Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0021051 (immunodeficiency)
 71,517 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Here, we describe the isolation and characterization of the rhesus macaque homolog for human DC-SIGN, a dendritic cell-specific C-type lectin. mac-DC-SIGN is 92% identical to hu-DC-SIGN. mac-DC-SIGN preserves the virus transmission function of hu-DC-SIGN, capturing and efficiently transducing simian and human immunodeficiency virus to target CD4(+) T cells. Surprisingly, however, mac-DC-SIGN plays no discernable role in the ability of rhesus macaque dendritic cells to capture and transmit primate lentiviruses. Expression and neutralization analyses suggest that this process is DC-SIGN independent in macaque, although the participation of other lectin molecules cannot be ruled out. The ability of primate lentiviruses to effectively use human and rhesus dendritic cells in virus transmission without the cells becoming directly infected suggests that these viruses have taken advantage of a conserved dendritic cell mechanism in which DC-SIGN family molecules are significant contributors but not the only participants.
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PMID:Rhesus macaque dendritic cells efficiently transmit primate lentiviruses independently of DC-SIGN. 1181 54

Fusion of the human immunodeficiency virus (HIV) to the plasma membrane of target cells is mediated by interaction of its envelope glycoprotein, gp120, with CD4 and appropriate chemokine receptors. gp120 additionally binds to DC-SIGN, a C-type lectin expressed on immature dendritic cells. This interaction does not result in viral fusion, but instead contributes to enhanced infection in trans of target cells that express CD4 and chemokine receptors. Here we show that DC-SIGN mediates rapid internalization of intact HIV into a low pH nonlysosomal compartment. Internalized virus retains competence to infect target cells. Removal of the DC-SIGN cytoplasmic tail reduced viral uptake and abrogated the trans-enhancement of T cell infection. We propose that HIV binds to DC-SIGN to gain access to an intracellular compartment that contributes to augmentation or retention of viral infectivity.
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PMID:DC-SIGN-mediated internalization of HIV is required for trans-enhancement of T cell infection. 1182 72

DC-SIGN, a type II membrane-spanning C-type lectin that is expressed on the surface of dendritic cells (DC), captures and promotes human and simian immunodeficiency virus (HIV and SIV) infection of CD4(+) T cells in trans. To better understand the mechanism of DC-SIGN-mediated virus transmission, we generated and functionally evaluated a panel of seven monoclonal antibodies (MAbs) against DC-SIGN family molecules. Six of the MAbs reacted with myeloid-lineage DC, whereas one MAb preferentially bound DC-SIGNR/L-SIGN, a homolog of DC-SIGN. Characterization of hematopoietic cells also revealed that stimulation of monocytes with interleukin-4 (IL-4) or IL-13 was sufficient to induce expression of DC-SIGN. All DC-SIGN-reactive MAbs competed with intercellular adhesion molecule 3 (ICAM-3) for adhesion to DC-SIGN and blocked HIV-1 transmission to T cells that was mediated by THP-1 cells expressing DC-SIGN. Similar but less efficient MAb blocking of DC-mediated HIV-1 transmission was observed, indicating that HIV-1 transmission to target cells via DC may not be dependent solely on DC-SIGN. Attempts to neutralize DC-SIGN capture and transmission of HIV-1 with soluble ICAM-3 prophylaxis were limited in success, with a maximal inhibition of 60%. In addition, disrupting DC-SIGN/ICAM-3 interactions between cells with MAbs did not impair DC-SIGN-mediated HIV-1 transmission. Finally, forced expression of ICAM-3 on target cells did not increase their susceptibility to HIV-1 transmission mediated by DC-SIGN. While these findings do not discount the role of intercellular contact in facilitating HIV-1 transmission, our in vitro data indicate that DC-SIGN interactions with ICAM-3 do not promote DC-SIGN-mediated virus transmission.
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PMID:Functional evaluation of DC-SIGN monoclonal antibodies reveals DC-SIGN interactions with ICAM-3 do not promote human immunodeficiency virus type 1 transmission. 1202 23

