Immune Pathophysiology of Aplastic Anemia and Immunosuppressive Treatments

再生障碍性贫血的免疫病理生理学和免疫抑制治疗

• 批准号: 8746560
• 负责人: NEAL S YOUNG
• 金额: $ 221.98万
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8746560
• 关键词: Acute Myelocytic Leukemia; Adipocytes; Aftercare; Agonist; Ancillary Study; Anemia; Animal Model; Antithymoglobulin; Aplastic Anemia; Apoptosis; Benzene; Binding; Biological Assay; Blood; Blood Circulation; Blood Platelets; Bone Marrow; Bone Marrow Aspiration; Bone Marrow Transplantation; CD34 gene; CD4 Positive T Lymphocytes; CD8B1 gene; Cell Count; Cells; Cellularity; Cessation of life; Chemical Agents; Chemical Exposure; Chromosome abnormality; Chronic; Clinical; Clinical Protocols; Complication; Cyclosporine; Data; Data Analyses; Development; Disease; Dose; Drug Kinetics; Drug usage; Dysmyelopoietic Syndromes; Enrollment; Equus caballus; Erythrocytes; Event; Failure; Fatty acid glycerol esters; Frequencies; Functional disorder; Future; Genes; Hematology; Hematopoietic; Hemorrhage; Hepatitis; Human; Idiopathic Thrombocytopenic Purpura; Immune; Immune response; Immune system; Immunologics; Immunosuppression; Immunosuppressive Agents; In complete remission; Infection; Infiltration; Inflammatory; Infusion procedures; Interferon Type II; Investigation; Laboratories; Link; Lymphocyte; Lymphocyte Subset; Marrow; Mediating; Medical; Mental Depression; Minor; Modeling; Molecular; Mus; Oryctolagus cuniculus; PPAR gamma; Pancytopenia; Pathway interactions; Patients; Pattern; Peroxisome Proliferator-Activated Receptors; Persons; Pharmaceutical Preparations; Plasma; Population; Pregnancy; Preparation; Prevalence; Production; Proteins; Protocols documentation; Publications; Publishing; Radiation; Recovery; Refractory; Regimen; Regulatory T-Lymphocyte; Relapse; Risk; Sampling; Serum Sickness; Specificity; Stem Cell Factor; Stem cells; Syndrome; T-Lymphocyte; Testing; Thrombopoietin; Toxic effect; Transfusion; Transplantation; Ursidae Family; White Blood Cell Count procedure; Work; base; bone; chemotherapy; cohort; conditioning; cytokine; cytopenia; cytotoxic; falls; human disease; improved; inhibitor/antagonist; lipid biosynthesis; lymph nodes; mimetics; neutrophil; novel; peripheral blood; prevent; research study; response; translational study

In aplastic anemia, the bone marrow is replaced by fat, and peripheral blood counts - - of white blood cells, red blood cells, and platelets - - fall to extremely low levels, leading to death from anemia, bleeding or infection. Aplastic anemia is a disease of young persons, and in its severe form is almost invariably fatal untreated. Historically, aplastic anemia has been linked to chemical exposures, in particular benzene; it is an idiosyncratic complication of some medical drug use; it occurs as a rare event in pregnancy and following seronegative hepatitis; and the diseases associated with certain immunologic conditions. The chance observation that some patients post-bone marrow transplant recovered their own marrow function led to the inference that the immunosuppressive conditioning regimen might have treated an underlying immune-mediated pathophysiology. Purposeful administration of antithymocyte globulin (ATG) has led to hematologic recovery in the majority of treated patients. Laboratory data have also revealed abnormalities of the immune system: lymphocyte populations that induce apoptosis in hematopoietic target cells by the Fas-mediated pathway, and oligoclones of effector T cells which express type 1 cytokines, especially gamma-interferon. The Hematology Branch has been a leader in both the scientific and medical studies of aplastic anemia pathophysiology and treatment. Several major clinical protocols have been completed or are in progress. We have determined that prolonging cyclosporine administration from the standard six month period to two years post-ATG delays but does not prevent relapse. Approximately the same 1/3 of patients will eventually require further immunosuppression, whether or not additional cyclosporine is prescribed. However, analysis of the data suggests that most relapse occurs at relatively low doses of cyclosporine, and future protocols might aim to treat patients at 1-2 ml/kg beyond six months; this dose is unlikely to result in serious toxicities. We have continued our studies of eltrombopag, a thrombopoietin mimetic which can be administered orally and is