The Effect of HLA Polymorphisms on the Recognition of Gag Epitopes in HIV-1 CRF01_AE Infection

IntroductionThe design of a globally effective vaccine rests on the identification of epitopes capable of eliciting effective cytotoxic T lymphocyte (CTL) responses across multiple HIV clades in different populations. This study aims to discern the effect of HLA polymorphisms and the cross-clade reactivity or clade-specificity of epitopes in Thailand where HIV-1 CRF01_AE is circulating. Materials and Methods14 peptides based on consensus HIV-1 CRF01_AE amino acid sequences were designed for use in IFN-γ ELISpot assays and 51Cr release assays among 66 HIV-1 CRF01_AE-infected Thai patients. For ELISpot responders carrying HLA alleles currently unknown to restrict CRF01_AE epitopes, in silico epitope-HLA prediction was performed. Results29/66 (43.9%) patients recognized at least one peptide. In total 79 responses were seen against all 14 peptides. 28/79 (35.4%) of the responses were in patients with HLA alleles previously reported to restrict CRF01_AE epitopes, 24/79 (30.4%) responses were in individuals with HLA alleles previously reported to restrict epitopes of HIV clades other than CRF01_AE, and the remaining 27/79 (34.2%) responses were not associated with HLA alleles previously known to restrict HIV epitopes. In silico epitope prediction detected 19 novel, epitope-HLA combinations, and 11/19 (57.9%) were associated with HLA-C alleles. We further confirmed a novel HLA restriction of a previously identified HIV-1 Gag epitope [p24122–130: PPIPVGDIY (PY9)] by HLA-B*40:01 with a standard 51Cr release assay. DiscussionCTL recognition sites in HIV-1 Gag were similar among different clades but the HLA restriction differed in Thai patients. This disparity in HLA restriction along different populations illustrated the importance of clade- and population-specific HLA analysis prior to CTL vaccine design.

引言
全球高效疫苗的研发，核心在于鉴定出可在不同人群中跨多种HIV亚型激发有效细胞毒性T淋巴细胞（cytotoxic T lymphocyte, CTL）应答的表位（epitope）。本研究旨在探究HIV-1 CRF01_AE亚型流行的泰国人群中，人类白细胞抗原（HLA）多态性以及表位的跨亚型反应性或亚型特异性所产生的影响。

材料与方法
基于HIV-1 CRF01_AE亚型的共有氨基酸序列，我们设计了14条肽段，用于在66名感染HIV-1 CRF01_AE的泰国患者中开展干扰素-γ酶联免疫斑点（IFN-γ ELISpot）试验与铬-51释放（51Cr release）试验。对于ELISpot检测呈阳性且携带目前尚未被证实可限制性识别CRF01_AE表位的HLA等位基因的受试者，我们实施了计算机模拟（in silico）的表位-HLA结合预测分析。

结果
66名患者中共有29名（43.9%）可识别至少1条肽段。针对全部14条肽段，共计检测到79条特异性应答。其中28条（35.4%）应答来自携带此前已被报道可限制性识别CRF01_AE表位的HLA等位基因的患者，24条（30.4%）应答来自携带此前已被报道可限制性识别非CRF01_AE亚型HIV表位的HLA等位基因的个体，剩余27条（34.2%）应答则与此前已知的可限制性识别HIV表位的HLA等位基因无关联。计算机模拟表位预测共鉴定出19种全新的表位-HLA结合组合，其中11种（57.9%）与HLA-C等位基因相关。我们通过标准铬-51释放试验，进一步证实了HLA-B*40:01对此前已鉴定的HIV-1衣壳蛋白（Gag）表位[p24122–130: PPIPVGDIY (PY9)]的全新限制性识别作用。

讨论
不同HIV亚型的CTL识别位点在HIV-1 Gag蛋白中具有保守性，但泰国患者的HLA限制性识别模式存在差异。不同人群间HLA限制性识别模式的差异，提示在开展CTL疫苗研发前，针对特定亚型与特定人群的HLA分析具有至关重要的意义。