Assembly, structure, and antigenic properties of virus-like particles rich in HIV-1 envelope gp120

In order to improve the immunogenicity of HIV-1 envelope glycoproteins, we have fused gp120 to a carrier protein, hepatitis B surface antigen (HBsAg), which is capable of spontaneous assembly into virus-like particles. The HBsAg-gp120 hybrid proteins assembled efficiently into 20-30 nm particles. The particles resemble native HBsAg particles in size and density, consistent with a lipid composition of about 25% and a gp120 content of about 100 per particle. Particulate gp120 folds in its native conformation and is biologically active, as shown by high affinity binding of CD4. The particles express conformational determinants targeted by a panel of broadly cross-reactive neutralizing antibodies, and they show tight packing of gp120. Because the particles are lipoprotein micelles, an array of gp120 on their surface closely mimics gp120 on the surface of HIV-1 virions. These gp120-rich particles can enhance the quality, as well as quantity, of antibodies elicited by a gp120 vaccine.     

Cloning and analysis of the envelope protein clone of HIV-1, CHNHLJ03009c34 from an infected individual in Heilongjiang province

Envelopeglycoprotein(Env)ofHIV1isacom plexoftwononcovalentlyassociatedsubunits,Gp120andGp41.Gp120isanexternalsubunit thatbindsthecellularreceptorCD4andachemo kinereceptor,suchasCXCR4orCCR5.Gp41isatransmembranesubunit,responsibleforthere ceptor mediatedmembranefusion[1,2].Because ofthehighvariabilityofHIV1,theaminoacid sequenceaswellasthestructureofviralenvelope canvaryandresultinthechangeofviraltropism withtimeextensionanddiseaseprogressionafter infection.DuringtheearlyphaseofHIVinfec…     

Epitope mapping and characterization of a novel CD4-induced human monoclonal antibody capable of neutralizing primary HIV-1 strains

Human immunodeficiency virus (HIV-1) enters target cells by binding its gp120 exterior envelope glycoprotein to CD4 and one of the chemokine receptors, CCR5 or CXCR4. CD4-induced (CD4i) antibodies bind gp120 more efficiently after CD4 binding and block the interaction with the chemokine receptor. Examples of CD4i antibodies are limited, and the prototypes of the CD4i antibodies exhibit only weak neutralizing activity against primary, clinical HIV-1 isolates. Here we report the identification of a novel antibody, E51, that exhibits CD4-induced binding to gp120 and neutralizes primary HIV-1 more efficiently than the prototypic CD4i antibodies. The E51 antibody blocks the interaction of gp120-CD4 complexes with CCR5 and binds to a highly conserved, basic gp120 element composed of the beta 19-strand and surrounding structures. Thus, on primary HIV-1 isolates, this gp120 region, which has been previously implicated in chemokine receptor binding, is accessible to a subset of CD4i antibodies.     

HIV-1 黑龙江省分离株CHNHLJ03009包膜克隆及分析

目的 分析黑龙江省Ⅰ型人免疫缺陷病毒（human irnmunodeficiency virus type 1，HIV-1）原代分离株包膜糖蛋白的变异性及表型特征。方法从一名HIV阳性但未发病的感染者外周血单个核细胞提取DNA，采用保守引物进行HIV包膜直接克隆，进行序列分析及系统树分析。构建了一株带该包膜蛋白的伪病毒并利用表达CXCR4和CCR5的靶细胞进行了感染实验，观察该病毒包膜利用辅助受体的表型特征。结果共获得2个有功能全长env克隆，分别命名为CHNHIJ03009c34（GenBank序列号为AY905493）和CHNHIA03009c33。用全长env氨基酸序列与国内外分离株进行同源性比较分析发现，与分离株CHNHLJ03009c34的包膜同源性最高的病毒为云南的HIV-1 B’亚型分离株RIA2，同源性为91．52％。系统发育分析结果表明，该株为泰国B’亚型，与云南分离株RIA2的遗传距离最近。对包膜蛋白结构分析结果显示，分离株CHNHLJ03009c34包膜在抗原性和亲水性上与RIA2没有明显差别。感染性检测结果显示该病毒只能感染U87．CD4．CCR5细胞，不能感染U87．CD4．CX-CR4细胞。结论本研究从黑龙江省一名HIV-1阳性者克隆到HIV-1CHNHLJ03009病毒的包膜基因，该病毒属于B’亚型（泰国亚型），为R5亲嗜性毒株。该包膜基因克隆为首次报道的黑龙江分离株。     

