Local CD4 and CD8 T-Cell Reactivity to HSV-1 Antigens Documents Broad Viral Protein Expression and Immune Competence in Latently Infected Human Trigeminal Ganglia

Herpes simplex virus type 1 (HSV-1) infection results in lifelong chronic infection of trigeminal ganglion (TG) neurons, also referred to as neuronal HSV-1 latency, with periodic reactivation leading to recrudescent herpetic disease in some persons. HSV-1 proteins are expressed in a temporally coordinated fashion during lytic infection, but their expression pattern during latent infection is largely unknown. Selective retention of HSV-1 reactive T-cells in human TG suggests their role in controlling reactivation by recognizing locally expressed HSV-1 proteins. We characterized the HSV-1 proteins recognized by virus-specific CD4 and CD8 T-cells recovered from human HSV-1–infected TG. T-cell clusters, consisting of both CD4 and CD8 T-cells, surrounded neurons and expressed mRNAs and proteins consistent with in situ antigen recognition and antiviral function. HSV-1 proteome-wide scans revealed that intra-TG T-cell responses included both CD4 and CD8 T-cells directed to one to three HSV-1 proteins per person. HSV-1 protein ICP6 was targeted by CD8 T-cells in 4 of 8 HLA-discordant donors. In situ tetramer staining demonstrated HSV-1-specific CD8 T-cells juxtaposed to TG neurons. Intra-TG retention of virus-specific CD4 T-cells, validated to the HSV-1 peptide level, implies trafficking of viral proteins from neurons to HLA class II-expressing non-neuronal cells for antigen presentation. The diversity of viral proteins targeted by TG T-cells across all kinetic and functional classes of viral proteins suggests broad HSV-1 protein expression, and viral antigen processing and presentation, in latently infected human TG. Collectively, the human TG represents an immunocompetent environment for both CD4 and CD8 T-cell recognition of HSV-1 proteins expressed during latent infection. HSV-1 proteins recognized by TG-resident T-cells, particularly ICP6 and VP16, are potential HSV-1 vaccine candidates.

1型单纯疱疹病毒（Herpes simplex virus type 1, HSV-1）感染可导致三叉神经节（trigeminal ganglion, TG）神经元发生终身慢性感染，该过程亦称神经元HSV-1潜伏感染；部分感染者会因病毒周期性激活而引发复发性疱疹性疾病。HSV-1蛋白在裂解性感染期间呈时序协调模式表达，但目前学界对其在潜伏感染阶段的表达模式仍未完全明确。人类三叉神经节中选择性滞留HSV-1反应性T细胞，提示这类细胞可通过识别局部表达的HSV-1蛋白，在调控病毒激活过程中发挥作用。我们对从感染HSV-1的人类三叉神经节中分离得到的病毒特异性CD4和CD8 T细胞所识别的HSV-1蛋白进行了系统表征。由CD4与CD8 T细胞共同构成的T细胞簇环绕神经元，并表达符合原位抗原识别与抗病毒功能特征的mRNA与蛋白。全HSV-1蛋白质组扫描结果显示，三叉神经节内的T细胞应答包含针对每名感染者1至3种HSV-1蛋白的CD4和CD8 T细胞。在8名HLA（人类白细胞抗原，Human Leukocyte Antigen）型别不一致的供体中，有4名的CD8 T细胞靶向HSV-1蛋白ICP6。原位四聚体染色实验证实，HSV-1特异性CD8 T细胞紧邻三叉神经节神经元分布。经HSV-1肽段水平验证的病毒特异性CD4 T细胞在三叉神经节内的滞留现象，提示病毒蛋白可从神经元转运至表达HLA II类分子的非神经元细胞，以完成抗原呈递。靶向各类动力学与功能类别的病毒蛋白的三叉神经节T细胞所识别的病毒蛋白种类多样，这表明潜伏感染的人类三叉神经节中存在广泛的HSV-1蛋白表达，以及病毒抗原的加工与呈递过程。综上，人类三叉神经节是一个具备免疫活性的微环境，可支持CD4和CD8 T细胞识别潜伏感染期间表达的HSV-1蛋白。三叉神经节驻留T细胞所识别的HSV-1蛋白，尤其是ICP6和VP16，有望成为潜在的HSV-1疫苗候选靶点。