靶向CD19的CAR修饰的NK细胞对B细胞淋巴瘤的杀伤

目的:利用鼠杂交瘤技术筛选和制备治疗性CD19单克隆抗体,探讨以CD19 scFv序列构建CD19-CAR(pCD19-CAR)修饰的NK细胞对CD19+B细胞淋巴瘤细胞的杀伤作用.方法:用偶联多肽免疫小鼠制备CD19单克隆抗体,然后用基因测序法获得抗体的序列.分析抗体序列,并通过基因合成和分子克隆技术构建pCD19-CAR片段,然后将其克隆到慢病毒载体上,病毒包装制备后,转染NK-92MI细胞.最后,用流式细胞术检测不同的pCD9-CAR-NK-92MI细胞对CD19+细胞的杀伤率.结果:(1)成功筛出特异性强的CD19单克隆抗体-pCD19;(2)抗体检测结果显示CD19+的Ramos细胞的阳性率为84.3％,Raji为85.6％,与商业化抗体结果相似;(3)被pCD19-CAR修饰的CD19-CAR阳性率为28.72％的NK-92MI细胞对CD19+的Ramos和Raji细胞的杀伤效率明显高于未被修饰的NK-92MI细胞株对Ramos和Raji细胞的杀伤率[(47.1±1.7)％vs(24.7±6.2)％和(51.8±7.9)％vs(27.6±9.6)％,均P＜0.05];对CD19-细胞Jurkat,不论是未被pCD19-CAR修饰的NK-92MI或是被修饰的NK-92MI细胞,几乎都不存在特异性杀伤作用[(16.1±0.7)％vs(17.7±2.9)％,P＞0.05].结论:成功构建pCD19-CAR,被pCD19-CAR修饰的NK-92MI细胞能特异性的识别CD19抗原并杀伤CD19+B细胞淋巴瘤细胞.     

嵌合抗原受体修饰的NK-92MI细胞对 HER2 阳性乳腺癌细胞的杀伤

目的:探讨用特异性靶向HER2抗原的嵌合抗原受体(HER2-CAR)修饰的NK-92MI细胞对HER2阳性乳腺癌细胞的杀伤效率.方法:通过PCR获得HER2-CAR片段,运用常规分子克隆技术,将其构建到慢病毒载体上,利用包装的慢病毒颗粒对NK-92MI细胞进行转染;应用流式细胞术检测细胞转染效率以及转染前后NK-92MI的IFN-γ和颗粒酶分泌差异;使用7-AAD和流式细胞术体外检测HER2-CAR-NK92MI细胞对乳腺癌细胞的杀伤效率;构建小鼠乳腺癌原位肿瘤模型进行体内细胞毒性的检测.结果:用HER2-CAR修饰的NK-92MI细胞对HER2阳性乳腺癌肿瘤细胞MCF-7和T47D的杀伤效率明显高于未被基因修饰的NK-92MI细胞[分别为(62.4±1.3)％ vs (22.1±1.2)％和(50.0±1.9)％vs(16.9±0.6)％,P＜0.01];而两者对HER2阴性的乳腺癌细胞MDA-MB-468的杀伤效率没有明显差异[(13.6±1.4)％vs(12.7±0.8)％,P＞0.05].同时,经HER2-CAR修饰的NK-92MI细胞相比未被基因修饰的NK-92MI细胞,IFN-γ的分泌明显升高(P＜0.01).结论:经HER2-CAR修饰的NK-92MI细胞对HER2阳性乳腺癌细胞的杀伤效率明显提高,且具有特异性靶向,此为治疗乳腺癌等恶性肿瘤提供了临床依据.     

