Infection with cagA- and vacA-positive and -negative strains of Helicobacter pylori in a mouse model.

To study the role of cytotoxin-associated protein (cagA) and vacuolating cytotoxin (vacA) in Helicobacter pylori infection in an experimental murine model, mice were infected with seven strains with different cagA and vacA status. Groups of 10 NMRI mice were challenged and were killed 5 weeks later. In a second study, 20 mice were challenged with a mixture of the same seven strains and killed 1, 3, 15 and 17 weeks post-inoculation. All seven strains were found to colonize the mice for the 5-week experimental period. Animals infected with vacA-positive strains, regardless of cagA status, showed an elevation of antibody titers. Two cagA-negative and vacA-positive strains and one cagA- and vacA-positive strain were found to 'take over' in the mixed infection as analyzed by the randomly amplified polymorphic DNA-polymerase chain reaction technique and in one mouse stomach we found coexistence of two of the strains. We found no evidence of the different strains colonizing different parts of the stomach.