The role of adaptive NK cells in the control of SARS-CoV-2 infection

自然杀伤(NK)细胞是抵御急性病毒感染的第一道防线。最近，一种新型的病毒特异性适应性NK细胞被发现，它在急性巨细胞病毒(CMV)感染期间扩增，通常对抗体刺激超敏，从而产生高效、快速的抗体介导的细胞毒(ADCC)。这些适应性(也称为记忆)NK细胞的一个特点是表达刺激受体NKG2C，它是人类白细胞抗原E(人类白细胞抗原E)的特异性。我们最近发现，适应性NKG2C+NK细胞在30%-40%的HCMV+病例中稳定地保持大规模克隆性扩增。此外，我们还发现这些扩增的大小与KIR2DL受体的共表达有关，KIR2DL受体是人类白细胞抗原-C和高度多态的KIR家族成员的抑制性受体。由于其高ADCC潜能，适应性NK细胞可能在SARS-CoV-2感染中起关键作用，而SARS-CoV-2感染往往与较强的抗体反应有关。事实上，最近的研究表明，患有严重疾病的患者在循环中表现出适应性NK细胞的增加。重要的是，与传统的NK细胞相比，适应性NK细胞可以持续多年，因此有可能有助于防止再次感染的长期保护。在这个项目中，我们想要了解适应性NKG2C+NK细胞如何影响SARS-CoV-2感染的结局。我们将在新冠肺炎恢复期患者(MU)的样本以及新冠肺炎(LW)的灵长类动物模型中解决这一问题。杜塞尔多夫团队已经收集了130例SARS-CoV-2病例的样本和临床数据，并希望通过多色流式细胞术将相关的临床参数，如疾病严重程度、病毒载量、SARS-CoV-2特异性IgM和IgG滴度以及CMV状态与适应性NK细胞的存在相关联。此外，基于最近观察到的SARS-CoV-2刺突蛋白SP1导致肺上皮细胞中人类白细胞抗原-E的上调，我们将在体外探索这一机制是否通过人类白细胞抗原-E/NKG2C轴刺激和扩增适应性自然杀伤细胞。德国灵长类中心(DPZ)的Göttingen团队已经在新开发的针对猕猴NKG2C和KIR的单抗的基础上，证明了类似CMV相关扩张在猕猴中的存在。因此，我们希望通过实验感染恒河猴来研究适应性NK细胞在SARS-CoV-2感染急性期的作用。血液样本和组织切片的分析将给我们提供独特的机会来监测适应性NK细胞在这个灵长类动物模型中的分布和功能作用。如果适应性NK细胞真的参与控制SARS-CoV-2感染，这种很容易在体外扩增的先天性免疫细胞类型可能为新冠肺炎患者的异基因细胞治疗提供一个非常有趣的新选择。

Natural killer (NK) cells are part of the first line of defense against acute viral infections. Recently, a novel type of virus-specific adaptive NK cell was identified that expands during acute cytomegalovirus (CMV) infection and is generally hypersensitive to stimulation by IgG antibodies leading to highly efficient and rapid antibody-mediated cellular cytotoxicity (ADCC). A hallmark of these adaptive (also known as memory) NK cells is the expression of the stimulatory receptor NKG2C, which is specific for the Human Leucocyte Antigen E (HLA-E). We have recently shown that adaptive NKG2C+ NK cells are stably maintained as large clonal expansions in 30-40% of HCMV+ cases. Furthermore, we have shown that the size of these expansions correlates with the coexpression of KIR2DL receptors, which are inhibitory receptors for HLA-C and members of the highly polymorphic KIR family. Due to their high ADCC potential, adaptive NK cells could play a critical role in SARS-CoV-2 infection, which is often associated with strong IgG antibody responses. Indeed, it was recently shown that patients with severe disease exhibited increased presence of adaptive NK cells in the circulation. Importantly, in contrast to conventional NK cells, adaptive NK cells can persist for many years and thus have the potential to contribute to long-term protection against re-infection. In this project, we would like to find out how adaptive NKG2C+ NK cells influence the outcome of SARS-CoV-2 infection. We will address this in samples from convalescent COVID-19 patients (MU) as well as in a primate model of Covid-19 (LW). The Düsseldorf team has already collected samples and clinical data on >130 SARS-CoV-2 cases and would like to correlate the relevant clinical parameters such as disease severity, virus load, SARS-CoV-2-specific IgM and IgG titer, and CMV status with the presence of adaptive NK cells by multicolor flow cytometry. Furthermore, based on the recent observation that the SARS-CoV-2 spike protein SP1 leads to upregulation of HLA-E in lung epithelial cells, we will explore in vitro if this mechanism leads to stimulation and expansion of adaptive NK cells via the HLA-E/NKG2C axis. The Göttingen team at the German Primate Center (DPZ) could already demonstrate the presence of similar CMV-associated expansions in macaques on the basis of newly-developed mAbs specific for macaque NKG2C and KIR. We would thus like to study the contribution of adaptive NK cells in the acute phase of SARS-CoV-2 infection, employing experimentally infected rhesus macaques. The analysis of blood samples as well as tissue sections will give us the unique opportunity to monitor the distribution and functional role of adaptive NK cells in this primate model. If adaptive NK cells are indeed involved in control of SARS-CoV-2 infection, this innate immune cell type, which can be easily expanded in vitro, could provide a highly interesting novel option for allogeneic cellular therapy of COVID-19 patients.