抗CD19 嵌合受体修饰的NK-92 细胞的构建及其对CD19 阳性非霍奇金淋巴瘤细胞的杀伤作用

目的：构建表达CD19 的二代CAR-NK-92 细胞系,探讨其对CD19 阳性非霍奇金淋巴瘤细胞的特异性杀伤作用。方法：构建表达CD19-CAR基因的载体并包装慢病毒颗粒,感染NK-92 细胞,流式细胞术检测感染率,并进一步分选阳性细胞,Western blotting 检测CD19-CAR 在NK-92 细胞中的表达;以CD19 阴性骨髓瘤细胞U-266、CD19 阳性的非霍奇金淋巴瘤细胞ARH-77 和HS-Sultan 细胞为靶细胞,以CD19CAR-NK-92 为效应细胞,流式细胞术检测细胞杀伤实验中存活肿瘤细胞的绝对数量并计算杀伤率。结果: 成功构建慢病毒载体pLVX-CD19-CAR并包装病毒颗粒,感染NK-92 细胞后CD19CAR-NK-92 细胞纯度高于90%;Western blotting 分析显示CD19-CAR已经成功表达在NK-92 中。CD19CAR-NK-92 对ARH-77[ （70.10±1.86）% vs （1.95±0.63）%,P<0.01]和HS-Sultan[ （74.98±1.60）% vs（0.58±1.49）%,P<0.01]细胞的杀伤率显著高于空载体对照组ZsGreen-NK-92 细胞,对U266 的杀伤率无显著差别（P>0.05）。结论：成功构建了表达CD19CAR的NK-92 细胞系,其对CD19 阳性的非霍奇金淋巴瘤细胞有特异性杀伤作用。     

CD7纳米抗体衍生的CAR-T细胞对CD7阳性急性髓系白血病细胞的杀 伤活性

目的：针对CD7阳性的急性髓系白血病（acute myeloid leukemia,AML）细胞开发一种新型的CD7嵌合抗原受体修饰 的T细胞（CD7-CAR-T）,观察其对CD7阳性AML细胞的杀伤作用。方法：基于CD7纳米抗体序列、CD28和4-1BB共刺激域序 列构建CD7-CAR慢病毒载体,包装病毒颗粒并与CD7蛋白阻断剂（protein expression blocker,PEBL）慢病毒共感染人T细胞, 制 备CD7-CAR-T;应用实时无标记动态细胞分析技术（real time cellular analysis,RTCA）验证CD7-CAR-T对CD7过表达的293T细 胞的特异性杀伤能力,流式细胞术检测CD7-CAR-T对CD7高、中、低表达的AML细胞（KG-1、HEL、Kasumi-1细胞）的增殖和细 胞因子分泌的影响。结果：成功构建CD7-CAR-T 细胞并阻断其表面 CD7 的表达,与 T 细胞相比,CD7-CAR-T 细胞可以抑 制 CD7-293T 细胞的增殖并促进其分泌 TNF、Granzyme B 和 INF-γ,可显著促进 CD7 阳性的 KG-1 细胞和 HEL细胞的凋亡 （t=147.1、 P＜0.01; t=23.57、 P＜0.01）和细胞 因 子 分 泌（P＜0.05 或 P＜0.01）,而对低表达 CD7 的 Kasumi-1 细胞无显著影响 （t=0.7058、 P＞0.05）。结论： CD7-CAR-T细胞能够特异性杀伤CD7阳性的AML细胞。     

嵌合抗原受体修饰的CD19-CAR-T的体外构建、扩增及初步功能鉴定

目的： 探索一种特异性靶向 CD19 分子的嵌合抗原受体修饰的 CD19-CAR-T 的构建方法,并明确其体外杀伤 靶细胞的效果。 方法： 运用分子克隆技术,将 PCR 获得的 CD19-CAR 片段构建到 pCDH-GFP 慢病毒载体上,利用包装 的慢病毒颗粒转染供者 CD3 + T 细胞,通过流式细胞术及 PCR鉴定转染效率,并通过 7-AAD染色鉴定扩增得到的CD19- CAR-T细胞体外杀伤CD19 + Ramos靶细胞的效果。 结果： 经慢病毒转染T细胞在体外培养 10 d 后,CD3 + T 扩增达（78.8± 23.2）倍, （58.3±5.4）%的 CD3 + T 细胞表达 GFP,CD19-CAR-T 体外杀伤 CD19 + Ramos 靶细胞在效靶比5∶1时效率为（57.4± 9.3）%。 结论： 本实验成功建立了一种有效的体外构建及扩增CD19-CAR-T的方法,且具有明显靶向性,为CD19 + B细胞肿瘤临 床治疗提供实验依据。     

