Division of Clinical Microbiology, ANA Futura Laboratory, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
Division of Infectious Diseases, ANA Futura Laboratory, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden.
Front Immunol. 2021 Apr 19;12:669347. doi: 10.3389/fimmu.2021.669347. eCollection 2021.
Untreated HIV-1 infection leads to a slow decrease in CD4 T cell lymphocytes over time resulting in increased susceptibility to opportunistic infections (acquired immunodeficiency syndrome, AIDS) and ultimately death of the infected individual. Initially, the host's immune response controls the infection, but cannot eliminate the HIV-1 from the host. Cytotoxic lymphocytes are the key effector cells in this response and can mediate crucial antiviral responses through the release of a set of proteases called granzymes towards HIV-1-infected cells. However, little is known about the immunological molecular mechanisms by which granzymes could control HIV-1. Since we noted that HIV-1 subtype C (HIV-1C) Gag with the tetrapeptide insertion PYKE contains a putative granzyme M (GrM) cleavage site (KEPL) that overlaps with the PYKE insertion, we analyzed the proteolytic activity of GrM towards Gag. Immunoblot analysis showed that GrM could cleave Gag proteins from HIV-1B and variants from HIV-1C of which the Gag-PYKE variant was cleaved with extremely high efficiency. The main cleavage site was directly after the insertion after leucine residue 483. GrM-mediated cleavage of Gag was also observed in co-cultures using cytotoxic lymphocytes as effector cells and this cleavage could be inhibited by a GrM inhibitor peptide. Altogether, our data indicate towards a noncytotoxic immunological mechanism by which GrM-positive cytotoxic lymphocytes target the HIV-1 Gag protein within infected cells to potentially control HIV-1 infection. This mechanism could be exploited in new therapeutic strategies to treat HIV-1-infected patients to improve immunological control of the infection.
未经治疗的 HIV-1 感染会导致 CD4 T 细胞淋巴细胞随时间缓慢减少，从而增加机会性感染（获得性免疫缺陷综合征，艾滋病）的易感性，并最终导致感染个体死亡。最初，宿主的免疫反应控制感染，但不能将 HIV-1 从宿主中清除。细胞毒性淋巴细胞是该反应的关键效应细胞，可通过释放一组称为颗粒酶的蛋白酶对 HIV-1 感染细胞进行关键的抗病毒反应。然而，对于颗粒酶如何控制 HIV-1 的免疫分子机制知之甚少。由于我们注意到 HIV-1 亚型 C（HIV-1C）Gag 带有四肽插入 PYKE，其中包含一个假定的颗粒酶 M（GrM）切割位点（KEPL），与 PYKE 插入重叠，我们分析了 GrM 对 Gag 的蛋白水解活性。免疫印迹分析表明，GrM 可以从 HIV-1B 和 HIV-1C 的变体中切割 Gag 蛋白，其中 Gag-PYKE 变体被极高效地切割。主要切割位点直接位于亮氨酸残基 483 之后的插入处。在用细胞毒性淋巴细胞作为效应细胞的共培养物中也观察到 GrM 介导的 Gag 切割，并且这种切割可以被 GrM 抑制剂肽抑制。总之，我们的数据表明，GrM 阳性细胞毒性淋巴细胞通过一种非细胞毒性免疫机制靶向感染细胞内的 HIV-1 Gag 蛋白，从而有可能控制 HIV-1 感染。这种机制可以在新的治疗策略中得到利用，以治疗 HIV-1 感染患者，从而改善对感染的免疫控制。
