Immune response to MCMV infection in the salivary glands

β-疱疹病毒人类巨细胞病毒（HCMV）感染了大约50%的世界人口。虽然它在健康个体中仍然无症状，但它永远不会从宿主中完全清除，并可引起复发性感染，特别是在免疫抑制时期。HCMV对孕妇、新生儿和免疫功能低下者构成最大威胁，其症状往往更为严重。小鼠巨细胞病毒（MCMV）是HCMV的小鼠同源物，是一种具有良好特征的病毒感染动物模型。与HCMV一样，MCMV对唾液腺（SMG）有趋向性，并在初次感染后在该器官持续数月。我们已经证明，在脾脏和血液中至关重要的NK细胞在SMG中反应迟钝，这可以想象地解释MCMV在该器官中的持久性。有趣的是，我们的初步数据表明，唾液腺NK细胞在转移到不同组织时恢复了正常的MCMV效应功能，这表明唾液腺环境调节了NK细胞的功能。MCMV利用SMG作为病毒持续存在的关键位点，与肿瘤相似，SMG创造了一个免疫环境，其机制可以防止过度炎症和/或组织损伤。由于对癌症和感染的免疫反应具有共性，我们推断病原体清除和免疫病理之间的平衡可能部分由唾液腺内的检查点抑制剂调节，特别是在持续阶段。我们的数据表明，靶向KLRG1在一定剂量下可以改善MCMV的效应免疫应答和生存，但可能导致免疫病理，这取决于剂量。我们的数据还表明NK细胞可能通过PD-1途径抑制唾液腺中CD8+ T细胞的募集、增殖和效应功能。这得到了对已分类T细胞的CITE-seq/TotalSeq的支持，显示出独特的CD8+ T细胞簇的扩增。基于这些初步数据，我们假设NK细胞有助于CMV控制，同时通过限制CD8+ T细胞在唾液腺中的扩张来预防免疫病理。本提案的总体目标是揭示导致MCMV持久性的潜在机制。在特异性目标1中，我们将研究如何调节病原体清除和免疫病理之间的平衡。在特异性目标2中，我们将研究MCMV在唾液腺中的持久性是如何被调节的。在特异性目标3中，我们将研究NK细胞如何抑制T细胞积聚可能限制唾液腺的免疫病理。我们已经生成了大量的工具来调查本提案中提出的问题。我们现在处于进行拟议研究的绝佳位置。这些研究的结果可能与其他病毒引起的感染有关，并有助于设计在病毒感染期间操纵效应细胞的策略和治疗方法。

The β-herpesvirus human cytomegalovirus (HCMV) infects around 50% of the world population. Although it remains asymptomatic in healthy individuals, it is never completely cleared from the host and can cause recurrent infections, especially at times of immunosuppression. HCMV poses the biggest threat to pregnant women, neonates, and immunocompromised individuals, whose symptoms tend to be more severe. The mouse homolog of HCMV, murine cytomegalovirus (MCMV), is a well-characterized animal model of viral infection. Like HCMV, MCMV has a tropism for the salivary glands (SMG) and persists in this organ for several months after primary infection. We have demonstrated that NK cells, which are critical in the spleen and blood, are hyporesponsive in the SMG, conceivably explaining the MCMV persistence in this organ. Interestingly, our preliminary data show that salivary gland NK cells regain normal effector functions against MCMV when relocated to different tissues, indicating that the salivary gland environment regulates NK cell function. MCMV exploits the SMG as the key site of viral persistence, which, similar to tumors, creates an immune environment with mechanisms to preclude excessive inflammation and/or tissue damage. Because the immune response to cancer and infection exhibit commonalities, we reasoned that the balance between pathogen clearance and immunopathology is likely to be regulated in part by checkpoint inhibitors within the salivary glands, especially during the persistence phase. Our data demonstrate that targeting KLRG1 improves the effector immune response to MCMV and survival at certain doses, but can lead to immunopathology depending on the dose. Our data also suggest that NK cells may inhibit CD8+ T cell recruitment, proliferation and effector functions in the salivary glands via the PD-1 pathway. This is supported by CITE-seq/TotalSeq on sorted T cells, showing expansion of unique CD8+ T cell clusters. Based on this preliminary data, we hypothesize that NK cells contribute to CMV control while preventing immunopathology by limiting the expansion of CD8+ T cells in the salivary glands. The overall goal of this proposal is to reveal the underlying mechanisms leading to MCMV persistence. In Specific Aim 1, we will investigate how the equilibrium between pathogen clearance and immunopathology is regulated. In Specific Aim 2, we will investigate how MCMV persistence is regulated in the salivary glands. In Specific Aim 3, we will investigate how NK cells inhibit T cell accumulation possibly limiting immunopathology in the salivary glands. We have generated a large number of tools to investigate the questions asked in this proposal. We are now in an excellent position to conduct the proposed studies. The results from these studies are likely to have relevance to infections caused by other viruses and aid in the design of strategies and therapeutics directed at manipulating effector cells during viral infection.