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尽量减少器官排斥反应和免疫抑制剂的毒性，在每一个儿童肝移植（LTx）。前LTx淋巴细胞耗竭允许避免类固醇和降低对他克莫司免疫抑制的需要。如果更好地理解了潜在的机制，它们可以用于进一步减少原发性排斥（50%）和药物最小化期间的复发性排斥（30%）。初步工作使我们假设，在无类固醇淋巴细胞耗竭免疫抑制后出现早期排斥反应的儿童LTx中，供体特异性低反应性和调节抑制作用是在高度可变的时间间隔内实现的。我们进一步假设，这种免疫调节的变异性与扩展MHC区域基因中的单核苷酸多态性（SNP）模式相关，这些基因有助于增殖、凋亡、记忆和B细胞依赖性功能。我们中心的一项临床试验将对80名LTx儿童在耗尽5 mg/kg兔抗人胸腺细胞球蛋白（rATG）后给予无类固醇他克莫司。拟议的机制补充研究将需要在LTx之前和之后1个月、3个月和12个月对所有儿童进行连续外周血样本采集。具体目标是1。每个儿童的供体特异性同种异体反应性、T-reg/抑制细胞（CD 4 + CD 25+、CD 8 +28-）和抗HLA alto抗体的纵向特征，2.分布在14个MHC基因中的29个SNP的Pre-LTx表征，其初步分布模式在排斥者（LTx后60天活检证实的排斥）和非排斥者之间显著不同。这将在80名儿童及其亲生父母中进行。显示>或< 50%的预期从父母到拒绝者的传递并且其传递在拒绝者和非拒绝者之间显著不同的SNP将用于通过传递不平衡检验鉴定候选基因座，以及3.通过a）通过CFSE-MLR测量T细胞和B细胞亚群中的供体特异性增殖/凋亡/记忆应答，B）全基因组mRNA表达以补充SNP关联，并使假阳性最小化，和c）候选基因座的基因座特异性基因表达（mRNA）c），在结果组内筛选潜在的候选基因/基因座。如果成功，研究结果的未来应用可以改善LTx前药物的选择，例如，如果SNP模式预测排斥，则分配类固醇。此外，LTx后药物最小化可以变得更安全，例如，当出现T-reg/T-sup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.