Department of Pathology and Laboratory Medicine, Chemical Immunology Research Center, University of Texas Medical School at Houston, Houston, TX 77030, USA.
J Immunol. 2012 Dec 1;189(11):5367-81. doi: 10.4049/jimmunol.1200981. Epub 2012 Oct 22.
Failure to induce synthesis of neutralizing Abs to the CD4 binding determinant (CD4BD) of gp120, a central objective in HIV vaccine research, has been alternately ascribed to insufficient immunogen binding to Abs in their germline V region configuration expressed as BCRs, insufficient adaptive mutations in Ab V regions, and conformational instability of gp120. We employed peptide analogs of gp120 residues 421-433 within the CD4BD (CD4BD(core)) to identify Abs produced without prior exposure to HIV (constitutive Abs). The CD4BD(core) peptide was recognized by single-chain Fv fragments from noninfected humans with lupus that neutralized genetically diverse strains belonging to various HIV subtypes. Replacing the framework region (FR) of a V(H)4-family single-chain Fv with the corresponding V(H)3-family FRs from single-chain Fv JL427 improved the CD4BD(core) peptide-binding activity, suggesting a CD4BD(core) binding site outside the pocket formed by the CDRs. Replacement mutations in the FR site vicinity suggested the potential for adaptive improvement. A very small subset of serum CD4BD(core)-specific serum IgAs from noninfected humans without autoimmune disease isolated by epitope-specific chromatography neutralized the virus potently. A CD4BD(core)-specific, HIV neutralizing murine IgM with H and L chain V regions (V(H) and V(L) regions) free of immunogen-driven somatic mutations was induced by immunization with a CD4BD(core) peptide analog containing an electrophilic group that binds B cells covalently. The studies indicate broad and potent HIV neutralization by constitutive Abs as an innate, germline-encoded activity directed to the superantigenic CD4BD(core) epitope that is available for amplification for vaccination against HIV.
未能诱导针对 gp120 的 CD4 结合结构域（CD4BD）的中和抗体（Abs）的合成，这是 HIV 疫苗研究的一个核心目标，这一现象被交替归因于免疫原与以 B 细胞受体（BCR）形式表达的 Abs 的原始 V 区构型中的 Abs 结合不足、Ab V 区中的适应性突变不足以及 gp120 的构象不稳定。我们使用 gp120 的 CD4BD（CD4BD（核心））内的肽模拟物来鉴定未经 HIV 暴露就产生的 Abs（组成性 Abs）。CD4BD（核心）肽被来自未感染狼疮的人类的单链 Fv 片段识别，这些单链 Fv 片段能够中和属于各种 HIV 亚型的遗传多样性株。用来自单链 Fv JL427 的相应 V(H)3 家族 FR 替换 V(H)4 家族单链 Fv 的框架区（FR），提高了 CD4BD（核心）肽结合活性，这表明 CD4BD（核心）结合位点位于由 CDR 形成的口袋之外。FR 位点附近的替换突变表明具有适应性改善的潜力。通过表位特异性色谱法从没有自身免疫性疾病的未感染人类中分离出的非常小的血清 CD4BD（核心）特异性血清 IgA 亚群具有强大的中和病毒能力。通过用含有共价结合 B 细胞的亲电基团的 CD4BD（核心）肽模拟物免疫接种，诱导出具有无免疫原驱动体细胞突变的 H 和 L 链 V 区（V(H) 和 V(L) 区）的 CD4BD（核心）特异性、HIV 中和鼠 IgM。这些研究表明，组成性 Abs 通过先天的、种系编码的活性广泛而有效地中和 HIV，该活性针对超抗原性的 CD4BD（核心）表位，该表位可用于接种疫苗以预防 HIV。
