Modulation of Cytokine Release and Gene Expression by the Immunosuppressive Domain of gp41 of HIV-1

The transmembrane envelope protein gp41 of the human immunodeficiency virus HIV-1 plays an important role during infection allowing fusion of the viral and cellular membrane. In addition, there is increasing evidence that gp41 may contribute to the immunodeficiency induced by HIV-1. Recombinant gp41 and a synthetic peptide corresponding to a highly conserved domain in gp41, the immunosuppressive (isu) domain, have been shown to inhibit mitogen-induced activation of human peripheral blood mononuclear cells (PBMCs) and to increase release of IL-6 and IL-10 from these cells. We recently reported that a single mutation in the isu domain of gp41 abrogated the immunosuppressive properties and that HIV-1 sequences containing such abrogating mutations had never been isolated from infected individuals. Here, we studied the influence of the isu peptide on the release of 66 cytokines and the expression of 27,000 genes in PBMCs. Incubation of PBMCs with isu peptide homopolymers increased the expression of 16 cytokines among them IL-6 and IL-10, and decreased that of IL-2 and CXCL9. Interestingly, the extend of cytokine modulation was donor-dependent. Among the genes up-regulated were IL-6, IL-8, IL-10 but also MMP-1, TREM-1 and IL-1beta. Most importantly, genes involved in innate immunity such as FCN1 and SEPP1 were found down-regulated. Many changes in cytokine expression demonstrated in our experiments were also found in HIV-1 infected individuals. These data indicate that the isu domain of gp41 has a broad impact on gene expression and cytokine release and therefore may be involved in HIV-1 induced immunopathogenesis.

人类免疫缺陷病毒1型（HIV-1）的跨膜包膜蛋白gp41在病毒感染过程中发挥关键作用，介导病毒膜与细胞膜的融合。此外，越来越多的证据表明，gp41可能参与HIV-1诱导的免疫缺陷进程。已有研究证实，重组gp41以及对应gp41中高度保守的免疫抑制（isu）结构域的合成肽，可抑制丝裂原诱导的人外周血单个核细胞（PBMCs）活化，并促进这些细胞释放IL-6与IL-10。本团队此前曾报道，gp41的isu结构域发生单点突变可消除其免疫抑制活性，且从未从感染者体内分离到携带这类失活突变的HIV-1序列。本研究中，我们探究了isu肽对外周血单个核细胞（PBMCs）中66种细胞因子释放以及27000个基因表达的影响。将PBMCs与isu肽同聚物共同孵育后，可上调16种细胞因子的表达，其中包括IL-6与IL-10，同时下调IL-2与CXCL9的表达。值得注意的是，细胞因子的调控程度呈现供体依赖性。上调的基因除IL-6、IL-8、IL-10外，还包括MMP-1、TREM-1与IL-1β。最为关键的是，固有免疫相关基因如FCN1与SEPP1的表达被下调。本实验中观测到的诸多细胞因子表达变化，在HIV-1感染者体内也有发现。上述数据表明，gp41的isu结构域可广泛影响基因表达与细胞因子释放，因此可能参与HIV-1诱导的免疫致病过程。