STEM CELL TRANSPLANTATION FOR SICKLE CELL DISEASE: CAN WE REDUCE THE TOXICITY?

Since the genetic basis of sickle cell anemia was discovered over 50 years ago, many therapies have been developed for the treatment of this disorder. Hematopoietic cell transplantation offers curative potential, but it is associated with a 5-10% risk of dying. Patients who undergo allografting but develop stable donor-host hematopoietic chimerism appear to experience a significant clinical benefit. Our paper discusses the risks and benefits of hematopoietic cell transplantation in patients with sickle cell disease and summarizes the outcome of 147 patients who received allografts for sickle cell disease. We also review the development of new approaches to establish stable mixed chimerism after transplantation for sickle cell disease.     

Chimeric AAV Cap sequences alter gene transduction

Recombinant adeno-associated viruses (rAAV) are vectors for gene delivery. rAAVs occur in several serotypes shown to have different transduction capabilities. Capsid sequences of the serotypes are different suggesting that differences in gene delivery are in large part due to capsid structure. Since the available serotypes are inefficient transducers of cell lines on a particle per cell basis and inefficiently transduce desired target cells in vivo there have been numerous attempts to create better vectors by modifying the capsids. A question of interest is whether natural selection has led, and whether laboratory-based selection methods will lead, to viruses with a sharply defined optimal specificity. Here we created multiple randomly recombined capsid species using the known AAV serotype capsid sequences by STEP and shuffling methods. We then used selection to identify a viral capsid better adapted to Hep G2 cells than the known serotypes. This capsid was then tested with other cells to determine whether the selection produced a virus specifically tailored by the selection methodology or one of wider applicability. The selected virus turned out to be surprisingly limited by its target cell and method of selection.     

Evaluation of single-round infectious,chimeric dengue type 1 virus as an antigen for dengue functional antibody assays

Dengue fever and dengue hemorrhagic fever are endemic throughout tropical and subtropical countries. Four serotypes of dengue viruses (DENV-1 to DENV-4), each with several genotypes including various subclades, are co-distributed in most endemic areas. Infection–neutralizing and -enhancing antibodies are believed to play protective and pathogenic roles, respectively. Measurement of these functional antibodies against a variety of viral strains is thus important for evaluating coverage and safety of dengue vaccine candidates. Although transportation of live virus materials beyond national borders is increasingly limited, this difficulty may be overcome using biotechnology that enables generation of an antibody-assay antigen equivalent to authentic virus based on viral sequence information. A rapid system to produce flavivirus single-round infectious particles (SRIPs) was recently developed using a Japanese encephalitis virus (JEV) subgenomic replicon plasmid. This system allows production of chimeric SRIPs that have surface proteins of other flaviviruses. In the present study, SRIPs of DENV-1 (D1-SRIPs) were evaluated as an antigen for functional antibody assays. Inclusion of the whole mature capsid gene of JEV into the replicon plasmid provided higher D1-SRIP yields than did its exclusion in cases where a DENV-1 surface-protein-expressing plasmid was used for co-transfection of 293T cells with the replicon plasmid. In an assay to measure the balance between neutralizing and enhancing activities, dose (antibody dilution)-dependent activity curves in dengue-immune human sera or mouse monoclonal antibodies obtained using D1-SRIP antigen were equivalent to those obtained using DENV-1 antigen. Similar results were obtained using additional DENV-2 and DENV-3 systems. In a conventional Vero-cell neutralization test, a significant correlation was shown between antibody titers obtained using D1-SRIP and DENV-1 antigens. These results demonstrate the utility of D1-SRIPs as an alternative antigen to authentic DENV-1 in functional antibody assays. SRIP antigens may contribute to dengue vaccine candidate evaluation, understanding of dengue pathogenesis, and development of serodiagnostic systems.     