Thymic pathogenicity of an HIV-1 envelope is associated with increased CXCR4 binding efficiency and V5-gp41-dependent activity, but not V1/V2-associated CD4 binding efficiency and viral entry

We previously described a thymus-tropic HIV-1 envelope (R3A Env) from a rapid progressor obtained at the time of transmission. An HIV-1 molecular recombinant with the R3A Env supported extensive replication and pathogenesis in the thymus and did not require Nef. Another Env from the same patient did not display the same thymus-tropic pathogenesis (R3B Env). Here, we show that relative to R3B Env, R3A Env enhances viral entry of T cells, increases fusion-induced cytopathicity, and shows elevated binding efficiency for both CD4 and CXCR4, but not CCR5, in vitro. We created chimeric envelopes to determine the region(s) responsible for each in vitro phenotype and for thymic pathogenesis. Surprisingly, while V1/V2 contributed to enhanced viral entry, CD4 binding efficiency, and cytopathicity in vitro, it made no contribution to thymic pathogenesis. Rather, CXCR4 binding efficiency and V5-gp41-associated activity appear to independently contribute to thymic pathogenesis of the R3A Env. These data highlight the contribution of unique HIV pathogenic factors in the thymic microenvironment and suggest that novel mechanisms may be involved in Env pathogenic activity in vivo.     

The envelope glycoprotein of HIV-1 gp120 and human complement protein C1q bind to the same peptides derived from three different regions of gp41, the transmembrane glycoprotein of HIV-1, and share antigenic homology

Gp41, the transmembrane glycoprotein of HIV-1, has been shown to be non-covalently associated with gp120. We have shown that it also binds human C1q. To analyze the interaction site(s) of gp41 with these two molecules, we established an enzyme-linked immunosorbent assay (ELISA) system using recombinant soluble gp41 [amino acids (aa) 539–684] and peptides thereof. In the cell-external part of gp41 three sites (aa 526–538, aa 590–613 and aa 625–655) were found to bind both gp120 and C1q. That gp120 and C1q use the same sites was evidenced by the fact that these proteins competed with each other for the same sites in recombinant soluble gp41 and gp41 peptides. It could be demonstrated by ELISA, that rabbit antibodies against human C1q recognized gp120, and rabbit antibodies against gp120 cross-reacted with C1q. Rabbit anti-gp120, HIV-1-positive human sera and anti-gp120 obtained from such sera agglutinated sensitized sheep erythrocytes with human C1q (EAC1q). These data suggest that in addition to functional homology between C1q and gp120 structural homology between these two molecules exists. This molecular mimicry might become the basis for immunologically relevant autoimmune phenomena.     

Loss of the N-linked glycosylation site at position 386 in the HIV envelope V4 region enhances macrophage tropism and is associated with dementia

HIV infects macrophages and microglia in the central nervous system (CNS). Mechanisms that enhance HIV macrophage/microglial tropism are not well understood. Here, we identify an HIV Env variant in the V4 region of gp120, Asp 386 (D386), that eliminates an N-linked glycosylation site at position 386, enhances viral replication in macrophages, and is present at a higher frequency in AIDS patients with HIV-associated dementia (HAD) compared with non-HAD patients. D386 enhances HIV entry and replication in macrophages but not in microglia or peripheral blood mononuclear cells, possibly due to differential glycosylation in these cell types. A D386N mutation in the UK1br Env, which restores the N-linked glycan site, reduced neutralization sensitivity to the IgG1b12 (b12) monoclonal antibody, which recognizes a conserved neutralization epitope that overlaps the CD4 binding site. Molecular modeling suggested that loss of the glycan at position 386 increases exposure of the CD4 and b12 binding sites on gp120. Loss of a glycan at 386 was more frequent in Envs from HAD patients (26%; n=185) compared with non-HAD patients (7%; n=99; p<0.001). The most significant association of these Env variants with HAD was in blood or lymphoid tissue rather than brain. These findings suggest that increased exposure of the b12 epitope overlapping the CD4 binding site via elimination of a glycan at position 386 is associated with enhanced HIV macrophage tropism, and provide evidence that determinants of macrophage and microglia tropism are overlapping but distinct.     