Dendritic cells (DCs) play a critical role in the initiation of the immunological response against Leishmania parasites. However, the receptors involved in amastigote-dendritic cell interaction are unknown, especially in absence of opsonizing antibodies. We have studied the interaction of Leishmania pifanoi axenic amastigotes with the C-type lectin DC-specific intercellular adhesion molecule (ICAM)-3-grabbing nonintegrin (DC-SIGN, CD209), a receptor for ICAM-2, ICAM-3, human immunodeficiency virus gp120, and Ebola virus. L. pifanoi amastigotes interact with immature human dendritic cells and CD209-transfected K562 cells in a time- and dose-dependent manner. Leishmania amastigote binding to human dendritic cells and DC-SIGN-transfected cells is inhibited by a function-blocking DC-SIGN-specific monoclonal antibody. More importantly, this monoclonal antibody dramatically reduces internalization of Leishmania amastigotes by immature human DCs. These results constitute the first description of a nonviral pathogen ligand for DC-SIGN and provide evidence for a relevant role of DC-SIGN in Leishmania amastigote uptake by dendritic cells. Our finding has important implications for Leishmania host-cell interaction and the immunoregulation of cutaneous leishmaniasis.
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PMID:Dendritic cell (DC)-specific intercellular adhesion molecule 3 (ICAM-3)-grabbing nonintegrin (DC-SIGN, CD209), a C-type surface lectin in human DCs, is a receptor for Leishmania amastigotes. 1212 1

The C-type lectin human dendritic cell (DC)-specific intercellular adhesion molecule (ICAM)-3-grabbing non-integrin (DC-SIGN) plays important roles in pattern recognition by dendritic cells in the immune system. In addition to binding human immunodeficiency virus (HIV), this type II membrane protein binds with high affinity to the adhesion molecules ICAM-3 and -2 to promote important dendritic cell interactions with naive T cells and endothelial cells, respectively. DC-SIGNR, a human DC-SIGN homologue expressed on sinusoidal endothelial cells in liver and lymph node, also binds and transmits HIV virus. We describe the cloning and characterization of a family of murine complementary DNAs (cDNAs) called SIGNR1, expressed in skin and spleen, that encode C-type lectins highly related to human DC-SIGN and DC-SIGNR. We also report the genomic structure of the SIGNR1 gene and compare it to that of human DC-SIGN and DC-SIGNR. The different transcripts (alpha, beta, gamma, delta) are generated by differences in 5' untranslated sequences, alternative splicing and/or the use of different polyadenylation sites. The predicted open reading frames encoded by the cDNAs are most closely related to human DC-SIGN and DC-SIGNR in the cytoplasmic domain, the transmembrane region and the carbohydrate recognition domain. Moreover, the alternatively spliced transcripts encode proteins that lack the transmembrane region or have modified carbohydrate recognition domains. Northern hybridization experiments with several different SIGNR1 cDNA probes reveal transcripts of 1.3 and 2.1 kb that are expressed in a tissue-restricted fashion in murine skin, spleen and lung. In situ hybridization and immunocytochemistry experiments demonstrate that, like human DC-SIGN, the murine messenger RNAs are expressed in subsets of dendritic cells in the spleen and skin.
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PMID:Molecular characterization of the murine SIGNR1 gene encoding a C-type lectin homologous to human DC-SIGN and DC-SIGNR. 1213 41

