目标 本研究旨在探索适配体特异性结合幽门螺杆菌(BabA)与血型抗原结合粘附素(H.pylori)的能力，以阻断H.pylori对宿主细胞的粘附过程。 方法 使用培养的H.pylori菌株，提取其基因组作为模板，利用设计的引物进行聚合酶链式反应(PCR)扩增BabA基因。获得的BabA基因经克隆并构建到原核表达质粒中，通过异丙基β-D-半乳糖苷(IPTG)诱导表达并纯化目标蛋白。对能够特异性结合BabA的单链DNA (ssDNA) 适配体进行SELEX筛选。使用酶联寡核苷酸检测法（ELONA）检测和评估候选适配体的特性。通过体外流式细胞术和小鼠感染模型的细胞水平上进行的细胞计数实验，验证ssDNA适配体对H.pylori粘附的阻断效果。同时，利用ELISA检测小鼠胃黏膜细胞匀浆中白细胞介素6(IL-6)、IL-8、肿瘤坏死因子α（TNF-α）、IL-10和IL-4的水平。 结果 提取到H.pylori ATCC 43504菌株的基因组，并构建了重组质粒pET32a-BabA。诱导和纯化后，重组BabA蛋白的相对分子质量(Mr)约为39,000。通过肽段质量指纹(PMF)，验证了重组蛋白的氨基酸序列与BabA蛋白一致。通过SELEX筛选出了5个候选适配体，它们可以与上述重组BabA蛋白结合。适配体A10、A30和A42识别同一位点，而A3、A16和上述三个适配体各自识别不同位点。实验结果表明，这些适配体能够显著阻断H.pylori在体外的粘附。动物模型实验显示，通过胃内注射，适配体能够阻断H.pylori在胃黏膜的寄生，并减少炎症反应。适配体治疗模型组胃黏膜匀浆中IL-4、IL-6、IL-8和TNF-α的水平低于未经治疗的模型组。 结论 适配体能够通过结合BabA蛋白来阻断H.pylori与胃黏膜上皮细胞的粘附过程，从而减少H.pylori在胃黏膜定植过程中的寄生。

Objective To explore the aptamer specific binding blood group antigen-binding adhesin (BabA) of Helicobacter pylori (H.pylori) for blocking of H.pylori adhering host cell. Methods H.pylori strain was cultured and its genome was extracted as templates to amplify the BabA gene by PCR with designed primers. The BabA gene obtained was cloned and constructed into prokaryotic expression plasmid, which was induced by isopropyl beta-D-galactoside (IPTG) and purified as target. The single stranded DNA (ssDNA) aptamers that specifically bind to BabA were screened by SELEX. Enzyme-linked oligonucleotide assay (ELONA) was used to detect and evaluate the characteristics of candidate aptamers. The blocking effect of ssDNA aptamers on H.pylori adhesion was subsequently verified by flow cytometry and colony counting at the cell level in vitro and in mouse model of infection, respectively. Meanwhile, the levels of cytokines, interleukin 6 (IL-6), IL-8, tumor necrosis factor α (TNF-α), IL-10 and IL-4 in the homogenate of mouse gastric mucosa cells were detected by ELISA. Results The genome of H.pylori ATCC 43504 strains was extracted and the recombinant plasmid pET32a-BabA was constructed. After induction and purification, the relative molecular mass (Mr) of the recombinant BabA protein was about 39 000. The amino acid sequence of recombinent protein was consistent with BabA protein by peptide mass fingerprint (PMF). Five candidate aptamers were selected to bind to the above recombinent BabA protein by SELEX. The aptamers A10, A30 and A42 identified the same site, while A3, A16 and the above three aptamers identified different sites respectively. The aptamer significantly blocked the adhesion of H.pylori in vitro. Animal model experiments showed that the aptamers can block the colonization of H.pylori in gastric mucosa by intragastric injection and reduce the inflammatory response. The levels of IL-4, IL-6, IL-8 and TNF-α in gastric mucosal homogenates in the model group with aptamer treatment were lower than that of model group without treatment. Conclusion Aptamers can reduce the colonization of H.pylori in gastric mucosa via binding BabA to block the adhesion between H.pylori and gastric mucosal epithelial cells.