Helicobacter pylori sabA gene is associated with iron deficiency anemia (IDA) in childhood and adolescence

Background Gastric Helicobacter pylori colonization leads to iron deficiency anemia (IDA), especially in children and adolescents. However the pathogenesis is poorly understood. Objective We sought to identify specific H. pylori genes involved in IDA development, by comparing bacterial genome-wide expression profiling in patients affected or not. Methods H. pylori were isolated from four children with IDA and four from matched controls without IDA. Based on these isolates, cDNA microarrays under iron-replete or depleted conditions were systematically performed to compare gene expression profiles at the whole genome level. Real-time reverse-transcription (RT-) PCR and protein assays were performed for further assessing the profile differentiation of the identified H. pylori IDA-associated genes. Results We identified 29 and 11 genes with significantly higher or lower expression in the IDA isolates compared to non-IDA isolates, respectively. Especially notable were higher expression of sabA gene encoding sialic acid-binding adhesin in the IDA isolates, which was confirmed by real-time RT-PCR study. Moreover, iron-depletion in vitro led to up-regulation of fecA1 and frpB1 genes and down-regulation of pfr, as predicted. Known iron-regulated genes such as fur, pfr, fecA, and feoB did not significantly differ between both groups. The IDA isolates had significantly higher expression of vacuolating cytotoxin gene vacA than non-IDA isolates, consistent with the results of VacA protein assays. There were no significant differences in bacterial growth value between IDA and non-IDA isolates. Conclusions It is likely that H. pylori carrying high expression of sabA causes IDA, especially in children and adolescents who have increased daily iron demand. In addition, it is possible that several host-interactive genes, including vacA, may play a synergistic role for sabA in IDA development. The four H. pylori strains isolated from the IDA patients and 4 strains from other gastric disorder patients were analysed by DNA micro array. In addition, two samples from IDA patients and two control samples were treated with DFM.

**背景** 胃幽门螺杆菌（Helicobacter pylori）定植可导致缺铁性贫血（iron deficiency anemia, IDA），尤其好发于儿童及青少年群体，但其具体致病机制仍未被充分阐明。
**研究目的** 本研究旨在通过对比缺铁性贫血患者与非患者体内幽门螺杆菌的全基因组表达谱，筛选出参与缺铁性贫血发病过程的幽门螺杆菌特异性基因。
**研究方法** 本研究从4例缺铁性贫血患儿体内分离得到幽门螺杆菌菌株，同时从4例匹配的非缺铁性贫血对照儿童体内分离得到对应菌株。基于上述分离菌株，我们系统开展了铁充足与铁缺乏条件下的cDNA微阵列（cDNA microarray）实验，以在全基因组层面对比两组菌株的基因表达谱；此外通过实时逆转录聚合酶链式反应（real-time reverse-transcription PCR, RT-PCR）及蛋白检测实验，对筛选得到的缺铁性贫血相关幽门螺杆菌基因的表达差异进行进一步验证。
**研究结果** 相较于非缺铁性贫血菌株组，缺铁性贫血菌株组中分别有29个基因呈现显著高表达、11个基因呈现显著低表达。其中，编码唾液酸结合黏附素的sabA基因在缺铁性贫血菌株中的高表达已通过实时RT-PCR实验得到验证。正如预期，体外铁缺乏环境可使fecA1与frpB1基因表达上调，同时使pfr基因表达下调。已知的铁调控基因如fur、pfr、fecA及feoB在两组菌株间未呈现显著表达差异。缺铁性贫血菌株组的空泡细胞毒素基因vacA表达量显著高于非缺铁性贫血菌株组，这一结果与VacA蛋白检测结果一致。两组菌株的生长水平未存在显著差异。
**研究结论** 高表达sabA基因的幽门螺杆菌可能是引发缺铁性贫血的潜在致病因素，这一效应在每日铁需求量升高的儿童及青少年群体中尤为显著。此外，包括vacA在内的多种宿主互作基因可能与sabA基因协同参与缺铁性贫血的发病过程。本研究通过DNA微阵列（DNA microarray）分析了从缺铁性贫血患者体内分离得到的4株幽门螺杆菌，以及从其他胃部疾病患者体内分离得到的4株幽门螺杆菌；此外，本研究对2例缺铁性贫血患者样本与2例对照样本进行了DFM处理。