MULTIMERIC, RECOMBINANT UREASE VACCINE

Abstract: Methods and compositions are provided for preventing and/or treating Helicobacter (e.g., H. pylori) infection. The compositions of the invention, which are used in the methods of the invention (which include mucosal administration of the compositions), include compositions containing multimeric complexes of recombinant, enzymatically inactive Helicobacter urease in a pharmaceutically acceptable carrier or diluent; and compositions containing (a) a Helicobacter antigen, and (b) an antibiotic, an antisecretory agent, a bismuth salt, or a combination thereof.

Description: MULTIMERIC, RECOMBINANT UREASE VACCINE Background of the Invention This invention relates to methods and compositions for preventing and/or treating Helicobacter infection. Helicobacter is a genus of spiraJL, g_:a_--negative bacteria which colonize the gastrointestinal tracts of mammals. Several species colonize the stomach, most notably, H. pylori , H. heilmanii , H. felis, and H. inustelae . Although H. pylori is the species most commonly associated with human infection, H. heilmanii and H. felis have also been found to infect humans, but at lower frequencies than H. pylori . Helicobacter infects over 50% of adult populations in developed countries, and nearly 100% in developing countries and some Pacific rim countries, making it one of the most prevalent infections of humans worldwide. Infection with H. pylori results in chronic stomach inflammation in all infected subjects, although the clinical gastroduodenal diseases associated with Helicobacter infection generally appear from several years to several decades after the initial infection. H. pylori is the causative agent of most peptic ulcers and chronic superficial (type B) gastritis in humans. H. pylori infection is also associated with atrophy of the gastric mucosa, gastric adenocarcinoma, and non-Hodgkin's lymphoma of the stomach (see, e.g., Blaser, J. Infect . Dis . 161:626-633, 1990; Scolnick et al . , Infect . Agents Dis . 1:294-309, 1993; Goodwin et al . , Helicobacter pylori , Biology and Clinical Practice , CRC Press, Boca Raton, FL, 465 pp, 1993; Northfield et al . , Helicobacter pylori , Infection , Kluwer Acad. Pub., Dordrecht, 178 pp, 1994) . Summary of the Invention We have shown that vaccine compositions containing multimeric, recombinant Helicobacter urease are effective in preventing and treating Helicobacter infection. In addition, we have shown that a composition containing H. pylori urease and a mucosal adjuvant, in combination with an antibiotic and a bismuth salt, is more effective at treating Helicobacter infection than any of these components alone, or any combinations of three or less of these components. Accordingly, in a first aspect, the invention features a vaccine for inducing an immune response to Helicobacter (e .g. , H. pylori) in a patient (e .g. , a human patient) that (a) is at risk of developing, but does not have, a Helicobacter infection (a "protective" immune response) , or (b) is already infected by Helicobacter (a "therapeutic" immune response) . This vaccine contains multimeric complexes of recombinant, enzymaticaily inactive Helicobacter (e .g. , H. pylori) urease, and a pharmaceutically acceptable carrier or diluent (e . g. , sterile water or a 2% weight/volume sucrose solution) . The vaccine may contain a multimeric complex containing eight Urease A subunits and eight Urease B subunits, a multimeric complex containing six Urease A subunits and six Urease B subunits, a multimeric complex containing four Urease A subunits and four Urease B subunits, or a mixture thereof. In addition, the vaccine may contain a mucosal adjuvant, such as the heat-labile enterotoxin of enterotoxigenic Escherichia coli (LT) , a cholera toxin (CT) , a Clostridi m difficile toxin, or a subunit or derivative thereof lacking toxicity but still having adjuvant activity (e.g., a fragment, mutant, or toxoid) , or a mixture thereof. For example, a fragment containing the 794 carboxyl-terminal amino acids of C. difficile Toxin A (see, e.g., Dove et al . , supra , for the sequence of C. difficile Toxin A) may be used. Further, the multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease may be freeze-dried prior to use in the vaccines of the invention. In a second aspect, the invention features a method of inducing a protective and/or therapeutic mucosal immune response to Helicobacter (e .g. , H. pylori) in a patient (e.g., a human patient). In this method, a composition containing an immunogenically effective amount of multimeric complexes of recombinant, enzymaticaily inactive Helicobacter (e .g. , H. pylori) urease is administered to a mucosal surface (e.g., an oral or intranasal surface; or to a rectal surface by, e.g., anal suppository) of the patient. The composition may contain a multimeric complex containing eight Urease A subunits and eight Urease B subunits, a multimeric complex containing six Urease A subunits and six Urease B subunits, a multimeric complex containing four Urease A subunits and four Urease B subunits, or a mixture thereof. The composition may be administered without gastric neutralization by, e.g., sodium bicarbonate. In addition to the multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease, the composition used in this method may further contain a mucosal adjuvant. For example, the composition may contain the heat-labile enterotoxin of enterotoxigenic Escherichia coli (LT) , a cholera toxin (CT) , a Clostridium difficile toxin, or a subunit or derivative thereof lacking toxicity but still having adjuvant activity (e.g., fragments, mutants, or toxoids having adjuvant activity), or mixtures thereof. For example, a fragment containing the 794 carboxyl-terminal amino acids of C. difficile Toxin A (see, e.g.. Dove et al . , supra , for the sequence of C. difficile Toxin A) may be used. Further, the multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease in the composition may be freeze-dried prior to use in this method. In a third aspect, the invention features a composition for treating Helicobacter (e.g. , H. pylori) infection in a patient (e.g., a human). This composition contains (a) a Helicobacter (e . g. , H. pylori ) antigen (e.g., urease), and (b) an antibiotic, an antisecretory agent, a bismuth salt, or a combination thereof. An example of a Helicobacter urease antigen which may be used in this composition is one containing multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease, as is described above. Other Helicobacter antigens which may be used include, e .g. , HspA, HspB, AlpA, AlpB, ClpB, and the antigen recognized by monoclonal antibody IgG 50 (see below) . This composition may further contain a mucosal adjuvant (or a combination of mucosal adjuvants) , such as those which are listed above. Antibiotics which may be included in this composition include, but are not limited to, amoxicillin, clarithromycin, tetracycline, metronidizole, and erythroπvycin; and bismuth salts which may be included are, e.g., bismuth subcitrate and bismuth subsalicylate. Antisecretory agents which may be included in the composition are, e.g., proton pump inhibitors (e . g. , omeprazole, lansoprazole, and pantoprazole) , H 2 -receptor antagonists (e.g., ranitidine, cimetidine, famotidine, nizatidine, and roxatidine) , and prostaglandin analogs (e . g. , misoprostil or enprostil) . In a final aspect, the invention features a method for treating Helicobacter (e . g. , H. pylori ) infection in a patient (e . g. , a human patient). In this method, a composition containing (a) a Helicobacter (e .g. , H. pylori) antigen (e.g., the antigens listed above), and (b) an antibiotic, an antisecretory agent, a bismuth salt, or a combination thereof, is administered to the patient. Any standard mode of administration, or a combination of standard modes, may be employed. For example, mucosal administration (e.g., administration to an oral or intranasal surface, or administration to a rectal surface by, e.g., anal suppository) may be used. A composition administered to a mucosal surface in this method may further contain a mucosal adjuvant (or a combination of mucosal adjuvants), e.g., the mucosal adjuvants which are described above. Antibiotics, bismuth salts, and antisecretory agents which may be included in the composition used in this method are described above. By "vaccine" is meant a composition containing at least one antigen (e .g. , an antigen from a pathogenic microorganism, such as H. pylori ) which, when administered to a patient, elicits or enhances an immune response to the antigen that is effective in the prevention of disease (e.g., disease caused by infection by the microorganism) , or in the treatment of a pre¬ existing disease. By "immunogenically effective amount" is meant an amount of an antigen (e.g., multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease, or any of the other antigens listed above) which is effective to elicit an immune response (e.g., a humoral or a mucosal immune response) when administered to a patient, such as a human patient. By "Helicobacter" is meant any bacterium of the genus Helicobacter , particularly a Helicobacter which infects humans (e.g., H. pylori ) . By "urease" is meant an enzyme (e .g. , H. pylori urease) which catalyzes the conversion of urea into ammonium hydroxide and carbon dioxide. By "multimeric complex" is meant a macromolecular complex of polypeptides (e.g., urease polypeptides). The polypeptides may be associated in the complex by a variety of intermolecular interactions, such as covalent bonds (e.g., disulfide bonds), hydrogen bonds, and ionic bonds. By "mucosal adjuvant" is meant a compound (e.g., an immunomodulator) which non-specifically stimulates or enhances a mucosal immune response (e.g., production of IgA antibodies) . Administration of a mucosal adjuvant in combination with an immunogenic composition facilitates the induction of a mucosal immune response to the antigen in the composition. By "antibiotic" is meant a compound derived from a mold or bacterium that inhibits the growth of other microorganisms. Other features and advantages of the invention will be apparent from the following detailed description and from the claims. Detailed Description The drawings are first described. Drawings Pig. 1 is a diagram showing the restriction enzyme map of the 2.5 kb PCR product cloned from pSCPl. The numbers above the map indicate nucleotide positions using the first base pair (bp) of BL1 as nucleotide #1. Locations of ureA and ureB genes and the direction of transcription of these genes are shown. The locations of restriction enzyme cleavage sites are shown below the genes. The numbers next to the name of each restriction enzyme indicate the locations of the first base pair in the recognition sequence for the enzyme indicated. Pig. 2 is a diagram of the genetic map of the expression plasmid pORV214. The ureA and ureB genes are shown as open bars with arrows. The solid arrow and solid bar represent the T7 promoter and terminator sequences, respectively. Thin lines represent pBR322 DNA. The phage and plasmid origins of replication on the plasmid are shown by large shaded arrows, denoted "fl origin" and "ori," respectively, and indicate the direction of DNA synthesis. The genes encoding kanamycin resistance (kan) and the lactose repressor (lad) are shown as shaded bars. The BamHI and EcoRI sites used for cloning the PCR product are indicated. Arrows within bars representing lad , ureA, ureB , and kan genes indicate the direction of transcription. Pig. 3 is a schematic representation of the nucleotide sequence of the H. pylori locus encoding the ureA and ureB genes, as well as the transcriptional regulatory sequences from pORV214 (SEQ ID N0:1). The predicted amino acid sequences of ureA (SEQ ID NO:2) and ureB (SEQ ID NO:3) are shown above the DNA sequence. Numbers to the left of the sequence correspond to nucleotide positions and those on the right indicate amino acid positions. The sequences corresponding to the PCR primers are underlined and the BamHI and EcoRI sites used to clone the PCR product are indicated. The predicted transcriptional initiation site (G) and direction of transcription are shown with an arrow. The ribosomal binding site (RBS) is indicated. The sequences which regulate transcriptional initiation (T7 promoter and lac operator) and termination are underlined and labeled. Fig. 4 is a graph showing analytical size exclusion HPLC for recombinant urease. Fig. 5 is a series of graphs showing the bacterial score versus the levels of serum IgA, serum IgG, and fecal IgA antibodies from mice immunized with recombinant H. pylori urease and cholera toxin (CT) . Pig. 6 is a series of graphs showing the bacterial score versus the levels of serum IgA, serum IgG, and fecal IgA antibodies from mice immunized with recombinant H. pylori urease and enterotoxigenic E. coli heat-labile toxin. Fig. 7 is a table showing the experimental protocol used for comparing intranasal and oral immunization routes for recombinant urease. Pig. 8 is a series of graphs showing the serum IgG (Serum G) , serum IgA (Serum A) , fecal IgA (Fecal A) , and salivary IgA (Sal A) levels in groups of mice treated according to the protocol illustrated in Fig. 7. Pig. 9 is a table showing the experimental protocol used for comparing intranasal and intragastric immunization routes for recombinant urease. Pig. 10 is a series of graphs showing the results of urease tests carried out on the mice treated according to the protocol illustrated in Fig. 9. Pig. 11 is a graph showing that rUrease (10 μg) given by the intranasal route with CT (5 μg) is at least as effective as rUrease (25 μg) given by the oral route with CT (10 μg) in preventing infection with H . felis . Pig. 12 is a graph showing that immunization of mice with rUrease + 10 μg LT reduces or eradicates established H. felis infection. When these animals were reinfected with H . felis , they were protected against challenge. Pig. 13 is a graph showing the mean antibody response of mice 4 and 10 weeks after therapeutic immunization with either recombinant H. pylori urease and CT, or CT alone. Pig. 14 is a graph showing numbers of IgA antibody secreting cells in gastric mucosa of immunized and unimmunized mice before, and at intervals after, infection with H. felis . Pig. 15 is a graph showing the clearance of H. felis infection in mice previously immunized with recombinant H. pylori urease and CT. Cloning of the ureA and ureB genes The structural genes encoding urease, ureA, and ureB , have been cloned (Clayton et al., Nucl . Acids . Res . 