Although allogeneic hematopoietic cell transplantation (HCT) is a potentially curative therapy for hematologic neoplasms, one of its limiting toxicities continues to be graft-versus-host disease, both acute (aGVHD) and chronic (cGVHD). Sirolimus is a mammalian target of rapamycin inhibitor that has proven effective in GVHD prophylaxis in combination with a calcineurin inhibitor, such as tacrolimus. The impact of sirolimus on immune reconstitution has not been comprehensively investigated in vivo thus far, however. Here we present an ancillary analysis of the randomized study BMT-CTN 0402 that examined the effect of sirolimus on immune subsets post-transplantation. We further examine the association between different lymphocyte subsets and outcomes post-transplantation in each arm. BMT-CTN 0402 was a randomized trial (n = 304) comparing 2 GVHD prophylaxis regimens, tacrolimus/sirolimus (Tac/Sir) and tacrolimus/methotrexate (Tac/MTX), in patients with acute myelogenous leukemia, acute lymphoblastic leukemia, or myelodysplastic syndrome undergoing myeloablative HLA-matched HCT. There were no differences in 114-day GVHD-free survival (primary endpoint), aGVHD, cGVHD, relapse, or overall survival (OS) between the 2 arms. Of the 304 patients, 264 had available samples for the current immune reconstitution analysis. Blood samples were collected at 1, 3, 6, 12, and 24 months post-HCT. Multiparameter flow cytometry was performed at the project laboratory (Esoterix Clinical Trials Services) in a blinded fashion, and results for the 2 arms were compared. Multivariable Cox regression models, treating each phenotypic parameter as a time-dependent variable, were constructed to study the impact of reconstitution on clinical outcomes. There were no significant differences in patient and transplantation characteristics between the Tac/Sir and Tac/MTX arms in this analysis. Absolute lymphocyte count and CD3+ cell, CD4+ cell, and conventional T cell (Tcon) counts were significantly decreased in the Tac/Sir arm for up to 3 months post-HCT, whereas CD8+ cells recovered even more slowly (up to 6 months) in this arm. Interestingly, there was no clear difference in the absolute number of regulatory T cells (Tregs, defined as CD4+CD25+ cells) between the 2 arms at any point post-HCT; however, the Treg:Tcon ratio was significantly greater in the Tac/Sir arm in the first 3 months after HCT. B lymphocyte recovery was significantly compromised in the Tac/Sir arm from 1 month to 6 months after HCT, whereas natural killer cell reconstitution was not affected in the Tac/Sir arm. In the outcomes analysis, higher numbers of CD3+ cells, CD4+ cells, CD8+ cells, and Tregs were associated with better OS. Neither Treg numbers nor the Treg:Tcon ratio was correlated with GVHD. Our findings indicate that Tac/Sir has a more profound T cell suppressive effect than the combination of Tac/MTX in the early post-transplantation period, and particularly compromises the recovery of CD8+ T cells, which have been implicated in aGVHD. Sirolimus used in vivo with tacrolimus does not appear to result in increased absolute numbers of Tregs, but might have a beneficial effect on the Treg:Tcon balance in the first 3 months after transplantation. Nonetheless, no differences in aGVHD or cGVHD between the 2 arms were observed in the parent randomized trial. Calcineurin-inhibitor free, sirolimus-containing GVHD prophylaxis strategies, incorporating other novel agents, should be investigated further to maximize the potential favorable effect of sirolimus on Treg:Tcon balance in the post-transplantation immune repertoire. Sirolimus significantly compromises B cell recovery in the first 6 months post-HCT, with potential complex effects on cGVHD that merit further study.

中文翻译：

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西罗莫司对异基因异体干细胞移植后免疫重建的影响：他克莫司/西罗莫司和他克莫司/甲氨蝶呤比较的随机对照试验的一项辅助分析（血液和骨髓移植临床试验网络/ BMT CTN 0402）。

尽管同种异体造血细胞移植（HCT）是血液肿瘤的潜在治疗方法，但其局限性毒性之一仍然是移植物抗宿主病，无论是急性（aGVHD）还是慢性（cGVHD）。西罗莫司是雷帕霉素抑制剂的哺乳动物靶标，已证明与钙调神经磷酸酶抑制剂（如他克莫司）组合可有效预防GVHD。迄今为止，尚未在体内对西罗莫司对免疫重建的影响进行全面研究。在这里，我们介绍了一项随机研究BMT-CTN 0402的辅助分析，该研究检查了西罗莫司对移植后免疫亚群的影响。我们进一步检查了每个手臂中不同淋巴细胞亚群与移植后结局之间的关联。BMT-CTN 0402是一项随机试验（n = 304），对急性骨髓性白血病，急性淋巴细胞性白血病或骨髓增生异常患者的2种GVHD预防方案，他克莫司/西罗莫司（Tac / Sir）和他克莫司/甲氨蝶呤（Tac / MTX）进行了比较进行清髓性HLA匹配HCT的综合征。两组之间的114天无GVHD生存期（主要终点），aGVHD，cGVHD，复发或总生存期（OS）没有差异。在304例患者中，有264例可用于当前免疫重建分析的样本。HCT后1、3、6、12和24个月收集血液样本。在项目实验室（Esoterix临床试验服务）以盲法进行了多参数流式细胞术，并比较了2组的结果。多变量Cox回归模型，将每个表型参数作为时间依赖性变量进行处理，以研究重构对临床结果的影响。在此分析中，Tac / Sir和Tac / MTX臂之间的患者和移植特征无显着差异。Tac / Sir组中的绝对淋巴细胞计数和CD3 +细胞，CD4 +细胞以及常规T细胞（Tcon）计数在HCT后长达3个月的时间内显着降低，而CD8 +细胞的恢复甚至更慢（长达6个月）。这条手臂。有趣的是，在HCT之后的任何时刻，两个臂之间的调节性T细胞（Tregs，定义为CD4 + CD25 +细胞）的绝对数量没有明显的差异。然而，在HCT后的前三个月，Tac / Sir组的Treg：Tcon比值明显更高。HCT后1个月至6个月，Tac / Sir组的B淋巴细胞恢复受到显着损害，而Tac / Sir组的自然杀伤细胞重构不受影响。在结果分析中，更多的CD3 +细胞，CD4 +细胞，CD8 +细胞和Treg与更好的OS相关。Treg数目或Treg：Tcon比率均与GVHD无关。我们的发现表明，在移植后早期，Tac / Sir比Tac / MTX的结合具有更深刻的T细胞抑制作用，特别是损害了与aGVHD有关的CD8 + T细胞的恢复。与他克莫司在体内使用的西罗莫司似乎并未导致绝对的Treg数量增加，但可能在移植后的前3个月对Treg：Tcon平衡产生有益的影响。尽管如此，在父母随机试验中，两组之间的aGVHD或cGVHD没有差异。不含钙调神经磷酸酶抑制剂，不含西罗莫司的GVHD预防策略，以及其他新药，应进一步研究，以最大限度地提高西罗莫司对移植后免疫组学中Treg：Tcon平衡的潜在有利作用。西罗莫司在HCT后的前6个月严重损害了B细胞的恢复，对cGVHD的潜在复杂影响值得进一步研究。移植后免疫组库中的Tcon平衡。西罗莫司在HCT后的前6个月严重损害了B细胞的恢复，对cGVHD的潜在复杂影响值得进一步研究。移植后免疫组库中的Tcon平衡。西罗莫司在HCT后的前6个月严重损害了B细胞的恢复，对cGVHD的潜在复杂影响值得进一步研究。