Carbohydrate-binding agents (CBAs) inhibit HIV-1 infection in human primary monocyte-derived macrophages (MDMs) and efficiently prevent MDM-directed viral capture and subsequent transmission to CD4+ T lymphocytes

Carbohydrate-binding agents (CBAs) have been proposed as innovative anti-HIV compounds selectively targeting the glycans of the HIV-1 envelope glycoprotein gp120 and preventing DC-SIGN-directed HIV capture by dendritic cells (DCs) and transmission to CD4(+) T-lymphocytes. We now show that CBAs efficiently prevent R5 HIV-1 infection of human primary monocyte-derived macrophage (MDM) cell cultures in the nanomolar range. Both R5 and X4 HIV-1 strains were efficiently captured by the macrophage mannose-binding receptor (MMR) present on MDM. HIV-1 capture by MMR-expressing MDM was inhibited by soluble mannose-binding lectin and MMR antibody. Short pre-exposure of these HIV-1 strains to CBAs is able to prevent virus capture by MDM and subsequent syncytia formation in cocultures of the CBA-exposed HIV-1-captured MDM and uninfected CD4(+) T-lymphocytes. The potential of CBAs to impair MDM in their capacity to capture and to transmit HIV to T-lymphocytes might be an important property to be taken into consideration in the eventual choice to select microbicide candidate drugs for clinical investigation.     

Potency of HIV-1 envelope glycoprotein gp120 antibodies to inhibit the interaction of DC-SIGN with HIV-1 gp120

The interaction of DC-SIGN with gp120 provides an attractive target for intervention of HIV-1 transmission. Here, we have investigated the potency of gp120 antibodies to inhibit the DC-SIGN-gp120 interaction. We demonstrate that although the V3 loop is not essential for DC-SIGN binding, antibodies against the V3 loop partially inhibit DC-SIGN binding, suggesting that these antibodies sterically hinder DC-SIGN binding to gp120. Polyclonal antibodies raised against non-glycosylated gp120 inhibited both low and high avidity DC-SIGN-gp120 interactions in contrast to polyclonal antibodies raised against glycosylated gp120. Thus, glycans present on gp120 may prevent the generation of antibodies that block the DC-SIGN-gp120 interactions. Moreover, the polyclonal antibodies against non-glycosylated gp120 efficiently inhibited HIV-1 capture by both DC-SIGN transfectants and immature dendritic cells. Therefore, non-glycosylated gp120 may be an attractive immunogen to elicit gp120 antibodies that block the binding to DC-SIGN. Furthermore, we demonstrate that DC-SIGN binding to gp120 enhanced CD4 binding, suggesting that DC-SIGN induces conformational changes in gp120, which may provide new targets for neutralizing antibodies.     

Specific interaction of CXCR4 with CD4 and CD8alpha: functional analysis of the CD4/CXCR4 interaction in the context of HIV-1 envelope glycoprotein-mediated membrane fusion

We investigated possible interactions between HIV-1 receptor (CD4) and the main coreceptors CXCR4 and CCR5. We found that CD4 and CXCR4 coexpressed in 293T cells form a complex that can be immunoprecipitated with antibodies directed against the extracellular domain of either protein. Mutagenesis revealed that the CD4/CXCR4 interaction maps to two previously uncharacterized basic motifs in the cytoplasmic domain of CD4. HIV-1 envelope glycoprotein-mediated membrane fusion was found to be independent of the ability of CD4 and CXCR4 to interact, whether fusion was studied in a virus-cell or a cell-cell model. However, this interaction might explain the adaptation of HIV-1 to CXCR4 as an alternative to CCR5. We found that CXCR4 also interacts with the cytoplasmic domain of CD8alpha in a way that is similar to the CD4/CXCR4 interaction. The CD4/CXCR4 and CD8alpha/CXCR4 interactions may thus be involved in cellular signaling pathways shared by the CD4 and CD8alpha molecules.     

Role of Human CD4 D1D2 Domain in HIV-1 Infection

Broadly neutralizing antibodies and appropriate immunogens are critical for preexposure prophylaxis and therapeutic HIV vaccines. In this study, we aimed to explore effective antibodies against the genetically diverse HIV-1 strains by investigating the roles of human CD4 D1D2 domain and nonvariable immugens. The human CD4 D1D2 domain and the chimeric protein of mouse D1 domain/human D2 domain were expressed in Sf9 insect cells and purified by gel-filtration chromatography. The human CD4 D1D2 domain potently inhibited the infection of 77.8% HIV-1 pseudoviruses, including the clades AE, B’ and BC, with less than 20 μg/mL of IC₅₀. pcDNA3.1-mhD1D2m and pcDNA3.1-mhD2m plasmids were used for the production of mouse anti-human CD4 polyclonal antibodies. The neutralizing activities of the polyclonal antibodies were determined by using pseudotyped HIV-1 viruses. The antibodies induced by plasmids containing human CD4 D1D2 domain were able to potently inhibit all pseudotyped HIV-1 strains. The antibodies from mhD1D2m-immunized mice also showed strong binding capacity to CD4 expressed on the surface of TZM-bl cells. The potent and broad inhibitory activity of antibodies against the human CD4 D1D2 domain may be used to develop effective passive immunization agent to control the spread of HIV infection.     

