中国HIV/AIDS典型进展者与疾病长期不进展者中和抗体保守表位氨基酸变异比较研究

目的 研究中国HIV/AIDS典型进展者及疾病长期不进展者(LTNP)中和抗体保守表位氨基酸变异,探讨中和抗体表位变异与疾病进展关系,为开展中和抗体免疫治疗和疫苗设计奠定理论基础.方法 RT-PCR及巢式PCR扩增HIV/AIDS典型进展者及LTNP的HIV-1 gp120 C2～C3区基因,双脱氧终止法进行核酸序列测定,翻译为氨基酸序列,与HIV-1 Sequence Database参考毒株比对识别中和抗体保守表位氨基酸变异.结果 HIV/AIDS典型进展者CD4结合位点(CD4BS)、CD4诱导(CD4i)、2G12中和抗体保守表位氨基酸均存在变异,LTNP 2G12中和抗体保守表位氨基酸存在变异;LTNP各表位突变率较典型进展的HIV感染者/AIDS患者有降低趋势,但差异无统计学意义(P＞0.05);CD4BS、CD4i、2G12变异表位构成比分别为25.0%、22.9%、52.1%,2G12表位变异明显高于CD4BS和CD4i表位,差异有统计学意义(P＜0.01);CD4BS和CD4i保守表位变异多见于E370Q(10.8%),2G12保守表位变异多见于N295V(18.9%)和T297I(9.5%).结论 中国HIV感染人群中,LTNP中和抗体保守表位氨基酸构成相对稳定,变异较典型进展的HIV感染者/AIDS患者少见,目前发现2G12中和抗体表位存在较低水平变异.中和抗体表位中,2G12表位变异较CD4BS和CD4i表位多见,各类型中和抗体保守表位氨基酸位点的变异程度存在差异.     

中国92例HIV/AIDS患者HIV-1 gp41 2F5和4E10中和抗体表位变异研究

目的 探讨92例HIV/AIDS患者HIV-1病毒近膜端(membrane proximal external re-gion,MPER)中和抗体2F5和4E10保守表位ELDKWA、NWFDIT氨基酸变异特点,为中国HIV/AIDS患者免疫治疗以及疫苗设计提供数据.方法 Nest-PCR扩增HIV-1 env区gp41段基因,核酸序列测定,翻译为氨基酸与HIV-1 Sequence Database HXB Ⅱ参考株中和抗体表位数据比对,分析2F5、4E10中和表位氨基酸变异情况.结果 92例HIV/AIDS患者HIV-1外膜蛋白env gp41段中和抗体2F5、4E10保守表位氨基酸均存在突变;2F5中和抗体表位主要有E662A(14.1%)、K665S(17.4%)、A667K(16.3%)突变;4E10中和抗体表位主要有N671S(13.0%)、D674S(3.3%)、T676S(16.3%)突变;CRF_B'C亚型与B'亚型的2F5和4E10表位氨基酸突变差异具有统计学意义(P<0-05);CRF_B'C与CRF01_AE亚型2F5表位突变差异具有统计学意义(P<0.05);B'亚型缓慢进展者、HIV感染者和AIDS患者的4E10表位氨基酸突变差异具有统计学意义(P<0.05).结论 92例HIV/AIDS患者HIV.1包膜蛋白env gp41段中和抗体2F5、4E10中和表位氨基酸存在突变,且变异多样化;不同亚型中和抗体保守表位氨基酸位点变异有差异;B'亚型4E10中和抗体表位变异可能与疾病进展有一定联系.     

HIV-1广谱中和性单克隆抗体的研究进展

从HIV感染患者血清中分离的针对HIV-1包膜上保守表位的中和性单克隆抗体(mAb)很多,识别的表位分别是HIV-1gp120上CD4结合位点(CD4bs),gp41的跨膜前域MPER,gp120表面包膜的高甘露聚糖,gp120上V2/V3环,这些抗体对HIV-1疫苗免疫原的研究设计至关重要.本文主要综述了各中和性单克隆抗体的结构特征,识别的表位,抗体与病毒包膜之间的相互作用.     

