NCP型BVDV急性感染中BTLA调控CD8+TLs活化、增殖及杀伤功能的机制研究

牛病毒性腹泻病毒（BVDV）急性感染可导致牛外周血淋巴细胞减少症，引起免疫抑制，其发病机制尚不明确。我们前期研究发现NCP和CP型BVDV依赖PD-1通路抑制了T淋巴细胞（TLs）的增殖，引发凋亡和TLs减少。然而，NCP型BVDV感染中阻断PD-1并未完全恢复CD8+TLs增殖和功能，被感染的CD8+TLs表面B/T淋巴细胞衰减因子（BTLA）高表达，增殖被抑制。推测BTLA协同PD-1负调控了CD8+TLs的活化和增殖。本研究拟结合免疫检查点联合阻断干预策略，利用CFSE荧光标记、抗体阻断和基因沉默等技术，确定NCP型BVDV感染中BTLA表达与CD8+TLs活化和增殖的相关性及其对杀伤功能及病毒复制的影响，揭示BTLA与PD-1分子的协同作用和信号转导通路响应机制。对于探索BVDV感染引起免疫抑制的分子机制有重要意义，为2019新型冠状病毒等引发的淋巴细胞减少症提供新的治疗思路。

Acute infection with bovine viral diarrhea virus (BVDV) can results in peripheral blood lymphopenia and immunosuppression. However, the pathogenesis of lymphopenia and immunosuppression remains unclear. Our previous study found that NCP and CP BVDV inhibited the proliferation of T lymphocytes (TLs) and promoted the apoptosis and reduction of TLs by PD-1 pathway. However, PD-1 blockade during NCP BVDV infection did not fully restore the proliferation and function of CD8+TLs. Meanwhile, B and T lymphocyte attenuator (BTLA) on the infected CD8+TLs was highly expressed and the TLs proliferation was inhibited. We hypothesized that BTLA and PD-1 negatively regulated the activation and proliferation of CD8+TLs. In this study, the correlation between BTLA expression and CD8+TLs activation and proliferation and the effect of BTLA on cytotoxicity and virus replication were determined during by antibody blocking, gene silencing and CFSE fluorescence labeling during NCP BVDV infection. The aim is to reveal the synergistic effect between BTLA and PD-1 and the response mechanism of signal transduction pathway. This study is of great significance for exploring the molecular mechanism of immunosuppression induced by BVDV infection, and provides a new therapeutic approach for lymphopenia induced by SARS-CoV-2 and other viruses.