抗体依赖增强效应发生机制研究进展

在各类病原体特别是病毒的感染中,抗体依赖增强效应(Antibody-dependent enhancement,ADE)可使原有的感染加重,引起严重疾病。研究发现多种病原体的感染过程中均有抗体依赖增强效应ADE现象,且可能存在不同的发生机制。随着抗体依赖增强效应ADE现象产生机制研究的不断深入,有助于相应病原体疫苗的改造,从而使疫苗效用最大化,对控制包括寨卡病毒在内的病原体的感染将提供巨大帮助。本文就近年来抗体依赖增强效应ADE发生机制的研究进展进行综述,包括Fc段受体依赖、补体系统介导、非中和抗体介导、病毒表面蛋白介导及细胞活动介导的抗体依赖增强效应ADE机制,同时以登革病毒、人类免疫缺陷病毒、柯萨奇病毒、埃博拉病毒、寨卡病毒及其他病原体为例进行分类介绍。     

HCV相关抗体研究现状及其临床应用前景

研究表明人体丙型肝炎病毒（hepatitis Cvirus，HCV）感染可诱导毒株特异性抗体免疫应答，通过抗体包被或使病毒结构蛋白构象改变，中和抗体可阻止病毒结合于细胞受体并使其不能进入肝细胞，继而使之失活。体液应答在病毒感染的预防及恢复等方面起着至关重要的作用。由于病毒与宿主接触的第一步是通过病毒的外壳与细胞表面受体结合，中和这一步有望成为预防病毒感染的治疗模式之一。本文综述HCV相关抗体的研究进展及其临床应用前景。     

急性丙型肝炎中，CD4T细胞效应与中和性抗体及CD8T细胞效应的不同作用

背景和目的：在大多数患者中急性丙型肝炎病毒（HCV）的感染将转为慢性。虽然HCV特异性CD4T细胞的效应与HCV的清除有关，但对于病毒特异性CD8T细胞或者中和性抗体（nAb）的效应及在诱导两者中CD4的辅助作用方面知之甚少。     

HCV感染人滋养层细胞过程中抗体依赖性增强作用的初步研究

目的研究丙喇肝炎病毒（HCV）在感染人滋养层细胞的过程中是否存在抗体依赖性感染增强（ADE）作用，探讨HCV母婴传播的分子机制。方法将HCV阳性血清以4种不同方式感染体外培养人滋养层细胞，应用RT-PCR法对标本进行HCV RNA定性检测，并进一步评估不同浓度CD16单抗对感染过程的阻断作用。此外，应用免疫电镜技术观察滋养层细胞感染HCV病毒颗粒情。结果HCV RNA在全血清组、CD81单抗阻断组及LDL-R单抗阻断组多个标本均为阳性表达，且平均拷贝数较高，在FcγRⅢ（CD16）单抗阻断组多个标奉内未能检测到HCV RNA的表达，且阳性标本拷贝数较低；CD16单抗对感染的阻断作用随浓度的升高而增强；在全血清组、CD81单抗阻断组及LDL-R单抗阻断组多个标本细胞内可间断测得未脱壳的HCV病毒颗粒，CD16单抗阻断组细胞内未能检出。结论滋养层细胞膜CD81和LDL-R分子不参与HCV感染滋养层细胞的过程，而FcγRⅢ分子则与此过程密切相关。HCV感染人滋养层细胞过程中存在抗体依赖性增强作用。     

丙型肝炎

HCV的Core—NS3嵌合抗原在大肠杆菌中的表达、纯化及初步应用；老年HCV感染的临床随访研究；丙型肝炎免疫机制及其疫苗的研究进展（综述）；HCV核心抗原测定与HCV抗体测定的比较分析；VIP在慢性丙型肝炎病毒感染中的表达及意义；ELISA联合RT-nPCR检测慢性丙型肝炎病毒感染者结果分析；     

体外感染实验探讨丙型肝炎病毒的ADE分子机制

目的研究丙型肝炎病毒(HCV)在感染人滋养层细胞的过程中是否存在抗体依赖性感染增强(ADE)作用,以探讨HCV母婴传播的分子机制。方法将HCV阳性血清以4种不同方式感染人滋养层细胞,以免疫电镜观察HCV病毒颗粒在滋养层细胞中的表达,应用RT-PCR法、免疫组化法检测细胞内外的HCVRNA正链、负链,HCVNS5、NS3及C区抗原。结果在滋养层细胞胞浆内发现了HCV病毒颗粒,HCVRNA正链、负链,HCVNS5、NS3、C区抗原仅在全血清感染细胞内或上清中间断测得。结论HCV可以在滋养层细胞中复制。HCV感染滋养层细胞的过程中存在ADE机制,抗体和补体均参与了HCV的跨膜转运过程。     

