艾滋病毒广谱中和抗体诱导成熟的机理研究

HIV-1 has evolved various mechanisms to escape human immune surveillance. So far, there is no effective HIV/AIDS vaccine. Broadly neutralizing antibodies (bnAbs) are likely to be a key component of protective immunity conferred by an effective HIV-1 vaccine. Potent bnAbs are uncommon in natural infections. Although extensive characterization of known broadly neutralizing monoclonal antibodies (bnmAbs) isolated from few HIV-1-infected elite controllers have revealed their conserved structural determinants, elicitation of the same or similar bnAbs by vaccination has yet to be achieved. We and others have reported that, known HIV-1 bnmAbs were highly divergent from their germline predecessors, and the germline Abs lacked measurable binding to HIV-1 envelope (Env) glycoprotein. Based on these observations, we hypothesized that extensive somatic hypermutation may be required for development of HIV-specific bnAbs and their somatic maturation may be initiated by non-HIV primary immunogen(s), leading to elicitation of intermediate Abs (iAbs) that can bind to Env and quickly mature to bnAbs upon HIV-1 infection or vaccination by secondary immunogen(s). Such iAbs may exist in some uninfected human individuals due to pre-exposure to the primary immunogen(s), which enables the immune system to rapidly respond to HIV-1 infection, thus effectively contain the virus. This proposed study is to test our hypothesis using known bnmAbs b12 and VRC01 as model Abs. Our recent study indicates the existence of b12 iAbs in nonimmune human and rhesus macaque antibody repertoires and the existence of possible primary immunogens for b12, which rationalize our study. In this study, we will identify b12 and VRC01 iAbs from nonimmune human and macaque antibody repertoires, identify possible primary immunogens that may trigger the somatic maturation of na?ve B-cells expressing b12 and VRC01 germline Abs, and further test the primary immunogens in combination with Env trimer for immunogenicity in rhesus macaques. Guiding the immune response using primary and secondary immunogens is a novel approach for HIV/AIDS vaccine development. Our study may eventually lead to development of an effective HIV/AIDS vaccine that can elicit high titers of potent bnAbs.

艾滋病毒具有多种逃避人体免疫监控的机制。人类迄今没有有效的艾滋疫苗。广谱中和抗体很有可能是有效艾滋疫苗诱导的免疫反应的关键组分。广谱中和抗体只在极少数自然感染者中产生，从他们体内分离到的广谱中和单克隆抗体在被动免疫中可有效预防病毒感染。尽管人们对它们的结构和抗原结合表位进行了广泛研究，然而诱导相同或相似的广谱中和抗体的努力都未能成功。我们的研究发现，艾滋病毒广谱中和抗体都具有很高程度的体细胞变异；而且其原始抗体不能与病毒膜蛋白结合。由此我们假说：非艾滋病毒来源的初级免疫原可能启动广谱中和抗体原始抗体的体细胞成熟过程，从而刺激机体产生中间抗体，而这些中间抗体能够结合病毒膜蛋白，并且能在病毒感染或次级免疫原免疫后迅速成熟为广谱中和抗体。本研究旨在以广谱中和单抗b12和VRC01为模型抗体验证该假说。利用二元免疫定向诱导免疫反应是疫苗研究的新途径。本研究的成功将有助于研发有效的艾滋病毒疫苗。

艾滋病毒具有多种逃避人体免疫监控的机制。人类迄今没有有效的艾滋疫苗。广谱中和抗体很有可能是有效艾滋疫苗诱导的免疫反应的关键组分。广谱中和抗体只在极少数自然感染者中产生，从他们体内分离到的广谱中和单克隆抗体在被动免疫中可有效预防病毒感染。尽管人们对它们的结构和抗原结合表位进行了广泛研究，然而诱导相同或相似的广谱中和抗体的努力都未能成功。我们的研究发现，艾滋病毒广谱中和抗体都具有很高程度的体细胞变异；而且其原始抗体不能与病毒膜蛋白结合。由此我们假说：非艾滋病毒来源的初级免疫原可能启动广谱中和抗体原始抗体的体细胞成熟过程，从而刺激机体产生中间抗体，而这些中间抗体能够结合病毒膜蛋白，并且能在病毒感染或次级免疫原免疫后迅速成熟为广谱中和抗体。本研究旨在以广谱中和单抗b12和VRC01为模型抗体验证该假说。利用二元免疫原定向诱导免疫反应是疫苗研究的新途径。我们收集了各种植物叶子，昆虫，水生微生物，实验用大肠杆菌等材料，提取了它们的基因组DNA，并分别构建了3个大库容的酵母表达基因组片段库（植物叶子+昆虫，水生微生物，实验用大肠杆菌）。我们用生物素标记的b12的中间抗体混合物作钓饵，利用酵母表面表达技术和细胞流式计数技术筛选到5个多肽。分离到的多肽与艾滋病毒表面蛋白不具有同源性，但它们都能与b12原始抗体和人或恒河猴的中间抗体很好结合，其亲和力均高于刺激B细胞受体（抗体）成熟所需的1uM。所有筛选的多肽都可与兔子b12原始抗体结合。我们用这些多肽作为初始免疫原，单独免疫或与艾滋病毒表面蛋白共免疫或顺序免疫兔子，鉴定了它们的免疫原性及刺激诱导兔子b12原始抗体体细胞成熟的可能性。本研究的成功将有助于研发有效的艾滋病毒疫苗。