HIV, Cytokine Expression and Potential Therapies

总结： 巨噬细胞在HIV感染的发病机制中起着关键作用，既作为病毒复制的靶点，又作为多功能细胞因子的来源。我们的早期研究表明，用HIV-1包膜蛋白gp 120刺激的正常人单核细胞产生HIV调节细胞因子TNF-α、IL-1b、IL-6和GM-CSF（JI 1991）和有效的血管活性肽ET-1（JI 1993）。我们对单核细胞衍生的巨噬细胞（MDM）的研究表明，HIV-1感染在体外不能诱导这些后一种细胞因子，但始终诱导M-CSF产生，其动力学与病毒复制平行（JI 1995）。M-CSF通过增强HIV受体CD 4和CCR 5的表达，促进分化并增加MDM对HIV感染的易感性。我们使用一组单链RNA病毒（包括HIV-1、HIV-2、麻疹和呼吸道合胞病毒（MV & RSV））确定了MDM中M-CSF产生的病毒特异性，发现只有HIV-1（JI 2000）和HIV-2的单嗜性毒株导致M-CSF产生增强。HIV-1感染的MDM也产生趋化因子，如MIP-1a/B和MCP-1，但HIV-2不产生，这表明建立病毒库需要趋化因子和M-CSF，或者趋化因子的产生可能与致病性相关（in prep，2001）。我们使用抗逆转录病毒药物（AZT和利托那韦）进行的其他研究表明，在HIV感染的MDM中，病毒复制和M-CSF的产生是密不可分的，因此，抑制一种导致另一种的共同抑制（AIDS，已提交）。由于HIV是由SIV的跨种属传播引起的，并且从一种良性疾病发展为高致病性疾病，最初的感染以MDM为目标，因此我们正在研究SIV感染原代人巨噬细胞并诱导M-CSF和其他细胞因子或趋化因子的能力。使用原代分离株，我们发现来自多个谱系的SIV能够在人MDM中复制。正在进行的研究将确定受体的使用和细胞因子的产生，以深入了解这些慢病毒对人群的致病决定因素，希望能确定治疗干预的新靶点。 由于星形胶质细胞包围着大脑中的HIV产生细胞，这可能会影响病毒的复制，我们研究了它们对人类MDM中HIV表达的影响。HIV感染的MDM与原代人星形胶质细胞的共培养导致HIV复制减少，除了诱导型一氧化氮合酶（iNOS）的表达和星形胶质细胞NO的产生（Blood 1999）之外，还部分由未鉴定的星形胶质细胞分泌因子介导（AIDS 1999）。我们的数据表明，星形胶质细胞通过产生HIV调节细胞因子和iNOS/NO的表达，在确定神经系统HIV疾病的过程中起着关键作用。这也使我们推测，在HIV疾病中观察到的神经系统损伤可能是由于星形胶质细胞长时间、高水平产生NO，这可能反映了宿主试图抑制病毒复制。

Summary: Macrophages play a critical role in the pathogenesis of HIV infection, both as targets for virus replication and as sources of multifunctional cytokines. Our early studies showed that normal human monocytes stimulated with the HIV-1 envelope protein, gp120, produce the HIV-modulatory cytokines, TNF-a, IL-1b, IL-6 and GM-CSF (JI 1991) and the potent vasoactive peptide, ET-1 (JI 1993). Our studies with monocyte derived macrophages (MDM) revealed that HIV-1 infection fails to induce these latter cytokines in vitro, but consistently induces M-CSF production with a kinetics paralleling virus replication (JI 1995). M-CSF facilitates differentiation and increases the susceptibility of MDM to HIV infection by enhancing expression of the HIV receptors, CD4 and CCR5. We determined the viral specificity of M-CSF production in MDM using a panel of single-stranded RNA viruses, including HIV-1, HIV-2, measles and respiratory syncytial viruses (MV & RSV) and found that only monocytropic strains of HIV-1 (JI 2000) and HIV-2 caused enhanced production of M-CSF. Chemokines, such as MIP-1a/b and MCP-1, were also produced by HIV-1 infected MDM, but not HIV-2, suggesting that both chemokines and M-CSF are needed to establish a viral reservoir or that chemokine production may correlate with pathogenicity (in prep, 2001). Our other studies using anti-retroviral agents (AZT and Ritonavir) suggest that virus replication and M-CSF production are inextricably linked in HIV-infected MDM, such that inhibition of one leads to comcommitant inhibition of the other (AIDS, submitted). Since HIV arose from cross-species transmission of SIV and progressed from a benign to highly pathogenic disease with initial infections targeting MDM, we are investigating the ability of SIV to infect primary human macrophages and induce M-CSF and other cytokines or chemokines. Using primary isolates, we are finding that SIV from multiple lineages are able to replicate in human MDM. Ongoing studies will determine receptor usage and cytokine production to obtain insight into pathogenic determinants of these lentiviruses for the human population with the hope of identifying novel targets for therapeutic intervention. Since astrocytes surround HIV-producing cells in the brain, which might influence virus replication, we studied their effect on HIV expression in human MDM. Co-culture of HIV-infected MDM with primary human astrocytes resulted in reduced HIV replication mediated in part by an unidentified astrocyte secreted factor (AIDS 1999) in addition to expression of inducible nitric oxide synthase (iNOS) and production of NO by astrocytes (Blood 1999). Our data suggest that astrocytes play a pivotal role in determining the course of neurologic HIV disease via production of HIV modulating cytokines and expression of iNOS/NO. It also leads us to speculate that neurologic damage observed in HIV disease may ensue from prolonged, high level production of NO by astrocytes, which may reflect a host attempt to inhibit virus replication.