Major virulence factors, VacA and CagA, are commonly positive inHelicobacter pylori isolates in Japan

Background—VacA and CagA proteins have beenreported to be major virulence factors of Helicobacterpylori. However, antibodies against these proteins arefrequently found in the sera of Japanese patients regardless of theirgastroduodenal status.
Aim—To evaluate the expression of VacA and CagAproteins by H pylori strains isolated in Japan.
Methods—By using specific antibodies raisedagainst recombinant VacA and CagA proteins, the expression of VacA andCagA was evaluated in 68 H pylori strains isolated fromJapanese patients; a vacuolating assay and genotyping of thevacA gene were also used in the evaluation. The resultswere analysed in relation to the gastroduodenal diseases of the hosts.
Results—VacA and CagA proteins were expressed in59/68 (87%) and in 61/68 (90%) isolates respectively. The vacuolatingassay was positive in 57/68 (84%) isolates, indicating that mostimmunologically VacA positive strains produced active cytotoxin. Theprevalence of infection with strains expressing CagA and positive forvacuolating activity (Type I) was very high, 54/68 (79%), irrespectiveof the gastroduodenal status of the host.
Conclusion—Most H pylori isolates inJapan are positive for vacuolating cytotoxin and CagA, and thus thesevirulence factors cannot be used as markers to discern the risk ofdeveloping serious gastroduodenal pathologies in the hosts. However,the high prevalence of infection with strains positive for vacuolatingcytotoxin and CagA may contribute to the characteristics of Hpylori infection in Japan.

Keywords:VacA; Helicobacter pylori; CagA; ulcer; non-ulcer dyspepsia