人类白细胞抗原I类(HLA-I)分子在预防严重的人类巨细胞病毒(HCMV)疾病的NK和T细胞反应中起着核心作用。为病毒传播创造机会,几种HCMV编码的免疫evasin采用不同的策略来靶向HLA-I。其中,到目前为止,糖蛋白US10的研究还不够充分。虽然据报道US10干扰HLA-G表达,其操纵经典HLA-I抗原呈递的能力仍然未知.在这项研究中,我们证明US10识别并结合所有HLA-I(HLA-A,-B,-C,-E,-G)重链。此外,观察到肽负载复合物的HLA-I募集受损。值得注意的是,相关效应显著变化取决于HLA-I基因型和同种异型:(i)HLA-A分子逃避了US10的下调,(ii)塔塔蛋白依赖性HLA-B分子显示受损的成熟和细胞表面表达,和(iii)β2m组装的HLA-C,特别是HLA-C*05:01和-C*12:03,以及HLA-G与US10在内质网中被强烈保留在复合物中。通过无偏倚的HLA-I配体组分析证实了这些对HLA-I的基因型特异性作用。此外,在HCMV感染的成纤维细胞中,重叠的US10和US11转录的抑制对HLA-A几乎没有影响,而是诱导HLA-B抗原呈递。因此,US10介导的对HLA-I的影响以迄今为止无与伦比的多模态方式导致多种基因型和同种异型效应.
在病毒感染期间,免疫系统必须区分健康细胞和受感染细胞,以选择性地杀死受感染细胞。健康细胞在其表面上具有被统称为HLA-I的不同类型的分子。这些分子从细胞中呈现蛋白质的小片段,称为抗原,巡逻免疫细胞,称为CTL或自然杀伤细胞。虽然CTL忽略来自人类蛋白质的抗原(表明细胞是健康的),它们可以结合并识别病毒蛋白的抗原,这会触发它们激活杀死被感染细胞的免疫反应。然而,一些病毒可以阻止受感染的细胞在其表面呈递HLA-I分子,作为逃避免疫系统的策略。自然杀伤细胞已经进化来克服这一挑战。它们本身与HLA-I分子结合,这导致他们保持不活跃。然而,如果HLA-I分子缺失,NK细胞可以更容易地打开并杀死靶细胞。人巨细胞病毒是导致人类终生感染的常见病毒。虽然它很少引起健康个体的疾病,它可能危及新生婴儿和免疫系统较弱的人的生命。以前发现一种称为US10的人巨细胞病毒蛋白与HLA-I结合,而不会降低细胞表面上这些分子的水平。然而,其确切作用尚不清楚。Gerkeetal.使用几种生物化学和细胞生物学方法来研究US10是否操纵三种类型的HLA-I的质量,这可能会影响CTL和NK细胞的识别。实验表明,US10对各种HLA-I的作用不同。对于一种类型,它在细胞内强烈结合,阻止它到达表面。US10还阻止了另一种类型的HLA-I正常成熟和呈递抗原,但不影响第三种类型的HLA-I。这些发现表明US10干扰不同HLA-I类型以特定方式呈递抗原的能力。需要进一步的研究来测量US10活性如何影响免疫细胞,这可能最终有助于开发针对人类巨细胞病毒和其他类似病毒的新疗法。
Human leucocyte antigen class I (HLA-I) molecules play a central role for both NK and T-cell responses that prevent serious human cytomegalovirus (HCMV) disease. To create opportunities for viral spread, several HCMV-encoded immunoevasins employ diverse strategies to target HLA-I. Among these, the glycoprotein US10 is so far insufficiently studied. While it was reported that US10 interferes with HLA-G expression, its ability to manipulate classical HLA-I antigen presentation remains unknown. In this study, we demonstrate that US10 recognizes and binds to all HLA-I (HLA-A, -B, -C, -E, -G) heavy chains. Additionally, impaired recruitment of HLA-I to the peptide loading complex was observed. Notably, the associated effects varied significantly dependending on HLA-I genotype and allotype: (i) HLA-A molecules evaded downregulation by US10, (ii) tapasin-dependent HLA-B molecules showed impaired maturation and cell surface expression, and (iii) β2m-assembled HLA-C, in particular HLA-C*05:01 and -C*12:03, and HLA-G were strongly retained in complex with US10 in the endoplasmic reticulum. These genotype-specific effects on HLA-I were confirmed through unbiased HLA-I ligandome analyses. Furthermore, in HCMV-infected fibroblasts inhibition of overlapping US10 and US11 transcription had little effect on HLA-A, but induced HLA-B antigen presentation. Thus, the US10-mediated impact on HLA-I results in multiple geno- and allotypic effects in a so far unparalleled and multimodal manner.
During a viral infection, the immune system must discriminate between healthy and infected cells to selectively kill infected cells. Healthy cells have different types of molecules known collectively as HLA-I on their surface. These molecules present small fragments of proteins from the cell, called antigens, to patrolling immune cells, known as CTLs or natural killer cells. While CTLs ignore antigens from human proteins (which indicate the cell is healthy), they can bind to and recognize antigens from viral proteins, which triggers them to activate immune responses that kill the infected cell. However, some viruses can prevent infected cells from presenting HLA-I molecules on their surfaces as a strategy to evade the immune system. Natural killer cells have evolved to overcome this challenge. They bind to the HLA-I molecules themselves, which causes them to remain inactive. However, if the HLA-I molecules are missing, the NK cells can more easily switch on and kill the target cell. The human cytomegalovirus is a common virus that causes lifelong infection in humans. Although it rarely causes illness in healthy individuals, it can be life-threatening to newborn babies and for individuals with weakened immune systems. One human cytomegalovirus protein known as US10 was previously found to bind to HLA-I without reducing the levels of these molecules on the surface of the cell. However, its precise role remained unclear. Gerke et al. used several biochemical and cell biology approaches to investigate whether US10 manipulates the quality of the three types of HLA-I, which could impact both CTL and NK cell recognition. The experiments showed that US10 acted differently on the various kinds of HLA-I. To one type, it bound strongly within the cell and prevented it from reaching the surface. US10 also prevented another type of HLA-I from maturing properly and presenting antigens but did not affect the third type of HLA-I. These findings suggest that US10 interferes with the ability of different HLA-I types to present antigens in specific ways. Further research is needed to measure how US10 activity affects immune cells, which may ultimately aid the development of new therapies against human cytomegalovirus and other similar viruses.