to DC-SIGN in the modulation of postnatal HIV transmission through breast-feeding and in the natural host defence against HIV-1 in infected individuals.

Tonsil Epithelial Factors May Influence Oropharyngeal Human Immunodeficiency Virus Transmission

Tonsil epithelium has been implicated in human immunodeficiency virus (HIV) pathogenesis, but its role in oral transmission remains controversial. To study characteristics of this tissue, which may influence susceptibility or resistance to HIV, we performed microarray analysis of the tonsil epithelium. Our data revealed that genes related to immune functions such as antibody production and antigen processing were increasingly expressed in tonsil compared with the epithelium of another oropharyngeal site, the gingival epithelium. Importantly, tonsil epithelium highly expressed genes associated with HIV entrapment and/or transmission, including the HIV co-receptor CXCR4 and the potential HIV-binding molecules FcRgammaIII, complement receptor 2, and various complement components. Immunohistochemical staining confirmed the increased presence of CXCR4 in the tonsil epithelium compared with multiple oral epithelial sites, particularly in basal and parabasal layers. This increased expression of molecules involved in viral recognition, binding, and entry may favor virus-epithelium interactions in an environment with reduced innate antiviral mechanisms. Specifically, secretory leukocyte protease inhibitor, an innate molecule with anti-HIV activity, was minimal in the tonsil epithelium, in contrast to oral mucosa. Collectively, our data suggest that increased expression of molecules associated with HIV binding and entry coupled with decreased innate antiviral factors may render the tonsil a potential site for oral transmission.

Inhibition of Coreceptor-Independent Cell-to-Cell Human Immunodeficiency Virus Type 1 Transmission by a CD4-Immunoglobulin G2 Fusion Protein

We have previously shown (J. Blanco et al., J. Biol. Chem. 279:51305-51314, 2004) that the contact between HIV producing cells and primary CD4(+) T cells may induce the uptake of human immunodeficiency virus (HIV) particles by target cells in the absence of HIV envelope-mediated membrane fusion or productive HIV replication. HIV uptake by CD4(+) T cells was dependent on cellular contacts mediated by the binding of gp120 to CD4 but was independent of the expression of the appropriate HIV coreceptor, CCR5 or CXCR4. Here, we have characterized the effect of agents blocking gp120 binding to CD4 on cell-to-cell HIV transmission. A recombinant CD4-based protein (CD4-immunoglobulin G2 [IgG2]), that is currently being evaluated in clinical trials, completely inhibited the uptake of HIV particles by CD4(+) T cells from persistently infected cells expressing R5, X4, or X4/T-20-resistant HIV-1 envelope glycoproteins. Consequently, both the release of viral particles from endocytic vesicles and the infection of reporter U87-CD4 cells were also prevented. The polyanionic anti-HIV agent dextran sulfate failed to prevent the intracellular uptake of virions by CD4(+) T cells. Indeed, it increased HIV uptake in a dose-dependent manner, suggesting functional differences between the specific gp120-targeting CD4-IgG2 agent and nonspecific HIV binding inhibitors. Thus, the inhibition of the specific interaction between gp120 and CD4 protein could be an effective strategy to inhibit HIV binding to CD4(+) T cells, and the mechanism by which CD4(+) T cells lacking the appropriate coreceptor may be converted in HIV carriers.

RNAi-directed inhibition of DC-SIGN by dendritic cells: Prospects for HIV-1 therapy

Drug-resistant human immunodeficiency virus (HIV) infections are increasing globally, especially in North America. Therefore, it is logical to develop new therapies directed against HIV binding molecules on susceptible host cells in addition to current treatment modalities against virus functions. Inhibition of the viral genome can be achieved by degrading or silencing posttranslational genes using small interfering (si) ribonucleic acids (RNAs) consisting of double-stranded forms of RNA. These siRNAs usually contain 21-23 base pairs (bp) and are highly specific for the nucleotide sequence of the target messenger RNA (mRNA). These siRNAs form a complex with helicase and nuclease enzymes known as "RNA-induced silencing complex" (RISC) that leads to target RNA degradation. Thus, siRNA has become a method of selective destruction of HIV now used by various investigators around the globe. However, given the sequence diversity of the HIV genomes of infected subjects, it is difficult to target a specific HIV sequence. Therefore, targeting nonvariable HIV binding receptors on susceptible cells or other molecules of host cells that are directly or indirectly involved in HIV infections may be an interesting alternative to targeting the virus itself. Thus, the simultaneous use of siRNAs specific for HIV and host cells may be a unique, new approach to the therapy of HIV infections. In this article, we present evidence that siRNA directed at the CD4 independent attachment receptor (DC-SIGN) significantly inhibits HIV infection of dendritic cells (DCs). This effect may be mediated by modulation of p38 mitogen activated protein kinase (MAPK).

