Genetic analysis of the cytotoxin-associated gene and the vacuolating toxin gene in Helicobacter pylori strains isolated from Taiwanese patients.
OBJECTIVE
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Yang
J C
JC
Department of Internal Medicine, National Taiwan University Hospital, Taipei.
Wang
T H
TH
Wang
H J
HJ
Kuo
C H
CH
Wang
J T
JT
Wang
W C
WC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000097:blood; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D001483:Base Sequence; D015139:Blotting, Southern; D003603:Cytotoxins; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010437:Peptic Ulcer / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013045:Species Specificity; D013624:Taiwan
D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D003603:Cytotoxins; D012336:RNA, Ribosomal, 16S; C074689:VacA protein, Helicobacter pylori; C080866:cagA protein, Helicobacter pylori