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  Pharmaceutical Patents  

 

Title:  Enzyme treatment of foodstuffs for Celiac Sprue
United States Patent: 
7,928,056 
Issued: 
April 19, 2011
Inventors:  Hausch; Felix (Langenselbold, DE), Gray; Gary (Stanford, CA), Shan; Lu (Houston, TX), Khosla; Chaitan (Palo Alto, CA)
Assignee:  The Board of Trustees of the Leland Stanford Junior University (Palo Alto, CA)
Appl. No.:
 11/927,533
Filed:
 October 29, 2007


 

George Washington University's Healthcare MBA


Abstract

Administering an effective dose of glutenase to a Celiac or dermatitis herpetiformis patient reduces levels of toxic gluten oligopeptides, thereby attenuating or eliminating the damaging effects of gluten.

Description of the Invention

SUMMARY OF THE INVENTION

The present invention provides methods for treating the symptoms of Celiac Sprue and/or dermatitis herpetiformis by decreasing the levels of toxic gluten oligopeptides in foodstuffs, either prior to or after ingestion by a patient. The present invention relates to the discovery that certain gluten oligopeptides resistant to cleavage by gastric and pancreatic enzymes, that the presence of such peptides results in toxic effects, and that enzymatic treatment can remove such peptides and their toxic effects. By digestion with glutenases, these toxic oligopeptides are cleaved into fragments, thereby preventing or relieving their toxic effects in Celiac Sprue or dermatitis herpetiformis patients. In one aspect of the invention, a foodstuff is treated with a glutenase prior to consumption by the patient. In another aspect of the invention, a glutenase is administered to a patient and acts internally to destroy the toxic oligopeptides. In another aspect of the invention, a recombinant organism that produces a glutenase is administered to a patient. In another aspect of the invention, gene therapy is used to provide the patient with a gene that expresses a glutenase that destroys the toxic oligopeptides.

In one aspect, the invention provides methods for the administration of enteric formulations of one or more glutenases, each of which may be present as a single agent or a combination of active agents. In another aspect of the invention, stabilized forms of glutenases are administered to the patient, which stabilized forms are resistant to digestion in the stomach, e.g. to acidic conditions. Alternative methods of administration include genetic modification of patient cells, e.g. enterocytes, to express increased levels of peptidases capable of cleaving immunogenic oligopeptides of gliadin; pretreatment of foods with glutenases; the introduction of micro-organisms expressing such peptidases so as to transiently or permanently colonize the patient intestinal tract; and the like.

In another aspect, the invention provides pharmaceutical formulations containing one or more glutenases and a pharmaceutically acceptable carrier. Such formulations include formulations in which the glutenase is contained within an enteric coating that allows delivery of the active agent to the intestine and formulations in which the active agents are stabilized to resist digestion in acidic stomach conditions. The formulation may comprise one or more glutenases or a mixture or "cocktail" of agents having different activities.

In another aspect, the invention provides foodstuffs derived from gluten-containing foods that have been treated to remove or to reduce to non-toxic levels the gluten-derived oligopeptides that are toxic to Celiac Sprue patients, and methods for treating foods to hydrolyze toxic gluten oligopeptides. In other aspects, the invention provides recombinant microorganisms useful in hydrolyzing the gluten-derived oligopeptides that are toxic to Celiac Sprue patients from foodstuffs; methods for producing glutenases that digest the gluten-derived oligopeptides that are toxic to Celiac Sprue patents; purified preparations of the glutenases that digest the gluten-derived oligopeptides that are toxic to Celiac Sprue patents; and recombinant vectors that code for the expression of glutenases that digest the gluten-derived oligopeptides that are toxic to Celiac Sprue patents.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Celiac Sprue and/or dermatitis herpetiformis are treated by digestion of gluten oligopeptides contained in foodstuffs consumed by individuals suffering from one or both conditions. Gluten oligopeptides are highly resistant to cleavage by gastric and pancreatic peptidases such as pepsin, trypsin, chymotrypsin, and the like. By providing for digestion of gluten oligopeptides with glutenase, oligopeptides are cleaved into fragments, thereby preventing the disease-causing toxicity.

