A Directed Molecular Evolution Approach to Improved Immunogenicity of the HIV-1 Envelope Glycoprotein

A prophylactic vaccine is needed to slow the spread of HIV-1 infection. Optimization of the wild-type envelope glycoproteins to create immunogens that can elicit effective neutralizing antibodies is a high priority. Starting with ten genes encoding subtype B HIV-1 gp120 envelope glycoproteins and using in vitro homologous DNA recombination, we created chimeric gp120 variants that were screened for their ability to bind neutralizing monoclonal antibodies. Hundreds of variants were identified with novel antigenic phenotypes that exhibit considerable sequence diversity. Immunization of rabbits with these gp120 variants demonstrated that the majority can induce neutralizing antibodies to HIV-1. One novel variant, called ST-008, induced significantly improved neutralizing antibody responses when assayed against a large panel of primary HIV-1 isolates. Further study of various deletion constructs of ST-008 showed that the enhanced immunogenicity results from a combination of effective DNA priming, an enhanced V3-based response, and an improved response to the constant backbone sequences.

亟需一款预防性疫苗以延缓人类免疫缺陷病毒1型（HIV-1）的传播。优化野生型包膜糖蛋白以制备可诱导有效中和抗体的免疫原，是当前的研究重点。本研究以10个编码B亚型HIV-1 gp120包膜糖蛋白的基因为起始材料，借助体外同源DNA重组技术构建嵌合gp120变体，并通过结合中和性单克隆抗体的能力对变体开展筛选。最终筛选得到数百个具备全新抗原表型的变体，这些变体呈现出显著的序列多样性。利用这些gp120变体对家兔进行免疫实验，结果显示绝大多数变体均可诱导针对HIV-1的中和抗体。其中一款命名为ST-008的新型变体，在针对大规模原发性HIV-1毒株库进行检测时，诱导的中和抗体应答水平得到显著提升。对ST-008的各类缺失突变体开展进一步研究后发现，其免疫原性的增强源于有效DNA初免、基于V3区的免疫应答增强以及针对保守骨架序列的免疫应答改善三者的协同效应。