Antigenic properties of the V1/V2 domain of HIV-1 gp120

描述(由申请人提供)：尽管迫切需要艾滋病毒疫苗，但目前的疫苗方法取得的成功有限。我们已经证明，许多来自原始病毒的包膜病毒对标准抗体中和的抵抗力的一个主要因素是V1/V2结构域对敏感的中和靶点的掩蔽。这表明，通过更好地了解这种耐药机制，并通过识别不容易受到这种阻断作用的其他免疫靶点，将有助于开发有效的疫苗。我们已经在主要HIV-1包膜蛋白的V2结构域中确定了一个特定的区域，该区域是对几种单抗极其敏感的中和靶点。C108G针对构象和糖依赖的V2表位，以比几乎任何其他已知抗体更强的效力中和包含其表位的病毒。2909针对的是在完整病毒粒子上特异表达的四元表位，而不是可溶性的Env蛋白，对SF162和Jr-FL变异体具有更强的中和活性。2909与病毒粒子的结合需要在环境中同时存在V2和V3结构域。我们最近已经证明，2909表位的V3决定因素非常广泛，2909的类型特异性是由于要求V2中的残基映射到与C108g决定簇完全相同的区域。虽然这些单抗是类型特异性的，但C108G和2909表位都与公认的分支B V2序列仅在单个残基上不同。这些单抗的无与伦比的效力认为，它们结合到一个特别敏感的中和区域，并表明这些表位的保守形式可能成为重要的疫苗靶点。这一建议将进一步绘制负责中和掩蔽的V1/V2决定簇，研究V1/V2结构域在自体中和中和中的作用，更完整地定义V2中介导有效中和的表位，分离和鉴定更多具有更广泛中和活性的V2特异性单抗，并确定这些Fab与适当的V1/V2抗原之间形成的复合体的结构。最后，这些数据将被用来设计优化的微型蛋白质，以高度免疫原性的形式呈现关键的V2表位，并在几种动物模型中测试这种免疫原诱导广谱中和抗体的能力。

DESCRIPTION (provided by applicant): Despite the desperate need for an HIV vaccine, current approaches towards a vaccine has had limited success. We have shown that a major factor in the resistance of many Envs derived from primary viruses to neutralization by standard antibodies is masking of sensitive neutralization targets by the V1/V2 domain. This suggests that the development of an effective vaccine would be facilitated by a better understanding of this resistance mechanism, and by the identification of additional immune targets that are not susceptible to such blocking effects. We have identified a particular region in the V2 domain of primary HIV-1 Envs that is an extremely sensitive neutralization target to several mAbs. C108g, directed against a conformational and glycan-dependent V2 epitope, neutralizes viruses containing its epitope with greater potency than that of almost any other known antibody. 2909, directed against a quaternary epitope specifically expressed on intact virions but not soluble Env proteins, possesses even more potent neutralizing activity for SF162 and a JR-FL variant. 2909 binding to virions requires the presence of both the V2 and V3 domains in Env. We have recently shown that the V3 determinants of the 2909 epitope are very broad, and that the type-specificity of 2909 is due to the requirement for residues in V2 that map to precisely the same region as the C108g determinants. Although these mAbs are type-specific, both the C108g and 2909 epitopes differ from the consensus clade B V2 sequence only at single residues. The unrivalled potency of these mAbs argues that they bind to a particularly sensitive neutralization domain, and suggests that conserved forms of these epitopes could be important vaccine targets. This proposal will further map V1/V2 determinants responsible for neutralization masking, examine the role of the V1/V2 domain in autologous neutralization, more completely define epitopes in V2 that mediate potent neutralization, isolate and characterize additional V2- specific mAbs with broader neutralizing activities and determine the structures of complexes formed between such Fabs and appropriate V1/V2 antigens. Finally, this data will be used to design optimized miniproteins that present the critical V2 epitopes in highly immunogenic forms and to test the ability of such immunogens to induce broadly neutralizing antibodies in several animal models.