DC-SIGN特异性适配子的筛选及鉴定

目的:筛选高特异性、高亲合力结合DC-SIGN的单链DNA适配子,为开发抗HIV、HCV和结核杆菌感染的新型预防和治疗试剂奠定基础。方法:采用基于细胞表面展示的SELEX技术(TECS-SELEX),筛选出具有高亲合力结合DC-SIGN的单链DNA(ssDNA)适配子;运用流式细胞术(FCM)检测该适配子的亲合力;对最高亲合力适配子库进行克隆和测序;ELISA和FCM方法检测单适配子ZD8与DC-SIGN蛋白结合的剂量相关性;MTT法测定IC50观察适配子对细胞的毒性。结果:第14轮筛选的适配子库亲和力最高;DC-SIGN抗体能抑制适配子结合表达DC-SIGN蛋白的细胞;第14轮库中筛选的单适配子ZD8与DC-SIGN蛋白的结合率呈剂量依赖性;所筛选的单适配子对肝细胞几乎无毒性。结论:成功筛选出DC-SIGN蛋白的ssDNA适配子,为防治HIV、HCV和结核杆菌感染等DC-SIGN相关性疾病,提供新型预防和治疗的候选试剂和小分子药物。     

DC-SIGN (CD209) Carbohydrate Recognition Domain Is Not Polymorphic in Dengue Virus-Infected Indonesian Patients

Dengue virus (DENV) infection is a significant burden in Indonesia and other tropical countries. DENV infection has a wide spectrum of clinical manifestations, i.e. asymptomatic, dengue fever, dengue hemorrhagic fever and dengue shock syndrome. The variety of clinical manifestations may be due to the diversity of genetic constitution of the host. The C-type lectin DC-SIGN (CD209) has been identified as the major dengue receptor on human dendritic cells. There are at least five polymorphisms in exon 5 and 6 of the DC-SIGN encoded gene which have been identified and recorded in dbSNP. The aim of this work is to measure the frequency of these polymorphisms among asymptomatic and hospitalized DENV-infected patients. We enrolled 23 hospitalized and 73 asymptomatic DENV-infected patients. Among the subjects, we performed PCR amplification and DNA direct seqencing for 23 hospitalized DENV-infected patients and 24 asymptomatic DENV-infected patients. The result showed that there were no polymorphic nucleotides in the CD209 encoded gene among the patients.     

Association of CD209 polymorphisms with tuberculosis in an Indonesian population

Tuberculosis (TB) caused by Mycobacterium tuberculosis is a major cause of morbidity and mortality worldwide. Thus far, many candidate genes have been investigated for their possible association with TB. Dendritic cell-specific ICAM-3 grabbing nonintegrin (DC-SIGN) encoded by CD209 is the major receptor of M tuberculosis on human dendritic cells. Previous studies reported inconsistent results on the association between CD209 polymorphisms and TB. We examined whether 9 single nucleotide polymorphisms (SNPs) of CD209 are associated with TB in 2 southeast Asian populations (Indonesian and Vietnamese) by Fisher's exact test. The SNP at -939 in the promoter region exhibited a significant association with TB in Indonesian (GG vs GA + AA, p = 0.0051, odds ratio [OR] = 0.68, 95% confidence interval [CI] = 0.52-0.89) but not in Vietnamese populations. Further extensive studies are required to confirm the contribution of CD209 polymorphisms to TB susceptibility.     

树突状细胞DC-SIGN在免疫介导实验性肾炎肾小管间质损伤中的作用及抗P选择素功能域单抗的干预调节

目的 探讨树突状细胞（DC）表面特异的胞间黏附分子3捕获非整合素 （DC-SIGN）在免疫介导肾毒血清性肾炎（NTN）肾小管间质损伤中的作用,以及抗P选择素功能域单抗（PsL-EGFmAb）的干预调节。 方法 WKY大鼠随机分为正常对照组、模型组及 PsL-EGFmAb干预组。模型组注射预制的兔抗大鼠肾毒血清1 ml/kg;PsL-EGFmAb组在注射肾毒血清同时及注射后2 h,注入PsL-EGFmAb 2 mg/kg;正常对照组则注射等量生理盐水。随后于实验第4、7、14 天,分别观察大鼠肾功能及肾组织病理变化,并采用免疫荧光法检测肾组织DC-SIGN+DC分布;实时定量 PCR 检测P选择素、T细胞表达和分泌因子（RANTES）、肿瘤坏死因子?琢（TNF-?琢）、白细胞介素（IL）-10、干扰素（IFN）-?酌、IL-4的mRNA 表达;流式细胞仪检测肾脏分离DC表面主要组织相容性复合体Ⅱ（MHCⅡ）、DC-SIGN、CD80表达;细胞迁移试验及混合淋巴细胞反应（MLR）检测DC迁移与刺激 T 细胞的能力;ELISA法测定MLR上清中IFN-γ、IL-4含量。 结果 NTN大鼠第4 天起,未成熟DC-SIGN+ DC即以肾间质为主浸润并于14 d成熟,且迁移及刺激 T 细胞增殖能力增强,其肾内分布与新月体形成、肾小管间质损伤程度及肾功能改变呈正相关。此外,大鼠第4 天起肾内趋化因子及促炎因子RANTES、 TNF-?琢 mRNA表达持续上调,而抗炎因子IL-10 mRNA于第4 天明显增强随后呈下调趋势;至14 d时IFN-γ/IL-4 mRNA比值增高,与DC成熟状况呈正相关。经PsL-EGFmAb干预,伴随DC 表面 DC-SIGN 及相应共刺激分子CD80表达下降,DC成熟、迁移及刺激 T 细胞增殖能力受抑,肾内促炎因子下降而抗炎因子上调,Th1/Th2 偏移受到抑制。同时大鼠肾内新月体形成减少,肾小管间质损伤程度减轻,且肾功能改善。 结论 DC-SIGN介导了DC 肾间质浸润,并可能是局部免疫反应失衡以及肾小管间质病变的重要调控因素。PsL-EGFmAb在抑制DC 迁移的同时可通过靶向DC-SIGN调抑 DC成熟及功能,进而发挥防治效应。     