丙型肝炎

HCV的Core—NS3嵌合抗原在大肠杆菌中的表达、纯化及初步应用；老年HCV感染的临床随访研究；丙型肝炎免疫机制及其疫苗的研究进展（综述）；HCV核心抗原测定与HCV抗体测定的比较分析；VIP在慢性丙型肝炎病毒感染中的表达及意义；ELISA联合RT-nPCR检测慢性丙型肝炎病毒感染者结果分析；[编者按]     

HCV C-Fc融合基因修饰的树突状细胞疫苗抗HCV功能研究

目的　探讨丙型肝炎病毒 (HCV)C Fc基因修饰的树突状细胞 (DCs)能否诱导抗HCV细胞和体液免疫反应。方法　将pcDNA3 HCV Fc质粒用电穿孔法转染经过白介素 4 (IL 4 ) ,粒 巨噬细胞集落刺激因子 (GM CSF)刺激增殖的小鼠DCs前体细胞 ,观察HCV、Fc抗原表达 ;将制备的 5×10 5/ 10 0 μlDC疫苗皮下免疫Balb/c小鼠 ,两周后检测特异性抗体、脾脏CD4 、CD8 细胞增殖作用以及诱导的细胞毒性T淋巴细胞 (CTL)反应。结果　HCVC Fc基因电穿孔法转染细胞在上述细胞因子作用下发育成能有效表达HCVC Fc并具有典型形态学与表型特征的DCs。免疫小鼠后 ,HCVC Fc基因转染DCs能诱导产生抗HCV特异性抗体和较强的CTL反应。结论　HCVC Fc基因修饰的DCs能增强对HCV特异性CTL效应的诱导能力 ,提示它在抗病毒疫苗发展中的潜力     

丙型肝炎疫苗研究的新理念、挑战与策略

丙型肝炎病毒（HCV）感染是引起慢性肝病的主要原因之一,严重危害人类健康,目前抗病毒治疗的标准方案为聚乙二醇干扰素α（PEG-IFN-α）联合利巴韦林,其有效率仅为50%70%,且疫苗研究进展缓慢,已成为严峻的公共卫生问题。近10多年来,对HCV感染发病机制、保护性免疫应答和病毒持续感染机制的认识取得了很大进展,中和抗体以及CD4＋和CD8＋T细胞在内的强烈的T细胞免疫应答已被证明与HCV的清除相关,这将是研制丙型肝炎疫苗的希望所在。当前HCV疫苗的研究主要集中在多肽疫苗、核酸疫苗、病毒载体疫苗、重组多表位疫苗、以抗原递呈细胞为载体的树突状细胞（DC）疫苗等,已有多种疫苗正在研制并进行进入临床试验前的测试。我们结合多年来对HCV的研究基础,通过与国内外同行交流,提出变＂单纯预防＂为＂防治结合,以诱导持续免疫应答和维持病毒抑制状态为基本目标＂的HCV疫苗研究新理念,发展以诱导细胞免疫为主的预防和治疗性疫苗,尤其是既能在体内有效激发HCV特异性细胞毒性T淋巴细胞（CTL）反应,又能维持CD4＋记忆T细胞功能的治疗性细胞疫苗。本文综述关于HCV保护性免疫应答及持续感染的机制,HCV疫苗研究新理念,目前面临的挑战以及研究策略。     

联合HCV抗原抗体免疫分析方法早期诊断HCV

据医学空间网12月23日报道（原载J Viral Hepat,2006 Jan：13（1）：5-10），缩短HCV病毒感染的窗口期对于输血机构及诊断机构来说是一项重要的任务。一种同时探测HCV抗原抗体的分析方法近来有所发展，更有学评价了此项检测方法与传统商业用方法的敏感性及特异性差异。有400份普通人群样本及100份“困难”样本即HCV抗体阴性的样本被用来进行该项研究。     