Patterns of antibody reactivity to selected human immunodeficiency virus type 1 (HIV-1) gp160 epitopes in infected individuals grouped according to CD4+ cell levels

We examined sera from 160 HIV-infected individuals for antibodies reactive to HIV-1 gp160 epitopes defined by seven synthetic peptides. Seropositive individuals were placed into three groups based upon levels of circulating CD4+ cells. These groups consisted of individuals with (1) more than 400 CD4+ cells, (2) 200–400 CD4+ cells, and (3) fewer than 200 CD4+ cells/mm³. The percentage of sera containing antibodies reactive with two immunodominant gp160 epitopes (a.a. 304–321 and 600–611) was unchanged between groups, regardless of CD4 cell numbers. The percentage of sera containing antibodies reactive with weakly immunogenic gp160 epitopes, such as those defined by peptides 425–448 and 846–860, declined in the groups as CD4 values decreased. Our results suggest that the patterns of antibody reactivity to gp160 epitopes change as CD4 levels decline. A narrowing of the humoral immune response to epitopes on the envelope of HIV-1 appears to occur with disease progression.     

The role of N-glycosylation sites on the CXCR4 receptor for CXCL-12 binding and signaling and X4 HIV-1 viral infectivity

The chemokine receptor CXCR4 functions as one of the HIV-1 coreceptors and can be considered as an attractive target for the development of novel anti-HIV drugs. Here, we investigated the effect of its two known N-glycosylation sites g1 (NYT) and g2 (NVS) on the antiviral potential of several classes of entry inhibitors. The lack of g1 clearly affected the binding of the amino-terminal directed 2B11 mAb, but not the 12G5 mAb. No dramatic effects on CXCL-12 binding and CXCL-12-induced intracellular calcium responses were observed. Importantly, the anti-HIV-1 activity and antagonistic activity of the prototype compound of CXCR4 inhibitors, AMD3100, were not affected by the presence or absence of the CXCR4 N-glycans. Since CXCR4 N-glycans play a less important role in viral entry compared to the N-glycans on the HIV envelope, cells expressing CXCR4 N-glycosylation mutants might be no relevant alternative to allow HIV-1 escape from antivirals.     

Human progenitor cell recruitment via SDF-1α coacervate-laden PGS vascular grafts

Host cell recruitment is crucial for vascular graft remodeling and integration into the native blood vessel; it is especially important for cell-free strategies which rely on host remodeling. Controlled release of growth factors from vascular grafts may enhance host cell recruitment. Stromal cell-derived factor (SDF)-1α has been shown to induce host progenitor cell migration and recruitment; however, its potential in regenerative therapies is often limited due to its short half-life in vivo. This report describes a coacervate drug delivery system for enhancing progenitor cell recruitment into an elastomeric vascular graft by conferring protection of SDF-1α. Heparin and a synthetic polycation are used to form a coacervate, which is incorporated into poly(glycerol sebacate) (PGS) scaffolds. In addition to protecting SDF-1α, the coacervate facilitates uniform scaffold coating. Coacervate-laden scaffolds have high SDF-1α loading efficiency and provide sustained release under static and physiologically-relevant flow conditions with minimal initial burst release. In vitro assays showed that coacervate-laden scaffolds enhance migration and infiltration of human endothelial and mesenchymal progenitor cells by maintaining a stable SDF-1α gradient. These results suggest that SDF-1α coacervate-laden scaffolds show great promise for in situ vascular regeneration.     

Purification and partial characterization of R5, R5X4, and X4 HIV-1 subtype C envelope glycoproteins expressed in insect cells

Biological properties of four recombinant HIV-1 subtype C envelope glycoproteins from viruses with different phenotypic characteristics (CCR5 and/or CXCR4-utilizing) were investigated. The gp160 genes were cloned, expressed in Spodoptera frugiperda insect cells, purified, and their biological characteristics were examined. The conformational and functional integrity of the HIV-1 subtype C rgp160 was intact since they reacted with the A32, C11, IgG1b12, 7B2, and 17b conformational dependant monoclonal antibodies (MAb), sCD4, and patient sera. Baculovirus derived rgp160 can be used for further structural, functional, antigenic, and immunological studies.     

