One of the hallmarks of HIV-1 disease is the association of heightened CD4+ T-cell activation with HIV-1 replication. Parasitic helminths including filarial nematodes have evolved numerous and ...complex mechanisms to skew, dampen and evade human immune responses suggesting that HIV-1 infection may be modulated in co-infected individuals. Here we studied the effects of two filarial nematode products, adult worm antigen from Brugia malayi (BmA) and excretory-secretory product 62 (ES-62) from Acanthocheilonema viteae on HIV-1 infection in vitro. Neither BmA nor ES-62 influenced HIV-1 replication in CD4+ enriched T-cells, with either a CCR5- or CXCR4-using virus. BmA, but not ES-62, had the capacity to bind the C-type lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN) thereby inhibiting HIV-1 trans-infection of CD4+ enriched T-cells. As for their effect on DCs, neither BmA nor ES-62 could enhance or inhibit DC maturation as determined by CD83, CD86 and HLA-DR expression, or the production of IL-6, IL-10, IL-12 and TNF-α. As expected, due to the unaltered DC phenotype, no differences were found in CD4+ T helper (Th) cell phenotypes induced by DCs treated with either BmA or ES-62. Moreover, the HIV-1 susceptibility of the Th-cell populations induced by BmA or ES-62 exposed DCs was unaffected for both CCR5- and CXCR4-using HIV-1 viruses. In conclusion, although BmA has the potential capacity to interfere with HIV-1 transmission or initial viral dissemination through preventing the virus from interacting with DCs, no differences in the Th-cell polarizing capacity of DCs exposed to BmA or ES-62 were observed. Neither antigenic source demonstrated beneficial or detrimental effects on the HIV-1 susceptibility of CD4+ Th-cells induced by exposed DCs.
Five docking tools, namely AutoDock, FRED, CDOCKER, FlexX and GOLD, have been critically examined, with the aim of selecting those most appropriate for use as docking tools for docking molecules to ...the lectin dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin (DC-SIGN). This lectin has been selected for its rather non-druggable binding site, which enables complex interactions that guide the binding of the core monosaccharide. Since optimal orientation is crucial for forming coordination bonds, it was important to assess whether the selected docking tools could reproduce the optimal binding conformation for several oligosaccharides that are known to bind DC-SIGN. Our results show that even widely used docking programs have certain limitations when faced with a rather shallow and featureless binding site, as is the case of DC-SIGN. The FRED docking software (OpenEye Scientific Software, Inc.) was found to score as the best tool for docking ligands to DC-SIGN. The performance of FRED was further assessed on another lectin, Langerin. We have demonstrated that this validated docking protocol could be used for docking to other lectins similar to DC-SIGN.
The novel dendritic cell (DC)-specific human immunodeficiency virus type 1 (HIV-1) receptor DC-SIGN plays a key role in the dissemination of HIV-1 by DC. DC-SIGN is thought to capture HIV-1 at ...mucosal sites of entry, facilitating transport to lymphoid tissues, where DC-SIGN efficiently transmits HIV-1 to T cells. DC-SIGN is also important in the initiation of immune responses by regulating DC-T cell interactions through intercellular adhesion molecule 3 (ICAM-3). We have characterized the mechanism of ligand binding by DC-SIGN and identified the crucial amino acids involved in this process. Strikingly, the HIV-1 gp120 binding site in DC-SIGN is different from that of ICAM-3, consistent with the observation that glycosylation of gp120, in contrast to ICAM-3, is not crucial to the interaction with DC-SIGN. A specific mutation in DC-SIGN abrogated ICAM-3 binding, whereas the HIV-1 gp120 interaction was unaffected. This DC-SIGN mutant captured HIV-1 and infected T cells in trans as efficiently as wild-type DC-SIGN, demonstrating that ICAM-3 binding is not necessary for HIV-1 transmission. This study provides a basis for the design of drugs that inhibit or alter interactions of DC-SIGN with gp120 but not with ICAM-3 or vice versa and that have a therapeutic value in immunological diseases and/or HIV-1 infections.