Epitopes required for antibody-dependent enhancement of Ebola virus infection

We have shown that antibody-dependent enhancement (ADE) of infection with Zaire Ebola virus (ZEBOV) is mediated by interaction of virus-specific antibodies with Fc receptors or complement component C1q and its receptors in vitro. ADE activities of the antisera to the viral glycoprotein (GP) were virus species specific and were primarily correlated with immunoglobulin (Ig) G2a and IgM levels but not with IgG1 levels. Interestingly, compared with ZEBOV, Reston Ebola virus (REBOV) had substantially weaker potential to induce ADE antibodies. Using monoclonal antibodies, we identified ZEBOV-specific ADE epitopes. To confirm epitope specificity, we constructed a chimeric ZEBOV GP, the ADE epitopes of which were replaced with the corresponding regions of REBOV GP. We found that mouse antisera to the chimeric ZEBOV GP showed less potential to induce ADE activity than did mouse antisera to wild-type ZEBOV GP, although they retained neutralizing activity. These data suggest that GP lacking the ADE-inducing epitopes may increase the potential of GP as a vaccine antigen.     

Comparison of P388D1 mouse macrophage cell line and human monocytes for assay of dengue-2 infection-enhancing antibodies

Tissue culture-adapted dengue 2 virus (DEN 2), strain 16681, exhibits antibody-dependent enhancement of infection (ADE) in P388D1 cells, a mouse macrophage-like cell line. ADE is dependent upon maintaining DEN 2 multiplicity of infection at between 0.1 and 0.001, and can be simply measured in multi-well plastic plates. The assay uses either trypsinized or non-trypsinized P388D1 cells at 5 x 10(5) cells per ml, an appropriate dilution of DEN 2 virus, and a source of antibody, and is most conveniently performed without further washing of stationary cultures, which are incubated in 5% CO2. Trypsinization of P388D1 cells prior to the addition of virus-serum mixtures reduced infection in control cultures thus increasing ADE. When cells were washed after incubation of virus-serum mixtures for 1 hour, a paradoxical increase of infection in cultures exposed to virus plus normal serum was noted, which reduced the sensitivity of the ADE assay. Using human cord blood sera, ADE titers measured in human monocytes and P388D1 cells were closely similar. This convenient and economical assay will facilitate large scale biological and epidemiological studies of dengue virus enhancing antibodies.     

寨卡病毒与登革热病毒交叉反应抗体引发严重性疾病的关系

登革病毒(DENV)不同血清型感染后,易导致抗体依赖增强反应(ADE)的严重性疾病发生。2015年5月巴西流行寨卡病毒(ZIKV)后,截止至2016年11月,流行已扩散到60多个国家和地区,毗邻我国的一些东南亚国家也有报告ZIKV感染病例。近期有研究显示,ZIKV和DENV的包膜(E)蛋白EDI和EDII两表位引发的抗体或由此产生的单克隆抗体具有很强的交叉反应性,易引起ADE的发生。我国沿海省份历年时有DENV病毒流行,今后ZIKV流行事件极有可能发生,因此,由该病毒流行引起的严重性疾病发生我们必须要关注和提出应对措施。     

Antibody-Dependent Enhancement of SARS-CoV-2 Infection of Human Immune Cells: In Vitro Assessment Provides Insight in COVID-19 Pathogenesis

Patients with COVID-19 generally raise antibodies against SARS-CoV-2 following infection, and the antibody level is positively correlated to the severity of disease. Whether the viral antibodies exacerbate COVID-19 through antibody-dependent enhancement (ADE) is still not fully understood. Here, we conducted in vitro assessment of whether convalescent serum enhanced SARS-CoV-2 infection or induced excessive immune responses in immune cells. Our data revealed that SARS-CoV-2 infection of primary B cells, macrophages and monocytes, which express variable levels of FcγR, could be enhanced by convalescent serum from COVID-19 patients. We also determined the factors associated with ADE, and found which showed a time-dependent but not viral-dose dependent manner. Furthermore, the ADE effect is not associated with the neutralizing titer or RBD antibody level when testing serum samples collected from different patients. However, it is higher in a medium level than low or high dilutions in a given sample that showed ADE effect, which is similar to dengue. Finally, we demonstrated more viral genes or dysregulated host immune gene expression under ADE conditions compared to the no-serum infection group. Collectively, our study provides insight into the understanding of an association of high viral antibody titer and severe lung pathology in severe patients with COVID-19.     

Studies of antibody-dependent enhancement of human immunodeficiency virus (HIV) type 1 infection mediated by Fc receptors using sera from recipients of a recombinant gp160 experimental HIV-1 vaccine.