HIV-2 gp105重组鸡痘病毒引起小鼠细胞和体液免疫应答

人免疫缺陷病毒Ⅱ型（human immunodeficiency virus type 2，HIV-2）于1986年在几内亚一比绍被发现。起初HIV-2仅在西非呈区域性流行，随后在欧洲、美洲和亚洲也出现了感染者和发病者。我国的首例HIV-2感染者于1998年在福建省发现，并检测出HIV-1与HIV-2的共感染患者。因此，研究有效的HIV-2疫苗势在必行。HIV-2env基因编码前体蛋白gp140，后者裂解后生成外膜蛋白gp105和跨膜蛋白g036。gp105是病毒的主要抗原，其表面具有大量的Ab表位、TH表位和CTL表位，能诱导机体产生强烈而广泛的中和抗体和细胞毒（CTL）反应，因此是基因工程疫苗研究的重要靶点。本研究将已构建的HIV-2 gp105重组鸡痘病毒大量制备后免疫BALB／c小鼠，观察其在小鼠体内的免疫原性，以获得第一手的实验资料。     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

HIV-1中和抗体b12的研究进展

HIV-1由于其外膜糖蛋白结构多变可以很容易逃避抗体介导的中和作用.b12抗体是目前少数几种被证明具有广谱抗HIV-1活性的中和抗体,近来关于gp120结构研究表明在gp120上有一个保守的中和位点,且b12抗体可以和这个位点结合从而阻断靶细胞CD4与gp120作用,这一发现预示b12抗体对于新一代艾滋病疫苗设计具有重要的作用.本文即对b12抗体的有关研究进展作一综述.     

Identification of amino acids in the V3 region of gp120 critical for virus neutralization by human HIV-1-specific antibodies.

The importance of the dependence on single amino acids in the V3 region of HIV-1 gp120 was evaluated for virus neutralization and antibody-dependent cellular cytotoxicity (ADCC). Synthetic overlapping 15-mer peptides and a set of omission peptides covering amino acids 301-317 were used. Sera from 29 HIV-1-infected individuals at different stages of disease were tested for neutralization, ADCC and specific IgG reactivity. Six HIV-1 neutralizing monoclonal antibodies (mAb) acted as controls. All mAb reacted with a region (amino acids 304-318) of gp120, previously shown to induce neutralizing antibodies. The amino acids essential for reactivity were identified to be within the sequence GPGR (amino acids 312-315). The importance of this region for occurrence of neutralizing antibodies in infected humans was investigated using the same set of peptides. Out of 29 individuals, 21 were found to have neutralizing antibodies in titres between 100 and 1000. Among the neutralization-positive sera, 17/21 (81%) reacted with amino acids 304-318, compared with only one of eight sera (13%) negative in neutralization. When any of the four amino acids G, P, G or R were deleted, the seroreactivity decreased considerably. The conserved sequence GPGR was therefore considered to be the most important for neutralization in this region in human sera as well. Thus, the conserved sequence GPGR in the V3 region of gp120 is critical for virus neutralization by human HIV-1-specific antibodies.     

Amino acid residues of the human immunodeficiency virus type I gp120 critical for the binding of rat and human neutralizing antibodies that block the gp120-sCD4 interaction.

We have characterized the discontinuous epitopes recognized by two rat and three human neutralizing monoclonal antibodies (mAb) by examining the effect of single amino acid changes in conserved residues of gp120 on mAb recognition. A human mAb derived from an infected individual, 448D, and two rat mAbs, 39.13g and 39.3b, respectively, derived by immunization with native recombinant gp120, recognize similar epitopes. Recognition of the envelope glycoproteins by these mAbs was affected by changes in gp120 amino acid residues 88, 113, 117, 257, 368, or 370. The gp120 amino acids 257, 368, and 370 have previously been reported to be important for CD4 binding, which is consistent with the ability of these mAbs to block the gp120-CD4 interaction. Residues 88, 113, and 117 are not thought to be important for CD4 binding, suggesting that the antibody epitopes overlap, but are distinct from, the CD4 binding region. We also found that some alterations in gp120 residues 88, 117, 368, or 421 reduced the ability of polyclonal sera from HIV-1-infected individuals to inhibit the interaction of the mutant gp120 glycoproteins with soluble CD4. Thus, changes in the HIV-1 gp120 glycoprotein that minimally affect the receptor binding may allow escape from neutralizing antibodies directed against the CD4 binding region.     

