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

细胞毒性T淋巴细胞（CTL）对次要组织相容性抗原（mHAgs）具有特异性，其组织表达仅限于造血细胞，可用于异基因造血细胞移植（HCT）后复发的白血病/淋巴瘤的免疫治疗。我们鉴定了4个mHAg，包括3个新的mHAg和一个HA-1 mHAg，由HLA-A2亚型呈现，而不是原来的HLA-A^*0201。(1)发现HLA-A^*3101和a ^*3303限制性mHAg表位，其表达受组织蛋白酶H （CTSH）基因的SNP控制。CTSH蛋白的表达相对普遍，但在单核细胞中表达最高。然而，CTSH特异性CTL克隆并没有溶解任何非造血细胞，尽管原因尚不清楚。(2)通过连锁分析，hla - b44限制性CTL识别的mHAg基因定位在18q23上。表达克隆表明mHAg是由HMSD基因的剪接变体编码的。该变异是由于内含子2 SD位点的一个SNP导致外显子2被排除，从而通过选择性剪接产生的，这是mHAg产生的新机制。HMSD在髓系和浆细胞恶性肿瘤中高表达，提示HMSD编码的mHAg(s)应作为AML和骨髓瘤免疫治疗的良好靶点。(3)利用中间跨越HA-1^H表位的29-mer肽，我们从HA-1错配移植患者的移植后外周血样本中分离出HLA-A^*0206限制性CTL。发现该表位与HLA-A^*0201分子呈现的表位相同，表明HA-1^H mHAg也可以被HLA-A^*0206呈现，这与已知的HLA-A^*0206分子的结合基序完全出乎意料。(4)我们已经开始招募符合mhag免疫治疗条件的患者。本临床研究目前使用的靶mHAgs为ACC-1、ACC-2和HA-1，预计将覆盖30%以上的日本同种异体移植患者。

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.