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.

在性贫血中，骨髓被脂肪所取代，白细胞，红细胞和血小板的外周血计数 - - 跌至极低的水平，导致贫血，流血或感染导致死亡。 性贫血是一种年轻人的疾病，其严重形式几乎总是致命治疗。 从历史上看，性贫血与化学暴露有关，特别是苯。这是某种医学药物使用的特殊并发症。这是怀孕和血清肝炎的罕见事件。以及与某些免疫条件相关的疾病。 偶然的观察结果是，一些患者在骨髓移植后恢复了自己的骨髓功能，从而推断了免疫抑制条件方案可能已经治疗了一种潜在的免疫介导的病理生理学。 有目的的抗杀菌细胞球蛋白（ATG）导致大多数治疗患者的血液恢复。 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型细胞因子的效应T细胞的寡球，尤其是Gamma-Interterferon。 血液学分支一直是性贫血病理生理学和治疗的科学和医学研究的领导者。 几种主要的临床方案已经完成或正在进行中。 我们已经确定，将环孢素的延长从标准的六个月延长到ATG延迟后两年，但不能阻止复发。 大约相同的1/3患者最终将需要进一步的免疫抑制，无论是否开了其他环孢菌素。 但是，对数据的分析表明，大多数复发发生在相对较低剂量的环孢菌素，未来的方案可能旨在以1-2 mL/kg的速度治疗六个月以上的患者。这种剂量不太可能导致严重的毒性。 我们继续研究Eltrombopag，这是一种可以口服的血小板蛋白模拟物，并批准用于难治性特发性血小板细胞减少紫红色。 去年，我们发表了40-50％的一小部分患有难治性的严重性性障碍性贫血患者对Eltrombopag的血液学反应。 由于这些反应是鲁棒的，因此发生在三利链球菌中，并伴随着骨髓细胞的增加，因此假设Eltrombopag充当干细胞因子。 难治性研究已扩展，额外的患者显示出大致相同的比例和反应模式。 此外，我们已经将近二十名患者纳入了一种新的新方案，该方案将标准的免疫抑制与马ATG和环孢菌素与Eltrombopag结合在一起。 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％，并且反应较早并且更健壮，导致ATG后一个月后不再输血的患者比例更高，并且在三个月后几乎完成了完全反应。 在这项研究中，辅助实验室测定显示骨髓中CD34细胞数的显着增加，这与干细胞刺激机制一致。 但是，在我们对难治性和治疗纳维病的研究中，主要关注点仍然刺激了可恶的克隆，这些克隆具有细胞遗传学异常，可能与难治性细胞质，骨髓发育不全和急性髓样白血病有关。 当前对分支机构的Eltrombopag的研究包括治疗低风险骨髓增生综合征和中等性障碍性贫血的患者。 我们已经完成了与地标性出版物有关的翻译研究，表明马ATG优于兔子ATG。 我们利用了该试验中接受治疗的120名患者的样本来评估对这些异源蛋白制剂的免疫反应差异，以及血清疾病的相关性，而ATG治疗是人类的好模型。 我们发现，兔子ATG在血液中可检测到比马ATG更长的时间，并且在循环中注入淋巴细胞。 兔子ATG治疗的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。 兔子ATG诱导了某些淋巴细胞亚群的较高频率，但其对CD4细胞的耗竭作用淹没了T调节性细胞发育的增强。 血浆兔ATG水平预测了血清疾病的发生，其患病率在第二周左右达到峰值，同时与血液中的ATG清除以及多种细胞因子的产生。 因此，马ATG和兔子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，这可能与它们的疗效和毒性有关。 在小鼠的研究中，我们在主要H2或较小的组织相容性基因座中不同的淋巴结细胞的输注基于淋巴结细胞的输注基于免疫介导的骨髓衰竭模型的早期描述。 我们已经开发了一种利用FVB淋巴结细胞的B6小鼠骨髓衰竭的模型，该模型似乎创造了一种更慢性的骨髓抑郁模型，从而使全年症后的治疗方法进行了研究，从而更加模仿人类疾病。 在一个单独的项目中，我们研究了脂肪细胞是产生造血抑郁症的重要因素的可能性。 但是，与突出的工作相反，我们只在免疫介导的骨髓衰竭的情况下观察到这种相关性。 用特定的化学剂抑制脂肪形成可有效改善我们的性障碍性障碍性障碍性障碍模型，但在移植后或化学疗法诱导的骨髓衰竭中，但不能有效。 这种差异的解释是脂肪生成的抑制剂PPARγ剂也作用于T细胞以抑制其功能。 这些实验取决于PPARγ和PPAR拮抗剂的特异性及其特异性。 除了通过微阵列确定的抑制脂肪形成外，据称特定的PPARγ激动剂还减少了血浆中骨髓和炎症细胞因子水平的CD8和CD4 T细胞浸润。 另外，根据微阵列确定的炎性体基因也减少了。