18:362, 1990; Labigne et al. , J. Bacteriol . 173:1920- 1931, 1991) , and the recombinant urease encoded by these genes has been purified (Hu et al . , Infect . Immun . 60:2657-2666, 1992). For use in the present invention, urease was cloned from a clinical isolate of H. pylori (CPM630) obtained from a clinical specimen provided by Dr. Soad Tabaqchali, St. Bartholomew's Medical College, University of London. A genomic DNA library of strain CPM630 was prepared in the lambda phage vector EMBL3. Plaques were screened for reactivity with rabbit anti -Helicobacter urease polyclonal antibody, and a single reactive plaque was isolated. This clone contained a 17 kb Sail fragment that encoded the ureA and ureB genes. The 17 kb fragment was subcloned onto pUClδ and designated pSCPl. A 2.7 kb TagI fragment was subcloned (pTCP3) and completely sequenced. The 2.7 kb TagI fragment encoded both ureA and ureB . The primers BL1 (CGG GAT CCA CCT TGA TTG CGT TAT GTC T; SEQ ID NO:4) and BL2 (CGG AAT TCA GGA TTT AAG GAA GCG TTG; SEQ ID NO:5) were used to amplify and clone a 2.5 kb fragment from pSCPl. BL1 and BL2 correspond to nucleotides 2605-2624 of GenBank accession number M60398 (the BL1 primer) and nucleotides 2516-24998 of EMBL accession number X17079 (the BL2 primer) . A restriction enzyme map of the 2.5 kb fragment PCR product is shown in Fig. 1. The 2.5 kb fragment contains the entire coding region of ureA and ureB, as well as translational start signals from H . pylori upstream of ureA. Expression of recombinant urease The purified 2.5 kb PCR fragment containing the genes encoding ureA and ureB was digested with EcoRI and BamHI and inserted into the expression vector pET24+ (Novagen, Madison, Wisconsin) to produce the plasmid PORV214 (Fig. 2) . pET24+ contains the colEl origin of replication, the filamentous phage (fl) origin of replication for single strand rescue, and the kanamycin resistance gene of Tn903. The fragment was inserted downstream of the T7 promoter, which provides transcription initiation for the urease genes. Lactose operator (lacO) sequences are present between the T7 promoter and the cloning sites to provide inducible expression of the urease genes. A T7 transcription terminator sequence is located downstream of the cloning sites. The vector also contains the lactose repressor gene (lacJ) to ensure complete repression of expression. Other sequences present in the vector are derived from pBR322, which served as the backbone for vector construction. The initial ligation mixture, containing the 2.5 kb PCR EcoRI-BamHI fragment and the pET24+ vector digested with EcoRI and BamHI , was used to transform XLl-Blue (Stratagene, La Jolla, CA) prepared by the CaCl 2 method. XLl-Blue is an E. coli strain that does not express T7 RNA polymerase. Kanamycin resistant colonies were directly screened by PCR using urease specific primers. Plasmid DNA from several positive colonies was extracted using Qiagen minispin columns (Qiagen, Chatsworth, CA) and checked for the correct restriction digestion pattern. Purified pORV214 DNA was used to transform the E. coli strain BL21-DE3 (Novagen, Madison, Wisconsin) prepared by the CaCl 2 method. BL21-DE3 is an E. coli B strain that is lysogenized with lambda phage DE3, a recombinant phage that encodes T7 RNA polymerase under the control of the 2avC7V5 promoter. BL21 is deficient in Ion and ompT proteases, as well as the hsdS B restriction/modification system and dcm DNA methylation. DNA was prepared from kanamycin resistant colonies with Qiagen mini spin columns and screened by restriction enzyme analysis using BamHI and EcoRI to confirm the presence of the plasmid. Urease expression was assessed by examination of BL21-DE3 (pORV214) cell lysates by SDS-PAGE and Western blot. Several positive clones had the correct restriction endonuclease digestion pattern and expressed urease. A single clone containing pORV214 was selected, grown on LB plates containing kanamycin (50 μg/ml) , harvested, and stored at -80°C in LB containing 50% glycerol. A research cell bank was prepared by growing a sample from the glycerol stock on LB plates containing kanamycin, selecting an isolated colony, and inoculating a LB broth culture containing kanamycin. This culture was grown to OD 600 of 1.0, pelleted, and resuspended in an equal volume of LB containing 50% glycerol. These research cell bank (RCB) aliquots (100 μl) were then stored at -80°C. A master cell bank (MCB) was similarly prepared using an isolated colony from the research cell bank, and a manufacturer's working cell bank (MWCB) was prepared using an isolated colony from the MCB. The MCB and MWCB cells were viable, kanamycin resistant, and displayed a normal E. coli colony morphology. T7 RNA polymerase expression and lambda phage lysogeny was confirmed using appropriate tests, which are well known in the art. Urease expression was IPTG-inducible in the MCB and MWCB cells, as determined by examination of cultures grown in the presence of IPTG, and analysis of lysates from these cell cultures on SDS-PAGE. Production of 60 kD and 29 kD proteins (UreB and UreA, respectively) by the MCB and MWCB cells increased with the incubation tine. Plasmid DNA was isolated from the MCB and MWCB cells and was tested by restriction enzyme analysis, restriction fragment length polymorphism (RFLP) , and DNA sequence analysis to confirm plasmid structure. The MCB contained a plasmid with the appropriate restriction endonuclease digestion pattern with no deletions or rearrangements of the plasmid. Likewise, there were no differences between the RFLP fingerprint of pSCPl and the RFLP fingerprints of plasmid DNA from MCB and MWCB, indicating that the urease genes had not undergone detectable (> 50 bp) deletions or rearrangements in the cloning process or in the manufacture of the cell banks. The coding regions of ureA and ureB, and the sequences of the promoter and termination regions of the plasmid isolated from MCB cells, were sequenced. Sequencing reactions were performed using the Di-Deoxy Cycle Sequencing Kit, according to the manufacturer's instructions (Applied Biosystems, Inc., Foster City, CA) , using fluorescent-labeled dideoxynucleotides. The sequences of the ureA and ureB genes, with predicted protein sequences, as well as the DNA sequences of flanking regions are shown in Fig. 3. Large-scale production of recombinant urease The fermentor(s) to be used was cleaned and sterilized according to approved procedures. The culture medium contained 24 g/L yeast extract, 12 g/L tryptone, 6-15 g/L glycerol, in RO/DI water. Since pORV214 was sufficiently stable in the absence of antibiotics, no antibiotics were present in the large-scale fermentation cultures. Antifoam was added and the unit was sterilized in place. For production in the 40 liter fermentor, a vial of the MWCB was thawed and used to inoculate a four liter shaker flask containing one liter of LB broth (1% tryptone, 0.5% yeast extract, 1% NaCl) without antibiotics. The culture was shaken at 37 β C for 16-24 hours. The inoculum was then transferred to the 40 liter fermentor (30 liter working volume) containing the production media described above. Fermentation was carried out with aeration and agitation until the cell density determined by OD 600 was approximately 8-10. Isopropyl 3-D-thiogalactopyranoside (IPTG) was then added to a final concentration of 0.1 mM, and induction was allowed to proceed for 16-24 hours. The cells were harvested by centrifugation and the wet paste was aliquoted into polypropylene storage containers and stored at -80 β C. For production at the 400 liter scale (300 liter working volume) , the inoculum and culture in the 40 liter vessel were prepared as described above. When the 40 liter vessel reached an OD 600 of approximately 5.0, it was used to inoculate the 400 liter fermentor. The culture was further incubated to an OD 600 of 8-10. The culture was then induced, harvested, and stored, as is described above. This procedure required 2-3 generations more than the 40 liter process. Purification of recombinant H. pylori urease Containers of cell paste produced by the fermentation processes described above were removed from storage, thawed at room temperature, and resuspended in 20 mM sodium phosphate/1 mM EDTA buffer, pH 6.8. The resuspended cells were disrupted by extrusion through a narrow orifice under pressure (Microfluidizer Cell Disruptor) . The disrupted cells were centrifuged at 4°C to sediment cell debris and the supernatant containing soluble urease was collected. A solution of 3 M sodium chloride was added to the cell supernatant to a final concentration of o.l M. The supernatant was then applied to a DEAE-Sepharose column equilibrated in 20 mM sodium phosphate/1 mM EDTA, and the pass-through was collected for further processing. The pass-through was diafiltered into 20 mM sodium phosphate/1 mM EDTA, pH 6.8, with a 100 kD cutoff membrane to remove low molecular weight contaminants and to reduce ionic strength. This material was applied to a second DEAE-Sepharose column equilibrated in 20 mM sodium phosphate/1 mM EDTA. The pass-through was discarded and the column rinsed with 20 mM sodium phosphate/l mM EDTA, pH 6.8. The bound material was eluted with approximately three column volumes of 0.1 M NaCl/1 mM 0-mercaptoethanol. Effective elution of the bound urease was controlled by the volume and flow rate of the elution buffer. The partially purified urease was diafiltered against 25 mM Tris-HCl, pH 8.6, and applied to a Q-Sepharose column. The column was washed with approximately two column volumes of the same buffer and the pass-through containing highly purified urease was collected. The pass-through from the Q-Sepharose step was then concentrated and diafiltered into 2% sucrose in water for injection (WFI) , pH 7.5. Characterization of the antigenicitv and subunit composition of purified recombinant H. pγlori urease To compare the antigenicity and subunit composition of recombinant H. pylori urease to native H. pylori urease, native H. pylori urease was purified and used as an antigen to produce polyclonal anti-urease antibodies, as well as mono-specific polyclonal anti-UreA, anti-UreB, and anti-urease holoenzyme antibodies. Native H. pylori urease was purified using a modification of the procedure reported by Hu and Mobley (Infect . Immun . 58:992-998, 1990). H. pylori strain ATCC 43504 (American Type Culture Collection, Rockville, MD) was grown on Mueller-Hinton agar (Difco Laboratories, Detroit, MI) containing 5% sheep red blood cells (Crane Labs, Syracuse, NY) and antibiotics (5 μg/ml trimethoprim, 10 μg/ml vancomycin and 10 u/ml polymyxin B sulfate) (TVP, Sigma Chemical Co., St. Louis, MO). Plates were incubated 3-4 days at 37 β C in 7% C0 2 and 90% humidity, and bacteria were harvested by centrifugation. The bacteria were suspended in water or 20 mM phosphate, 1 mM EDTA, 1 mM 3-mercaptoethanol (pH 6.8) containing protease inhibitors, lysed by sonication and clarified by centrifugation. The clarified supernatant was mixed with 3 M sodium chloride to a final sodium chloride concentration of 0.15 M and passed through DEAE-Sepharose (Fast Flow) . Active urease that passed through the column was collected, concentrated in a Filtron Macrosep 100 centrifugal filtration unit, and then passed through a Superose-12 or Superdex 200 size exclusion column. Size-exclusion chromatography was performed using Pharmacia FPLC pre-packed columns. The fractions containing urease activity were pooled, concentrated, and further purified by FPLC anion-exchange chromatography on a Mono-Q sepharose column prepacked by Pharmacia. The bound urease was eluted using a sodium chloride gradient. The fractions with urease activity were pooled and concentrated using Macrosep 100 centrifugal filters from Filtron Inc. For some lots, a final purification was achieved by analytical size-exclusion FPLC on Superose-12 columns. Polyclonal antiserum to H. pylori urease was produced by immunizing three female New Zealand white rabbits with purified native H. pylori urease. The animals were pre-bled to confirm non-immune status and then immunized subcutaneously with 150 μg urease in complete Freund's adjuvant. Two booster doses of 150 μg each were administered subcutaneously 27 and 45 days later with Freund's incomplete adjuvant. After confirmation of the immune response by ELISA and Western blotting against purified urease, the animals were exsanguinated. The blood was clotted at 4°C overnight and serum was harvested by centrifugation. Serum IgG was purified by ammonium sulfate precipitation (50%) overnight at 4°C. The precipitate was resuspended in PBS and dialyzed to remove ammonium sulfate. The anti-urease titer of the IgG from each animal was found to be 1:10 7 and the antibodies from the three animals were pooled. The protein concentration was determined to be 17.3 mg/ml. Aliquo s of 0.2 ml each were prepared and stored at -80°C. Mouse polyclonal ascites against H . pylori urease holoenzyme ("MPA3") was prepared by injecting five mice subcutaneously with 10 μg native urease holoenzyme in complete Freund's adjuvant on Day 0. The mice were boosted on Days 10 and 17, bled on day 24 to confirm anti-urease immune response, and boosted again on Day 