Construction and evaluation of a chimeric pseudoinfectious virus vaccine to prevent Japanese encephalitis

Multiple vaccines exist to control Japanese encephalitis (JE), but all suffer from problems. We have developed a new type of flavivirus vaccine, a pseudoinfectious virus (RepliVAX WN) that prevents West Nile virus (WNV)-induced disease. Here, we describe production of a chimeric RepliVAX (RepliVAX JE) that expresses the JE virus (JEV) prM and E proteins. Our prototype RepliVAX JE replicated poorly in cells, but blind passage produced a better-growing derivative, and analyses of this derivative allowed us to engineer a second-generation RepliVAX (RepliVAX JE.2) that grew to high titers. RepliVAX JE.2 elicited neutralizing antibodies in both mice and hamsters and provided 100% protection from a lethal challenge with JEV or WNV, respectively. These results demonstrate the utility our RepliVAX platform for producing a JE vaccine.     

细胞表面Toll样受体4在小鼠急性坏死性胰腺炎中的作用

目的 探索髓系细胞(中性粒细胞、血小板)及内皮细胞表面Toll样受体4(toll-like receptor 4,TLR4)表达在小鼠急性坏死性胰腺炎(ANP)中性粒细胞招募中的作用.方法 将C3H/He-J和C3H/He-N小鼠通过骨髓移植的方法制作髓系细胞TLR4-/一和内皮细胞TLR4+/+、髓系细胞TLR4+/+和内皮细胞TLR4+/+、髓系细胞TLR4+/+和内皮细胞TLR4-/-、髓系细胞TLR4-/-和内皮细胞TLR4-/-4组嵌入体或纯合体小鼠,另设1个对照组.腹腔注射蛙皮素、尾静脉注射脂多糖复制ANP模型.榆测血清淀粉酶含量,行胰腺病理检查、胰腺组织萘酚AS-D氯乙酸脂酶染色计数、髓过氧化物酶(MPO)活性测定、TLR4蛋白表达检测及RT-PCR检测外周血粒细胞TLR4 mRNA表达.结果 各实验组小鼠血清淀粉酶均较对照组显著升高,但组间无显著性差异.4个实验组胰腺病理分值分别为5.52±1.21、5.18±1.02、2.03±0.82、1.92±0.78;胰腺MPO水平分别为(1.834±0.170)U/g、(2.596±0.138)U/g、(0.367±0.018)U/g、(0.202±0.018)U/g;AS-D计数分别为(66.88±2.17)个、(75.00±2.43)个、(21.50±2.38)个、(20.00±2.19)个;外周血粒细胞TLR4 mRNA表达量分别为0.037±1.047E-2、1.489±8.084 E-2、1.470±5.210E-2、0.017±6.668 E-3;内皮细胞TLR4+/+的2组小鼠胰腺内血管内皮细胞TLR4蛋白强阳性表达,内皮细胞TLR4-/-的2组不表达.内皮细胞TLR4+/+的2组小鼠的胰腺损伤、MPO活性、AS-D计数及TLR4蛋白表达均显著高于内皮细胞TLR4-/-的2组小鼠.结论 内皮细胞而非外周血粒细胞在ANP中性粒细胞聚集及病理损伤中起关键作用.     

嵌合体形成及其对产前筛查及诊断结果的影响

随着细胞分子生物学时代的来临,产前筛查和诊断方法也随之发生改变,更多的数据需要正确解读,这对产前诊断医生无疑是一项挑战。其中,染色体嵌合是影响产前筛查与诊断准确性的重要因素之一,受母亲、父亲以及胎盘等多种因素影响,人类普遍存在染色体嵌合,嵌合形成的主要原因是有丝分裂期染色体错误分离。受多种因素的影响,嵌合的临床表现对每个个体都具有唯一性。嵌合对产前筛查和诊断的影响主要为2个方面：①母血中胎儿游离细胞DNA（cell-free fetal DNA,cfDNA）筛查（无创产前筛查）。虽然大量文献报道无创产前筛查对于２１,１８,１３三体有较高的检出率,但由于其检测的母血中cfDNA来源于胎盘,并非真正的胎儿自身DNA,因此当发生胎盘局限性嵌合时会严重影响无创产前筛查结果的准确性。②绒毛染色体核型分析提示存在嵌合时需要行羊膜腔穿刺进行验证。总之,正确认识染色体嵌合的起源、机制和临床结果,可以为病人提供更多有价值的遗传信息,是做好产前筛查与诊断工作并提供遗传咨询的重要前提。     

