Latency reversal agents modulate HIV antigen processing and presentation to CD8 T cells

Latency reversal agents (LRA) variably induce HIV re-expression in CD4 T cells but reservoirs are not cleared. Whether HIV epitope presentation is similar between latency reversal and initial infection of CD4 T cells is unknown yet crucial to define immune responses able to detect HIV-infected CD4 T cells after latency reversal. HIV peptides displayed by MHC comes from the intracellular degradation of proteins by proteasomes and post-proteasomal peptidases but the impact of LRAs on antigen processing is not known. Here we show that HDAC inhibitors (HDCAi) reduced cytosolic proteolytic activities while PKC agonists (PKCa) increased them to a lesser extent than that induced by TCR activation. During the cytosolic degradation of long HIV peptides in LRA-treated CD4 T cells extracts, HDACi and PKCa modulated degradation patterns of peptides and altered the production of HIV epitopes in often opposite ways. Beyond known HIV epitopes, HDACi narrowed the coverage of HIV antigenic fragments by 8-11aa degradation peptides while PKCa broadened it. LRAs altered HIV infection kinetics and modulated CD8 T cell activation in an epitope- and time-dependent manner. Interestingly the efficiency of endogenous epitope processing and presentation to CD8 T cells was increased by PKCa Ingenol at early time points despite low levels of antigens. LRA-induced modulations of antigen processing should be considered and exploited to enhance and broaden HIV peptide presentation by CD4 T cells and to improve immune recognition after latency reversal. This property of LRAs, if confirmed with other antigens, might be exploited to improve immune detection of diseased cells beyond HIV.潜伏逆转剂（Latency Reversal Agents，LRA）可在不同程度上诱导CD4⁺ T细胞中的HIV再激活，但无法清除HIV病毒储存库。目前尚不明确潜伏逆转过程与CD4⁺ T细胞初始感染过程中，HIV表位呈递是否具有相似性，而该问题的阐明对于定义能够在潜伏逆转后检测HIV感染CD4⁺ T细胞的免疫应答至关重要。主要组织相容性复合体（Major Histocompatibility Complex，MHC）所呈递的HIV肽段，来源于蛋白酶体及蛋白酶体后肽酶对胞内蛋白的降解，但潜伏逆转剂对抗原加工过程的影响尚未可知。本研究显示，组蛋白去乙酰化酶抑制剂（HDAC inhibitors，HDCAi）可降低胞浆蛋白水解活性，而蛋白激酶C激动剂（Protein Kinase C agonists，PKCa）对胞浆蛋白水解活性的提升幅度，则低于T细胞受体（T Cell Receptor，TCR）激活所诱导的水平。在经潜伏逆转剂处理的CD4⁺ T细胞提取物中进行长HIV肽段的胞浆降解实验时，组蛋白去乙酰化酶抑制剂与蛋白激酶C激动剂可分别调控肽段的降解模式，且常以相反的方式改变HIV表位的产生量。除已知的HIV表位外，组蛋白去乙酰化酶抑制剂会使8-11个氨基酸长度的HIV抗原降解肽段的覆盖范围缩小，而蛋白激酶C激动剂则会扩大该覆盖范围。潜伏逆转剂可改变HIV感染动力学，并以表位和时间依赖的方式调控CD8⁺ T细胞的活化。值得注意的是，尽管抗原水平较低，英格诺尔（PKCa类激动剂）在早期即可提升内源性表位的加工及呈递给CD8⁺ T细胞的效率。在设计潜伏逆转策略时，应考虑并利用潜伏逆转剂对抗原加工的调控作用，以增强并拓宽CD4⁺ T细胞对HIV肽段的呈递能力，进而改善潜伏逆转后的免疫识别效果。若该特性在其他抗原中得到验证，则可用于提升免疫细胞对病变细胞的检测能力，其应用范围可不限于HIV感染。