Structural elements of primary CCR5-using HIV-1 gp120 proteins influencing sensitivity and resistance to the broadly neutralizing monoclonal antibody b12

Structure-guided approaches to HIV-1 vaccine design depend on knowledge of the presentation of neutralizing epitopes on gp120, such as the epitope for the broadly neutralizing mAb b12. Here, we characterized predicted three-dimensional structures of functionally diverse gp120 proteins in their b12-bound conformation, to better understand the gp120 determinants that expose or occlude the b12 epitope. Mapping the gp120-b12 binding interface identified amino acid polymorphisms within the C2, C3, C4 and V5 regions of gp120 associated with augmented b12 binding, and importantly, identified residues in the b12-exclusive binding domain of gp120 that are important for b12 neutralization resistance. Structural studies suggest that these b12 resistance variants promote reduced conformational flexibility in the b12 recognition site, which we show involves structural alterations within the gp120 CD4 binding loop and the V4 loop. Together, our studies provide new mechanistic insights into the gp120 determinants influencing sensitivity and resistance to HIV-1 neutralization by b12.     

A single amino acid substitution in the C4 region in gp120 confers enhanced neutralization of HIV-1 by modulating CD4 binding sites and V3 loop

Identification of vulnerability in the HIV-1 envelope (Env) will aid in Env-based vaccine design. We recently found an HIV-1 clade C Env clone (4-2.J45) amplified from a recently infected Indian patient showing exceptional neutralization sensitivity to autologous plasma in contrast to other autologous Envs obtained at the same time point. By constructing chimeric Envs and fine mapping between sensitive and resistant Env clones, we found that substitution of highly conserved isoleucine (I) with methionine (M) (ATA to ATG) at position 424 in the C4 domain conferred enhanced neutralization sensitivity of Env-pseudotyped viruses to autologous and heterologous plasma antibodies. When tested against monoclonal antibodies targeting different sites in gp120 and gp41, Envs expressing M424 showed significant sensitivity to anti-V3 monoclonal antibodies and modestly to sCD4 and b12. Substitution of I424M in unrelated Envs also showed similar neutralization phenotype, indicating that M424 in C4 region induces exposure of neutralizing epitopes particularly in CD4 binding sites and V3 loop.     

Structure-based,targeted deglycosylation of HIV-1 gp120 and effects on neutralization sensitivity and antibody recognition

The human immunodeficiency virus (HIV-1) exterior envelope glycoprotein, gp120, mediates receptor binding and is the major target for neutralizing antibodies. Primary HIV-1 isolates are characteristically more resistant to broadly neutralizing antibodies, although the structural basis for this resistance remains obscure. Most broadly neutralizing antibodies are directed against functionally conserved gp120 regions involved in binding to either the primary virus receptor, CD4, or the viral coreceptor molecules that normally function as chemokine receptors. These antibodies are known as CD4 binding site (CD4BS) and CD4-induced (CD4i) antibodies, respectively. Inspection of the gp120 crystal structure reveals that although the receptor-binding regions lack glycosylation, sugar moieties lie proximal to both receptor-binding sites on gp120 and thus in proximity to both the CD4BS and the CD4i epitopes. In this study, guided by the X-ray crystal structure of gp120, we deleted four N-linked glycosylation sites that flank the receptor-binding regions. We examined the effects of selected changes on the sensitivity of two prototypic HIV-1 primary isolates to neutralization by antibodies. Surprisingly, removal of a single N-linked glycosylation site at the base of the gp120 third variable region (V3 loop) increased the sensitivity of the primary viruses to neutralization by CD4BS antibodies. Envelope glycoprotein oligomers on the cell surface derived from the V3 glycan-deficient virus were better recognized by a CD4BS antibody and a V3 loop antibody than were the wild-type glycoproteins. Absence of all four glycosylation sites rendered a primary isolate sensitive to CD4i antibody-mediated neutralization. Thus, carbohydrates that flank receptor-binding regions on gp120 protect primary HIV-1 isolates from antibody-mediated neutralization.     

Characterization of human monoclonal antibodies selected with a hypervariable loop-deleted recombinant HIV-1(IIIB) gp120

