BACKGROUND Studies in Western populations suggest that cagA, iceA, and vacAgene status in Helicobacter pylori isolates is associated with increased virulence and peptic ulcer disease.

AIM To investigate the relationship between peptic ulcer and expression of Lewis (Le) antigens as well as cagA, iceA, and vacA inH pylori isolates in Singapore.

RESULTS Of 108H pylori isolates, 103 (95.4%) expressed Le^x and/or Le^y, while Le^a and Le^b were expressed in 23 (21.3%) and 47 (43.5%) isolates, respectively. Expression of two or more Le antigens (Le^x, Le^y, Le^a, or Le^b) was significantly higher in H pylori isolated from ulcer patients than in non-ulcer patients (89.6%v 73.2%, p=0.035). There were no significant differences in the prevalence ofcagA or iceA1 inH pylori isolates from peptic ulcer and non-ulcer patients (86.6% v 90.2% forcagA; 70.1% v68.3% for iceA1), and no association of peptic ulcer with any specific vacAgenotype.

CONCLUSIONS The present study indicates that peptic ulcer disease is associated with increased expression of Lewis antigens but notcagA, iceA, orvacA genotype in H pylori isolates in our population. This suggests thatcagA, iceA, andvacA are not universal virulence markers, and that host-pathogen interactions are important in determining clinical outcome.