Methods and compositions are provided for the administration of one or more glutenases inhibitors to a patient suffering from Celiac Sprue and/or dermatitis herpetiformis. In some patients, these methods and compositions will allow the patient to ingest glutens without serious health consequences, much the same as individuals that do not suffer from either of these conditions. In some embodiments, the formulations of the invention comprise a glutenase contained in an enteric coating that allows delivery of the active agent(s) to the intestine; in other embodiments, the active agent(s) is stabilized to resist digestion in acidic stomach conditions. In some cases the active agent(s) have hydrolytic activity under acidic pH conditions, and can therefore initiate the proteolytic process on toxic gluten sequences in the stomach itself. Alternative methods of administration provided by the invention include genetic modification of patient cells, e.g. enterocytes, to express increased levels of glutenases; and the introduction of micro-organisms expressing such glutenases so as to transiently or permanently colonize the patient's intestinal tract. Such modified patient cells (which include cells that are not derived from the patient but that are not immunologically rejected when administered to the patient) and microorganisms of the invention are, in some embodiments, formulated in a pharmaceutically acceptable excipient, or introduced in foods. In another embodiment, the invention provides foods pretreated or combined with a glutenase and methods for treating foods to remove the toxic oligopeptides of gluten.

The methods of the invention can be used for prophylactic as well as therapeutic purposes. As used herein, the term "treating" refers both to the prevention of disease and the treatment of a disease or a pre-existing condition. The invention provides a significant advance in the treatment of ongoing disease, to stabilize or improve the clinical symptoms of the patient. Such treatment is desirably performed prior to loss of function in the affected tissues but can also help to restore lost function or prevent further loss of function. Evidence of therapeutic effect may be any diminution in the severity of disease, particularly as measured by the severity of symptoms such as fatigue, chronic diarrhea, malabsorption of nutrients, weight loss, abdominal distension, anemia, and other symptoms of Celiac Sprue. Other disease indicia include the presence of antibodies specific for glutens, the presence of antibodies specific for tissue transglutaminase, the presence of pro-inflammatory T cells and cytokines, damage to the villus structure of the small intestine as evidenced by histological or other examination, enhanced intestinal permeability, and the like.

Patients that can benefit from the present invention may be of any age and include adults and children. Children in particular benefit from prophylactic treatment, as prevention of early exposure to toxic gluten peptides can prevent initial development of the disease. Children suitable for prophylaxis can be identified by genetic testing for predisposition, e.g. by HLA typing; by family history, by T cell assay, or by other medical means. As is known in the art, dosages may be adjusted for pediatric use.

Although the present invention is not to be bound by any theory of action, it is believed that the primary event in Celiac Sprue requires certain gluten oligopeptides to access antigen binding sites within the lamina propria region interior to the relatively impermeable surface intestinal epithelial layer. Ordinarily, oligopeptide end products of pancreatic protease processing are rapidly and efficiently hydrolyzed into amino acids and/or di- or tri-peptides by gastric peptidases before they are transported across the epithelial layer. However, glutens are particularly peptidase resistant, which may be attributed to the usually high proline content of these proteins, a residue that is inaccessible to most gastric peptidases.