approved for use in refractory idiopathic thrombocytopenic purpura. We published last year that 40-50% a small cohort of patients with refractory severe aplastic anemia showed hematologic responses to eltrombopag. As these responses were robust, occurred in trilineages, and were accompanied by increased bone marrow cellularity, eltrombopag was hypothesized to act as a stem cell factor. The refractory study has been extended, with additional patients showing approximately the same proportion and pattern of response. Further, we have enrolled almost two dozen patients in a novel new protocol, which combines standard immunosuppression with horse ATG and cyclosporine with eltrombopag in severe treatment nave disease. Preliminary data from this ongoing trial suggests that the response rate may be higher than the usual 65%, and that responses are occurring earlier and are more robust, leading to a higher proportion of patients who are free of transfusion as soon as one month after ATG and who have achieved almost complete responses at three months. In this study, ancillary laboratory assays show a marked increase in CD34 cell number in bone marrow, consistent with the stem cell stimulation mechanism. However, in both our studies of refractory and treatment-nave disease, the major concerns remains stimulation of abhorrent clones, which bear cytogenetic abnormalities and may be associated with refractory cytopenias, myelodysplasia, and acute myeloid leukemia. Other current studies of eltrombopag in the Branch include treatment of patients with low risk myelodysplastic syndrome and with moderate aplastic anemia. We have completed translational studies related to our landmark publication showing that horse ATG is superior to rabbit ATG. We utilized samples from the 120 patients treated in this trial to assess differences in the immune response to these heterologous protein preparations, as well as correlates of serum sickness, for which ATG treatment is a good model in humans. We found that rabbit ATG was detectable in the blood for a much longer period than was horse ATG, and was bound to lymphocytes in the circulation. Neutrophil numbers were much lower in rabbit ATG-treated patients. Rabbit ATG also resulted in the production of multiple cytokines detectable in the plasma. While rabbit ATG induced higher frequencies of certain lymphocyte subsets, its depletion effect on CD4 cells overwhelmed enhancement of T-regulatory cell development. Plasma rabbit ATG levels predicted the occurrence of serum sickness, and its prevalence peaked around week two, concurrent with the clearance of ATG from blood and the production of a variety of cytokines. Horse ATG and rabbit ATG therefore have very different pharmacokinetics as well as effects on cell subsets and cytokines, differences likely related to both their efficacy and toxicity. In studies in the mouse, we have expanded on earlier descriptions on a model for an immune-mediated bone marrow failure based on infusion of lymph node cells different in either major H2 or minor histocompatability loci. We have developed a model for marrow failure in B6 mice utilizing infusion of FVB lymph node cells, which appears to create a more chronic model of marrow depression, allowing investigation of treatments after pancytopenia develops, thus more closely mimicking the human disease. In a separate project, we have investigated the possibility that adipocytes are important factors in producing hematopoietic depression. However, in contrast to prominently published work, we only observed this correlation in the setting of immune-mediated bone marrow failure. Inhibition of adipogenesis with specific chemical agents was effective in improving bone cellularity and blood counts in our aplastic anemia model but not after transplantation, or in radiation or chemotherapy induced bone marrow failure. The explanation for this discrepancy is that the inhibitors of adipogenesis, PPAR γ agents, also act on T cells to suppress their function. These experiments depend on the specificity of PPAR gamma and PPAR antagonists and their specificity. In addition to inhibiting adipogenesis, as determined by micro arrays, the purportedly specific PPAR γ agonist reduced CD8 and CD4 T cell infiltration in the bone marrow and inflammatory cytokine levels in plasma. In addition, inflammasome genes were also decreased as determined by microarrays.