靶向PSCA的CAR-NK-92细胞对宫颈癌的抗瘤作用

目的：构建并验证靶向前列腺干细胞抗原（prostate stem cell antigen,PSCA）的嵌合抗原受体（chimeric antigen receptor,CAR）修饰的NK-92细胞对宫颈癌的抗瘤活性。方法：构建PSCA靶向的CAR慢病毒表达载体,利用慢病毒感染法获得PSCA CAR-NK-92细胞。用流式细胞术及Western blotting实验检测宫颈癌细胞中PSCA的表达水平。通过体外效靶细胞共孵育实验以及体内裸鼠移植瘤模型中的治疗情况,验证PSCA CAR-NK-92细胞对宫颈癌Hela及MS751细胞杀伤能力及其裸鼠移植瘤生长的抑制能力。结果：成功构建 PSCA CAR-NK-92 细胞,PSCA 在宫颈癌细胞中高表达（均 P<0.01）。体外共孵育结果显示,PSCA CAR-NK-92细胞可以以剂量依赖的方式裂解PSCA+的宫颈癌细胞;体内抗肿瘤数据表明,PSCA CAR-NK-92细胞较转染空载体的NK-92细胞显著抑制宫颈癌移植瘤的生长（P<0.01）,并且可以有效地浸润肿瘤组织并高水平分泌TNF-α和IFN-（γ 均P<0.01）。结论：靶向PSCA的CAR-NK-92细胞在体内外都显示出了良好的对PSCA+肿瘤细胞的杀伤能力,有潜力成为一种针对宫颈癌的潜在治疗策略。     

抑制c-myc基因表达对HL-60细胞表面分化抗原CD13、CD33的影响

目的：利用重组反义c-myc腺病毒载体（Ad-AS-c-myc）抑制HL-60细胞c-myc基因表达,检测细胞表面分化抗原CD13、CD33变化,了解抑制HL-60细胞c-myc表达,对细胞分化及分化抗原的影响。方法：重组Ad-AS-c-myc病毒按感染强度（MOI）为100的转染剂量,转染HL-60细胞。RT-PCR检测c-myc表达。流式细胞仪检测CD13、CD33阳性细胞率。同时对转染细胞行Wright＇s染色,观察细胞形态变化。结果：Ad-AS-c-myc转染HL-60细胞后,c-myc基因表达降低,CD13阳性细胞率升高,CD33阳性细胞率降低。结论：抑制c-myc基因表达,使HL-60细胞CD13表达增强,CD33表达降低。细胞形态向成熟粒细胞方向分化。     

CD13、CD33在BCR-ABL+急性淋巴细胞白血病患者骨髓中的表达及其与临床特征和预后的相关性

目的:探讨髓系抗原CD13、CD33在BCR-ABL+急性淋巴细胞白血病（acute lymphoblastic leukemia,ALL）患者骨髓中的表达及其与临床特征和预后的相关性。方法:应用实时荧光定量聚合酶链反应（real time quantitative-polymerase chain reaction,RQ-PCR）检测119例初诊ALL患者骨髓BCR-ABL表达水平。用流式细胞学检查检测ALL的抗原表达水平。对照分析单纯BCR-ABL+患者中CD13+和CD13-以及CD33+和CD33-患者在初次诱导缓解率（initial-induction remission rate,CR1）和总生存率（overall survival rate,OS）的区别。结果:在BCR-ABL+ 的ALL患者中,初诊时CD13+患者较CD13-患者具有较低的首次诱导缓解率,差异具统计学意义（P＜0.05）,但CD33+患者较CD33-患者首次诱导缓解率无统计学差异。CD13+组及CD33+的OS显著低于CD13-组及CD33-组（P＜0.05）。结论:BCR-ABL+ALL患者中CD13+及CD33+提示预后不良。     

靶向CD19 抗原的CAR-NK-92MI和CAR-CD19-T 细胞对套细胞淋巴瘤的体外杀伤

[摘要] 目的：探讨靶向CD19 抗原的CAR-NK-92MI和CAR-CD19-T 细胞对套细胞淋巴瘤（mantle cell lymphoma,MCL）的体外杀伤作用。方法：利用近年来在B细胞急性淋巴细胞白血病（B-lineage acute lymphoblastic leukemia, B-ALL）临床试验中获得的成功嵌合抗原受体基因修饰的T（CAR-T 细胞）技术,针对MCL高表达CD19 抗原的情况,分别构建了靶向CD19 抗原的CAR-CD19-T和CAR-NK-92MI细胞,运用LDH释放法检测两者对MCL细胞的体外杀伤作用,另外通过流式细胞术对其杀伤作用进行了验证。结果：相对于对照,无论是CAR-NK-92MI细胞还是CAR-CD19-T 细胞,都对MCL细胞具有极高的杀伤能力（均P <0.01）,都对K562-CD19 细胞具有非常高的毒性（均P <0.01）,而对K562 细胞基本不起作用。CAR-NK-92MI细胞组MCL细胞的死亡率比对照组高30%~40%,CAR-CD19-T 细胞组MCL细胞的死亡率比对照组高40%~50%。结论：CAR-NK-92MI和CARCD19-T细胞在体外对MCL细胞具有强的特异性杀伤作用。     