The normal assimilation of dietary proteins by the human gut can be divided into three major phases: (i) initiation of proteolysis in the stomach by pepsin and highly efficient endo- and C-terminal cleavage in the upper small intestine cavity (duodenum) by secreted pancreatic proteases and carboxypeptidases; (ii) further processing of the resulting oligopeptide fragments by exo- and endopeptidases anchored in the brush border surface membrane of the upper small intestinal epithelium (jejunum); and (iii) facilitated transport of the resulting amino acids, di- and tripeptides across the epithelial cells into the lamina propria, from where these nutrients enter capillaries for distribution throughout the body. Because most proteases and peptidases normally present in the human stomach and small intestine are unable to hydrolyze the amide bonds of proline residues, it is shown herein that the abundance of proline residues in gliadins and related proteins from wheat, rye and barley can constitute a major digestive obstacle for the enzymes involved in phases (i) and (ii) above. This leads to an increased concentration of relatively stable gluten derived oligopeptides in the gut. Furthermore, because aminopeptidase and especially carboxypeptidase activity towards oligopeptides with proline residues at the N- and C-termini, respectively, is low in the small intestine, detoxification of gluten oligopeptides in phase (iii) above is also slow. By administering peptidases capable of cleaving such gluten oligopeptides in accordance with the methods of the invention, the amount of toxic peptides is diminished, thereby slowing or blocking disease progression.

Tissue transglutaminase (tTGase), an enzyme found on the extracellular surface in many organs including the intestine, catalyzes the formation of isopeptide bonds between glutamine and lysine residues of different polypeptides, leading to protein-protein crosslinks in the extracellular matrix. The enzyme tTGase is the primary focus of the autoantibody response in Celiac Sprue. Gliadins, secalins and hordeins contain several sequences rich in Pro-Gln residues that are high-affinity substrates for tTGase; tTGase catalyzed deamidation of at least some of these sequences dramatically increases their affinity for HLA-DQ2, the class II MHC allele present in >90% Celiac Sprue patients. Presentation of these deamidated epitopes by DQ2 positive antigen presenting cells effectively stimulates proliferation of gliadin-specific T cells from intestinal biopsies of most Celiac Sprue patients. The toxic effects of gluten include immunogenicity of the gluten oligopeptides, leading to inflammation; the lectin theory predicts that gliadin peptides may also directly bind to surface receptors.

The present invention relates generally to methods and reagents useful in treating foodstuffs containing gluten with enzymes that digest the oligopeptides toxic to Celiac Sprue patients. Although specific enzymes are exemplified herein, any of a number of alternative enzymes and methods apparent to those of skill in the art upon contemplation of this disclosure are equally applicable and suitable for use in practicing the invention. The methods of the invention, as well as tests to determine their efficacy in a particular patient or application, can be carried out in accordance with the teachings herein using procedures standard in the art. Thus, the practice of the present invention may employ conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry and immunology within the scope of those of skill in the art. Such techniques are explained fully in the literature, such as, "Molecular Cloning: A Laboratory Manual", second edition (Sambrook et al., 1989); "Oligonucleotide Synthesis" (M. J. Gait, ed., 1984); "Animal Cell Culture" (R. I. Freshney, ed., 1987); "Methods in Enzymology" (Academic Press, Inc.); "Handbook of Experimental Immunology" (D. M. Weir & C. C. Blackwell, eds.); "Gene Transfer Vectors for Mammalian Cells" (J. M. Miller & M. P. Calos, eds., 1987); "Current Protocols in Molecular Biology" (F. M. Ausubel et al., eds., 1987); "PCR: The Polymerase Chain Reaction" (Mullis et al., eds., 1994); and "Current Protocols in Immunology" (J. E. Coligan et al., eds., 1991); as well as updated or revised editions of all of the foregoing.

As used herein, the term "glutenase" refers to an enzyme useful in the methods of the present invention that is capable, alone or in combination with endogenous or exogenously added enzymes, of cleaving toxic oligopeptides of gluten proteins of wheat, barley, oats and rye into non-toxic fragments. Gluten is the protein fraction in cereal dough, which can be subdivided into glutenins and prolamines, which are subclassified as gliadins, secalins, hordeins, and avenins from wheat, rye, barley and oat, respectively. For further discussion of gluten proteins, see the review by Wieser (1996) Acta Paediatr Suppl. 412:3-9, incorporated herein by reference.

