IMMUNIZATION AGAINST NATURAL HELICOBACTER-PYLORI INFECTION IN NONHUMAN-PRIMATES

Helicobacter pylori infection is widespread in some breeding groups of a rhesus monkey colony (71% H. pylori positive by 1 year), and the ra te of seroconversion is also high, As a result, these groups can be us ed to test the safety and efficacy of an anti-H. pylori vaccine. Nine- month-old female animals were randomized to receive either 8 mg of rec ombinant urease (rUre) plus 25 mu g of Escherichia coli heat-labile en terotoxin (LT) (n = 26) or placebo plus LT (n = 29), given four times at I-week intervals followed by a booster 1 month later. Ten months af ter the start of the immunization, the animals were subjected to endos copy and biopsy samples were obtained, H. pylori negativity was define d as no H. pylori growth by culture and no H. pylori observed at histo logy, By this criterion, 2 (7%) of 29 animals receiving placebo and 8 (31%) of 26 immunized animals were H. pylori negative (P < 0.035), In addition, antral gastritis score was significantly less in H. pylori-n egative immunized monkeys than in H. pylori-positive animals, whether they were given rUre plus LT or placebo plus LT (P < 0.02 or P < 0.01, respectively), Interestingly, antral gastritis was also significantly less in H. pylori-positive animals given rUre plus LT than in H. pylo ri-positive animals given placebo pins LT (P < 0.02). However, quantit ative cultures did not demonstrate significant differences between the two latter groups, It is concluded that oral administration of rUre v accine plus LT significantly protects nonhuman primates against H. pyl ori infection while not causing undesirable side effects.