CD20 和CD19 双靶点CAR-T细胞对B淋巴细胞肿瘤的杀伤作用

目的：设计同时靶向B淋巴细胞表面CD20 和CD19 两个抗原蛋白的双特异嵌合抗原受体（chimeric antigen receptor,CAR）并制备BiCAR-T 细胞,检测其对B淋巴细胞肿瘤细胞的杀伤作用以及对免疫缺陷B-NSG 小鼠白血病模型的治疗效果。方法：构建基于鼠源CD19 和人源化CD20 scFv 的双靶点CAR分子,将CAR基因装载于慢病毒载体中,在293T细胞中包装慢病毒,感染健康人T 细胞制备BiCAR-T 细胞。构建表达CD19 和CD20 的K562-CD19-GFP、K562-CD20-GFP 以及表达Luciferase 的Nalm6-Luc-GFP 细胞作为靶细胞,将BiCAR-T 细胞与靶细胞共同孵育,检测其对靶细胞杀伤能力及释放IFN-γ 水平。使用Nalm6-Luc-GFP 细胞构建白血病小鼠模型,尾静脉注射BiCAR-T细胞,通过小动物成像方法观察BiCAR-T细胞对荷瘤小鼠的治疗作用。结果：健康人来源的BiCAR-T 细胞经7 d 培养后扩增良好,扩增倍数为20~50 倍,阳性率为10%~92%,显示成功制备BiCAR-T细胞。在效靶比为10∶1 时,BiCAR-T细胞对Nalm-6、K562-CD19-GFP 和K562-CD20-GFP 的杀伤率显著高于对照组细胞[ （76.7±7.4）% vs（8.7±2.4）%、（93.3±5.2）% vs（46.7±6.2）、（51.0±0.8）vs（30.7±0.5）%,均P<0.01];与对照组相比,与Nalm-6细胞共孵育后BiCAR-T 细胞分泌IFN- γ 量显著增加[（872.7±7.7）vs（101.0±5.3）pg/ml ,P<0.01]。动物实验表明,BiCAR-T细胞对B-NSG小鼠白血病模型治疗效果明显,注射BiCAR-T细胞后白血病细胞逐渐减少,第50 天时基本消失,小鼠全部存活至第70 天被安乐死;PBS和对照T细胞组小鼠分别在（19±3）和（20±1）d 全部死亡。结论：成功设计了表达CD19 和CD20 的双靶点CAR分子后成功制备了BiCAR-T 细胞,该细胞能够有效杀伤表达CD19 和/或CD20 的B淋巴细胞肿瘤细胞,与靶细胞共同孵育后能够分泌大量IFN-γ,对B-NSG免疫缺陷小鼠白血病模型具有明显的治疗效果。     

抑制c-myc基因表达对HL-60细胞表面分化抗原CD13、CD33的影响

目的:利用重组反义c-myc腺病毒载体(Ad-AS-c-myc)抑制HL-60细胞c-myc基因表达,检测细胞表面分化抗原CD13、CD33变化,了解抑制HL-60细胞c-myc表达,对细胞分化及分化抗原的影响。方法:重组Ad-AS-c-myc病毒按感染强度(MOI)为100的转染剂量,转染HL-60细胞。RT-PCR检测c-myc表达。流式细胞仪检测CD13、CD33阳性细胞率。同时对转染细胞行Wright’s染色,观察细胞形态变化。结果:Ad-AS-c-myc转染HL-60细胞后,c-myc基因表达降低,CD13阳性细胞率升高,CD33阳性细胞率降低。结论:抑制c-myc基因表达,使HL-60细胞CD13表达增强,CD33表达降低。细胞形态向成熟粒细胞方向分化。     