In one embodiment, the term "glutenase" as used herein refers to a protease or a peptidase enzyme that meets one or more of the criteria provided herein. Using these criteria, one of skill in the art can determine the suitability of a candidate enzyme for use in the methods of the invention. Many enzymes will meet multiple criteria, including two, three, four or more of the criteria, and some enzymes will meet all of the criteria. The terms "protease" or "peptidase" can refer to a glutenase and as used herein describe a protein or fragment thereof with the capability of cleaving peptide bonds, where the scissile peptide bond may either be terminal or internal in oligopeptides or larger proteins. Prolyl-specific peptidases are glutenases useful in the practice of the present invention.

Glutenases of the invention include protease and peptidase enzymes having at least about 20% sequence identity at the amino acid level, more usually at least about 40% sequence identity, and preferably at least about 70% sequence identity to one of the following peptidases: prolyl endopeptidase (PEP) from F. meningosepticum (Genbank accession number D10980), PEP from A. hydrophila (Genbank accession number D14005), PEP form S. capsulate (Genbank accession number AB010298), DCP I from rabbit (Genbank accession number X62551), DPP IV from Aspergillus fumigatus (Genbank accession number U87950) or cysteine proteinase B from Hordeum vulgare (Genbank accession number U19384; Protein Information Resource number JQ1110).

In one embodiment of the present invention, the glutenase is a PEP. Homology-based identification (for example, by a PILEUP sequence analysis) of prolyl endopeptidases can be routinely performed by those of skill in the art upon contemplation of this disclosure to identify PEPs suitable for use in the methods of the present invention. PEPs are produced in microorganisms, plants and animals. PEPs belong to the serine protease superfamily of enzymes and have a conserved catalytic triad composed of a Ser, His, and Asp residues. Some of these homologs have been characterized, e.g. the enzymes from F. meningoscepticum, Aeromonas hydrophila, Aeromonas punctata, Novosphingobium capsulatum, Pyrococcus furiosus and from mammalian sources are biochemically characterized PEPs. Others such as the Nostoc and Arabidopsis enzymes are likely to be PEPs but have not been fully characterized to date. Yet others, such as the E. coli and M. xanthus enzymes, may not be PEPs but are homologous members of the serine protease superfamily, and can be useful starting materials in protein engineering to make a PEP useful in the practice of the present invention. Relative to the F. meningoscepticum enzyme, the pairwise sequence identity of this family of enzymes is in the 30-60% range. Accordingly, PEPs include enzymes having >30% identity to the F. meningoscepticum enzyme (as in the Pyrococcus enzymes), or having >40% identity (as in the Novosphingobium enzymes), or having >50% identity (as in the Aeromonas enzymes) to the F. meningoscepticum enzyme.

A glutenase of the invention includes a peptidase or protease that has a specific activity of at least 2.5 U/mg, preferably 25 U/mg and more preferably 250 U/mg for cleavage of a peptide comprising one of more of the following motifs: Gly-Pro-pNA, Z-Gly-Pro-pNA (where Z is a benzyloxycarbonyl group), and Hip-His-Leu, where "Hip" is hippuric acid, pNA is para-nitroanilide, and 1 U is the amount of enzyme required to catalyze the turnover of 1 .quadrature.mole of substrate per minute.

A glutenase of the invention includes an enzyme belonging to any of the following enzyme classifications: EC 3.4.21.26, EC 3.4.14.5, or EC 3.4.15.1.

