SELECTING ENV TRIMERS IN HIV-VLP VACCINE PRESENTATIONS

描述（由申请人提供）：在HIV-1感染期间，包膜蛋白（Env）以多种形式呈递给免疫系统。在目前接受的模型中，Env的功能形式是gp 120/gp 41异二聚体的三聚体复合物。Env的非功能性形式的实例包括单体gp 120、未裂解的gp 160前体和gp 41，其中gp 120已从gp 41解离。功能性三聚体已经进化为紧凑的结构;事实上，虽然大多数单克隆抗体（mAb）仅识别Env的非功能性形式，但中和mAb似乎也结合功能性Env三聚体。从颗粒和感染细胞释放的Env片段被认为是对HIV-1感染的中和反应质量通常较差的原因。然而，新的证据表明，感染性HIV-1颗粒也携带非功能性形式的Env。在追求开发能够引发有效中和抗体的HIV-1疫苗的目标时，我们选择HIV-1假病毒体作为模型免疫原。在具体目标1中，我们将使用一套全面的技术，试图产生假病毒体，只携带功能性三聚体，只有通过中和单克隆抗体识别。鉴于三聚体复合物的紧凑、抗体抗性性质，我们将在特定目标2中扩展我们的研究，以包括Env的受体接合形式作为替代中和靶标。Env-受体结合诱导暴露其他隐蔽结构。尽管这些结构在自然感染中仅短暂暴露，但它们是由充分表征的中和mAb识别的合理的中和靶标，例如2F 5。为此，我们已经产生了一个假病毒突变体，它附着在易感细胞上，但只以氧化还原依赖的方式融合。使用这个模型，我们将研究附着后中和HIV-1+血清。在特定目标3中，我们将检测i）仅携带功能性三聚体的假病毒体和ii）附着于自体猕猴淋巴细胞的受体接合假病毒体的免疫原性。

DESCRIPTION (provided by applicant): During HIV-1 infection, the envelope protein (Env) is presented to the immune system in many forms. In the currently accepted model, the functional form of Env is a trimeric complex of gp120/gp41 heterodimers. Examples of non-functional forms of Env include monomeric gp120, uncleaved gp160 precursor and gp41 from which gp120 has dissociated. The functional trimer has evolved to be a compact structure; indeed, while most monoclonal antibodies (mAbs) recognize only non-functional forms of Env, neutralizing mAbs appear to also bind the functional Env trimer. Env fragments released from particles and infected cells have been considered responsible for the generally poor quality neutralizing response to HIV-1 infection. However, new evidence suggests that infectious HIV-1 particles also bear non-functional forms of Env. In pursuing the goal of developing an HIV-1 vaccine able to elicit potent neutralizing antibodies, we have chosen HIV-1 pseudovirions as model immunogens. In Specific Aim 1, we will use a comprehensive set of techniques in an attempt to generate pseudovirions that exclusively bear functional trimers that are only recognized by neutralizing mAbs. Given the compact, antibody-resistant nature of the trimeric complex, we will expand our studies in Specific Aim 2 to include the receptor-engaged form of Env as an alternative neutralization target. Env-receptor binding induces exposure of otherwise cryptic structures. Although these structures are only transiently exposed in natural infection, they are plausible neutralization targets recognized by well-characterized neutralizing mAbs, exemplified by 2F5. To this end, we have generated a pseudovirion mutant that attaches to susceptible cells but only fuses in a redox-dependent manner. Using this model, we will investigate post-attachment neutralization in HIV-I+ serum. In Specific Aim 3, we will test the immunogenicity of i) pseudovirions bearing only functional trimers and ii) receptor-engaged pseudovirions attached to autologous macaque lymphocytes.