DC-SIGNR is a human immunodeficiency virus (HIV)-binding C-type lectin that is expressed on endothelium in the hepatic sinusoids, lymph node sinuses and placenta. Like closely related DC-SIGN, DC-SIGNR can bind both ICAM-3 and HIV and can potentiate HIV infection of T lymphocytes in trans. In the present study we have investigated reasons underlying the restricted distribution of DC-SIGNR and have examined DC-SIGNR expression in relation to HIV entry receptors. We show that DC-SIGNR expression does not depend on endothelial cell specialization or on activation state. DC-SIGNR-positive endothelium continues to express DC-SIGNR in conditions of hyperplasia, whereas the molecule is lost after neoplastic transformation, most likely as a result of changes in the microenvironment of the endothelial cells. We have further shown that CCR5, but not CD4, is coexpressed with DC-SIGNR on hepatic sinusoidal and placental capillary endothelial cells. However, CD4-positive CCR5-positive cells, such as hepatic Kupffer cells, placental Hofbauer cells, and CD4-positive T lymphocytes in lymph nodes, can be found adjacent to DC-SIGNR-positive endothelium. Therefore, DC-SIGNR may be able to mediate HIV infection of these cells in trans. Finally, we demonstrate that DC-SIGN and DC-SIGNR can be coexpressed on lymph node sinus endothelial cells, which may lead to modulation of the function of both molecules.
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PMID:Expression of human immunodeficiency virus (HIV)-binding lectin DC-SIGNR: Consequences for HIV infection and immunity. 1215 66

Dendritic cells (DCs) are among the first cells encountered by human and simian immunodeficiency virus (HIV and SIV) following mucosal infection. Because these cells efficiently capture and transmit virus to T cells, they may play a major role in mediating HIV and SIV infection. Recently, a C-type lectin protein present on DCs, DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), was shown to efficiently bind and present HIV and SIV to CD4(+), coreceptor-positive cells in trans. However, the significance of DC-SIGN for virus transmission and pathogenesis in vivo remains unclear. Because SIV infection of macaques may represent the best model to study the importance of DC-SIGN in HIV infection, we cloned and characterized pig-tailed macaque DC-SIGN and generated monoclonal antibodies (MAbs) against it. We demonstrate that, like human DC-SIGN, pig-tailed macaque DC-SIGN (ptDC-SIGN) is expressed on DCs and macrophages but not on monocytes, T cells, or B cells. Moderate levels of ptDC-SIGN expression were detected on the surface of DCs, and low-level expression was found on macrophages. Additionally, we show that ptDC-SIGN efficiently binds and transmits replication-competent SIVmne variants to CD4(+), coreceptor-positive cells. Moreover, transmission of virus between pig-tailed macaque DCs and CD4(+) T cells is largely ptDC-SIGN dependent. Interestingly, MAbs directed against ptDC-SIGN vary in the capacity to block transmission of different SIVmne variants. These data demonstrate that ptDC-SIGN plays a central role in transmitting virus from macaque DCs to T cells, and they suggest that SIVmne variants may differ in their interactions with ptDC-SIGN. Thus, SIVmne infection of pig-tailed macaques may provide an opportunity to investigate the significance of DC-SIGN in primate lentiviral infections.
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PMID:Capture and transfer of simian immunodeficiency virus by macaque dendritic cells is enhanced by DC-SIGN. 1241 25

Mannose-binding lectin (MBL), a C-type lectin component of the human innate immune system, binds to the gp120 envelope glycoprotein of human immunodeficiency virus type 1 (HIV-1). The objective of this study was to assess the effects of inhibitors of endoplasmic reticulum glucosidases and Golgi mannosidase as well as neuraminidase (NA) on the interaction between HIV and MBL. Production of HIV in the presence of the mannosidase I inhibitor deoxymannojirimycin (dMM) significantly enhanced binding of HIV to MBL and increased MBL neutralization of an M-tropic HIV primary isolate. In contrast, culturing HIV in the presence of alpha-glucosidase I and II inhibitors castanospermine and deoxynojirimycin only slightly affected virus binding and neutralization by MBL. Removal of sialic acid from HIV by NA also significantly enhanced virus binding and neutralization by MBL. Treatment of virus grown in the presence of dMM with endoglycosidase F1 substantially reduced binding to MBL, indicating that dMM increased MBL binding by increasing high-mannose carbohydrates on the virus. In contrast, endoglycosidase F1 did not decrease the MBL interaction with NA-treated virus, suggesting that NA exposed novel MBL binding sites. Treatment with dMM increased the immunocapture of HIV by monoclonal antibodies 2F5 and 2G12, indicating that altering the glycosylation of viral glycoproteins increases the accessibility or reactivity of some epitopes. This study shows that specific alterations of the N-linked carbohydrates on HIV gp120/gp41 can enhance MBL-mediated neutralization of virus by strengthening the interaction of HIV-1 with MBL.
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PMID:Glycosylation inhibitors and neuraminidase enhance human immunodeficiency virus type 1 binding and neutralization by mannose-binding lectin. 1256 May 67