26. On Day 28 the mice were injected intraperitoneally with Sarcoma 180 cells. A final intraperitoneal booster dose of 10 μg urease was given on Day 31, and ascitic fluids collected seven days later. The ascitic fluids were incubated for two hours at room temperature and then at 4°C for 16 hours; clots were disrupted by vortexing and removed by centrifugation at 10,000 rpm for 10 minutes. After overnight incubation at 4°C in plastic tubes, the fluids formed solid clots. These were homogenized, diluted five-fold with PBS, and re-clarified by centrifugation at 10,000 rpm for 10 minutes. Thirty-six ml of diluted ascitic fluids were collected and frozen at -20 β C in 300 μl aliquots. Western blot analyses confirmed that the antibody reacts with UreA and UreB subunits. An endpoint titer of 1:300,000 was achieved in ELISA against urease. Mouse polyclonal ascites against H. pylori UreA ("MPA4") was prepared by injecting mice subcutaneously with native UreA subunit H. pylori urease isolated by electroelution from SDS-PAGE gels. Subsequent steps in the preparation of anti-ureA ascites were performed as described above for generation of antibodies against the holoenzyme. Mouse polyclonal ascites against native H. pylori UreB subunit ("MPA6") was prepared by injecting mice subcutaneously with native UreB isolated by electroelution from SDS-PAGE gels. Subsequent steps in the preparation of anti-UreB ascites were performed as described above for generation of antibodies against the holoenzyme. MAB71 is an IgA monoclonal antibody against H. felis urease which recognizes a protective epitope on the B subunit. Preparation of this antibody is described in Czinn et al . , J. Vaccine 11(6) :637-642, 1993, and the hybridoma cell line which produces it was deposited with the ATCC and designated deposit number HB 11514. The antibodies described above were used in Western blot experiments to characterize the purified recombinant H. pylori urease. SDS-PAGE and Western blot analysis of recombinant urease Recombinant urease was first analyzed by SDS-PAGE (12.5%) run under reducing conditions. Two major protein bands (29 kD and 60 kD) and several lighter bands (approximately 38 kD) were evident. To identify the proteins in these bands. Western blots were performed using the anti-urease and anti-urease subunit antibodies described above. The 60 kD protein reacted with MPA3 (anti-urease holoenzyme) and MPA6 (anti-UreB) , but not with MPA4 (anti-UreA) . The 29 kD protein reacted with MPA3 (anti-urease holoenzyme) and MPA4 (anti-UreA) , but not with MPA6 (anti-UreB) . The lighter 38 kD band reacted with MPA3 anti-urease holoenzyme) and MPA6 (anti- UreB) , indicating that this protein is a portion of UreB. Two faint high molecular weight (>150 kD) bands were evident in SDS-PAGE gels. Both bands reacted faintly with antibodies to both UreA and UreB, indicating that a minor portion of recombinant urease subunits form covalent units resistant to sulfhydryl reduction under the conditions used. No other protein bands were apparent in Coomassie-stained gels. Thus, all proteins detected in the purified product are either UreA, UreB, or a derivative of UreA or UreB. The wet Coomassie-stained SDS-PAGE gel was scanned using an Ultroscan XL laser densitometer and a Gel Scan XL software program (Pharmacia-LKB Biotechnology, Piscataway, NJ) . The densitometry data were consistent with a 1:1 molar ratio of the UreA:UreB subunits, as expected from the structure of native H. pylori urease. UreA and UreB accounted for more than 95% of the total protein present in the purified urease preparation. The estimated average value for the combined UreA + UreB peaks was 95.2% ± 1.2%. Analytical size-exclusion HPLC of purified recombinant urease The purity and molecular composition of purified recombinant urease was determined by analytical size-exclusion high performance liquid chromatography. Chromatography was performed using a Beckman System Gold HPLC consisting of Pump 126, diode array dual wavelength detector 168, System Gold Software Version V7.ll, Progel-TSK G4000SWXL (5 mm x 30 cm i.d.) column (Beckman Instruments, Brea, California), and SWXL guard column from Supel Co. Chromatography was performed under isocratic conditions using 100 mM phosphate, 100 mM sodium chloride buffer, pH 7.0. The column was calibrated using molecular weight markers from Pharmacia-LKB. A typical HPLC separation profile of representative purified bulk sample is shown in Fig. 4. The purified urease product shows a prominent protein peak with a retention time between that of thyroglobulin (MW 669 kD) and ferritin (MW 440 kD) . An apparent molecular weight of 550-600 kD was estimated based on a series of runs. This peak was tentatively designated as hexameric urease. The area of this hexameric urease was at least 70% of the total protein in different lots of product. A second prominent protein peak with a lower retention time (higher molecular weight) was also detected. The area of this peak ranged from 5-20%. This peak, with a molecular weight >600 kD, was designated as octomeric urease. The total area of the octomeric plus hexameric urease peaks was over 90%. These two characteristic peaks were isolated for further characterization. The two peaks were purified by HPLC from a preparation of reconstituted, freeze-dried urease and stored at 4 β C for over one week. During storage for this period of time, octomeric urease increases while the hexameric form decreases. The separated peak fractions were analyzed by reducing SDS-PAGE and ELISA reactivity with monoclonal and polyclonal antibodies to urease. On SDS-PAGE, both peaks showed urease A and B bands in comparable ratios. In addition, both showed nearly identical immunoreactivity in ELISA with polyclonal anti-urease holoenzyme antibodies (MPA3) and a monoclonal anti-UreB antibody (MAB71) . Enzvmatic furea hvdrolvtic) activity of recombinant urease Three methods were used to investigate the enzymatic activity of recombinant urease: urease-specific silver staining following electrophoresis, the pH-sensitive phenol red urea broth assay, and direct detection of ammonia. Urease-specific silver staining, described by deLlano et al . (Anal . Biochem . 177:37-40, 1989), is based on the reaction of urease with urea to produce ammonia. The reaction leads to a localized increase in pH which facilitates a photographic redox reaction leading to disposition of metallic silver. Enzymatic activity of native H. pylori urease was detected with only a 1.0 μg sample. In contrast, 20 μg purified recombinant urease exhibited no urease activity. The pH-sensitive phenol red broth assay, which is well known in the art, is based on a change in pH due to ammonia generation as a result of urea hydrolysis. Urease activity was demonstrated with as little as 0.2 μg/ml purified H. pylori urease. In contrast, no urease activity was associated with purified recombinant urease, even at concentrations up to 750 μg/ml. Direct estimation of ammonia produced by hydrolysis of urea by urease was quantitated using Nesslers' reagent (Koch et al . , J. Am . Chem . Society 46:2066-2069, 1924). Urease activity of native H. pylori urease was detectable at a concentration of 1 μg/ml. No activity was detected in assays containing up to 500 μg/ml purified recombinant urease. Based on the results of the urease-specific silver staining assay, the pH-sensitive phenol red broth assay, and direct estimation of ammonia, there is no detectable urease activity in the recombinant urease product. Protective and therapeutic efficacy of purified recombinant urease The H. felis-mouse model was used to test the efficacy of recombinant H. pylori urease in the prevention and treatment of Helicobacter infection. In this model, colonization of the stomach is readily established and is accompanied by gastric inflammation. This animal model is a well established system for the study of Helicobacter, and has been used extensively in laboratory investigations of the pathogenesis and treatment of Helicobacter-induced disease (see, e .g. , Fox et al . , Infect . Immun . 61:2309-2315, 1993; Goodwin and Worsley, Helicobacter pylori , Biology and Clinical Practice , CRC Press, Boca Raton, FL, 465 pp, 1993) . Antigenic cross-reactivity between H. pylori and H. felis ureases allows use of the human vaccine candidate of the invention, recombinant H. pylori urease (rUre) , to immunize animals infected, or subsequently challenged, with H. felis . Both germ-free and conventional mice are susceptible to infection by H. felis , and develop life-long infection of the gastric epithelium, characterized by infiltration of inflammatory cells (Fox et al . , supra) . Dose response studies indicated that 100% of Swiss-Webster specific pathogen-free (SPF) mice become infected after a single oral challenge with 10* H. felis . Unless otherwise specified, a single dose of 10 7 was used to infect mice prior to therapeutic immunization or challenge mice after prophylactic immunization. A challenge of -10 3 times the infectious dose (I.D. 90 ) with this Helicobacter represents a severe test of immunity. Assays for gastric infection Several methods were used to detect Helicobacter in gastric tissue, including measurement of gastric urease activity, histologic examination, and culture of gastric tissue. Gastric urease activity was measured both qualitatively (presence or absence) and quantitatively. In the qualitative assay, stomachs were divided longitudinally into two halves from the gastroesophageal sphincter to the pylorus. One longitudinal piece, representing approximately 1/4 of the stomach, was placed in 1 mL of urea broth (0.1 g yeast extract, 0.091 g monopotassium phosphate, 0.095 g disodium phosphate, 20 g urea, and 0.1 g/L phenol red, pH 6.9). A distinctive color change (due to hydrolysis of urea by the enzyme, production of ammonia, and increased pH) after four hours incubation at room temperature indicated a positive result. For quantitative determinations, urease activity was determined by measuring absorbance at 550 nm of clarified urea broth incubated with whole stomach sections for 4 hours. This assay can detect as few as 1-2 x 10 4 H . felis/0. 1 g stomach tissue. This assay provides the same sensitivity as commercially available urease test kits used for human samples. Commercial kits have proven to be 100% specific and 90-92% sensitive compared to biopsy/histology (Szeto et al . , Postgrad. Med. J. 64:935- 936, 1988: Borromeo et al . J. Clin . Pathol . 40:462-468, 1987) . Quantitative gastric urease assays by spectrophotometric measurement of A 550 were slightly more sensitive than visual determinations, and allowed estimation of the severity of infection. The cut-off value for a negative urease assay was defined as 2 standard deviations above the mean A 550 for unchallenged/uninfected mice. The cut-off for a positive gastric urease assay was defined by 2 standard deviations below the mean A 550 of unimmunized/challenged mice. Individual animals with low-grade infections had values intermediate between the negative and positive cut-offs. Visual grading of the urease response identified 11/12 (92%) of the positive samples. Histologic examination was performed by fixing stomach tissue in 10% formalin. The tissue was then embedded in paraffin, sectioned and stained with a modified Warthin-Starry silver stain (Steiner's stain; Garvey, et al . Histotechnology 8:15-17, 1985) to visualize H. felis , and by hematoxylin and eosin stain to assess inflammatory responses in the tissue. Stained sections were examined by an experienced pathologist blinded to the specimen code. A semi-quantitative grading system was used to determine the number of bacteria and intensity of inflammation. The system used is a modification of the widely-accepted Sydney System for histological characterization of gastritis in humans (Price, Gastroenterol . Hepatol . 