Ⅰ型人类免疫缺陷病毒包膜糖蛋白CD4结合位点修饰诱导小鼠体液免疫反应的实验研究

目的 探讨Ⅰ型人类免疫缺陷病毒(HIV-1)包膜糖蛋白(Env) gp120的CD4结合位点(CD4BS)核心区第423、425和431位氨基酸三联突变ING/MKE对其诱导体液免疫反应的影响.方法 构建HIV-1原代毒株06044包膜gp120 ING/MKE三联突变表达载体pcT22-06044 gp120T-ING/MKE(gp120T-ING/MKE),在体外转染的HEK293T细胞表达三聚化野生型gp120Twt蛋白和突变体gp120T-ING/MKE蛋白.免疫BALB/c小鼠后检测结合抗体、中和抗体和骨髓抗原特异性浆细胞.结果 获得真核表达载体gp120T-ING/MKE.转染后,在293T细胞培养上清中检测到了三聚化重组蛋白.末次免疫后14 d,gp120Twt和gp120T-ING/MKE免疫血清中结合抗体滴度都大于1∶1 000,但两组血清抗体滴度无显著差异.突变体组骨髓特异性浆细胞分泌水平和非特异浆细胞水平均低于野生型gp120免疫组.野生型和突变体免疫诱导血清抗体的中和活性均不强.结论 HIV-1包膜蛋白CD4结合区423、425和431位三联突变没有改善gp120蛋白的免疫原性.     

HIV-1蛋白诱导T细胞产生IFN-γ反应特征及对HIV-1感染者病情进展的影响

目的 探讨HIV-1特异性T细胞反应特征及对HIV-1感染者病情进展的影响.方法 通过合成重叠肽技术及ELISPOT技术,采用队列研究方法对37名HIV-1感染者的病毒特异性T细胞免疫反应进行分析.结果 83.78%(31/37)的HIV-1感染者对1个或多个合成肽反应(反应强度大于50 SFU/106 PBMCs).HIV-1B型病毒不同蛋白均可激发HIV-1感染者的特异性T细胞反应,其中HIV-1 Gag蛋白被识别的频率最高,81%的HIV-1感染者识别HIV-1 Gag而且HIV-1 Gag蛋白诱导的T细胞反应强度最高,相对强度达到28.25%,明显高于其他蛋白,差异具有统计学意义(F=17.969,P<0.001);重叠肽诱导T细胞分泌IFN-γ反应频率、反应强度在HIV-1感染无症状期和艾滋病期无明显区别,但是HIV-1 Gag蛋白诱导的T细胞反应强度在无症状期明显高于艾滋病期.结论 HIV-1B型病毒不同基因编码蛋白激发T细胞分泌IFN-γ反应小同,其中HIV-1 Gag蛋白特异性T细胞在控制病情进展方面发挥了重要作用.     

Prevalence of CXCR4-tropic viruses in clustered transmission chains at the time of primary HIV-1 infection

During 2003–2010, 555 strains isolated from sexually-infected patients at the time of primary HIV-1 infection (PHI) were characterized. Tree topology revealed that 11.7% of PHIs segregated into transmission clusters. CXCR4-usage was identified in 27 strains (4.9%) and was significantly associated with subtype B (p 0.003) and low CD4 cell count (p 0.01). In clustered and unique PHIs, the prevalence of CXCR4-tropic strains was 1.5% and 5.3%, respectively (p 0.35). Our results are in line with the hypothesis of a mucosal bottleneck contributing to the high prevalence of CCR5 variants during PHI.     

SDF-1/CXCR4生物轴活化诱导对鼠骨髓源性内皮祖细胞生物学性能的影响

目的 观察基质细胞衍生因子-1( SDF-1)及其特异性受体CXCR4生物轴对体外培养的鼠骨髓源性内皮祖细胞(EPCs)生物学性能的影响.方法 以密度梯度离心法获取大鼠骨髓单个核细胞,由Dil-ac-LDL和FITC-UEA-1荧光双染鉴定后确认为EPCs.传代培养后,加入不同浓度SDF-1溶液,培养48 h,然后分别...