Primary CD33-targeting CAR-NK cells for the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a malignant disorder derived from neoplastic myeloid progenitor cells characterized by abnormal proliferation and differentiation. Although novel therapeutics have recently been introduced, AML remains a therapeutic challenge with insufficient cure rates. In the last years, immune-directed therapies such as chimeric antigen receptor (CAR)-T cells were introduced, which showed outstanding clinical activity against B-cell malignancies including acute lymphoblastic leukemia (ALL). However, the application of CAR-T cells appears to be challenging due to the enormous molecular heterogeneity of the disease and potential long-term suppression of hematopoiesis. Here we report on the generation of CD33-targeted CAR-modified natural killer (NK) cells by transduction of blood-derived primary NK cells using baboon envelope pseudotyped lentiviral vectors (BaEV-LVs). Transduced cells displayed stable CAR-expression, unimpeded proliferation, and increased cytotoxic activity against CD33-positive OCI-AML2 and primary AML cells in vitro. Furthermore, CD33-CAR-NK cells strongly reduced leukemic burden and prevented bone marrow engraftment of leukemic cells in OCI-AML2 xenograft mouse models without observable side effects.Subject terms: Translational research, Preclinical research     

Enhanced myeloid specificity of CD117 compared with CD13 and CD33

The c-kit proto-oncogene encodes a 145 kd tyrosine kinase transmembrane receptor, which plays a key role in haemopoiesis. The c-kit has been classified as CD117 and is especially useful in the differential diagnosis of acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL). We analysed 104 consecutive cases (55 AML, 23 B-cell lineage ALL, three T-cell ALL, 11 blast crisis of chronic myeloproliferative disorders and 12 cases of myelodysplastic syndromes with more than 10% of blasts) referred to our Hospital for immunophenotypic diagnosis and compared the expression pattern of CD13, CD33 and CD117 using the same fluorochrome (phycoerythrin-PE). The recommendations of the EGIL group were followed in order to establish lineage involvement of the blastic population. The threshold used to assign positivity for CD117 was 10%. Bcr/abl, TEL/AML-1 and MLL rearrangements were assessed by molecular methods. CD117 expression was detected in 91% of AML and MDS. All the negative cases corresponded to acute monocytic leukemias. The calculated specificity for myeloid involvement was 0.86 for CD117, 0.36 for CD13 and 0.44 for CD33 (P < 0.005). CD117 was also positive in four cases of ALL. None of these cases showed bcr/abl or MLL rearrangements. In the light of these findings, CD117 expression should yield a higher score, at least one point, in the system currently applied for the diagnosis of biphenotypic acute leukemias (BAL) as its myeloid specificity is greater than that of CD13 and CD33. Moreover, its absence in AML could identify two subgroups of M5b cases. The coexpression of CD117 with cytoplasmic CD79a is often associated with CD7 reactivity, suggesting a stem cell disorder. CD117 should be included on a routine basis for the immunophenotypic diagnosis of acute leukemias.     

Transgenic expression of IL-33 activates CD8 T cells and NK cells and inhibits tumor growth and metastasis in mice

IL-33 is a multifunctional cytokine in immune regulation that activates Th1 cells, Th2 cells, CD8⁺ T cells and NK cells. Our study showed that transgenic expression of IL-33 attenuated tumor metastasis in the B16 melanoma and Lewis lung carcinoma (LLC) metastatic models. The percentages and cytotoxicity of CD8⁺ T cells and NK cells and their infiltration into the tumor tissues were significantly increased by the transgenic expression of IL-33 in tumor-bearing mice. Treatment with recombinant IL-33 could also increase the cytotoxicity of CD8⁺ T cells and NK cells in vitro. In addition, depletion of CD8⁺ T cells and NK cells using anti-CD8 or anti-asialo GM1 antibody abolished the pulmonary metastasis inhibition mediated by IL-33. Furthermore, IL-33 stimulated the activation of NF-κB and increased CD69 expression, which is a marker of the activated form of the two cell subsets, in CD8⁺ T cells and NK cells. Our results suggest that IL-33 stimulated NF-κB signaling and promoted the proliferation, activation and infiltration of CD8⁺ T cells and NK cells, which resulted in the inhibition of pulmonary metastasis in B16 melanoma and LLC mice models.     

