Severe, recurrent or atypical Herpes simplex virus (HSV) infections are still posing clinical and diagnostic problem in clinical immunology facilities. However, the molecular background of this disorder is still unclear. The aim of this study was to investigate the expression of activating receptors on NK cells (CD16, NKp46, NKG2D, NKp80, 2B4, CD48 and NTB-A) and checkpoint molecule PD-1 on T lymphocytes and NK cells, in patients with severe and/or recurrent infections with HSV and age-matched healthy control subjects. As a result, we noticed that patients with severe and/or recurrent infection with HSV had significantly lower percentage of CD16^brightCD56^dim and higher percentage of CD16^dimCD56^bright NK cell subsets, when compared to control subjects, which may be associated with abnormal NK cell maturation during chronic HSV infection. Patients had also significantly downregulated expression of CD16 receptor on CD16^bright NK cells. The expression of activating receptors was significantly reduced on patients’ NK cells - either both the percentage of NK cells expressing the receptor and MFI of its expression (NKp46, NKp80 and 2B4 on CD16^brightCD56^dim cells and NKp46 on CD16^dimCD56^bright cells) or only MFI (NKG2D on both NK cell subsets). It should be noted that the reduction of receptor expression was limited to NK cells, since there was no differences in the percentage of receptor-positive cells or MFI on T cells. However, NTB-A receptor was the only one which expression was not only simultaneously changed in patients’ NK and T cells, but also significantly upregulated on CD16^dimCD56^bright NK cell and CD8⁺ cell subsets. Patients had also upregulated proportion of CD4⁺ T cells expressing PD-1. Thus, we suggest that an increased percentage of PD-1⁺ cells may represent an independent indirect mechanism of downregulation of antiviral response, separate from the reduction of NK cell activating receptors expression. Altogether, our studies indicate two possible mechanisms which may promote perpetuation of HSV infection: 1) selective inhibition of activating receptors on NK cells, but not on T cells, and 2) upregulation of checkpoint molecule PD-1 on CD4⁺ T cells.

严重、复发或非典型单纯疱疹病毒 (HSV) 感染仍然是临床免疫学设施中的临床和诊断问题。然而，这种疾病的分子背景仍不清楚。本研究的目的是研究 NK 细胞激活受体（CD16、NKp46、NKG2D、NKp80、2B4、CD48 和 NTB-A）和 T 淋巴细胞和 NK 细胞上检查点分子 PD-1 的表达，在重症患者中和/或 HSV 反复感染和年龄匹配的健康对照受试者。结果，我们注意到患有严重和/或复发性 HSV 感染的患者 CD16^亮CD56^暗的百分比显着降低，CD16^暗CD56^亮的百分比显着增加与对照组相比，NK 细胞亚群可能与慢性 HSV 感染期间的异常 NK 细胞成熟有关。^{患者的 CD16明亮}NK 细胞上 CD16 受体的表达也显着下调。患者 NK 细胞上激活受体的表达显着降低 - 表达受体的 NK 细胞百分比和其表达的 MFI（CD16^亮CD56^暗细胞上的 NKp46、NKp80 和 2B4 和 CD16^暗CD56^{亮细胞上的 NKp46}细胞）或仅 MFI（两个 NK 细胞亚群上的 NKG2D）。应该注意的是，受体表达的减少仅限于 NK 细胞，因为 T 细胞上受体阳性细胞或 MFI 的百分比没有差异。然而，NTB-A受体是唯一一种不仅在患者的NK细胞和T细胞中表达同时发生变化，而且在CD16 ^dim CD56 ^bright NK细胞和CD8 ⁺细胞亚群上显着上调的受体。患者还上调了表达 PD-1 的 CD4 ⁺ T 细胞的比例。因此，我们建议增加 PD-1 ⁺细胞可能代表抗病毒反应下调的独立间接机制，与 NK 细胞激活受体表达的降低不同。总而言之，我们的研究表明了两种可能促进 HSV 感染持续存在的机制：1）选择性抑制 NK 细胞上的激活受体，而不是 T 细胞上的激活受体，2）CD4 ⁺ T 细胞上检查点分子 PD-1 的上调。