6:209-222, 1991). Full-thickness mucosal sections were examined for the intensity of inflammation (increase in lymphocytes, plasma cells, neutrophils and presence of lymphoid follicles) and depth of infiltration of these cells and graded on a scale of 0-4+. Grading the density of H. felis was accomplished by counting the number of bacterial cells with typical spiral morphology in an entire longitudinal section of gastric antrum (or corpus, if specified) . Grades were assigned according to a range of bacteria observed (0 = none; 1+ = 1-20 bacteria; 2+ - 21-50 bacteria; 3+ = 51-100 bacteria; and 4+ = >ιoo bacteria) . Route of immunization The effect of the route of administration upon the efficacy of the vaccine of the invention was examined in the mouse infection model. Six to eight week-old female specific pathogen free (SPF) Swiss-Webster mice were immunized with 200 μg recombinant H. pylori urease, either with or without 0.24 M NaHC0 3 . The recombinant urease was co-administered with 10 μg of cholera toxin (CT) as a mucosal adjuvant in all animals. Intragastric (IG) immunization was performed by delivering the antigen in 0.5 ml through a 20-gauge feeding needle to anesthetized animals. Oral immunization was performed by delivering the antigen in a 50 μl volume via a pipette tip to the buccal cavity of unanesthetized animals. For parenteral immunization, mice received 10 μg recombinant urease subcutaneously. Freund's complete adjuvant was used in the first subcutaneous immunization and Freund's incomplete adjuvant was used in subsequent boosters. For all routes of administration, a total of four doses of vaccine were administered at seven day intervals. Mice were challenged with 10 7 H. felis two weeks after the final vaccine dose, and necropsied two weeks after challenge. Gastric H. felis infection was detected by urease activity and histology. Protection in an individual mouse was defined by a negative urease assay and by a 0 or 1+ bacterial score by histology. Oral and intragastric administration of recombinant urease provided significant protection to challenge with H. felis (86-100%) (Table 1) . Oral administration was effective both with and without co- administration of NaHC0 3 with the recombinant urease. Intragastric administration was more effective when the recombinant urease was co-administered with NaHC0 3 . Parenteral injection of the vaccine antigen was least effective. Immunized mice had significantly lower numbers of bacteria in gastric tissue after challenge than unimmunized controls. IgA antibody responses in serum and secretions were highest in mice immunized by the oral route. IgA antibodies were not elicited by parentera1 immunization. Table 1 Recombinant H. pylori urease protects mice from challenge with H. felis after mucosal but not parental immunization VACCINE ROUTE OP ADJUVANT BICARBONATE *1 % PROTECTED IMMUNIZATION (# PROTECTED/TOTAL) UREASE ASSAY HISTOLOGY* 5 PBS oral CT No 0 (0/8) 0 (0/7) 200 μg rUre oral CT No 100 (8/8)* 100 (7/7)* 200 μg rUre oral CT Yes 100 (7/7)* 86 (6/7)* a. 200 μg rUre intragastric CT No 75 (6/8)* 38 (3/8) 200 μg rUre intragastric CT Yes 100 (7/7)* 100 (7/7)* 10 10 μg rUre subcutaneous Freund'β NA 38 (3/8) 25 (2/8) a 0.24 M sodium bicarbonate was administered with vaccine and adjuvant. Percent protected (number mice with 0-1+ bacterial score/number tested) p<0.01. Fisher's exact test, compared to mice given CT alone. The effect of immunization route upon the anti-urease antibody response was examined in mice. Swiss-Webster mice were immunized four times at ten day intervals with either: 1) 200 μg recombinant purified H. pylori urease with 10 μg CT, either with or without NaHC0 3 , by oral administration; 2) 200 μg recombinant purified H. pylori urease and 10 μg CT with NaHC0 3 , by intragastric administration; or 3) 10 μg recombinant purified H. pylori urease with Freund's adjuvant by subcutaneous administration. One week after the fourth vaccine dose, mucosal and serum antibody responses were examined by ELISA using microtiter plates coated with 0.5 μg of native H. pylori urease. Serum samples were diluted 1:100 and assayed for urease-specific IgA and IgG. Fresh fecal pellets, extracted with a protease inhibitor buffer (PBS containing 5% non-fat dry milk, 0.2 μM AEBSF, 1 μg aprotinin per ml, and 10 μM leupeptin) , were examined for fecal anti-urease IgA antibody. In some experiments, fecal antibody values were normalized for total IgA content determined by ELISA, with urease-specific fecal IgA expressed in A 405 units/mg total IgA in each sample. Saliva samples were collected after stimulation with pilocarpine under keta ine anesthesia, and tested for urease-specific IgA at a dilution of 1:5. No significant differences between antibody responses of mice immunized orally with or without NaHC0 3 were detected, and the data were pooled for analysis. Mice given subcutaneous antigen developed urease-specific serum IgG, but serum and fecal IgA responses were elicited only when antigen was delivered by mucosal routes (oral or intragastric) . Mice immunized either orally or intragastrically with urease/CT were challenged with 10 7 H. felis . The pre-challenge antibody levels of orally or intragastrically immunized mice were correlated with histologically-determined bacterial scores after H. felis challenge (Fig. 5) . Although IgA responses varied considerably between individual mice, on the whole, mice with higher serum and fecal IgA levels had reduced bacterial scores. These data indicate a role for IgA in suppression of, and protection from, infection. In contrast, serum IgG antibodies did not correlate with protection. While some protected mice had no detectable IgA antibodies, high levels of anti-urease IgA were not observed in animals that developed 4+ infections after challenge. These results not only support a role for mucosal immune responses in protection, but also suggest that immune mediators other than fecal and serum IgA play a role in eradication of H. felis infection. These data show that: i) mucosal immunization is required for protective immunity; ii) the oral route of immunization is as effective, or more effective, than the intragastric route; iii) neutralization of gastric acid with NaHC0 3 is required for effective intragastric (but not oral) immunization; and iv) parenteral immunization does not stimulate mucosal immunity or provide effective protection against challenge. Schedule of immunization Alternative immunization schedules were compared in order to determine the optimal immunization time-table to elicit a protective mucosal immune response. Swiss-Webster mice were immunized with 100 μg recombinant urease in two, three, or four oral administrations, on a schedule shown in Table 2. The mucosal adjuvant CT (10 μg) was co-administered with the recombinant urease. As assessed by qualitative gastric urease assay, mice which received four weekly doses of antigen exhibited the highest levels of protection. Significant protection was also observed in mice given three doses of antigen on days 0, 7, and 21. Secretory IgA antibody responses were highest for mice given a total of four doses of recombinant urease at one week intervals. On the basis of protection ratio and antibody responses, the latter schedule was selected for further evaluation of the therapeutic and prophylactic efficacy of the vaccine. Table 2 Effect of different schedules of oral immunization on the prophylactic efficacy of urease vaccine VACCINE DOSE/ SCHEDULE (DAY IMMUNIZATION OP % PROTECTED GROUP (μg ) ' IMMUNIZATION) (#/TOXA_.) b 1 25 0, 7, 14, 21 70 (7/10)* 2 50 0, 14 20 (2/10) 3 50 0, 14 30 (3/9) 4 33.3 0, 7, 21 40 (4/10)* 5 50, 25, and 0, 7, 21 60 (6/10)* 25 6 None 0, 7, 14, 21 0 (0/10) a Each group of mice were immunized orally with a total dose of 100 μg recombinant H. pylori urease. CT (10 μg) was used at each immunization, suspended in sterile distilled water, as the mucosal adjuvant. Group 6 received CT alone on the same schedule as group 1 and acted as the control. Groups 4 and 5 compared the effect of booster doses administered after two previous weekly immunizations. b Percent protected (No. protected/No. tested) from a 10 7 challenge dose of H. felis two weeks post-immunization. Mice were sacrificed two weeks after challenge and protection was determined by the qualitative gastric urease assay. * p<0.05. Fisher's exact test, compared to mice given CT alone. The effect of different immunization schedules upon anti-urease antibody production was examined in mice. Antibody responses of mice immunized by one of the five different immunization schedules described in Table 2 were examined. Significant protection was observed in mice that received vaccine in four weekly doses or two weekly doses with a boost on day 21. Mice immunized by either of these two immunization schedules also had the highest average immune responses. The serum IgG and salivary IgA levels were highest in mice vaccinated on a schedule of four weekly doses. Dose-protection relationship Graded doses of recombinant urease were orally administered to mice to determine the minimal and optimal doses required for immunization and protection. Recombinant urease doses of 5, 10, 25, 50, and 100 μg were administered to groups of eight mice by the oral route with 10 μg CT in PBS. The antigen was given on a schedule of four weekly doses. As assessed by gastric urease and histologic bacterial score, significant protection of mice against challenge with H. felis was observed at all doses, with no significant differences between dose groups (Table 3) . A dose response effect was clearly demonstrated in serum and mucosal antibody responses to recombinant urease, with the highest immune response at the 100 μg dose level. Table 3 Recombinant H. pylori urease at doses of 5 ua or more, protects mice against challenge with * , H. felis % PROTECTED* ROUTE OF (# PROTECTED/TOTAL) VACCINE ADJUVANT IMMUNIZATION UREASE ASSAY HISTOLOGY none 10 μg CT Oral 0 (0/7) 0 (0/7) 5 μg rUre 10 μg CT Oral 86 (6/7)* 71 (5/7)* 10 μg rUre 10 μg CT Oral 88 (7/8)* 63 (5/8)* J ro 25 μg rUre 10 μg CT Oral 100 (9/9)* 100 (9/9)* 50 μg rUre 10 μg CT Oral 100 (8/8)* 88 (7/8)* 10 100 μg rUre 10 μg CT Oral 100 (7/7)* 71 (5/7)* A Percent protected (number mice with 0-20 bacteria per section/number tested) as determined by examination of silver-stained stomach sections. Comparison to sham-immunized controls. Fisher's exact test, p≤0.02. The effect of recombinant urease dosage upon the anti-urease antibody response was examined in mice. Swiss-Webster mice were immunized orally with graded doses (0, 5, 10, 25, 50, or 100 μg) of recombinant urease plus 10 μg CT as a mucosal adjuvant. IgA antibody responses in serum, feces, and saliva increased with the amount of recombinant urease administered. A 100 μg dose of recombinant urease produced the highest antibody levels. Swiss-Webster mice were orally immunized with graded doses (0, 5, 25, or 100 μg) of recombinant urease, with 25 μg enterotoxigenic E. coli heat-labile toxin (LT) as a mucosal adjuvant. One group of mice received 25 μg recombinant urease and 10 μg CT as a mucosal adjuvant for comparison. The mice were immunized orally 4 times every 7 days. Serum, feces, and saliva were collected 10 to 13 days after the last immunization and urease-specific antibody levels were determined by ELISA. Mice immunized with recombinant urease and LT developed serum and secretory antibodies against urease, with a clear dose- response effect. Strong salivary IgA antibody responses were observed in these animals. Mice immunized with urease and LT as described above were challenged with 10 7 H. felis (see Fig. 4) . The pre-challenge antibody responses of the urease/LT immunized mice were correlated with histologically- determined bacterial scores (Fig. 6) . Fully protected animals (0 bacterial score) and those with low-grade infections (1+ bacterial score) had higher levels of antibodies in all compartments than animals with more severe infections. A few protected mice had no detectable immune response, suggesting that immune mediators other than IgA antibodies play a role in eradication of H. felis infection. The ability of high doses of recombinant urease to elicit a mucosal immune response was examined by administering intragastrically 1 μg, 200 μg, or 5 mg without adjuvant. One group of mice were intragastrically immunized with 200 μg urease plus 10 μg CT as a control. Blood, feces, and saliva were collected 5 to 8 days after the last immunization. Animals were then challenged with 10 7 H. felis 10 days after the last immunization and sacrificed 14 days after challenge. H. felis infection was detected by urease activity in stomach tissue. High doses of recombinant urease elicited urease-specific serum IgG, but elicited comparatively low levels of mucosal antibodies as detected by ELISA. Animals which exhibited a urease-specific serum IgG response were fully susceptible to H. felis challenge, indicating that serum IgG does not play a role in protection. In summary, data from the above experiments investigating different administration routes, administration schedules, and mucosal adjuvants demonstrate that, when administered with an effective mucosal adjuvant, oral or intragastric administration of recombinant urease at relatively low doses elicits secretory IgA antibody and serum IgA and IgG responses. Secretory IgA antibody provides protection, while serum IgG responses do not. When protection is measured by histological bacterial counts, animals with higher IgA antibody titers were fully protected, or had significantly reduced infections, as compared to animals with lower IgA antibody titers. Animals which did not exhibit detectable IgA antibody levels developed severe infections after challenge. Antibody responses were dose-dependent and differed by the schedule of administration of antigen. The highest levels were achieved at antigen doses of 100-200 μg. Administration of four doses of antigen at one week intervals provided the optimal schedule for immunization. An additional administration route, intranasal, was investigated, as follows. Intranasal vaccination with recombinant urease Swiss Webster mice were immunized either orally or intranasally (IN) with recombinant urease or formalin-fixed urease. The amounts of antigen and adjuvant, routes of administration (IN or oral) , and immunization schedules are shown in Fig. 7. The formalin-fixed urease (Form-ure) was prepared according to the following protocol: (1) a vial containing 1 mg recombinant urease is reconstituted with 150 μL of RO/DI water; (2) 50 μL of formalin (37% formaldehyde) , diluted 1:1000 in RO/DI water, is added to the vial (final concentration of urease is 5 mg/ml) ; and (3) the vial is incubated at 35°C for 48 hours. Serum IgG, IgA, fecal IgA and salivary IgA responses in IN + CT group were higher than the oral + CT group, despite higher doses of rUrease and adjuvants that were used for oral immunization (Fig. 7 and Table 4) . Protection was measured by the urease test, as well as by determining bacterial scores on stomach tissues of sacrificed animals. One hundred percent protection was found in the IN group, as compared to 80% in the oral group, when protection was assayed by urease test. Seven of eight of the orally immunized mice were positive for bacteria on their stomach tissues, whereas only 1/10 of the mice in the IN group were positive for bacteria (see groups 3 and 6 in Table 4 and Fig. 8) . In a second experiment, mice were immunized either intragastrically (IG) or intranasally with rUrease co- administered with LT as mucosal adjuvant (see Fig. 9 for details of the experiment and the immunization schedule) . In this experiment, serum IgG, serum IgA, and salivary IgA responses in the IN + LT group were higher than in the IG + LT group, despite higher doses of antigen and adjuvant that were used for IG immunizations (Fig. 10 and Table 5, groups 4 and 8) . Mice in the IN + LT group were fully protected against H. felis challenge (10/10 compared with 3/9 untreated group) , as determined by urease test (see groups 4 and 5 of Table 5) . Table 5 Intranasal Immunization with recombinant urease and LT Ureaβe 2 week 1 sacrifice Mouse # Treatment serum IgG serum IgA salivary IgA Absorbanceςςn IAN 25 μg 5x IN 3.530 0.350 0.340 0.802 1AL 200 μg 2x IG 3.263 0.154 1.544 0.768 1AR 3.231 0.630 0.204 0.805 1ALL 3.233 0.318 0.251 0.806 1BN 3.344 0.401 0.112 0.726 1BL 3.322 0.724 2.015 0.168 1BR 3.424 0.225 0.426 0.748 I 1BLL 3.285 0.591 0.719 0.807 1BRR 3.262 0.141 0.202 0.675 1 2AN 25 μg 5x IN 3.164 0.054 0.014 0.814 2AL 200 μg lx IG 3.232 0.231 0.747 0.823 2AR 3.236 0.981 0.412 0.695 2ALL 3.303 0.122 0.832 0.813 | 2BN 3.357 0.690 0.993 0.747 I 2BL 3.264 1.002 0.840 0.704 2BR 3.284 1.377 .0934 0.161 2BLL 3.241 .0458 0.191 0.748 Further support for the efficacy of intranasal immunization is shown in Fig. 11. Briefly, this experiment showed that rUrease (10 μg) , administered by the intranasal route with CT (5 μg) , is at least as effective as rUrease (25 μg) given by the oral route with CT (10 μg) in preventing infection with H . felis. Selection of a mucosal adjuvant E. coli heat-labile toxin (LT) is a multisubunit toxin which is closely related, both biochemically and immunologically, to CT. Because the toxicity of LT is lower than CT, LT is a practical mucosal adjuvant for use in humans (Walker and Clements, Vaccine Res . 