Although CD4(+) cells represent the major target for HIV infection in blood, claims of complement-independent binding of HIV-1 to erythrocytes and the possible role of Duffy blood group antigen, have ...generated controversy. To examine the question of binding to erythrocytes, HIV-1 was incubated in vitro with erythrocytes from 30 healthy leukapheresis donors, and binding was determined by p24 analysis and adsorption of HIV-1 with reduction of infectivity for CD4(+) target cells. All of the cells, regardless of blood group type, bound HIV-1 p24. A typical preparation of erythrocytes bound <2.4% of the added p24, but erythrocytes selectively removed essentially all of the viral infectivity as determined by decreased infection of CD4(+) target cells; however, cell-associated HIV-1 was approximately 100-fold more efficient, via trans infection, than unadsorbed virus for infection of CD4(+) cells. All of the bound HIV-1 p24 was released by treatment of the cells with EDTA, and binding was optimized by adding Ca(2+) and Mg(2+) during the washing of erythrocytes containing bound HIV-1. Although the small number of contaminating leukocytes in the erythrocyte preparation also bound HIV-1 p24, there was no significant binding to CD4, and it thus appears that the binding occurred on leukocytes at non-CD4 sites. Furthermore, binding occurred to erythrocyte ghosts from which contaminating leukocytes had been previously removed. The results demonstrate that erythrocytes incubated in vitro with HIV-1 differentially adsorb all of the infectious HIV-1 virions (as opposed to non-infectious or degraded virions) in the absence of complement and independent of blood group, and binding is dependent on divalent cations. By analogy with HIV-1 bound to DC-SIGN on dendritic cells, erythrocyte-bound HIV-1 might comprise an important surface reservoir for trans infection of permissive cells.
Human immunodeficiency virus (HIV) infection is a global health burden which ultimately results in acquired immune deficiency syndrome (AIDS). There are multiple host factors which are capable of ...limiting HIV-1 replication. One of the most important host factors which inhibit HIV-1 DNA synthesis is the apolipoprotein B mRNA-editing enzyme, catalytic polypeptide- like 3G (APOBEC3G). Any genetic variation of this important host factor may influence the host susceptibility to viral infection.
The aim of the current study was to evaluate any correlation of APOBEC3G genetic variation rs8177832 with HIV-1 infection.
The study involved 142 healthy control and 100 HIV-1 infected subjects. The genetic variation rs8177832 of all studied subjects was determined by allele-specific polymerase chain reaction (AS-PCR).
The results showed that the distribution of rs8177832 genotypes AA, AG and GG in healthy subjects and HIV-1 subjects was; 42.253%, 42.957%, 14.788% and 66%, 27%, 7% respectively. Statistical analyses of data showed that there was a significant variation in rs8177832 genotype AA in healthy control and HIV-1 infected subjects (42.257% vs 66%; p-value<0.001).
Thus it was concluded that APOBEC3G rs8177832 AA genotype contributes in genetic predisposition to HIV-1 infection in Pakistani population.
Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. Dendritic cell-specific ICAM-3 grabbing-nonintegrin (DC-SIGN, also known as CD209) is an HIV-1 receptor ...that enhances its transmission to T cells and is expressed on placental macrophages.
We have investigated the association between DC-SIGN genetic variants and risk of MTCT of HIV-1 among Zimbabwean infants and characterized the impact of the associated mutations on DC-SIGN expression and interaction with HIV-1. DC-SIGN promoter (p-336C and p-201A) and exon 4 (198Q and 242V) variants were all significantly associated with increased risk of intrauterine (IU) HIV-1 infection. Promoter variants decreased DC-SIGN expression both in vitro and in placental CD163(+) macrophages (Hofbauer cells) of HIV-1 unexposed infants but not of HIV-1 exposed infants. The exon 4 protein-modifying mutations increased HIV-1 capture and transmission to T cells in vitro.
This study provides compelling evidence to support an important role of DC-SIGN in IU HIV-1 infection.
