Immunogenicity and safety of recombinantHelicobacter pylori urease in a nonhuman primate

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Abstract
Groups of squirrel monkeys (Saimiri spp.), predetermined to be free ofHelicobacter infections in the gastric mucosa, were immunized orally with 0.5–4.5 mg ofHelicobacter pylori recombinant urease (rUrease) and 25–500 µg ofEscherichia coli heat-labile enterotoxin (LT) adjuvant. Oral immunization with rUrease resulted in a markedly elevated serum immunoglobulin G (IgG) antibody response with peak levels at 45 days after immunization. No significant gastric inflammation or cytotoxicity was evident in rUrease immunized monkeys as determined by light and electron microscopy. Twenty-five micrograms of LT was a sufficient and safe adjuvant dosage, whereas higher dosages resulted in diarrhea and lethargy. Animals developed a serum IgG antibody response to LT that did not impede the production of anti-rUrease antibody levels. The results of this investigation indicate that rUrease is immunogenic in a nonhuman primate.