2:1-10, 1993) . Mice were orally immunized with 5 μg, 25 μg, or 100 μg recombinant urease and 25 μg recombinant LT (Swiss Serum Vaccine Institute, Berne, Switzerland) for a total of four weekly doses. Control mice received LT only or 25 μg urease vaccine with CT. Mice were challenged two weeks after the fourth dose and necropsied two weeks after challenge. Gastric urease assays indicated significant protection or suppression of the infection in immunized animals at all vaccine doses (Table 6) . Histological assessment confirmed significant reductions in bacterial scores in mice which received < 5 μg urease and LT. Protection was directly correlated with dose as determined by both gastric urease assay and histological examination, with the highest protection conferred by 100 μg of recombinant urease co-administered with LT. Antibody determinations confirmed a dose-response relationship, with highest mucosal immune responses at the 100 μg dose. When recombinant urease was administered at equivalent doses (25 μg) , LT was superior to CT as a mucosal adjuvant. These data indicate that while CT enhances the mucosal immune response to orally administered recombinant urease, LT is a better mucosal adjuvant and is thus the preferred over CT for co- administration with recombinant urease. Table 6 E. coli heat-labile enterotoxin (UP as a mucosal ad j uvant for immunization with recombinant H. pylori urease % PROTECTED VACCINE ADJUVANT (# PROTECTED/ TOTAL ) * UREASE ASSAY HISTOLOGY None 25 μg LT 0 ( 0/9 ) 0 ( 0/9 ) 25 μg rUre 10 μg CT 70 ( 7/10) * 60 (6/ 10) * 5 μg rUre 25 μg LT 787 (7/9 ) * 56 ( 5/9 ) * 25 μg rUre 25 μg LT 90 (9/10) * 80 (8/10) * 100 μg rUre 25 μg LT 100 (8/8 ) * 100 (8/8 ) * a Percent protected (number of mice with negative urease assay or bacterial score 0-l+/number tested) determined by bacterial scores of silver-stained stomach sections. * Comparison to sham-immunized controls, Fisher's exact test, p<0.03. To determine the adjuvant activity of lower doses of LT, mice were orally immunized with 25 μg of recombinant urease administered with 1, 5, 10, or 25 μg of LT. Similar protection ratios and antibody responses were observed at all LT doses. Several studies were performed to assess adjuvants other than CT and LT, and to determine whether the requirement for a mucosal adjuvant could be eliminated by administration of antigen alone at a high dose. Cholera toxin B subunit (CTB) was compared with CT as a mucosal adjuvant for urease immunization. No protective effect was observed when 200 μg urease was co-administered intragastrically with 100 μg CTB (Calbioche , La Jolla, CA) in 0.24 M sodium bicarbonate, whereas the same amount of urease with 10 μg CT gave 100% protection, as determined by gastric urease activity. An orally-active semi■synthetic analogue of muramyl dipeptide, GMDP, (N-acetylglucosaminyl-(bl-4)-N-acetyl- muramyl-L-alanyl-D-isoglutamine) , was co-administered with 25 μg urease at doses of 2, 20, and 200 μg. GMDP co-administered with recombinant urease failed to protect mice against H. felis challenge. Large doses (200 μg, l mg, or 5 mg) of recombinant urease with or without CT were intragastrically administered to mice once a week for four weeks. The intragastric route was required because volumes for high antigen doses exceeded those that could be given orally in a reproducible fashion. NaHC0 3 was co-administered to neutralize gastric acid. A total of four doses of antigen were administered at ten day intervals. Blood, feces, and saliva were collected five to eight days after the last immunization. Animals were challenged with 1 x 10 7 H. f lis , and infection was determined by urease activity in stomach tissue. In the absence of CT, high antigen doses did not confer protection against H . felis challenge, whereas controls given 200 μg of recombinant urease with CT were significantly protected (Table 7) . Urease-specific serum IgG was induced at the high recombinant urease doses without adjuvant, but serum, fecal, and salivary IgA responses were absent or minimal. Histological examination of coded specimens from animals given 5 mg doses of urease revealed no differences in bacterial scores or leukocytic infiltrates, compared with sham-immunized animals. BAD ORIGINAL Table 7 A mucosal adjuvant facilitates protection bv recombinant urease a Mean (±SD) urease-specific serum IgG or IgA expressed as A 05 units of serμ (diluted 1:100), fecal extract (diluted 1:20), or saliva (diluted 1:5). Means are sϊjown as > when 10 individual values of 4.0 (the maximum A 405 reading) were included in calculating the mean ' values. * Comparison to sham-immunized controls, Fisher's exact test, p=0.005. Therapeutic immunization of mice with H. felis gastritis The efficacy of the recombinant urease vaccine in treating Helicobacter infection in mice was evaluated by intragastrically infecting Balb/c mice with 10 7 H . felis , and, four weeks after infection, orally administering to the infected mice four weekly doses of 100 μg recombinant urease with 10 μg LT. Control mice received LT only (Fig. 12). Ten of the mice in each group were necropsied four weeks after the final immunization for examination of the degree of Helicobacter infection by quantitative gastric urease. Nine out of ten Balb/c mice were free from infection, as measured by quantitative urease assay, whereas all controls were infected. At four weeks, twelve animals receiving LT and 40 animals receiving urease + LT were reinfected with H. felis . Ten weeks after the challenge, the animals were sacrificed to determine the extent of infection by quantitative urease assay. Of nine animals which were given urease + LT, but not reinfected, 5 were still clear of infection (57%) , as determined by gastric urease activity. All twelve LT-treated animals which were re- challenged were infected. Thirty-seven of the 40 mice (93%) which were given urease + LT, and then re- challenged with H. felis , were protected as determined by reduced gastric urease activity. This experiment shows that urease vaccination not only eradicates an existing Helicobacter infection, but also protects the host against reinfection. Five of fourteen (36%) immunized Swiss-Webster mice were cured or had reduced infections, whereas all control animals were infected, although the differences in infection ratios between groups was not significant (p=0.26, Fisher's exact test, two-tailed). Infection in Swiss-Webster mice was more severe than in Balb/c mice, B^ORIG^ O 96/33732 PO7US96/0 - 51 - as measured by higher mean gastric urease activity in unimmunized animals (p < 0.0001, one-way ANOVA), possibly explaining the lower cure rates in Swiss-Webster versus Balb/c mice. Differences in susceptibility of mouse strains to H. felis has been noted (Sakagami et al . , Am. J. Gastrσmterol 89:1345, 199>4>>. By histologic assessment, all unimmunized Balb/c mice had 4+ infections (> 100 bacteria/section) , whereas reduced bacterial scores were seen in 43% of immunized mice at four weeks. At ten weeks, four of six had reduced urease activity, although only one of six had a reduced bacterial score. The role of antibodies in ffel σoJbacter therapy The role of anti-urease antibodies in Helicobacter therapy, i.e., the clearance of H. felis from infected mice, was examined by first infecting Balb/c mice with 10 7 H. felis . Four weeks after infection, the mice were orally immunized with 200 μg recombinant urease plus 10 μg CT. Control mice were given 10 μg CT only. Antigen was administered 4 times at one week intervals. Animals were sacrificed 4 and 10 weeks after the last immunization, and serum and fecal samples were collected for ELISA. Mice infected with H. felis produced serum anti- urease IgG antibodies, but no secretory anti-urease IgA response was detected. However, infected animals immunized with urease/CT exhibited high secretory anti- urease IgA antibody responses (Fig. 13) . There was no significant difference in urease specific mucosal IgA levels between immunized mice that remained infected and those with reduced bacterial scores. These data indicate that H . felis infection does not elicit a secretory anti-urease response. Thus, suppression of the IgA antibody response may play a role in the ability of H. felis to evade clearance by the immune system. In contrast, immunization of H. felis- infected mice with urease and a mucosal adjuvant resulted in strong mucosal anti-urease responses, which correlated with clearance of the H. felis infection. Correlation of protection against Helicobacter infection with gastric immune responses Several of the experiments using the mouse infection model showed that some animals rendered resistant to infection by recombinant urease vaccine lacked detectable antibody responses, or had low antibody levels, in serum, saliva, or feces. Thus, the immune response was measured in the gastric mucosa itself, in order to determine whether measurement of an immune response could be more precisely correlated with protection. Immune responses in gastric mucosa were assessed by detecting IgA antibodies and IgA-positive antibody secreting cells in intestinal and gastric murine tissue by immunohistochemistry. Portions of the stomach containing pylorus-proximal duodenum, antru , corpus, and cardia were mounted in OCT compound, flash-frozen, and cryosectioned. Sections (7 μm thick) were fixed in cold acetone, and IgA-positive cells were identified by staining with biotinylated monoclonal anti-IgA, followed by avidin conjugated to biotinylated glucose oxidase (ABC-GO, Vector Laboratories, Burlingame, CA) , and counterstained with methyl green. Urease-specific antibody secreting cells (ASC) were identified by sequentially incubating sections with recombinant urease, rabbit anti-urease, biotinylated donkey anti-rabbit Ig (Amersham, Arlington Heights, IL) , ABC-GO, TNBT, and methyl green. Control sections were incubated without urease or urease plus rabbit anti-urease to determine reactivity with the donkey secondary reagent and background endogenous glucose oxidase activity. Cryosections of cell pellets from a hybridoma which produces a monoclonal IgA antibody against H. felis ureB (MAB71) and an irrelevant IgA monoclonal (HNK20) against F glycoprσtein of respiratory syncytial virus served as positive and negative controls, respectively. Swiss-Webster mice were immunized orally with four weekly doses of 100 μg recombinant urease plus adjuvant (CT) . Control mice received adjuvant only. Groups of three mice each were necropsied at 3, 7, 14, or 21 days after the last immunization. Peyer's patches were removed from the intestines and lamina propria lymphocytes (LPL) were isolated by separation on a 40-70% Percoll gradient. IgA-positive B cells were detected by ELISPOT assays in 96-well filter plates coated with 1 μg/well recombinant urease and blocked with bovine serum albumin. Ten-fold serial dilutions of LPL were added to the wells, starting at 1 x 10 6 cells. IgA- positive ASC were detected with a biotinylated anti-mouse IgA reagent followed by streptavidin-alkaline phosphatase, and positive cells were counted by microscopy. Anti-urease IgA-positive ASC were found by ELISPOT in intestinal lamina propria as early as three days after the last immunization, peaked at seven days, and diminished thereafter (Table 8) . Urease-specific ASC represented -10% of the total IgA-positive cells observed on immunohistochemistry. Two-color immunofluorescence microscopy confirmed that urease-specific ASC were also IgA-positive. These observations confirm that an intense anti-urease IgA response occurs at the level of the intestinal mucosa after oral antigenic stimulation. The chronology and kinetics of this response are similar to those described for other oral vaccines (Czerkinsky et al., Infect . Immun . 59:996-1001, 1991; McGhee and Kyono, Infect . Agents Hum . Dis . 