Role Of Innate Immunity In The Initiation And Pathogenes

先天免疫是保护宿主免受包括艾滋病毒在内的病原体入侵的第一道防线。我们以前已经证明，自然杀伤(NK)细胞功能的抑制可能是深远的，并且它与HIV感染的阶段以及HIV血浆病毒血症的水平有关。我们的研究表明，HIV病毒血症损害了NK细胞分泌CC-趋化因子的能力，并改变了NK细胞上表达的各种抑制性和趋化因子受体的表达。进一步分析NK细胞表面受体，发现抑制性NK受体和趋化因子受体CCR5表达上调。此外，我们的数据显示，CCR5上调是免疫激活的结果，而iNKRs的诱导似乎是HIV诱导效应的直接结果。对NK细胞与R5和X4 HIV包膜相互作用的分析表明，暴露于这些包膜后，一般的NK细胞功能受到严重抑制。此外，在存在和不存在HIV包膜的情况下，对NK细胞的DNA微阵列分析描绘了几个在诱导细胞凋亡和抑制细胞增殖方面重要的基因上调。同样，暴露在HIV包膜中抑制了几个对细胞增殖和普通NK细胞功能至关重要的基因的表达。功能研究证实，HIV包膜对普通NK细胞的细胞毒性、增殖以及细胞因子和趋化因子的分泌等功能具有深刻的抑制作用。未来的研究将集中在描述R5和X4 HIV包膜与NK细胞之间相互作用的潜在机制。进一步的研究将解决这种HIV包膜诱导的NK细胞抑制效应的细胞和分子基础。NK细胞受体的特殊作用，特别是那些属于C型凝集素家族的受体，将被作为HIV包膜的潜在抗原进行研究。 对HIV病毒携带者NK细胞的DNA芯片分析表明，与HIV病毒携带者和HIV血清阴性的正常志愿者相比，干扰素诱导的基因表达上调。对这些基因簇的分析使我们找到了在HIV病毒状态下被异常调控的信号转导途径。我们进一步证明，来自HIV病毒感染者的NK细胞表面表达相对较高水平的Fas分子，并且在暴露于sFASL时容易受到Fas介导的细胞凋亡的影响。此外，来自HIV病毒感染者的NK细胞表面IL受体表达减少，细胞内Ki67水平显著升高，表明与HIV病毒感染状态相关的细胞激活水平更高。我们进一步证明，HIV感染者在病毒血症期间血清中循环的sFas和sFASL水平高于无菌状态下这些分子的水平。这些观察表明，HIV病毒状态对NK细胞的增殖能力、趋化能力以及最终在体内存活的能力有深远的影响。未来的实验将集中在评估BRDU给药后NK细胞在体内的周转。这样的实验将有助于我们了解在HIV病毒感染状态下NK细胞增殖和更新的本质。

Innate immunity is the first line of defense designed to protect the host from invading pathogens, including HIV. We have previously demonstrated that suppression of natural killer (NK) cell function can be profound and that it is related to the stage of HIV infection as well as the level of HIV plasma viremia. Our study revealed that HIV viremia impairs the ability of NK cells to secrete CC-chemokines and alters the expression of various inhibitory and chemokine receptors expressed on NK cells. Further analysis of NK-cell specific surface receptors revealed upregulation of inhibitory NK receptors and chemokine receptor CCR5. In addition, our data showed CCR5 upregulation to be induced as a result of immune activation while induction of iNKRs appeared to be a direct result of an HIV-induced effect. Analysis of NK cell interactions with R5 and X4 HIV envelopes showed profound suppression of generic NK cell function upon exposure to these envelopes. Furthermore, DNA microarray analyses of NK cells in the presence and absence of HIV envelopes delineated upregulation of several genes that were important in inducing apoptosis and suppression of cell proliferation. Similarly, exposure to HIV envelopes suppressed the expression of several genes critical for cell proliferation and generic NK cell function. Functional studies confirmed the profound suppresssive ability of HIV envelopes on generic NK cell functions such as cytotoxicity, proliferation, and secretion of cytokines and chemokines. Future studies will be focused on delineating the underlying mechanisms involved in the interaction between R5 and X4 HIV envelopes and NK cells. Further studies will address the cellular and molecular basis for this HIV envelope-induced suppressive effect on NK cells. Specific roles of NK cell receptors, particularly those belonging to the C-type lectin family will be investigated as potential igands for HIV envelopes. DNA microarray analyses of NK cells from HIV viremic patients showed upregulation of genes induced by interferon when compared with those from HIV aviremic individuals and HIV seronegative normal volunteers. Analyses of these gene clusters have lead us to identify pathways of signal transduction that are abnormally regulated in HIV viremic state. We have further demonstrated that NK cells from HIV viremic patients express relatively higher levels of fas molecule on their surface and are susceptible to fas-mediated apoptosis upon exposure to sFASL. In addition, NK cells from HIV viremic individuals have reduced surface expresssion of interleukin receptors and express significantly higher levels of intracellular Ki67, indicating a higher level of cellular activation associated with the HIV viremic state. We have further demonstrated that HIV-infected individuals have elevated levels of sfas and SFASL circulating in the serum during viremia when compared to the levels of these molecules during the aviremic state. These observations indicate a profound effect of HIV viremic state on the ability of NK cells to proliferate, undergo chemotaxis, and ultimately to survive in vivo. Future experiments will be focused on evaluating the turnover of NK cells in vivo after administration of BRDU. Such experiments will help us to understand the nature of NK cell proliferation and turnover in the HIV viremic state.