Lentivirus degradation and DC-SIGN expression by human platelets and megakaryocytes

BACKGROUND AND AIM: As platelets are able to endocytose human immunodeficiency virus (HIV), we have investigated the fate of lentiviruses when endocytosed by human platelets and megakaryocytes (MK), and have characterized a specific receptor directly involved in this function. METHODS: Genetically modified (non-replicative) lentiviruses with an HIV envelope (HIV-e) or with a vesicular stomatitis virus protein G envelope (VSV-e) were alternatively used and their interaction with platelets and MK analyzed by electron microscopy (EM) and immunoEM. RESULTS: When incubated with platelets, HIV-e and VSV-e lentiviruses were internalized in specific endocytic vesicles and trafficked to the surface connected canalicular system (SCCS). Double immunolabeling for the viral P24 core protein and alpha-granule markers showed that lentiviruses were degraded in the SCCS after contact with alpha-granule proteins. In culture MK, lentiviruses were found in endocytic vesicles and accumulated in acid phosphatase-containing multivesicular bodies (MVB). The expression of the pathogen receptor dendritic cell-specific ICAM-grabbing non-integrin (DC-SIGN) was then demonstrated in platelets by flow cytometry, immunoEM and Western blot. Anti-DC-SIGN antibodies decreased HIV-e lentivirus internalization by platelets, showing that the receptor is functional. Specific signals for DC-SIGN protein and mRNA were also found in MK. CONCLUSION: This study indicates that platelets and MK can internalize lentiviruses in a pathway, which either provide a shelter to lentiviral particles or alternatively disrupts viral integrity. The receptor DC-SIGN is involved in this function.     

Dendritic cells respond to nasopharygeal carcinoma cells through annexin A2-recognizing DC-SIGN

Dendritic cells (DCs) play an essential role in immunity and are used in cancer immunotherapy. However, these cells can be tuned by tumors with immunosuppressive responses. DC-specific intercellular adhesion molecule 3-Grabbing Nonintegrin (DC-SIGN), a C-type lectin expressed on DCs, recognizes certain carbohydrate structures which can be found on cancer cells. Nasopharyngeal carcinoma (NPC) is an epithelial cell-derived malignant tumor, in which immune response remains unclear. This research is to reveal the molecular link on NPC cells that induces the immunosuppressive responses in DCs. In this article, we report identification of annexin A2 (ANXA2) on NPC cells as a ligand for DC-SIGN on DCs. N-linked mannose-rich glycan on ANXA2 may mediate the interaction. ANXA2 was abundantly expressed in NPC, and knockdown of ANXA2 suppressed NPC xenograft in mice, suggesting a crucial role of ANXA2 in NPC growth. Interaction with NPC cells caused DC-SIGN activation in DCs. Consequently DC maturation and the proinflammatory interleukin (IL)-12 production were inhibited, and the immunosuppressive IL-10 production was promoted. Blockage of either DC-SIGN or ANXA2 eliminated the production of IL-10 from DCs. This report suggests that suppression of ANXA2 at its expression or glycosylation on NPC may improve DC-mediated immunotherapy for the tumor.     

INAUGURAL ARTICLE by a Recently Elected Academy Member:Identification of a receptor required for the anti-inflammatory activity of IVIG

The anti-inflammatory activity of intravenous Ig (IVIG) results from a minor population of the pooled IgG molecules that contains terminal α2,6-sialic acid linkages on their Fc-linked glycans. These anti-inflammatory properties can be recapitulated with a fully recombinant preparation of appropriately sialylated IgG Fc fragments. We now demonstrate that these sialylated Fcs require a specific C-type lectin, SIGN-R1, (specific ICAM-3 grabbing non-integrin-related 1) expressed on macrophages in the splenic marginal zone. Splenectomy, loss of SIGN-R1⁺ cells in the splenic marginal zone, blockade of the carbohydrate recognition domain (CRD) of SIGN-R1, or genetic deletion of SIGN-R1 abrogated the anti-inflammatory activity of IVIG or sialylated Fc fragments. Although SIGN-R1 has not previously been shown to bind to sialylated glycans, we demonstrate that it preferentially binds to 2,6-sialylated Fc compared with similarly sialylated, biantennary glycoproteins, thus suggesting that a specific binding site is created by the sialylation of IgG Fc. A human orthologue of SIGN-R1, DC-SIGN, displays a similar binding specificity to SIGN-R1 but differs in its cellular distribution, potentially accounting for some of the species differences observed in IVIG protection. These studies thus identify an antibody receptor specific for sialylated Fc, and present the initial step that is triggered by IVIG to suppress inflammation.     