Recombinant gp120 of the HIV-1(IIIB) isolate (BH10 clone) has been mutated to form the PR12 protein with the first 74 C-terminal amino acids and the V1, V2 and V3 hypervariable loops deleted. A variety of studies have shown that the CD4 binding domain (CD4bd) is very well exposed in PR12 in contrast to rgp120(LAI). Using PR12 for selection of human monoclonal antibodies (MAbs) from HIV-infected individuals, five MAbs were generated with specificities to the epitopes overlapping the CD4bd (1570A,1570C,1570D,1595 and 1599). The three MAbs, 1570A, C and D, generated from one HIV-infected individual, represent one MAb as determined by sequence analysis of the V(H)3 region. Since the epitopes overlapping the CD4bd exhibit variability among HIV-1 clades, the specificity of anti-CD4bd MAbs were distinguished by differing patterns of binding to recombinant envelope proteins derived from clade A, B, C, D and E viruses. The PR12-selected MAbs were also compared with a panel of gp120-selected anti-CD4bd MAbs and showed a different range of specificities. MAb 1599 is clade B specific, MAb 1595 reacts with the A, B and D clades, while MAb 1570 recognises the most conserved epitope, as it binds to all proteins. The results show that the exposure of different epitopes in the CD4bd of the PR12 protein allows this protein to serve as an immunogen and to induce anti-CD4bd antibodies.     

Phage-displayed mimotopes recognizing a biologically active anti-HIV-1 gp120 murine monoclonal antibody

Antibody-dependent cellular cytotoxicity (ADCC) is a host defense mechanism in which Fc receptor-bearing effector cells in combination with antigen-specific antibodies recognize and kill antigen-expressing target cells. The authors previously described a murine monoclonal antibody (MAb-ID6) that mediated ADCC activity against HIV-infected cells. It was demonstrated that the specificity of MAb-ID6 maps to the first 204 amino acids of gp120; however, the exact epitope was not identified. In the present work, by screening phage display libraries with MAb-ID6, the authors have mapped the corresponding epitope to amino acids 86-100 (HIV-1 gp120 sequence). This epitope lies within the C1 region of gp120 and is highly conserved among all subtypes and circulating recombinant forms of HIV-1. Thus, these phage mimotopes of C1 may serve as components of a vaccine for the induction of gp120-specific antibodies mimicking MAb-ID6.     

A virus binding assay for studying the antigenic landscape on intact, native, primary human immunodeficiency virus-type 1

This protocol describes a simple assay that can be used to study the nature of exposure of antigenic epitopes and antigenic relatedness of different intact, native HIV-1 strains. The assay is based on the principle that mAbs coated on microtiter wells bind to epitopes on the surface of intact, native virions. The bound virion is then lysed to release p24, which is then quantitated (pg/ml) to give a measure of the amount of virion bound to the mAb. High p24 levels released after lysis correlate with high level capture of virions by mAbs, and as such, reflect good exposure of the epitope on the virion. Likewise, binding patterns of a specific mAb with different virus strains reveal information on their antigenic relatedness. In establishing this assay, the nature of exposure of antigenic epitopes and the antigenic relatedness of six intact, native HIV-1 virions of clades A, B, C, D, F and G were examined using anti-HIV-1 mAbs directed at epitopes in the V2, V3, CD4bd and C5 of gp120, and in clusters I and II of the gp41 region. Analysis of the binding data shows that mAbs directed at epitopes in the V3, C5 and gp41 Cluster I region bound best to the viruses examined, suggesting that these are the regions most exposed and conserved on intact, native HIV-1 virions of different clades. Epitopes in the V2 and CD4bd of gp120, and in gp41 cluster II, are not exposed on intact, native virions.     

High-mannose-specific deglycosylation of HIV-1 gp120 induced by resistance to cyanovirin-N and the impact on antibody neutralization

HIV-1 uses glycans on gp120 to occlude its highly immunogenic epitopes. To better elucidate escape mechanisms of HIV-1 from carbohydrate-binding agents (CBA) and to understand the impact of CBA-escape on viral immune evasion, we generated and examined the biological properties of HIV-1 resistant to cyanovirin-N (CV-N) or cross-resistant to additional CBAs. Genotypic and phenotypic characterization of resistant env clones indicated that 3-5 high-mannose residues from 289 to 448 in the C2-C4 region of gp120 were mutated and correlated with the resistance levels. The specificity and minimal requirements of deglycosylation for CV-N resistance were further assessed by mutagenesis study. The sensitivity of resistant variants to a range of CBAs, immunoglobulins, sera and monoclonal antibodies (MAb) were investigated. For the first time, our data have collectively defined the high-mannose residues on gp120 affecting CV-N activity, and demonstrated that CBA-escape HIV-1 has increased sensitivity to immunoglobulins and sera from HIV patients, and particularly to V3 loop-directed MAbs. Our study provides a proof-of-concept that targeting HIV-1 glycan shields may represent a novel antiviral strategy.