Sreepian Apichai, Permmongkol Jongruk, Kantakamalakul Wannee, Siritantikorn Sontana, Tanlieng Nattaya, Sutthent Ruengpung
Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
J Immune Based Ther Vaccines. 2009 Oct 12;7:5. doi: 10.1186/1476-8518-7-5.
Conserved neutralizing epitopes are considered to be a key role for eliciting broadly neutralizing antibody (NAb). Previously, two conserved neutralizing epitopes of HIV-1 CRF01_AE envelope were identified at amino acid 93-112 of the C1 (C1E) and at 218-239 of the C2 (C2E) regions. To access the potency of antibody directed against conserved epitopes, a monoclonal antibody (MAb) specific to the C2E region was developed and characterized.
The immunogenicity of two epitopes was examined by immunizing BALB/c mice with the matching synthetic peptides. One MAb, C2EB5, directed against peptide C2E, was generated by conventional methods, while C1E1 and C1E2 peptides induced slight antibody response in mice. The neutralizing activity of MAb C2EB5 was examined using a peripheral blood mononuclear cell (PBMC) based method and various HIV-1 subtypes including A, B, C, D, and CRF01_AE; C2EB5 was compared with other known neutralizing MAbs (4E10, 447-52D) and with sCD4. The exposure of the C2 epitope on native virus was investigated using virus capture by these MAbs.
The MAb C2EB5 demonstrated cross-neutralization against various HIV-1 subtypes. The overall potency of MAb C2EB5 against 5 subtypes was ranked in the following order: subtype C> CRF01_AE> subtype D> subtype A> subtype B. The epitope exposure for MAb C2EB5 was also correlated with the neutralization properties of each subtype.
This study demonstrates the cross-clade neutralizing activity of a MAb directed against an epitope located in the C2 region of the HIV-1 env and highlights differences in the exposure of antigenic epitopes on the surface of various HIV-1 subtypes. The epitope for this newly identified neutralizing MAb made against a subtype CRF01_AE peptide is particularly exposed in subtype C viral isolates.
保守的中和表位被认为是引发广泛中和抗体（NAb）的关键因素。此前，已在HIV-1 CRF01_AE包膜蛋白的C1区（C1E）的氨基酸93 - 112位和C2区（C2E）的218 - 239位鉴定出两个保守的中和表位。为评估针对保守表位的抗体效力，研发并鉴定了一种针对C2E区的单克隆抗体（MAb）。
用匹配的合成肽免疫BALB/c小鼠，检测两个表位的免疫原性。通过常规方法产生了一种针对肽C2E的单克隆抗体C2EB5，而C1E1和C1E2肽在小鼠中诱导出轻微的抗体反应。使用基于外周血单个核细胞（PBMC）的方法以及包括A、B、C、D和CRF01_AE在内的多种HIV-1亚型检测单克隆抗体C2EB5的中和活性；将C2EB5与其他已知的中和单克隆抗体（4E10、447 - 52D）以及可溶性CD4进行比较。利用这些单克隆抗体进行病毒捕获，研究C2表位在天然病毒上的暴露情况。
单克隆抗体C2EB5对多种HIV-1亚型表现出交叉中和作用。单克隆抗体C2EB5对5种亚型的总体效力排序如下：C亚型>CRF01_AE亚型>D亚型>A亚型>B亚型。单克隆抗体C2EB5的表位暴露情况也与各亚型的中和特性相关。
本研究证明了一种针对HIV-1 env C2区表位的单克隆抗体的跨分支中和活性，并突出了各种HIV-1亚型表面抗原表位暴露情况的差异。这种针对CRF01_AE亚型肽产生的新鉴定中和单克隆抗体的表位在C亚型病毒分离株中特别暴露。