肾骨髓联合移植与嵌合体发生及急性排斥反应的关系

目的　研究肾骨髓联合移植与嵌合体发生及急性排斥反应的关系。方法　采用供体骨髓与肾脏联合移植 ,进行 2 4例造血干细胞微嵌合体诱导 ,采用聚合酶链反应 (PCR)技术检测受者嵌合状态 ,与单纯肾脏移植组 37例比较嵌合发生率及急性排斥反应发生率。结果　随访 1年 ,肾骨髓联合移植组术后嵌合体发生率 (87 5 % ,2 1/ 2 4 )明显高于单纯肾脏移植组 (40 5 % ,15 / 37) ,差异有显著意义 (P 0 0 0 1) ;嵌合阳性组急性排斥反应发性率 (19 4 % ,7/ 36 )与嵌合阴性组 (44 % ,11/ 2 5 )相比差异有显著意义 (P <0 0 5 )。结论　肾骨髓联合移植可诱导嵌合体发生并增加受者对供体器官的免疫耐受 ,降低急性排斥反应发生率 ,嵌合现象与免疫耐受具有相关性     

非清髓性方案在诱导大鼠后肢移植免疫耐受中的应用

目的 探讨基于淋巴细胞毒性相关抗原4-抗体重组腺病毒(AdCTLA4-Ig)的非清髓性方案在造血干细胞嵌合体诱导复合组织异体移植免疫耐受中的作用.方法 以近交系Brown Norway(RT1n)大鼠为供体,Lewis(RT11)大鼠为受体.以后肢移植当天记为day 0.实验分4组,A组:受体直接给予同种异体后肢移植,移植前不进行非清髓件预处理,移植后连续100 d,每天仅给予低剂量环胞素A(CsA),8 mg/kg腹腔注射.B组:受体先给予非清髓性预处理,移植前第33天至移植后第100天,每日用免疫抑制剂三联方案腹腔注射雷帕霉素(RAPA,0.2 mg/kg)+麦考(MMF,20 mg/kg)+甲泼尼龙(MP,10 mg/kg),在移植当日及移植前及移植后第30天分3次尾静脉注射AdCTLA4-Ig(5×109 PFU/d),后肢移植前30 d接受单次3 Gy(照射率0.5 Gy/min)低强度全身照射,不予骨髓移植(BMT).C组:受体预处理方案同B组,移植前30 d,在低强度全身照射后4 h内给予单次尾静脉注射供体骨髓细胞(100×106 cells).D组:受体预处理方案及BMT方法同C组,但大鼠后肢移植供体为第三方动物WF大鼠.在后肢移植后第100天开始,B、C及D组均停止免疫抑制剂三联方案,每日仅给予低剂量CsA(8 mg/kg),连续100 d,直至大鼠后肢移植物发生排异反应而坏死.通过外周血嵌合率检测、移植物抗宿主病检测、后肢移植物存活情况观察、移植物组织病理学检查与评价及混合淋巴细胞反应对免疫耐受状态进行分析评价.结果 C组外周血嵌合率移植当口为(38.8±10.6)%,并长期保持稳定,移植后第300天为(29.3±11.9)%,均未发生移植物抗宿主病,停止免疫抑制剂三联方案后移植物存活>200 d,A、B、D组均发生免疫排异,后肢移植物分别存活(8±2)、(18±3)及(20±2)d,与C组相比,差异有统计学意义(P<0.01).C组移植物病理学检查显示无毛囊炎及血管周围炎等慢性免疫排异现象,混合淋巴细胞反应显示为供体特异性免疫耐受状态.结论 基于AdCTLA4-Ig的非清髓性BMT方案可以诱导长期稳定的造血干细胞嵌合体状态,并可以诱导受体对大鼠后肢移植物的供体特异性部分性免疫耐受.     

45,X/46,XY嵌合体一例并文献复习

45,X/46,XY嵌合体是临床罕见的性染色体发育异常,属于混合性性腺发育不良,可导致性腺及外生殖器发育异常、身材矮小以及性腺恶变等。一般与Y染色体以及性别决定基因异常有关。现报道1例45,X/46,XY嵌合体表型为女性的患者临床资料,并对该病的发病机制、临床表现、生育问题等进行文献复习和讨论,以期增加对该病的认识,对此类患者做到更好的管理和随访。