Yang J C, Wang T H, Wang H J, Kuo C H, Wang J T, Wang W C
Department of Internal Medicine, National Taiwan University Hospital, Taipei.
Am J Gastroenterol. 1997 Aug;92(8):1316-21.
Two virulence factors encoded by the cytotoxin-associated (cagA) gene and the vacuolating toxin (vacA) gene of Helicobacter pylori are known to be associated with gastroduodenal pathologic conditions. In this report, nucleotide sequence of cagA and vacA and the serum antibody response to the CagA antigen in H. pylori isolates from Taiwanese patients were studied.
cagA and vacA were characterized in 173 H. pylori strains by polymerase chain reaction and DNA hybridization analyses. The presence of serum IgG antibodies against CagA was assessed by Helico-blot Western blot system. Sequence analysis of polymerase chain reaction-amplified vacA and cagA was performed for two strains.
cagA was detected in all the isolates with peptic ulcers and gastric cancer. Of 54 strains with non-ulcer dyspepsia, 51 were found to be cagA+. Serum antibodies to CagA were detected for 99.2% of cagA+ strains compared with 0% of strains lacking cagA. vacA was detected in all isolates. Sequence analysis of vacA and cagA indicated that sequences of two Taiwanese strains were closely related to each other (95.9% and 97% nucleotide identity, respectively) but less homologous to the published strains (90.9% and 91.4% mean nucleotide sequence identity, respectively).
The strong association (98%) of cagA+ strains with Taiwanese patients suggests that the cagA+ phenotype could not be used as a single marker of high-risk patients in Taiwan. Moreover, sequence analysis indicates that Taiwanese strains contain different genetic sequences from those in other geographic regions.
已知细胞毒素相关（cagA）基因和空泡毒素（vacA）基因编码的两种毒力因子与胃十二指肠病理状况相关。在本报告中，研究了台湾患者幽门螺杆菌分离株中cagA和vacA的核苷酸序列以及对CagA抗原的血清抗体反应。
通过聚合酶链反应和DNA杂交分析对173株幽门螺杆菌菌株中的cagA和vacA进行特征分析。采用Helico-blot Western印迹系统评估血清中抗CagA IgG抗体的存在情况。对两株菌株进行聚合酶链反应扩增的vacA和cagA的序列分析。
在所有消化性溃疡和胃癌分离株中均检测到cagA。在54例非溃疡性消化不良菌株中，51例为cagA阳性。99.2%的cagA阳性菌株检测到抗CagA血清抗体，而cagA阴性菌株中该比例为0%。所有分离株中均检测到vacA。vacA和cagA的序列分析表明，两株台湾菌株的序列彼此密切相关（核苷酸同一性分别为95.9%和97%），但与已发表菌株的同源性较低（平均核苷酸序列同一性分别为90.9%和91.4%）。
cagA阳性菌株与台湾患者的强相关性（98%）表明，cagA阳性表型不能作为台湾高危患者的单一标志物。此外，序列分析表明台湾菌株的基因序列与其他地理区域的不同。
