Predictors for drug selection and minimization in pediatric liver transplantation

描述（由申请人提供）：该项目的长期目标是在每个肝移植儿童（LTx）中最大限度地减少器官排斥和免疫抑制剂毒性。ltx前淋巴细胞耗竭允许类固醇避免和降低他克莫司免疫抑制的需要。如果对潜在的机制有更好的了解，它们可以用于进一步减少该方案中药物最小化期间的原发性排斥反应（50%）和复发性排斥反应（30%）。初步的工作使我们假设供体特异性低反应性和调节抑制作用在无类固醇淋巴细胞消耗免疫抑制后早期排斥的儿科LTx中实现的时间间隔是高度可变的。我们进一步假设，这种免疫调节的可变性与扩展mhcreregion基因的单核苷酸多态性（SNP）模式有关，这些基因服务于增殖、凋亡、记忆和b细胞依赖功能。本中心的一项临床试验将在80例LTx患儿中使用5 mg/kg兔抗人胸腺细胞球蛋白（rabbit anti-human thymocyte globulin, rATG）消耗后给予不含类固醇的他克莫司。拟议的机械性补充研究将需要在ltx治疗前、治疗后1、3和12个月采集所有儿童的外周血样本。具体目标：每个儿童供体特异性同种异体反应性、T-reg/抑制细胞（CD4+CD25+、CD8+28-）和抗hla抗体的纵向特征分析2。29个snp分布在14个MHC基因中，其初步分布模式在排斥者（ltx后60天活检证实排斥）和非排斥者之间存在显著差异。这项研究将在80名儿童和他们的亲生父母身上进行。2 .显示>或< 50%预期从父母传递给拒绝者的snp，其在拒绝者和非拒绝者之间的传递差异显著，将用于通过传递不平衡检验确定候选基因座。验证结果组内潜在的候选基因/位点，a)通过CFSE-MLR测量T和b细胞亚群中供体特异性增殖/凋亡/记忆反应，b)全基因组mRNA表达以补充SNP关联，并尽量减少假阳性，c)候选位点的位点特异性基因表达（mRNA） c)。如果成功，研究结果的未来应用可以改善ltx前的药物选择，例如，如果SNP模式预测排斥反应，则分配类固醇。此外，ltx后药物最小化可以更安全，例如，当T-reg/T-sup出现时。

DESCRIPTION (provided by applicant): The long term goal of this project is to minimize organ rejection and immunosuppressant toxicity, in each child with liver transplantation (LTx). Pre-LTx lymphocyte depletion permits steroid avoidance and lowers need for Tacrolimus immunosuppression. If underlying mechanisms were better understood, they could be used to reduce further, primary rejection (50%) and recurrent rejection during drug minimization (30%) on this protocol. Preliminary work leads us to hypothesize that donor-specific hyporeactivity and regulatorysuppressive effect are achieved at highly variable intervals among pediatric LTx with early rejection after steroid-free lymphocyte-depleting immunosuppression. We further hypothesize that this variability in immune-modulation is associated with patterns of single nucleotide polymorphisms (SNP) in extended MHCregion genes subserving proliferation, apoptosis, memory and B-cell-dependent functions. A clinical trial at our center will administer steroid-free Tacrolimus after depletion with 5 mg/kg rabbit anti-human-thymocyte globulin (rATG) to 80 children with LTx. The proposed mechanistic addendum study will entail serial peripheral blood samples from all children before and at 1, 3, and 12 months post-LTx. Specific aims are 1. Longitudinal characterization of donor-specific alloreactivity, T-reg/suppressor cells (CD4+CD25+, CD8+28-), and anti-HLA alto-antibodies in each child, 2. Pre-LTx characterization of 29 SNPs distributed among 14 MHC genes, whose preliminary distribution patterns differ significantly between rejectors (biopsy-proven rejection at 60 days post-LTx), and non-rejectors. This will be done in 80 children and their biologic parents. SNPs showing > or < 50% expected transmission from parents to rejectors and whose transmission differs significantly between rejectors and non-rejectors, will be used to identify candidate loci with the transmission disequilibrium test, and 3. Validate potential candidate genes/loci within outcome groups, by a) measuring donor-specific proliferative/apoptotic/memory responses in T- and B-cell subsets by CFSE-MLR, b) whole genome mRNA expression to complement SNP associations, and minimize false-positives, and c) locusspecific gene expression (mRNA) for candidate loci c). If successful, future application of study results could improve pre-LTx drug selection, e.g., allocating steroids if SNP patterns predict rejection. Also, post-LTx drug minimization could be made safer, e.g., when T-reg/T-sup appear.