The Nef Protein of Human Immunodeficiency Virus Establishes Superinfection Immunity by a Dual Strategy to Downregulate Cell-Surface CCR5 and CD4

Viruses frequently render cells refractory to subsequent infection with the same virus. This state of superinfection immunity counteracts potentially detrimental consequences for the infected cell and facilitates high-level replication and viral spread in the host. Here, we show that human immunodeficiency virus (HIV) employs its early gene product Nef to efficiently interfere with superinfection at the viral-entry step. In this context, we identify the downregulation of cell-surface CCR5, the major HIV coreceptor, as a novel and highly conserved activity of Nef. Nef targets the CCR5 coreceptor and the HIV binding receptor CD4 via distinct cellular machineries to enhance the endocytosis rate of both HIV receptor components and to accelerate their degradation. Functionally, these genetically separable actions by Nef synergized to efficiently protect cells from HIV superinfection at the level of fusion of the viral envelope with the plasma membrane. HIV has evolved two independent activities for Nef to downregulate the receptor complex and to facilitate its efficient replication and spread. This evasion strategy likely represents a mechanism by which the pathogenicity factor Nef elevates viral replication in vivo and thus promotes AIDS pathogenesis.

Selection of TAR RNA-binding chameleon peptides by using a retroviral replication system.

The interaction between the arginine-rich motif (ARM) of the human immunodeficiency virus (HIV) Tat protein and TAR RNA is essential for Tat activation and viral replication. Two related lentiviruses, bovine immunodeficiency virus (BIV) and Jembrana disease virus (JDV), also require Tat ARM-TAR interactions to mediate activation, but the viruses have evolved different RNA-binding strategies. Interestingly, the JDV ARM can act as a "chameleon," adopting both the HIV and BIV TAR binding modes. To examine how RNA-protein interactions may evolve in a viral context and possibly to identify peptides that recognize HIV TAR in novel ways, we devised a retroviral system based on HIV replication to amplify and select for RNA binders. We constructed a combinatorial peptide library based on the BIV Tat ARM and identified peptides that, like the JDV Tat ARM, also function through HIV TAR, revealing unexpected sequence characteristics of an RNA-binding chameleon. The results suggest that a retroviral screening approach may help identify high-affinity TAR binders and may provide new insights into the evolution of RNA-protein interactions.

Inhibition of DC-SIGN-mediated trans infection of T cells by mannose-binding lectin.

Some dendritic cells (DC) express a cell-surface lectin called 'dendritic cell-specific intracellular adhesion molecule 3 (ICAM-3)-grabbing non-integrin' (DC-SIGN). DC-SIGN has been shown to mediate a type of infection called 'trans' infection, where DC bind human immunodeficiency virus (HIV) and efficiently transfer the virus to T cells. We investigated the possibility that mannose-binding lectin (MBL), a soluble lectin that functions as a recognition molecule in innate immunity and that binds to HIV, could block trans infection mediated by DC-SIGN. Binding studies with glycoprotein (gp)120/gp41-positive and -negative virus preparations suggested that DC-SIGN and MBL bind primarily to glycans on gp120/gp41, as opposed to glycans on host-cell-derived proteins, indicating a close overlap in the binding site of the two lectins and supporting the notion that MBL could prevent binding of HIV to DC-SIGN. Preincubation of X4, R5 or dual-tropic HIV strains with MBL prevented DC-SIGN-mediated trans infection of T cells. The mechanism of MBL blocking trans infection of T cells was at least partly caused by blocking of virus binding to DC-SIGN positive cells. This study shows that MBL prevents DC-SIGN-mediated trans infection of T cells in vitro and suggests that in infected persons, MBL may inhibit DC-SIGN-mediated uptake and spread of HIV.