Subneutralizing concentrations of sera from human immunodeficiency virus (HIV)-1-infected patients augment HIV infection mediated by Fc receptor uptake by human monocytes and the monocytic cell line U937. Antibody-dependent enhancement (ADE) and neutralization activity were studied in the sera of HIV-1 antibody-negative volunteers who had been immunized with three 40-micrograms doses of a recombinant gp160 (rgp160) candidate HIV vaccine. Volunteers were vaccinated with rgp160 or a hepatitis B vaccine as a control on days 0, 30, and 180. Sera were obtained before and after three doses of vaccine and were tested for ADE and neutralization activity. Serum samples collected before vaccination showed neither neutralization nor ADE activity. Thirteen sera from volunteers who received gp160 and four from placebo recipients failed to show ADE. Three sera showed low levels of neutralization of strain IIIB of HIV. Vaccination with this dose of rgp160 produced neutralizing antibodies in some subjects but did not induce detectable enhancing antibodies.     

Dynamic effects of antibody-dependent enhancement on the fitness of viruses

Antibody-dependent enhancement (ADE), a phenomenon in which viral replication is increased rather than decreased by immune sera, has been observed in vitro for a large number of viruses of public health importance, including flaviviruses, coronaviruses, and retroviruses. The most striking in vivo example of ADE in humans is dengue hemorrhagic fever, a disease in which ADE is thought to increase the severity of clinical manifestations of dengue virus infection by increasing virus replication. We examine the epidemiological impact of ADE on the prevalence and persistence of viral serotypes. Using a dynamical system model of n cocirculating dengue serotypes, we find that ADE may provide a competitive advantage to those serotypes that undergo enhancement compared with those that do not, and that this advantage increases with increasing numbers of cocirculating serotypes. Paradoxically, there are limits to the selective advantage provided by increasing levels of ADE, because greater levels of enhancement induce large amplitude oscillations in incidence of all dengue virus infections, threatening the persistence of both the enhanced and nonenhanced serotypes. Although the models presented here are specifically designed for dengue, our results are applicable to any epidemiological system in which partial immunity increases pathogen replication rates. Our results suggest that enhancement is most advantageous in settings where multiple serotypes circulate and where a large host population is available to support pathogen persistence during the deep troughs of ADE-induced large amplitude oscillations of virus replication.     

Monoclonal antibody-mediated enhancement of dengue virus infection in vitro and in vivo and strategies for prevention

Infection with dengue virus (DENV) or any other flavivirus induces cross-reactive, but weakly neutralizing or nonneutralizing, antibodies that recognize epitopes involving the fusion peptide in the envelope glycoprotein. Humanized mAb IgG 1A5, derived from a chimpanzee, shares properties of cross-reactive antibodies. mAb IgG 1A5 up-regulated DENV infection by a mechanism of antibody-dependent enhancement (ADE) in a variety of Fc receptor-bearing cells in vitro. A 10- to 1,000-fold increase of viral yield in K562 cells, dependent on the DENV serotype, was observed over a range of subneutralizing concentrations of IgG 1A5. A significant increase of DENV-4 viremia titers (up to 100-fold) was also demonstrated in juvenile rhesus monkeys immunized with passively transferred dilutions of IgG 1A5. These results, together with earlier findings of ADE of DENV-2 infection by a polyclonal serum, establish the primate model for analysis of ADE. Considering the abundance of these cross-reactive antibodies, our observations confirm that significant viral amplification could occur during DENV infections in humans with prior infection or with maternally transferred immunity, possibly leading to severe dengue. Strategies to eliminate ADE were explored by altering the antibody Fc structures responsible for binding to Fc receptors. IgG 1A5 variants, containing amino acid substitutions from the Fc region of IgG2 or IgG4 antibodies, reduced but did not eliminate DENV-4-enhancing activity in K562 cells. Importantly, a 9-aa deletion at the N terminus of the CH(2) domain in the Fc region abrogated the enhancing activity.     

The complexity of antibody-dependent enhancement of dengue virus infection

Antibody-dependent enhancement (ADE) has been proposed as a mechanism to explain dengue hemorrhagic fever (DHF) in the course of a secondary dengue infection. Very recently, Dejnirattisai et al., 2010 [1], published an important article supporting the involvement of anti-prM antibodies in the ADE phenomenon. The complexity of ADE in the context of a secondary dengue infection is discussed here.