2:55-73, 1993) . Tflffle 8 Kinetics of induction of anti-urease iσA secreting cells after oral immunization with recombinant urease NUMBER OF ASC/ 10 LAMINA PROPRIA LYMPHOCYTES IMMUNIZATION DAY 3* DAY 7 DAY 14 DAY 21 recombinant 17 c 7400 10 2 urease + CT **3 PBS + CT 1 200 0 0 * Day after the last oral immunization. b Cholera toxin. c Average value from duplicate wells containing intestinal lymphocytes from three separate mice. To determine whether IgA-positive cells are recruited into the gastric mucosa, stomachs of orally immunized mice were examined by immunohistochemistry, as is described above. IgA-positive cells were virtually absent in gastric mucosa of immunized only and control mice, indicating that the stomach is immunologically "silent" until stimulated by Helicobacter challenge. The role of the stomach as an immunological effector organ in challenged, immunized mice was examined. Mice were given four weekly oral doses of 200 μg recombinant urease with 10 μg CT. Control mice received CT only. One week after immunization, the mice were challenged. Mice were necropsied prior to challenge and at 7, 14, 28, 70, and 133 days after challenge. Prior to challenge, no IgA-positive ASC were found. At all time intervals after challenge, IgA- positive ASC were present in large numbers in the gastric mucosae of immunized mice, with a peak at seven days (Fig. 14) . The number of IgA-positive ASC greatly exceeded that in unimmunized (CT only) mice, especially 7-28 days after challenge. The anatomical localization of IgA-positive ASC also differed, with immunized mice having cells throughout the mucosa, in the a-ύna propria, and around the crypts, but rarely under the surface epithelium. Urease-specific and IgA-positive ASC revealed that the majority of urease-specific cells in gastric mucosa were IgA-positive. These observations indicate that the gastric mucosa of animals primed by prior immunization becomes immunologically activated only after antigenic stimulation by H. felis . The resulting tissue response is characterized by rapid, intense, and long-lasting recruitment of IgA-positive B cells, many of which are urease specific. This response is quantitatively greater than in immunologically naive mice after challenge. Moreover, the localization of IgA-positive cells in immunized mice differs from that in immunologically naive mice that are challenged and become persistently infected with H. felis . The enhanced IgA-positive ASC response in gastric mucosa suggests a basis for the protection conferred by immunization against H. felis challenge. These data are concordant with studies of cholera vaccine, in which immunological memory responses triggered within hours after bacterial challenge were sufficient to provide protection (Lycke and Holmgren, Scand. J. Immunol . 25:407-412, 1987). Correlation of the gastric immune response and bacterial l3__ The relationship between the gastric tissue immune response and bacterial infection was defined at the structural level. Swiss-Webster mice were immunized with BADORIGINAL 4 weekly doses of 200 μg recombinant urease with 10 μg CT. One week after the last immunization, the mice were challenged with 10 7 H. felis . Animals were sacrificed 0, 1, 7, 14, 28, 70, and 133 days after challenge, and H. felis colonization was assessed by light and electron micr-σscopy. Within 24 hours after challenge, both immunized and unimmunized mice had substantial numbers of H. felis within the lumen of gastric pits (Fig. 15) . Within seven days after challenge, the bacteria were cleared from the immunized mice, but were still present in high numbers in the gastric pits and the lumens of unimmunized mice. Bacteria were also associated with the apical membrane of mucus-secreting cells of the unimmunized mice. The clearance of bacteria from the gastric mucosa of immunized mice corresponded to the appearance of IgA- positive ASC and anti-urease ASC in the gastric tissue. These results suggest the following sequence of events: 1) challenge of immunized mice results in transient colonization of gastric epithelium with H. felis; 2) unimmunized animals remain infected, while animals immunized with recombinant urease clear the bacteria from the stomach during the first week after challenge; and 3) clearance of infection is associated with the recruitment of IgA-positive urease-specific ASC to gastric mucosa. A similar mechanism may be responsible for the clearance of bacteria from the gastric mucosa of chronically infected animals that are subjected to therapeutic immunization. Antigenic conservation of urease among strains of fft pylori The ability of various antisera to bind multiple clinical isolates of H. pylori was tested. The antisera included MPA3, a hyperimmune rabbit serum prepared against purified H. pylori urease, and sera and secretions (gastric wick samples and saliva) from mice immunized with recombinant urease. Antibody preparations were tested by immunoblotting for recognition of the homologous H. pylori strain (Hp630) , ATCC 43504 type strain, and five clinical isrolatβs from ulcer patients at St. Bartholomew's Hospital, London, collected within the last five years. All antisera recognized the UreA and UreB subunits of all H. pylori strains, as well as purified native and recombinant H. pylori ureases, native and recombinant H. felis urease, and native H. mustelae urease. In addition, urease-specific IgA antibodies in gastric secretions and saliva of immunized mice reacted with both UreA and UreB of all H. pylori strains, as well as heterologous ureases. Immunologic recognition was greater for UreB than for UreA. Sham-immunized mice showed no reactivity with any urease subunits. These results demonstrate that H. pylori strains express ureases that are highly conserved at the antigenic level. Thus, antigenic variation among H. pylori strains is not a significant factor for development of a recombinant urease vaccine. Combination methods and compositions for treating Helicobacter infection Gastroduodenal infections, such as Helicobacter infection, may be treated by oral administration of a vaccine antigen (e . g. , H. pylori urease) and a mucosal adjuvant, in combination with an antibiotic, an antisecretory agent, a bismuth salt, an antacid, sucralfate, or a combination thereof. Examples of such compounds which may be administered with the vaccine antigen and the adjuvant are: antibiotics, including, e . g. , macrolides, tetracyclines, 0-lactams, aminoglycosides, quinolones, penicillins, and derivatives thereof (specific examples of antibiotics that may be used in the invention include, e.g., amoxicillin, clarithromycin, tetracycline, metronidizole, erythromycin, cefuroxime, and erythromycin) ; antisecretory agents, including, e .g. , H 2 -receptor antagonists (e.g., cimetidine, ranitidine, famotidine, nizatidine, and roxatidine) , proton pump inhibitors (e.g., omeprazole, lansoprazole, and pantoprazole) , prostaglandin analogs (e.g., misoprostil and enprostil) , and anticholinergic agents (e.g., pirenzepine, telenzepine, carbenoxolone, and proglumide) ; and bismuth salts, including colloidal bismuth subcitrate, tripotassiu dicitrate bismuthate, bismuth subsalicylate, bicitropeptide, and pepto-bismol (see, e .g. , Goodwin et al . , Helicobacter pylori , Biology and Clinical Practice, CRC Press, Boca Raton, FL, pp 366-395, 1993; Physicians" Desk Reference, 49 th edn. , Medical Economics Data Production Company, Montvale, New Jersey, 1995) . In addition, compounds containing more than one of the above-listed components coupled together, e .g. , ranitidine coupled to bismuth subcitrate, may be used. Amounts of the above-listed compounds used in the methods and compositions of the invention may readily be determined by one skilled in the art. In addition, one skilled the art may readily design treatment/immunization schedules. For example, the non-vaccine components may be administered on days 1-14, and the vaccine antigen + adjuvant may be administered on days 7, 14, 21, and 28. In addition to urease, other Helicobacter antigens may be used in the methods and compositions of the invention involving combination therapy. For example, Helicobacter heat shock proteins A or B (HspA or HspB; WO 94/26901) , Helicobacter adhesion lipoprotein A (AlpA; The nucleotide sequence encoding AlpA is set forth in SEQ ID NO:6 and the corresponding amino acid sequence of AlpA is in SEQ ID Nθ:7), Helicobacter (e . g. , H. pylori ) clpB (clpB is encoded by the insert in the plasmid in bacterial strain XLOLR HP CP6, which was deposited with the National Collections of Industrial & Marine Bacteria in Aberdeen, Scotland, and designated with NCIMB accession number 40748) , or the 16-19 kD Helicobacter antigen recognized by monoclonal antibody IgG 50 (IgG 50 may be obtained from hybridoma cell line #50-G 6 -B 7 , which was deposited with the ATCC and designated with ATCC accession number HB-11952) may be used. In addition, Helicobacter surface-exposed or secreted antigens identified using the transposon shuttle mutagenesis method of Haas et al . may be used as vaccine antigens in the invention (Haas et al . , Gene 130:23-31, 1993; Haas et al . , Abstract from the VI th Workshop on Gastroduodenal Pathology and Helicobacter pylori, Brussels, September 21-25, 1993; Odenbreit et al . , Gut, An International Journal of Gastroenterology and Hepatology, Abstract from the VIII th International Workshop on Gastro-duodenal Pathology and Helicobacter pylori , Edinburgh, Scotland, July 7-9, 1995). In this method, cloned H. pylori genes are mutagenized by transposon insertion mutagenesis in Escherichia coli . The inactivated genes are reintroduced into H. pylori by DNA transformation, and allelic replacement results in the generation of corresponding H. pylori mutants. The transposon used in one variation of this method carries blaM, which is a 5'-truncated version of the 0-lactamase gene. Use of this transposon facilitates tagging of genes encoding leader peptide- containing exported proteins, and thus direct selection of clones containing mutants of exported proteins (e.g., cell surface proteins such as adhesins and cytotoxins, as well as other potential cell surface virulence factors) , which are strong candidates for vaccine antigens. In O 96/33732 PCMJS96/05800 - 60 - addition to Helicobacter antigens, antigens from non- Helicobacter gastroduodenal pathogens may be used in methods and compositions for preventing and/or treating infection caused by their respective pathogens. Polypeptide fragments containing protective and/or therapeutic epitopes of the above-listed antigens may also be used in the invention. Adjuvants which may be used in the methods and compositions of the invention include mucosal adjuvants, e.g., the heat-labile enterotoxin of E . Coli (LT) , a cholera toxin, a C. difficile toxin, or derivatives (e.g., fragments, mutants, or toxoids having adjuvant activity) , or combinations thereof. For example, a fragment containing the 794 carboxyl-terminal amino acids of C. difficile Toxin A (see, e.g., Dove et al . , supra, for the sequence of C. difficile Toxin A) may be used. The amounts of vaccine antigen and adjuvant which may be used in these compositions and methods of the invention are described above. The efficacy of a composition containing a vaccine (H . pylori urease + LT) , an antibiotic (amoxicillin) , and a bismuth salt (pepto-bismol) in the treatment of Helicobacter infection is illustrated below. Combination therapy for Helicobacter infection of mice One month after infection with -10 7 H. felis , mice were treated with amoxicillin (1.5 mg/30 g mouse) and/or pepto-bismol (0.2 mg/30 g mouse) once per day for 14 days (days 1-14) , and/or a vaccine composition containing 100 μg recombinant H . pylori urease + 5 μg LT on days 7, 14, 21, and 28 (see Table 9 for an illustration of the combinations used) . Helicobacter infection in these mice was measured by quantitative gastric urease assay (see above) 1 week and 4 weeks after termination of the treatment (day 28). As is illustrated in Table 9, the most effective treatment regimen, achieving 100% clearance, involved administration of a vaccine (urease + LT) , an antibiotic (amoxicillin) , and a bismuth salt (pepto-bismol) . Table 9 % Mice Cleared of H. felis Infection treatment 1 week _____ amoxicillin 60% 40% pepto-bismol 0% 0% amoxicillin + pepto-bismol 80% 40% vaccine 70% 70% vaccine + amoxicillin 89% 56% vaccine + pepto-bismol -70% -70% vaccine + amoxicillin + pepto-bismol 100% 100% (vaccine = urease + adjuvant) Identification of human patients for administration of recombinant H. pylori urease vaccine The recombinant H. pylori urease vaccine of the invention may be administered to uninfected individuals as a prophylactic measure or to individuals infected with Helicobacter as an antibacterial therapy. Individuals selected for prophylactic administration of recombinant urease include any individual at risk of Helicobacter infection as based upon age, geographical location, or the presence of a condition which renders the individual susceptible to Helicobacter infection. Individuals at particularly high risk of infection, or who would be most severely affected by infection, include individuals in developing countries, infants and children in developing and in developed countries, individuals with naturally or artificially low gastric acid pH, submarine crews, and military personnel. Individuals who may receive the recombinant Η. pylori urease vaccine as a therapeutic include those individuals with symptoms of gastritis or other gastrointestinal disorders which may be associated with H . pylori infection. The clinical symptoms associated with gastritis, an inflammation of the stomach mucosa, include a broad range of poorly-defined, and generally inadequately treated, symptoms such as indigestion, "heart burn," dyspepsia, and excessive eructation. A general discussion of gastritis appears in Sleisenger and Fordtran, In Gastrointestinal Disease. 