Dendritic cells (DCs) can influence HIV-1 and SIV pathogenesis and protective mechanisms at several levels. First, HIV-1 productively infects select populations of DCs in culture, particularly immature DCs derived from blood monocytes and skin (Langerhans cells). However, there exist only a few instances in which HIV-1- or SIV-infected DCs have been identified in vivo in tissue sections. Second, different types of DCs reliably sequester and transmit infectious HIV-1 and SIV in culture, setting up a productive infection in T cells interacting with the DCs. This stimulation of infection in T cells may explain the observation that CD4+ T lymphocytes are the principal cell type observed to be infected with HIV-1 in lymphoid tissues in vivo. DCs express a C-type lectin, DC-SIGN/CD209, that functions to bind HIV-1 (and other infectious agents) and transmit virus to T cells. When transfected into the THP-1 cell line, the cytosolic domain of DC-SIGN is needed for HIV-1 sequestration and transmission. However, DCs lacking DC-SIGN (Langerhans cells) or expressing very low levels of DC-SIGN (rhesus macaque monocyte-derived DCs) may use additional molecules to bind and transmit immunodeficiency viruses to T cells. Third, DCs are efficient antigen-presenting cells for HIV-1 and SIV antigens. Infection with several recombinant viral vectors as well as attenuated virus is followed by antigen presentation to CD4+ and CD8+ T cells. An intriguing pathway that is well developed in DCs is the exogenous pathway for nonreplicating viral antigens to be presented on class I MHC products. This should allow DCs to stimulate CD8+ T cells after uptake of antibody-coated HIV-1 and dying infected T cells. It has been proposed that DCs, in addition to expanding effector helper and killer T cells, induce tolerance through T cell deletion and suppressor T cell formation, but this must be evaluated directly. Fourth, DCs are likely to be valuable in improving vaccine design. Increasing DC uptake of a vaccine, as well as increasing their numbers and maturation, should enhance efficacy. However, DCs can also capture antigens from other cells that are initially transduced with a DNA vaccine or a recombinant viral vector. The interaction of HIV-1 and SIV with DCs is therefore intricate but pertinent to understanding how these viruses disrupt immune function and elicit immune responses.
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PMID:The interaction of immunodeficiency viruses with dendritic cells. 1279 41

The unique capacity of dendritic cells (DCs) to capture and process pathogens for presentation to the immune system, combined with their capacity to express costimulatory and adhesion molecules as well as cytokines and chemokines, renders them powerful antigen-presenting cells. However, immunodeficiency viruses hijack DCs to facilitate virus dissemination while subverting effective immune activation. Depending on the activation level of the DC subset, human immunodeficiency virus can use different receptors (CD4, chemokine, and C-type lectin receptors) to bind to DCs. These aspects likely impact whether a DC is productively infected by or simply carries virus for transmission to more permissive targets. DCs efficiently transmit virus to CD4+ T cells, driving virus growth as well as providing signals to trigger virus expansion in virus-bearing CD4+ T cells. There is accumulating evidence that viral determinants (nef, tat) selectively modulate immature DC biology, fostering DC-T cell interactions and virus replication without up-regulating costimulatory molecules for effective immune function. In addition, virus-loaded, immature DCs activate CD4+ virus-specific T cells, and mature DCs stimulate CD4+ and CD8+ T cells. Thus, even if immature DCs entrap virus as it crosses the mucosae and initiate a CD4+ T cell response, this is likely insufficient to control infection. Appreciating how virus modulates DC function and what determines whether virus is processed for immune stimulation or transmitted between cells will unveil the exact role of these cells in the onset of infection and advance preventative microbicide and vaccine/therapeutic approaches.
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PMID:Immunodeficiency virus exploitation of dendritic cells in the early steps of infection. 1296 Feb 36


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