在再生障碍性贫血中，骨髓被脂肪取代，外周血计数（白细胞、红细胞和血小板）降至极低水平，导致因贫血、出血或感染而死亡。 再生障碍性贫血是年轻人的一种疾病，严重时如果不治疗几乎总是致命的。 从历史上看，再生障碍性贫血与化学物质接触有关，特别是苯；它是某些药物使用的特殊并发症；它在怀孕期间和血清阴性肝炎后发生为罕见事件；以及与某些免疫状况相关的疾病。 一些患者在骨髓移植后恢复了自己的骨髓功能，这一偶然观察导致了这样的推断：免疫抑制调理方案可能治疗了潜在的免疫介导的病理生理学。 有目的地施用抗胸腺细胞球蛋白（ATG）已使大多数接受治疗的患者的血液学恢复。 实验室数据还揭示了免疫系统的异常：通过Fas介导的途径诱导造血靶细胞凋亡的淋巴细胞群，以及表达1型细胞因子（尤其是γ-干扰素）的效应T细胞的寡克隆。 血液学分支一直是再生障碍性贫血病理生理学和治疗的科学研究和医学研究的领导者。 几个主要的临床方案已经完成或正在进行中。 我们已经确定，将环孢素给药时间从标准的六个月延长至 ATG 后两年可以延迟，但不能防止复发。 无论是否开具额外的环孢素，大约同样 1/3 的患者最终将需要进一步的免疫抑制。 然而，数据分析表明，大多数复发发生在环孢素剂量相对较低的情况下，未来的方案可能旨在以 1-2 ml/kg 的剂量治疗六个月以上的患者；这个剂量不太可能导致严重的毒性。 我们继续对艾曲波帕进行研究，艾曲波帕是一种血小板生成素模拟物，可以口服给药，并被批准用于治疗难治性特发性血小板减少性紫癜。 我们去年发表的研究表明，一小群难治性重度再生障碍性贫血患者中 40-50% 对艾曲波帕表现出血液学反应。 由于这些反应很强烈，发生在三系中，并且伴随着骨髓细胞数量的增加，因此假设艾曲波帕充当干细胞因子。 难治性研究已经扩大，更多的患者显示出大致相同的比例和反应模式。 此外，我们已经招募了近 20 名患者参加一项新颖的新方案，该方案将标准免疫抑制与马 ATG 以及环孢素与艾曲波帕相结合来治疗严重的初治疾病。 这项正在进行的试验的初步数据表明，缓解率可能高于通常的 65%，而且缓解发生得更早且更稳健，导致 ATG 后一个月内无需输血的患者比例更高他们在三个月内几乎获得了完全的反应。 在这项研究中，辅助实验室检测显示骨髓中 CD34+ 细胞数量显着增加，这与干细胞刺激机制一致。 然而，在我们对难治性和未治疗疾病的研究中，主要关注点仍然是刺激令人厌恶的克隆，这些克隆具有细胞遗传学异常，可能与难治性血细胞减少症、骨髓增生异常和急性髓系白血病有关。 该部门目前对艾曲波帕的其他研究包括治疗低危骨髓增生异常综合征和中度再生障碍性贫血患者。 我们已经完成了与我们具有里程碑意义的出版物相关的转化研究，表明马 ATG 优于兔 ATG。 我们利用本试验中接受治疗的 120 名患者的样本来评估对这些异源蛋白质制剂的免疫反应的差异，以及血清病的相关因素，对于这些，ATG 治疗是人类的一个很好的模型。 我们发现兔 ATG 在血液中的检测时间比马 ATG 长得多，并且与循环中的淋巴细胞结合。 接受 ATG 治疗的兔患者的中性粒细胞数量要低得多。 兔 ATG 还导致血浆中可检测到的多种细胞因子的产生。 虽然兔 ATG 诱导某些淋巴细胞亚群出现较高频率，但其对 CD4 细胞的消耗作用压倒了 T 调节细胞发育的增强作用。 兔血浆 ATG 水平预示着血清病的发生，其患病率在两周左右达到峰值，同时 ATG 从血液中清除，并产生多种细胞因子。 因此，马 ATG 和兔 ATG 具有非常不同的药代动力学以及对细胞亚群和细胞因子的影响，差异可能与其功效和毒性有关。 在小鼠研究中，我们扩展了早期对免疫介导的骨髓衰竭模型的描述，该模型基于主要 H2 或次要组织相容性基因座不同的淋巴结细胞的输注。 我们利用输注 FVB 淋巴结细胞在 B6 小鼠中开发了一种骨髓衰竭模型，这似乎创建了一种更慢性的骨髓抑制模型，允许在全血细胞减少症发生后研究治疗方法，从而更接近地模拟人类疾病。 在一个单独的项目中，我们研究了脂肪细胞是产生造血抑制的重要因素的可能性。 然而，与已发表的重要工作相反，我们仅在免疫介导的骨髓衰竭的情况下观察到这种相关性。 在我们的再生障碍性贫血模型中，用特定化学试剂抑制脂肪生成可有效改善骨细胞结构和血细胞计数，但在移植后或放疗或化疗引起的骨髓衰竭中则无效。 对这种差异的解释是，脂肪生成抑制剂 PPAR γ 剂也会作用于 T 细胞以抑制其功能。 这些实验取决于 PPAR γ 和 PPAR 拮抗剂的特异性及其特异性。 通过微阵列测定，除了抑制脂肪生成之外，据称特异性 PPAR γ 激动剂还减少了骨髓中 CD8 和 CD4 T 细胞的浸润以及血浆中炎症细胞因子的水平。 此外，根据微阵列测定，炎性体基因也减少了。