Abstract
Lipid rafts (LRs) play crucial roles in complex physiological processes, modulating innate and acquired immune responses to pathogens. The transmembrane C-type lectins human dendritic ...cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) and its mouse homolog SIGN-R1 are distributed in LRs and expressed on splenic marginal zone (MZ) macrophages. The DC-SIGN-C1q or SIGN-R1-C1q complex could mediate the immunoglobulin (Ig)-independent classical complement pathway against
Streptococcus pneumoniae
. Precise roles of LRs during this complement pathway are unknown. Here we show that LRs are indispensable for accelerating the DC-SIGN- or SIGN-R1-mediated classical complement pathway against
S. pneumoniae
, thus facilitating rapid clearance of the pathogen. The trimolecular complex of SIGN-R1-C1q-C4 was exclusively enriched in LRs of splenic MZ macrophages and their localization was essential for activating C3 catabolism and enhancing pneumococcal clearance, which were abolished in SIGN-R1-knockout mice. However, DC-SIGN replacement on splenic MZ macrophage’s LRs of SIGN-R1-depleted mice reversed these defects. Disruption of LRs dramatically reduced pneumococcal uptake and decomposition. Additionally, DC- SIGN, C1q, C4, and C3 were obviously distributed in splenic LRs of cadavers. Therefore, LRs on splenic SIGN-R1
+
or DC-SIGN
+
macrophages could provide spatially confined and optimal bidirectional platforms, not only for usual intracellular events, for example recognition and phagocytosis of pathogens, but also an unusual extracellular event such as the complement system. These findings improve our understanding of the orchestrated roles of the spleen, unraveling a new innate immune system initiated from splenic MZ LRs, and yielding answers to several long-standing problems, including the need to understand the profound role of LRs in innate immunity, the need to identify how such a small portion of splenic SIGN-R1
+
macrophages (<0.05% of splenic macrophages) effectively resist
S. pneumoniae
, and the need to understand how LRs can promote the protective function of DC-SIGN against
S. pneumoniae
in the human spleen.
To identify genes associated with the clinical presentation of dengue, 50 cases of probable or possible dengue hemorrhagic fever (DHF), 236 dengue fever (DF), and 236 asymptomatic infections were ...genotyped for 593 single-nucleotide polymorphisms (SNPs) in 56 genes across the type 1 interferon (IFN) response pathway as well as other important candidate genes. By single locus analysis comparing DHF with DF, 11 of the 51 markers with P<0.05 were in the JAK1 gene. Five markers were significantly associated by false discovery rate criteria (q<0.20 when P<6 × 10(-4)). The JAK1 SNPs showed differential distribution by ethnicity and ancestry consistent with epidemiologic observations in the Americas. The association remained significant after controlling for ancestry and income. No association was observed with markers in the gene encoding CD209 (DC-SIGN). An association between DHF and JAK1 polymorphisms is in agreement with expression profiles showing generalized decreased type 1 IFN-stimulated gene expression in these patients.
► Similar binding kinetics of CBAs for monomeric gp120 and trimeric gp140. ► Similar binding kinetics of the Ab 2G12 and sCD4 for monomeric gp120 and trimeric gp140. ► Two- to threefold stronger ...affinity of Ab b12 and DC-SIGN for trimeric gp140. ► SPR-directed binding kinetics with monomeric gp120 are relevant for native gp140 trimer.
The native HIV-1 Env complex consists of a gp120/gp41 trimer, but surface plasmon resonance (SPR)-directed binding studies for gp120-binding agents were almost exclusively performed on monomeric gp120. SPR-directed binding kinetics of monomeric gp120 and trimeric gp140 were investigated for a broad variety of envelope (Env)-binding agents. Similar kinetics for carbohydrate-binding agents (CBAs), the antibody 2G12 and sCD4 were observed, irrespective of the oligomeric state of gp120 that either contain the native mixture of complex and high-mannose N-glycans or that contain exclusively oligomannose N-glycans. The generally comparable kinetic properties of CBA, 2G12 and sCD4 binding to monomeric gp120 and trimeric gp140 indicate that monomeric gp120 is a good surrogate molecule for native HIV-1 Env trimer to investigate the binding affinities of Env-binding compounds.
gp120binds to GRFT by surface plasmon resonance (View Interaction: 1, 2)
gp120binds to UDA by surface plasmon resonance (View Interaction: 1, 2)
gp120binds to AH by surface plasmon resonance (View Interaction: 1, 2)
Proper immune system function is dependent on precisely evolved sensing and signal transduction events that occur at cellular and subcellular compartment boundaries. Recent immunotherapeutic efforts ...have generally focused on the roles that two specific protein superfamilies play in such events. This review is directed at a third superfamily, the C-type (Ca2+-dependent) lectin-type (CLEC) receptors and the nuanced, less traditionally acknowledged, yet quite important, role of endocytic-based calcium signaling. While extracellular recognition events rely heavily on the sophisticated structural diversity that lectins and glycobiology have to offer, the actual details of CLEC receptor-mediated, endocytic-based, calcium signal transduction have remained less appreciated. Because many CLEC receptor family members are emerging, not only as biomarkers for critical immune cell subpopulations, but also proving to be selective and pivotal modulators of immune function, this review seeks to promote the potential role CLEC receptor-initiated calcium signaling plays in immunotherapy. Given the importance of calcium signaling, these receptors provide a means to initiate a selective physiological response.
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