Specific targeting of CD33(+) leukemia cells by a natural killer cell line modified with a chimeric receptor

We directed the human natural killer (NK) cell line YT by gene transfer of a humanized chimeric immunoglobulin T cell receptor to CD33, a marker on myeloid leukemias. The chimeric receptor was generated using a CD33 specific single-chain Fv (scFv) fragment based on the humanized antibody HuM195, the human IgG1 Fc domains and the human CD3 zeta signal chain. YT cells transfected by electroporation with the chimeric receptor gene specifically lysed the acute myeloid leukemia (AML) cell line KG1. This gene-modified NK cell line available in unlimited source could be an attractive tool in immunotherapy.     

A child case of CD34, CD33, HLA-DR, CD7, CD56 stem cell leukemia with thymic involvement

It has been reported that the CD56⁺/CD7⁺/CD3⁻ phenotype of natural killer (NK) cells develop from the CD34⁺/HLA-DR⁻ bone marrow (BM) mononuclear cell population in long-term BM culture (LTBMC). An HLA-DR⁻/CD33⁺/CD56⁺/CD16⁻ myeloid/natural killer cell acute leukemia has been described. We report here a 7-year-old boy who developed stem cell acute leukemia with superior vena cava syndrome secondary to thymic involvement. Surface marker analyses revealed that the leukemia cells showed CD34⁺/HLA-DR⁻/CD33⁻/CD7⁺/CD56⁺ phenotype. When stimulated with phorbol ester in vitro the leukemic cells morphologically differentiated to myeloid cells developing CD13, CD15 and CD56 antigens. Our results suggest that CD34⁺/HLA-DR⁻/CD7⁺/CD56⁺ stem cell leukemia may arise from transformation of a pluripotent precursor cell, which could differentiate to both myeloid and NK cell lineages.     

白血病CD20、CD33、CD45及MDR表达和靶抗原筛选

目的观察白血病患者CD20、CD33、CD45及MDR表达及抗原强度的变化,筛选特异的靶抗原,探讨抗体靶向治疗的应用价值。方法应用间接免疫荧光法检测白血病细胞CD20、CD33、CD45及MDR表达和抗原强度变化。结果CD20、CD33、MDR阳性率分别为38.1%、81.5%、13.3%;髓性白血病中CD33抗原表达比CD45强,差异有显著性(P<0.05);CD33与MDR表达,差异无显著性。CD20与CD45、MDR在淋巴细胞白血病细胞上表达,差异无显著性。结论CD33特异性强,抗原性强,适合作靶抗原,MDR也是耐药白血病治疗的较好靶抗原。抗体靶向治疗将是白血病治疗的一条新途径。     

Heteroclitic CD33 peptide with enhanced anti-acute myeloid leukemic immunogenicity.

The goal of these studies was to engineer a synthetic CD33 peptide with enhanced immunogenicity for the induction of acute myeloid leukemia (AML)-specific CTLs. Eight modified CD33 peptides YLISGDSPV, YIGSGDSPV, YIIIGDSPV, YIILGDSPV, YIISGISPV, YIISGDLPV, YIISGDSWV and YIISGDSPL were designed for increased HLA-A2.1 or T cell receptor affinity and compared with the native CD33(65-73) peptide, AIISGDSPV, for enhanced immunogenicity. The YLISGDSPV peptide was found to be the most immunogenic epitope producing highly cytolytic CTLs against AML target cells. The CTLs generated withYLISGDSPV peptide showed CD33 peptide-specificity through targeting of both native (AIISGDSPV) and modified (YLISGDSPV) peptide presenting EBV-BLCL. The CTL cultures displayed a distinct phenotype consisting of a high percentage of activated memory (CD69(+)/CD45RO(+))-CD8(+)and a low percentage of naive (CD45RA(+)/CCR7(+))-CD8(+)cells. In addition, T-cell clones specific to the YLISGDSPV peptide were isolated and characterized to target AML cells. The clones exhibited both HLA-A2.1-restricted and AML cell-specific cytotoxicity that was mediated through a granule-dependent pathway. More importantly, the CTL clones did not lyse or inhibit the proliferation of normal CD34(+) progenitor cells. In conclusion, we report on the identification of a highly immunogenic heteroclitic YLISGDSPV CD33 epitope that is a promising candidate for immunotherapy targeting AML.