Key Points HLA-E*01:01, HLA-E*01:03, Mamu-E, and Qa-1b have unique motifs. Each MHC-E molecule binds alternative peptides with conserved main anchor residues. Nonanchor residues can play an important role in peptide binding to MHC-E. Ag presentation via the nonclassical MHC class Ib molecule HLA-E, with nearly complete identity between the two alleles expressed in humans, HLA-E*01:01 and HLA-E*01:03, can lead to the activation of unconventional T cells in humans. Despite this virtual genetic monomorphism, differences in peptide repertoires binding to the two allelic variants have been reported. To further dissect and compare peptide binding to HLA-E*01:01 and HLA-E*01:03, we used an UV-mediated peptide exchange binding assay and an HPLC-based competition binding assay. In addition, we investigated binding of these same peptides to Mamu-E, the nonhuman primate homologue of human HLA-E, and to the HLA-E–like molecule Qa-1b in mice. We next exploited the differences and homologies in the peptide binding pockets of these four molecules to identify allele specific as well as common features of peptide binding motifs across species. Our results reveal differences in peptide binding preferences and intensities for each human HLA-E variant compared with Mamu-E and Qa-1b. Using extended peptide libraries, we identified and refined the peptide binding motifs for each of the four molecules and found that they share main anchor positions, evidenced by conserved amino acid preferences across the four HLA-E molecules studied. In addition, we also identified differences in peptide binding motifs, which could explain the observed variations in peptide binding preferences and affinities for each of the four HLA-E–like molecules. Our results could help with guiding the selection of candidate pathogen-derived peptides with the capacity to target HLA-E–restricted T cells that could be mobilized in vaccination and immunotherapeutic strategies.

中文翻译：

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人类、非人灵长类动物和小鼠中 HLA-E 分子的肽结合揭示了独特的结合肽，但锚定残基非常保守


要点 HLA-E*01:01、HLA-E*01:03、Mamu-E 和 Qa-1b 具有独特的基序。每个 MHC-E 分子结合具有保守的主要锚定残基的替代肽。非锚定残基在肽与 MHC-E 的结合中发挥重要作用。通过非经典 MHC Ib 类分子 HLA-E 呈递 Ag，人类表达的两个等位基因 HLA-E*01:01 和 HLA-E*01:03 之间几乎完全一致，可导致非常规 T 细胞的激活在人类中。尽管存在这种虚拟的遗传单态性，但已报道了与两个等位基因变体结合的肽库的差异。为了进一步剖析和比较肽与 HLA-E*01:01 和 HLA-E*01:03 的结合，我们使用了 UV 介导的肽交换结合测定和基于 HPLC 的竞争结合测定。此外，我们还研究了这些相同肽与人类 HLA-E 的非人灵长类同源物 Mamu-E 以及小鼠中 HLA-E 样分子 Qa-1b 的结合。接下来，我们利用这四种分子的肽结合口袋的差异和同源性来识别跨物种肽结合基序的等位基因特异性和共同特征。我们的结果揭示了与 Mamu-E 和 Qa-1b 相比，每种人类 HLA-E 变体的肽结合偏好和强度存在差异。使用扩展肽文库，我们鉴定并精炼了这四个分子中每一个的肽结合基序，并发现它们共享主要锚定位置，这通过所研究的四个 HLA-E 分子的保守氨基酸偏好得到证明。此外，我们还发现了肽结合基序的差异，这可以解释观察到的四种 HLA-E 样分子中每种分子的肽结合偏好和亲和力的变化。 我们的结果可以帮助指导候选病原体衍生肽的选择，这些肽能够靶向 HLA-E 限制性 T 细胞，这些细胞可以在疫苗接种和免疫治疗策略中动员起来。