Identification of minor histocompatibility antigens as targets for allogeneic adoptive immunotherapy against hematological malignancies.

次要组织相容性抗原(MHAgs)特异性细胞毒性T淋巴细胞(CTL)的组织表达仅限于造血细胞，可用于异基因造血细胞移植(HCT)后复发白血病/淋巴瘤的免疫治疗。我们已经鉴定出4个mHAg，其中包括3个新的mHAg和1个不同于原始的HLAA^*0201的HLAA2亚型提出的MHAg。(1)我们发现了HLAA^*3101和-A^*3303限制性mHAg表位，其表达受组织蛋白酶H(CTSH)基因中的SNP控制。CTSH蛋白的表达相对普遍，但在单核细胞中的表达最高。然而，针对CTSH的CTL克隆不能溶解任何非造血细胞，尽管原因尚不清楚。(2)通过连锁分析，将人类白细胞抗原B44限制性CTL识别的mHAG基因定位于18q23。表达克隆表明，mHAg由HMSD基因的一个剪接变异体编码。该变异是通过选择性剪接产生的，这是由于内含子2 SD位点上的SNP导致外显子2被排除，这是mHAG产生的一种新机制。我们发现HMSD在髓系肿瘤和浆细胞肿瘤中高表达，提示HMSD编码的mHAg(S)可以作为治疗急性髓系白血病和骨髓瘤的良好靶点。(3)利用中间一个跨越HA-1^H表位的29肽，我们从一例HA-1不相合移植患者的移植后外周血中分离出了人类白细胞抗原-A^*0206限制性CTL。该表位与人类白细胞抗原A^0201分子所呈现的表位完全相同，表明HA-1H mHAg也可由人类白细胞抗原A^0206呈现，这与已知的结合基序完全不同。(4)我们已经开始招募符合条件的患者进行mHAg免疫治疗。到目前为止，这项临床研究中使用的靶向mHAgs是ACC-1、ACC-2和HA-1，预计将覆盖30%以上接受同种异体移植的日本患者。

Cytotoxic T lymphocytes (CTL) specific for minor histocompatibility antigens (mHAgs) whose tissue expression is limited to hematopoietic cells are useful for immunotherapy of relapsed leukemia/lymphoma following allogeneic hematopoietic cell transplantation (HCT). We have identified 4 mHAgs including 3 novel mHAgs and an HA-1 mHAg presented by HLA-A2 subtype other than the original HLA-A^*0201.(1)We found HLA-A^*3101 and-A^*3303-restricted mHAg epitopes whose expression was controlled by an SNP in Cathepsin H (CTSH) gene. CTSH protein was expressed relatively ubiquitously, but its expression was highest in monomyelocytic cells. Nevertheless, CTL clones specific for CTSH did not lyse any non-hematopoietic cells, although the reason remained unclear.(2)A mHAg gene recognized by HLA-B44-restricted CTL was localized to 18q23 by linkage analysis. Expression cloning revealed that the mHAg was encoded by a splice variant of HMSD gene. The variant was produced by alternative splicing due to an SNP in the intron 2 SD site leading to exclusion of exon 2, which is a novel mechanism in mHAg generation. The HMSD was found to be highly expressed in myeloid and plasma cell malignancies, suggesting the HMSD encoded mHAg(s) should serve as a good target for immunotherapy against AML and myeloma.(3)By using a 29-mer peptide spanning HA-1^H epitope in the middle, we isolated HLA-A^*0206-restricted CTL from posttransplant peripheral blood samples of a patient receiving HA-1 mismatched transplant. The epitope was found to be identical to that presented by HLA-A^*0201 molecule, indicating HA-1^H mHAg can also be presentable by HLA-A^*0206, which was totally unexpected from the known binding motif of HLA-A^*0206 molecule.(4)We have started recruiting patients eligible for mHAg-based immunotherapy. The target mHAgs used in this clinical study so far are ACC-1, ACC-2 and HA-1, which are expected to cover more than 30% of Japanese patients receiving allogeneic transplantation.