ORAL IMMUNIZATION WITH RECOMBINANT HELICOBACTER-PYLORI UREASE INDUCESSECRETORY IGA ANTIBODIES AND PROTECTS MICE FROM CHALLENGE WITH HELICOBACTER-FELIS

Helicobacter pylori, a gram-negative spiral bacterium, is the cause of chronic superficial (type B) gastritis and peptic ulcer disease. The urease enzyme of H. pylori was expressed as an inactive recombinant pr otein in Escherichia coli, purified as particulate structures of 550-6 00 kDa molecular mass with a diameter of similar to 12 nm. Given orall y, 5 mu g of urease with an appropriate mucosal adjuvant, such as the labile toxin of E. coli, protected 60%-100% of mice against challenge with virulent Helicobacter felis. Protection correlated with the level of secretory IgA antibodies against urease. Oral administration of an tigen was as effective or better than intragastric administration. Par enteral injection of antigen or intragastric administration of high-do se antigen without adjuvant elicited serum IgG but no IgA antibodies a nd did not confer protection. Recombinant urease as an oral vaccine ca ndidate deserves further investigation as an approach to the preventio n of Helicobacter-induced chronic gastroduodenal diseases in humans.