4th Edn. , Saunders Publishing Co., Philadelphia, PA, pp. 772-902, 1989. Individuals who have a gastrointestinal disorder may also be treated by administration of the vaccine of the invention. Gastrointestinal disorders includes any disease or other disorder of the gastrointestinal tract of a human or other mammal. Gastrointestinal disorders include, for example, disorders not manifested by the presence of ulcerations in the gastric mucosa (non- ulcerative gastrointestinal disorder) , including chronic or atrophic gastritis, gastroenteritis, non-ulcer dyspepsia, esophageal reflux disease, gastric motility disorders, and peptic ulcer disease (e .g. , gastric and duodenal ulcers) . Peptic ulcers involve ulceration and formation of lesions of the mucous membrane of the esophagus, stomach, or duodenum, and is generally characterized by loss of tissue due to the action of digestive acids, pepsin, or other factors. Alternatively, it may be desirable to administer the vaccine to asymptomatic individuals, particularly where the individual may have been exposed to H. pylori or has a condition rendering the individual susceptible to infection. Infection with Helicobacter can be readily diagnosed by a variety of methods well known in the art, including, e . g. , by serology, 13 C breath test, and/or gastrosσopic examination. Preparation of purified recombinant urease for administration to patients The process for formulation of recombinant urease involves combining urease with a stabilizer, (e.g., a carbohydrate mannitol) and freeze drying (i.e., lyophilizing) the product. This process prevents degradation by aggregation and fragmentation. In addition, the product is stable for months following lyophilization. The process which leads to instability involves formation of disulfide bonds between protein subunits, and is effectively inhibited by lyophilization. Recombinant urease is freeze-dried following the final purification step. The purified protein product (approximately 4 mg/ml) is dialyzed against 2% sucrose, and this solution is transferred to lyophilization vials. The vialed solution is either: (1) frozen in liquid nitrogen, and then placed into the lyophilizer, or (2) cooled to 4°C, and then placed in the lyophilizer, where it is frozen to -40°C, or lower. Lyophilization is carried out using standard methods. The freeze-dried product may be reconstituted in water. Mode of administration to human patients Recombinant H. pylori urease is administered to a mucosal surface of the individual in order to stimulate a mucosal immune response effective to provide protection to subsequent exposure to Helicobacter and/or facilitate clearance of a pre-existing Helicobacter infection. Preferably, recombinant urease is administered so as to elicit a mucosal immune response associated with production of anti-urease IgA antibodies and/or infiltration of lymphocytes into the gastric mucosa. The recombinant urease may be administered to any mucosal surface of the patient. Preferable mucosal surfaces are intranasal, oral, and rectal (e.g., by use of an anal suppository) . In addition to being administered to a single mucosal surface, the vaccine of the invention may be administered to combinations of mucosal surfaces (e.g., oral+rectal, oral+intranasal, or rectal+intranasal) . In the case of oral administration, it is preferable that the administration involves ingestion of the vaccine, but the vaccine may also be administered as a mouth wash, so that an immune response is stimulated in the mucosal surface of the oral cavity, without actual ingestion of the vaccine. Alternatively, a systemic mucosal immune response may be achieved by administration of the vaccine to a mucosal surface of the eye in the form of, e.g., an eye drop or an intraocular implant. Dosages of recombinant H . pylori urease administered to the individual as either a prophylactic therapy or an antibacterial therapy can be determined by one skilled in the art. Generally, dosages will contain between about 10 μg to 1,000 mg, for example, between about 10 mg and 500 mg, 30 mg and 120 mg, 40 mg and 70 mg, or 60 mg recombinant H. pylori urease. At least one dose of the recombinant H. pylori urease will be administered to the patient, for example, at least two doses, at least four doses, or with up to six or more total doses administered. It may be desirable to administer booster doses of the recombinant urease at one or two week intervals after the last immunization, generally one booster dose containing less than, or the same amount of, recombinant H. pylori urease as the initial dose administered. For example, the vaccine regimen may be administered in four doses at one week intervals. The priming and booster doses may be administered to the same or different mucosal surfaces. In the case of different mucosal surfaces, for example, an oral priming dose may be followed by intranasal or rectal boosters, an intranasal priming dose may be followed by oral or rectal boosters, or a rectal priming dose may be followed by oral or intranasal boosters. Recombinant H. pylori urease may be co- administered with a mucosal adjuvant. The mucosal adjuvant may be any mucosal adjuvant known in the art which is appropriate for human use. For example, the mucosal adjuvant may be cholera toxin (CT) , enterotoxigenic E. coli heat-labile toxin (LT) , or a derivative, subunit, or fragment of CT or LT which retains adjuvanticity. The mucosal adjuvant is co- administered with recombinant H. pylori urease in an amount effective to elicit or enhance a mucosal immune response, particularly a humoral and/or a mucosal immune response. The ratio of adjuvant to recombinant urease may be determined by standard methods by one skilled in the art. For example, the adjuvant may be present at a ratio of 1 part adjuvant to 10 parts recombinant urease. A buffer may be administered prior to administration of recombinant H. pylori urease in order to neutralize or increase the pH of the gastric acid. Any buffer that is effective in raising the pH of gastric acid and is appropriate for human use may be used. For example, buffers such as sodium bicarbonate, potassium bicarbonate, and sodium phosphate may be used. In the case of oral administration, the vaccine may be buffer- free, i.e., no amount of a pH-raising buffer compound effective to significantly affect gastric acid pH is administered to the patient either prior to, or concomitant with, administration of the vaccine recombinant urease. The vaccine formulation containing recombinant urease may contain a variety of other components, including stabilizers, flavor enhancers (e.g., sugar), or, where the vaccine is administered as an antibacterial therapeutic, other compounds effective in facilitating clearance and/or eradication of the infecting bacteria. For prophylactic therapy, the vaccine containing recombinant H . pylori urease may be administered at any time prior to contact with, or establishment of, Helicobacter infection. Because the vaccine can also act as an antibacterial therapy, there is no contraindication for administration of the vaccine if there is marginal evidence or suspicion of a pre-existing Helicobacter infection (e.g., an asymptomatic infection). For use of the vaccine as an antibacterial therapy, recombinant H. pylori urease may be administered at any time before, during, or after the onset of symptoms associated with Helicobacter infection or with gastritis, peptic ulcers or other gastrointestinal disorder. Although it is not a prerequisite to the initiation of therapy, one may confirm diagnosis of Helicobacter infection by, e .g. , a 13 C breath test, serology, gastroscopy, biopsy, or another Helicobacter detection method known in the art. The progress of immunized patients may be followed by general medical evaluation, screening for H. pylori infection by serology, 13 C breath test, and/or gastroscopic examination. Example of administration of recombinant H . pvlori urease to a human A vaccine composed of 60 mg of recombinant H. pylori urease in a total volume of 15 ml of water containing 2% weight/volume sucrose, pH 7.5 is orally administered to the patient. Administration of the vaccine is repeated at weekly intervals for a total of 4 doses. Symptoms are recorded daily by the patient. To determine adverse effects, physician interviews are performed weekly during the period of vaccine administration, as well as 1 week and 1 month after the last immunization. Anti-urease antibodies are measured in serum and saliva, and antibody-secreting cells are monitored in peripheral blood collected 7 days after the last immunization. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: OraVax, Inc. (ii) TITLE OF INVENTION: MULTIMERIC, RECOMBINANT UREASE VACCINE (iii) NUMBER OF SEQUENCES: 7 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: Fish & Richardson P.C. (B) STREET: 225 Franklin Street (C) CITY: Boston (D) STATE: MA (E) COUNTRY: USA (F) ZIP: 02110-2804 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy diβk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: PatentIn Release #1.0, Version #1.25 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: PCT/US96/ (B) FILING DATE: 23-APR-1996 (C) CLASSIFICATION: (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: 08/431,041 (B) FILING DATE: 28-APR-1995 (C) CLASSIFICATION (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: 08/568,122 (B) FILING DATE: 06-DEC-1995 (C) CLASSIFICATION ( iii) ATTORNEY/AGENT INFORMATION: (A) NAME: Clark, Paul T. (B) REGISTRATION NUMBER: 30,162 (C) REFERENCE/DOCKET NUMBER: 06132/020001 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: (617) 542-5070 (B) TELEFAX: (617) 542-8906 (2) INFORMATION FOR SEQ ID NO:l: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 2735 base pairβ (B) TYPE: nucleic acid (C) STRANDEDNESS: double (D) TOPOLOGY: linear (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:l: TAATACGACT CACTATAGGG GAATTGTGAG CGGATAACAA TTCATCCACC TTGATTGCGT 60 TATGTCTTCA AGGAAAAACA CTTTAAGAAT AGGAGAATGA GATGAAACTC ACCCCAAAAG 120 AGTTAGATAA GTTGATGCTC CACTACGCTG GAGAATTGGC TAAAAAACGC AAAGAAAAAG 180 GCATTAAGCT TAACTATGTA GAAGCAGTAG CTTTGATTAG TGCCCATATT ATGGAAGAAG 240 CGAGAGCTGG TAAAAAGACT GCGGCTGAAT TGATGCAAGA AGGGCGCACT CTTTTAAAAC 300 CAGATGATGT GATGGATGGC GTGGCAAGCA TGATCCATGA AGTGGGTATT GAAGCGATGT 360 TTCCTGATGG GACTAAACTC GTAACCGTGC ATACCCCTAT TGAGGCCAAT GGTAAATTAG 420 TTCCTGGTGA GTTGTTCTTA AAAAATGAAG ACATCACTAT CAACGAAGGC AAAAAAGCCG 480 TTAGCGTGAA AGTTAAAAAT GTTGGCGACλ GACCGGTTCA AATCGGCTCA CACTTCCATT 540 TCTTTGAAGT GAATAGATGC CTAGACTTTG ACAGAGAAAA AACTTTCGGT AAACGCTTAG 600 ACATTGCGAG CGGGACAGCG GTAAGATTTG AGCCTGGCGA AGAAAAATCC GTAGAATTGA 660 TTGACATTGG CGGTAACAGA AGAATCTTTG GATTTAACGC ATTGGTTGAT AGACAAGCAG 720 ACAACGAAAG CAAAAAAATT GCTTTACACA GAGCTAAAGA GCGTGGTTTT CATGGCGCTA 780 AAAGCGATGA CAACTATGTA AAAACAATTA AGGAGTAAGA AATGAAAAAG ATTAGCAGAA 840 AAGAATATGT TTCTATGTAT GGTCCTACTA CAGGCGATAA AGTGAGATTG GGCGATACAG 900 ACTTGATCGC TGAAGTAGAA CATGACTACA CCATTTATGG CGAAGAGCTT AAATTCGGTG 960 GCGGTAAAAC CCTAAGAGAA GGCATGAGCC AATCTAACAA CCCTAGCAAA GAAGAGTTGG 1020 ATTTAATTAT CACTAACGCT TTAATCGTGG ATTACACCGG TATTTATAAA GCGGATATTG 1080 GTATTAAAGA TGGCAAAATC GCTGGCATTG GTAAAGGCGG TAACAAAGAC ATGCAAGATG 1140 GCGTTAAAAA CAATCTTAGC GTAGGTCCTG CTACTGAAGC CTTAGCCGGT GAAGGTTTGA 1200 TCGTAACGGC TGGTGGTATT GACACACACA TCCACTTCAT TTCACCCCAA CAAATCCCTA 1260 CAGCTTTTGC AAGCGGTG A ACAACCATGA TTGGTGGTGG AACCGGTCCT GCTGATGGCA 1320 CTAATGCGAC TACTATCACT CCAGGCAGAA GAAATTTAAA ATGGATGCTC AGAGCGGCTG 1380 AAGAATATTC TATGAATTTA GGTTTCTTGG CTAAAGGTAA CGCTTCTAAC GATGCGAGCT 1440 TAGCCGATCA AATTGAAGCC GGTGCGATTG GCTTTAAAAT TCACGAAGAC TGGGGCACCA 1500 CTCCTTCTGC AATCAATCAT GCGTTAGATG TTGCGGACAA ATACGATGTG CAAGTCGCTA 1560 TCCACACAGA CACTTTGAAT GAAGCCGGTT GTGTAGAAGA CACTATGGCT GCTATTGCTG 1620 GACGCACTAT GCACACTTTC CACACTGAAG GCGCTGGCGG CGGACACGCT CCTGATATTA 1680 TTAAAGTAGC CGGTGAACAC AACATTCTTC CCGCTTCCAC TAACCCCACC ATCCCTTTCA 1740 CCGTGAATAC AGAAGCAGAG CACATGGACA TGCTTATGGT GTGCCACCAC TTGGATAAAA 1800 GCATTAAAGA AGATGTTCAG TTCGCTGATT CAAGGATCCG CCCTCAAACC ATTGCGGCTG 1860 AAGACACTTT GCATGACATG GGGATTTTCT CAATCACCAG TTCTGACTCT CAAGCGATGG 1920 GCCGTGTGGG TGAAGTTATC ACTAGAACTT GGCAAACAGC TGACAAAAAC AAGAAAGAAT 1980 TTGGCCGCTT GAAAGAAGAA AAAGGCGATA ACGACAACTT CAGGATCAAA CGCTACTTGT 2040 CTAAATACAC CATTAACCCA GCGATCGCTC ATGGGATTAG CGAGTATGTA GGTTCAGTAG 2100 AAGTGGGCAA AGTGGCTGAC TTGGTATTGT GGAGTCCAGC ATTCTTTGGC GTGAAACCCA 2160 ACATGATCAT CAAAGGCGGA TTCATTGCGT TAAGCCAAAT GGGCGATGCG AACGCTTCTA 2220 TCCCTACCCC ACAACCGGTT TATTACAGAG AAATGTTCGC TCATCATGGT AAAGCTAAAT 2280 ACGATGCAAA CATCACTTTT GTGTCTCAAG CGGCTTATGA CAAAGGCATT AAAGAAGAAT 2340 TAGGACTTGA AAGACAAGTG TTGCCGGTAA AAAATTGCAG AAATATCACT AAAAAAGACA 2400 TGCAATTCAA CGACACTACT GCTCACATTG AAGTCAATCC TGAAACTTAC CATGTGTTCG 2460 TGGATGGCAA AGAAGTAACT TCTAAACCAG CCAATAAAGT GAGCTTGGCG CAACTCTTTA 2520 GCATTTTCTA GGATTTTTTA GGAGCAACGC TTCCTTAAAT CCTGAATTCG AGCTCCGTCG 2580 ACAAGCTTGC GGCCGCACTC GAGCACCACC ACCACCACCA CTGAGATCCG GCTGCTAACA 2640 AAGCCCGAAA GGAAGCTGAG TTGGCTGCTG CCACCGCTGA GCAATAACTA GCATAACCCC 2700 TTGGGGCCTC TAAACGGGTC TTGAGGGGTT TTTTG 2735 (2) INFORMATION FOR SEQ ID NO:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 238 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: Met Lys Leu Thr Pro Lys Glu Leu Asp Lys Leu Met Leu His Tyr Ala 1 5 10 15 Gly Glu Leu Ala Lys Lys Arg Lys Glu Lys Gly lie Lys Leu Asn Tyr 20 25 30 Val Glu Ala Val Ala Leu lie Ser Ala His lie Met Glu Glu Ala Arg 35 40 45 Ala Gly Lys Lys Thr Ala Ala Glu Leu Met Gin Glu Gly Arg Thr Leu 50 55 60 Leu Lys Pro Asp Asp Val Met Asp Gly Val Ala Ser Met lie His Glu 65 70 75 80 Val Gly lie Glu Ala Met Phe Pro Asp Gly Thr Lye Leu Val Thr Val 85 90 95 His Thr Pro lie Glu Ala Asn Gly Lys Leu Val Pro Gly Glu Leu Phe 100 105 110 Leu Lys Asn Glu Asp lie Thr lie Asn Glu Gly Lys Lys Ala Val Ser 115 120 125 Val Lys Val Lys Asn Val Gly Asp Arg Pro Val Gin lie Gly Ser His 130 135 140 Phe His Phe Phe Glu Val Asn Arg Cys Leu Aβp Phe Asp Arg Glu Lys 145 150 155 160 Thr Phe Gly Lys Arg Leu Asp lie Ala Ser Gly Thr Ala Val Arg Phe 165 170 175 Glu Pro Gly Glu Glu Lys Ser Val Glu Leu lie Asp lie Gly Gly Asn 180 185 190 Arg Arg lie Phe Gly Phe Asn Ala Leu Val Asp Arg Gin Ala Asp Asn 195 200 205 Glu Ser Lys Lys lie Ala Leu His Arg Ala Lys Glu Arg Gly Phe His 210 215 220 Gly Ala Lye Ser Asp Aβp Asn Tyr Val Lys Thr lie Lys Glu 225 230 235 (2) INFORMATION FOR SEQ ID NO:3: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 566 amino acids (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3: Met Lys Lys lie