A multivalent inhibitor of the DC-SIGN dependent uptake of HIV-1 and Dengue virus

DC-SIGN is a C-type lectin receptor on antigen presenting cells (dendritic cells) which has an important role in some viral infection, notably by HIV and Dengue virus (DV). Multivalent presentation of carbohydrates on dendrimeric scaffolds has been shown to inhibit DC-SIGN binding to HIV envelope glycoprotein gp120, thus blocking viral entry. This approach has interesting potential applications for infection prophylaxis. In an effort to develop high affinity inhibitors of DC-SIGN mediated viral entry, we have synthesized a group of glycodendrimers of different valency that bear different carbohydrates or glycomimetic DC-SIGN ligands and have studied their DC-SIGN binding activity and antiviral properties both in an HIV and a Dengue infection model. Surface Plasmon Resonance (SPR) competition studies have demonstrated that the materials obtained bind efficiently to DC-SIGN with IC₅₀s in the μm range, which depend on the nature of the ligand and on the valency of the scaffold. In particular, a hexavalent presentation of the DC-SIGN selective antagonist 4 displayed high potency, as well as improved accessibility and chemical stability relative to previously reported dendrimers. At low μm concentration the material was shown to block both DC-SIGN mediated uptake of DV by Raji cells and HIV trans-infection of T cells.     

In vivo targeting of porcine reproductive and respiratory syndrome virus antigen through porcine DC-SIGN to dendritic cells elicits antigen-specific CD4T cell immunity in pigs

Immunogenicity of protein subunit vaccines may be dramatically improved by targeting them through antibodies specific to c-type lectin receptors (CLRs) of dendritic cells in mice, cattle, and primates. This novel vaccine development approach has not yet been explored in pigs or other species largely due to the lack of key reagents. In this study, we demonstrate that porcine reproductive and respiratory syndrome virus (PRRSV) antigen was targeted efficiently to dendritic cells through antibodies specific to a porcine CLR molecule DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin) in pigs. A recombinant PRRSV antigen (shGP45M) was constructed by fusing secretory-competent subunits of GP4, GP5 and M proteins derived from genetically-shuffled strains of PRRSV. In vaccinated pigs, when the PRRSV shGP45M antigen was delivered through a recombinant mouse-porcine chimeric antibody specific to the porcine DC-SIGN (pDC-SIGN) neck domain, porcine dendritic cells rapidly internalized them in vitro and induced higher numbers of antigen-specific interferon-γ producing CD4T cells compared to the pigs receiving non-targeted PRRSV shGP45M antigen. The pDC-SIGN targeting of recombinant antigen subunits may serve as an alternative or complementary strategy to existing vaccines to improve protective immunity against PRRSV by inducing efficient T cell responses.     

Expression of the chemokine receptor CCR1 in human renal allografts.

BACKGROUND: Chemokines are involved in the recruitment of leukocytes to vascularized allografts. CCR1 is a receptor for various proinflammatory chemokines and CCR1 blockade reduces renal allograft injury in rabbits. The purpose of the study was to characterize CCR1-positive cells in human renal allografts. METHODS: Formalin-fixed, paraffin-embedded allograft nephrectomies (n = 9) and non-involved parts of tumour nephrectomies (n = 10) were studied. Immunohistochemistry for CCR1, CD3 and CD68 was performed on consecutive sections. Double immunofluorescence for CCR1 and CD3, CD20, CD68, DC-SIGN and S100 was used on selected cases. Expression of CCR1 mRNA and the ligands CCL3 and CCL5 was studied in renal allograft biopsies with acute rejection (n = 10), with chronic allograft nephropathy (n = 8) and controls (n = 8). RESULTS: CCR1 protein was expressed by circulating cells in glomerular and peritubular capillaries, colocalizing with CD68. In renal allografts CCR1-positive cells were present within glomerular tufts, but only scattered CCR1-positive cells were found in tubulointerstitial infiltrates. CCR1 did not colocalize with the majority of CD68-positive cells in the interstitium. The small number of CCR1-positive interstitial cells were identified as CD20- or DC-SIGN-positive by double immunofluorescence. CCR1 mRNA was significantly increased in renal biopsies with acute allograft rejection (P < 0.001), and with chronic allograft nephropathy (P < 0.05), it correlated with the expression of CCL3 and CCL5, and with serum-creatinine. CONCLUSIONS: CCR1 mRNA expression was associated with renal function in allografts. CCR1 protein expression was restricted to monocytes, CD20-positive B cells and DC-SIGN-positive dendritic cells. Thus most interstitial macrophages were CCR1 negative, which may relate to down-regulation after migration into the interstitium in human renal allografts.