Researchers from Finland and the USA determined whether the proportion of subjects colonized by cagA+ or cagA- Helicobacter pylori strains has changed as the overall prevalence of H. pylori colonization has declined in developed countries.
Sera from 911 adults from Vammala, Finland, taken between 1973 and 1994, were examined.
The team looked for antibodies to the CagA antigen of H. pylori using a truncated CagA protein as the antigen in an ELISA.
The trend in acquisition and carriage of cagA+ strains was explored.
As expected, the prevalence of carriage of both cagA+ and cagA- strains fell between 1973 and 1994.
|Fall in prevalence of H. pylori strains (1973-94):|
cagA+: 34% to 8%
cagA-: 12% to 6%
However, the prevalence of cagA+ strains, among those less than 45 years, declined (34% to 8%) significantly more than for cagA- strains (12% to 6%).
Of 221 subjects with paired serum samples, 12 (5%) changed H. pylori status. The estimated seroconversion and reversion rates were found to be 0.4% and 0.1% per year, respectively.
Except for the few individuals who changed serostatus, absolute antibody levels to H. pylori antigens, including CagA, changed little over the 21-year period.
Guillermo I. Perez-Perez, of the New York University School of Medicine, New York, USA, said on behalf of the group, "The decline in CagA seroprevalence predominantly reflects declining acquisition of cag+ strains in younger subjects.
"In addition, these data confirm that H. pylori acquisition chiefly occurs during childhood, but continues to occur during adulthood, albeit at low rates, in developed countries," it was concluded.