Ser Arg Lys Glu Tyr Val Ser Met Tyr Gly Pro Thr 1 5 10 15 Thr Gly Asp Lys Val Arg Leu Gly Asp Thr Aβp Leu lie Ala Glu Val 20 25 30 Glu His Aβp Tyr Thr lie Tyr Gly Glu Glu Leu Lys Phe Gly Gly Gly 35 40 45 Lys Thr Leu Arg Glu Gly Met Ser Gin Ser Asn Aβn Pro Ser Lys Glu 50 55 60 Glu Leu Asp Leu lie lie Thr Asn Ala Leu lie Val Asp Tyr Thr Gly 65 70 75 80 lie Tyr Lys Ala Asp lie Gly lie Lys Asp Gly Lys lie Ala Gly lie 85 90 95 Gly Lys Gly Gly Asn Lys Asp Met Gin Asp Gly Val Lys Aβn Asn Leu 100 105 110 Ser Val Gly Pro Ala Thr Glu Ala Leu Ala Gly Glu Gly Leu lie Val 115 120 125 Thr Ala Gly Gly lie Asp Thr His lie His Phe lie Ser Pro Gin Gin 130 135 140 lie Pro Thr Ala Phe Ala Ser Gly Val Thr Thr Met lie Gly Gly Gly 145 150 155 160 Thr Gly Pro Ala Asp Gly Thr Asn Ala Thr Thr lie Thr Pro Gly Arg 165 170 175 Arg Aβn Leu Lye Trp Met Leu Arg Ala Ala Glu Glu Tyr Ser Met Aβn 180 185 190 Leu Gly Phe Leu Ala Lys Gly Aβn Ala Ser Aβn Aβp Ala Ser Leu Ala 195 200 205 Aβp Gin lie Glu Ala Gly Ala lie Gly Phe Lye lie Hie Glu Aβp Trp 210 215 220 Gly Thr Thr Pro Ser Ala lie Aβn Hie Ala Leu Aβp Val Ala Aβp Lye 225 230 235 240 Tyr Aβp Val Gin Val Ala lie Hie Thr Aβp Thr Leu Aβn Glu Ala Gly 245 250 255 Cyβ Val Glu Aβp Thr Met Ala Ala He Ala Gly Arg Thr Met Hie Thr 260 265 270 Phe Hie Thr Glu Gly Ala Gly Gly Gly Hie Ala Pro Asp He He Lye 275 280 285 Val Ala Gly Glu Hie Aβn He Leu Pro Ala Ser Thr Aβn Pro Thr He 290 295 300 Pro Phe Thr Val Asn Thr Glu Ala Glu His Met Aβp Met Leu Met Val 305 310 315 320 Cyβ Hie Hie Leu λβp Lye Ser He Lye Glu Aβp Val Gin Phe Ala Aβp 325 330 335 Ser Arg He Arg Pro Gin Thr He Ala Ala Glu Aβp Thr Leu Hie Aβp 340 345 350 Met Gly He Phe Ser He Thr Ser Ser Aβp Ser Gin Ala Met Gly Arg 355 360 365 Val Gly Glu Val He Thr Arg Thr Trp Gin Thr Ala Aβp Lye Aβn Lye 370 375 380 Lye Glu Phe Gly Arg Leu Lys Glu Glu Lys Gly Asp Asn Asp Aβn Phe 385 390 395 400 Arg He Lys Arg Tyr Leu Ser Lye Tyr Thr He Aβn Pro Ala He Ala 405 410 415 Hie Gly He Ser Glu Tyr Val Gly Ser Val Glu Val Gly Lye Val Ala 420 425 430 Aβp Leu Val Leu Trp Ser Pro Ala Phe Phe Gly Val Lys Pro Asn Met 435 440 445 He He Lys Gly Gly Phe He Ala Leu Ser Gin Met Gly Asp Ala Asn 450 455 460 Ala Ser He Pro Thr Pro Gin Pro Val Tyr Tyr Arg Glu Met Phe Ala 465 470 475 480 His Hie Gly Lys Ala Lys Tyr Asp Ala Asn He Thr Phe Val Ser Gin 485 490 495 Ala Ala Tyr Aβp Lye Gly He Lye Glu Glu Leu Gly Leu Glu Arg Gin 500 505 510 Val Leu Pro Val Lye Aβn Cys Arg Asn He Thr Lys Lye Aβp Met Gin 515 520 525 Phe Aβn Aβp Thr Thr Ala Hie He Glu Val Aβn Pro Glu Thr Tyr Hie 530 535 540 Val Phe Val Aβp Gly Lye Glu Val Thr Ser Lye Pro Ala Aβn Lye Val 545 550 555 560 Ser Leu Ala Gin Leu Phe 565 (2) INFORMATION FOR SEQ ID NO:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 28 baβe pairβ (B) TYPE: nucleic acid (C) STRANDEDNESS: both (D) TOPOLOGY: both (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4: CGGGATCCAC CTTGATTGCG TTATGTCT 28 (2) INFORMATION FOR SEQ ID NO:5: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 baβe pairβ (B) TYPE: nucleic acid (C) STRANDEDNESS: both (D) TOPOLOGY: both (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5: CGGAATTCAG GATTTAAGGA AGCGTTG 27 (2) INFORMATION FOR SEQ ID NO: : (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 1557 baβe pairβ (B) TYPE: nucleic acid (C) STRANDEDNESS: both (D) TOPOLOGY: both (ii) MOLECULE TYPE: cDNA (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6: ATGATAAAAA AGAATAGAAC GCTGTTTCTT AGTCTAGCCC TTTGCGCTAG CATAAGTTAT 60 GCCGAAGATG ATGGAGGGTT TTTCACCGTC GGTTATCAGC TCGGGCAAGT CATGCAAGAT 120 GTCCAAAACC CAGGCGGCGC TAAAAGCGAC GAACTCGCCA GAGAGCTTAA CGCTGATGTA 180 ACGAACAACA TTTTAAACAA CAACACCGGA GGCAACATCG CAGGGGCGTT GAGTAACGCT 240 TTCTCCCAAT ACCTTTATTC GCTTTTAGGG GCTTACCCCA CAAAACTCAA TGGTAGCGAT 300 GTGTCTGCGA ACGCTCTTTT AAGTGGTGCG GTAGGCTCTG GGACTTGTGC GGCTGCAGGG 360 ACGGCTGGTG GCACTTCTCT TAACACTCAA AGCACTTGCA CCGTTGCGGG CTATTACTGG 420 CTCCCTAGCT TGACTGACAG GATTTTAAGC ACGATCGGCA GCCAGACTAA CTACGGCACG 480 AACACCAATT TCCCCAACAT GCAACAACAG QTCACCTACT TGAATGCGGG GAATGTGTTT 540 TTTAATGCGA TGAATAAGGC TTTAGAGAAT AAGAATGGAA CTAGTAGTGC TAGTGGAACT 600 AGTGGTGCGA CTGGTTCAGA TGGTCAAACT TACTCCACAC AAGCTATCCA ATACCTTCAA 660 GGCCAACAAA ATATCTTAAA TAACGCAGCG AACTTGCTCA AGCAAGATGA ATTGCTCTTA 720 GAAGCTTTCA ACTCTGCCGT AGCCGCCAAC ATTGGGAATA AGGAATTCAA TTCAGCCGCT 780 TTTACAGGTT TGGTGCAAGG CATTATTGAT CAATCTCAAG CGGTTTATAA CGAGCTCACT 840 AAAAACACCA TTAGCGGGAG TGCGGTTATT AGCGCTGGGA TAAACTCCAA CCAAGCTAAC 900 GCTGTGCAAG GGCGCGCTAG TCAGCTCCCT AACGCTCTTT ATAACGCGCA AGTAACTTTG 960 GATAAAATCA ATGCGCTCAA TAATCAAGTG AGAAGCATGC CTTACTTGCC CCAATTCAGA 1020 GCCGGGAACA GCCGTTCAAC GAATATTTTA AACGGGTTTT ACACCAAAAT AGGCTATAAG 1080 CAATTCTTCG GGAAGAAAAG GAATATCGGT TTGCGCTATT ATGGTTTCTT TTCTTATAAC 1140 GGAGCGAGCG TGGGCTTTAG ATCCACTCAA AATAATGTAG GGTTATACAC TTATGGGGTG 1200 GGGACTGATG TGTTGTATAA CATCTTTAGC CGCTCCTATC AAAACCGCTC TGTGGATATG 1260 GGCTTTTTTA GCGGTATCCA ATTAGCCGGT GAGACCTTCC AATCCACGCT CAGAGATGAC 1320 CCCAATGTGA AATTGCATGG GAAAATCAAT AACACGCACT TCCAGTTCCT CTTTGACTTC 1380 GGTATGAGGA TGAACTTCGG TAAGTTGGAC GGGAAATCCA ACCGCCACAA CCAGCACACG 1440 GTGGAATTTG GCGTAGTGGT GCCTACGATT TATAACACTT ATTACAAATC AGCAGGGACT 1500 ACCGTGAAGT ATTTCCGTCC TTATAGCGTT TATTGGTCTT ATGGGTATTC ATTCTAA 1557 (2) INFORMATION FOR SEQ ID NO:7: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 618 amino acidβ (B) TYPE: amino acid (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7: Met He Lye Lye Aβn Arg Thr Leu Phe Leu Ser Leu Ala Leu Cyβ Ala 1 5 10 15 Ser He Ser Tyr Ala Glu Asp Aβp Gly Gly Phe Phe Thr Val Gly Tyr 20 25 30 Gin Leu Gly Gin Val Met Gin Aβp Val Gin Asn Pro Gly Gly Ala Lys 35 40 45 Ser Asp Glu Leu Ala Arg Glu Leu Asn Ala Aβp Val Thr Asn Asn He 50 55 60 Leu Aβn Aβn Aβn Thr Gly Gly Aβn He Ala Gly Ala Leu Ser Aβn Ala 65 70 75 80 Phe Ser Gin Tyr Leu Tyr Ser Leu Leu Gly Ala Tyr Pro Thr Lye Leu 85 90 95 Asn Gly Ser Asp Val Ser Ala Asn Ala Leu Leu Ser Gly Ala Val Gly 100 105 110 Ser Gly Thr Cyβ Ala Ala Ala Gly Thr Ala Gly Gly Thr Sβ>r Leu Aen 115 120 125 Thr Gin Ser Thr Cyβ Thr Val Ala Gly Tyr Tyr Trp Leu Pro Ser Leu 130 135 140 Thr Aβp Arg He Leu Ser Thr He Gly Ser Gin Thr Aβn Tyr Gly Thr 145 150 155 160 Aβn Thr Aβn Phe Pro Aβn Met Gin Gin Gin Leu Thr Tyr Leu Aβn Ala 165 170 175 Gly Aβn Val Phe Phe Asn Ala Met Aβn Lye Ala Leu Glu Aβn Lye Aβn 180 185 190 Gly Thr Ser Ser Ala Ser Gly Thr Ser Gly Ala Thr Gly Ser Aβp Gly 195 200 205 Gin Thr Tyr Ser Thr Gin Ala He Gin Tyr Leu Gin Gly Gin Gin Aβn 210 215 220 He Leu Aβn Aβn Ala Ala Aβn Leu Leu Lye Gin Aβp Glu Leu Leu Leu 225 230 235 240 Glu Ala Phe Aβn Ser Ala Val Ala Ala λβn He Gly Aβn Lye Glu Phe 245 250 255 Aβn Ser Ala Ala Phe Thr Gly Leu Val Gin Gly He He Asp Gin Ser 260 265 270 Gin Ala Val Tyr Aβn Glu Leu Thr Lye λβn Thr He Ser Gly Ser Ala 275 280 285 Val He Ser Ala Gly He Aβn Ser Aβn Gin Ala Aen Ala Val Gin Gly 290 295 300 Arg Ala Ser Gin Leu Pro Aβn Ala Leu Tyr Aβn Ala Gin Val Thr Leu 305 310 315 320 Aβp Lye He Aβn Ala Leu Aβn Aβn Gin Val Arg Ser Met Pro Tyr Leu 325 330 335 Pro Gin Phe Arg Ala Gly Aβn Ser Arg Ser Thr Aβn He Leu Aβn Gly 340 345 350 Phe Tyr Thr Lye He Gly Tyr Lye Gin Phe Phe Gly Lye Lys Arg Aβn 355 360 365 He Gly Leu Arg Tyr Tyr Gly Phe Phe Ser Tyr Aβn Gly Ala Ser Val 370 375 380 Gly Phe Arg Ser Thr Gin Aβn Asn Val Gly Leu Tyr Thr Tyr Gly Val 385 390 395 400 Gly Thr λβp Val Leu Tyr Aβn He Phe Ser Arg Ser Tyr Gin λen Arg 405 410 415 Ser Val Asp Met Gly Phe Phe Ser Gly He Gin Leu λla Gly Glu Thr 420 425 430 Phe Gin Ser Thr Leu Arg Aβp λβp Pro λβn Val Lye Leu Hie Gly Lye 435 440 445 He Aβn Aen Thr Hie Phe Gin Phe Leu Phe Aβp Phe Gly Met Arg Met 450 455 460 Aβn Phe Gly Lye Leu λβp Gly Lye Ser λβn Arg Hie λβn Gin Hie Thr 465 470 475 480 Val Glu Phe Gly Val Val Val Pro Thr He Tyr λβn Thr Tyr Tyr Lye 485 490 495 Ser Ala Gly Thr Thr Val Lye Tyr Phe Arg Pro Tyr Ser Val Tyr Trp 500 505 510 Ser Tyr Gly Tyr Ser Phe 515 What iβ claimed ie:

Claims: 1. A vaccine for inducing a mucosal immune response to Helicobacter in a patient, said vaccine comprising: a) multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease; and b) a pharmaceutically acceptable carrier or diluent. 2. The vaccine of claim 1, comprising a multimeric complex comprising eight Urease A subunits and eight Urease B subunits, a multimeric complex comprising six Urease A subunits and six Urease B subunits, and a multimeric complex comprising four Urease A subunits and four Urease B subunits, or a mixture thereof. 3. The vaccine of claim 1, comprising a multimeric complex comprising eight Urease A subunits and eight Urease B subunits, a multimeric complex comprising six Urease A subunits and six Urease B subunits, and a multimeric complex comprising four Urease A subunits and four Urease B subunits. 4. The vaccine of claim 1, further comprising a mucosal adjuvant. 5. The vaccine of claim 1, wherein said mucosal adjuvant is the heat-labile enterotoxin of enterotoxigenic Escherichia coli , a cholera toxin, a Clostridium difficile toxin, a subunit or derivative thereof lacking toxicity but still having adjuvant activity, or a mixture thereof. 6. The vaccine of claim 4, wherein said mucosal adjuvant is the heat-labile enterotoxin of enterotoxigenic Escherichia coli , or a subunit or derivative thereof lacking toxicity but retaining adjuvant activity. 7. The vaccine of claim 4, wherein said mucosal adjuvant is a cholera toxin, or a subunit or derivative -thereof lacking toxicity but retaining adjuvant activity. 8. The vaccine of claim 4, wherein said mucosal adjuvant is a Clostridium difficile toxin, or a subunit or derivative thereof lacking toxicity but retaining adjuvant activity. 9. The vaccine of claim 8, wherein said mucosal adjuvant comprises the carbohydrate binding domain of Clostridium difficile Toxin A. 10. The vaccine of claim 1, wherein said multimeric complexes of recombinant, enzymaticaily inactive Helicobacter urease have been freeze-dried. 11. The vaccine of claim 1, wherein said Helicobacter urease is Helicobacter pylori urease. 12. A composition for treating a gastroduodenal infection in a patient, said composition comprising (a) an antigen from a gastroduodenal pathogen, and (b) an antibiotic, an antisecretory agent, a bismuth salt, or a combination thereof. 13. The composition of claim 12, wherein said gastroduodenal pathogen is a Helicobacter. 14. The composition of claim 13, wherein said Helicobacter is Helicobacter pylori . 15. The composition of claim 13, wherein said antigen is a urease. 16. The composition of claim 13, wherein said antigen comprises multimeric complexes of recombinant, eirzyiβatically inactive Helicobacter urease. 17. The composition of claim 13, comprising a multimeric complex comprising eight Urease A subunits and eight Urease B subunits, a multimeric complex comprising six Urease A subunits and six Urease B subunits, and a multimeric complex comprising four Urease A subunits and four Urease B subunits, or a mixture thereof. 18. The composition of claim 13, comprising a multimeric complex comprising eight Urease A subunits and eight Urease B subunits, a multimeric complex comprising six Urease A subunits and six Urease B subunits, and a multimeric complex comprising four Urease A subunits and four Urease B subunits. 19. The composition of claim 12, wherein said Helicobacter infection is Helicobacter pylori infection. 20. The composition of claim 12, further comprising a mucosal adjuvant. 21. The composition of claim 20, wherein said mucosal adjuvant is the heat-labile enterotoxin of enterotoxigenic Escherichia coli , a cholera toxin, a Clostridium difficile toxin, a subunit or derivative thereof lacking toxicity but still having adjuvant activity, or a mixture thereof. 22. The composition of claim 20, wherein said mucosal adjuvant is the heat-labile enterotoxin of enterotoxigenic Escherichia coli , or a subunit or derivative thereof lacking toxicity but still having adjuvant activity. 23. The composition of claim 20, wherein said mucosal adjuvant is a cholera toxin, or a subunit or derivative thereof lacking toxicity but still having adjuvant activity. 24. The composition of claim 20, wherein said mucosal adjuvant is a Clostridium difficile toxin, or a derivative thereof lacking toxicity but still having adjuvant activity. 25. The composition of claim 24, wherein said mucosal adjuvant comprises the carbohydrate binding domain of Clostridium difficile Toxin A. 26. The composition of claim 12, wherein said antibiotic is selected from the group consisting of amoxicillin, clarithromycin, tetracycline, metronidizole, and erythromycin. 27. The composition of claim 12, wherein said bismuth salt is selected from the group consisting of bismuth subcitrate and bismuth subsalicylate. 28. The composition of claim 12, wherein said antisecretory agent is a proton pump inhibitor. 29. The composition of claim 28, wherein said proton pump inhibitor is selected from the group consisting of omeprazole, lansoprazole, and pantoprazole. 30. The composition of claim 12, wherein said antisecretory agent is an H 2 -receptor antagonist. 31. The composition of claim 30, wherein said H 2 - receptor antagonist is selected from the group consisting - of ranitidine, cimetidine, fa otidine, nizatidine, and roxatidine. 32. The composition of claim 12, wherein said antisecretory agent is a prostaglandin analog. 33. The composition of claim 32, wherein said prostaglandin analog is misoprostil or enprostil.

Inventors: ACKERMAN SAMUEL K, BHAGAT HITESH, ERMAK THOMAS, GUIRAKHOO FARSHAD, KLEANTHOUS HAROLD, LEE CYNTHIA K, MONATH THOMAS P, PAPPO JACQUES, SOMAN GOPALAN, SUSSMAN ILENE, THOMAS WILLIAM D JR, WELTZIN RICHARD A, ACKERMAN, SAMUEL, K., BHAGAT, HITESH, ERMAK, THOMAS, GUIRAKHOO, FARSHAD, KLEANTHOUS, HAROLD, LEE, CYNTHIA, K., MONATH, THOMAS, P., PAPPO, JACQUES, SOMAN, GOPALAN, SUSSMAN, ILENE, THOMAS, WILLIAM, D., JR., WELTZIN, RICHARD, A.
Applicants: ORAVAX INC, ORAVAX, INC.
Application year: 1996
Main classification: A61K38
IPC codes: A61K31, A61K39, A61K45, A61K51, A61P1, C12N9