A glutenase of the invention includes an enzyme having a kcat/Km of at least about 2.5 s.sup.-1 M.sup.-1, usually at least about 250 s.sup.-1 M.sup.-1 and preferably at least about 25000 s.sup.-1 M.sup.-1 for cleavage of any of the following peptides under optimal conditions: (SEQ ID NO:1) QLQPFPQPQLPY, (SEQ ID NO:3) PQPQLPYPQPQLPY, (SEQ ID NO:13) QPQQSFPQQQ, (SEQ ID NO:14) QLQPFPQPELPY, (SEQ ID NO:15) PQPELPYPQPELPY, (SEQ ID NO:16) QPQQSFPEQQ. A glutenase of the invention includes peptidase or protease having a specificity kcat/Km>2 mM.sup.-1 s.sup.-1 for the quenched fluorogenic substrate SEQ ID NO:28 Abz-QPQQP-Tyr(NO.sub.2)-D.

A glutenase useful in the practice of the present invention can be identified by its ability to cleave a pretreated substrate to remove toxic gluten oligopeptides, where a "pretreated substrate" is a gliadin, hordein, secalin or avenin protein that has been treated with physiological quantities of gastric and pancreatic proteases, including pepsin (1:100 mass ratio), trypsin (1:100), chymotrypsin (1:100), elastase (1:500), and carboxypeptidases A and B (1:100). Pepsin digestion may be performed at pH 2 for 20 min., to mimic gastric digestion, followed by further treatment of the reaction mixture with trypsin, chymotrypsin, elastase and carboxypeptidase at pH 7 for 1 hour, to mimic duodenal digestion by secreted pancreatic enzymes. The pretreated substrate comprises oligopeptides resistant to digestion, e.g. under physiological conditions.

The ability of a peptidase or protease to cleave a pretreated substrate can be determined by measuring the ability of an enzyme to increase the concentration of free NH2-termini in a reaction mixture containing 1 mg/ml pretreated substrate and 10 .quadrature.g/ml of the peptidase or protease, incubated at 37.degree. C. for 1 hour. A glutenase useful in the practice of the present invention will increase the concentration of the free amino termini under such conditions, usually by at least about 25%, more usually by at least about 50%, and preferably by at least about 100%. A glutenase includes an enzyme capable of reducing the residual molar concentration of oligopeptides greater than about 1000 Da in a 1 mg/ml "pretreated substrate" after a 1 hour incubation with 10 .mu.g/ml of the enzyme by at least about 2-fold, usually by at least about 5-fold, and preferably by at least about 10-fold. The concentration of such oligopeptides can be estimated by methods known in the art, for example size exclusion chromatography and the like.

A glutenase of the invention includes an enzyme capable of reducing the potency by which a "pretreated substrate" can antagonize binding of (SEQ ID NO:17) PQPELPYPQPQLP to HLA-DQ2. The ability of a substrate to bind to HLA-DQ is indicative of its toxicity; fragments smaller than about 8 amino acids are generally not stably bound to Class II MHC. Treatment with a glutenase that digests toxic oligopeptides, by reducing the concentration of the toxic oligopeptides, prevents a mixture containing them from competing with a test peptide for MHC binding. To test whether a candidate glutenase can be used for purposes of the present invention, a 1 mg/ml solution of "pretreated substrate" may be first incubated with 10 .mu.g/ml of the candidate glutenase, and the ability of the resulting solution to displace radioactive (SEQ ID NO:18) PQPELPYPQPQPLP pre-bound to HLA-DQ2 molecules can then be quantified, with a reduction of displacement, relative to a non-treated control, indicative of utility in the methods of the present invention.

A glutenase of the invention includes an enzyme that reduces the anti-tTG antibody response to a "gluten challenge diet" in a Celiac Sprue patient by at least about 2-fold, more usually by at least about 5-fold, and preferably by at least about 10-fold. A "gluten challenge diet" is defined as the intake of 100 g bread per day for 3 days by an adult Celiac Sprue patient previously on a gluten-free diet. The anti-tTG antibody response can be measured in peripheral blood using standard clinical diagnostic procedures, as known in the art.

Excluded from the term "glutenase" are the following peptidases: human pepsin, human trypsin, human chymotrypsin, human elastase, papaya papain, and pineapple bromelain, and usually excluded are enzymes having greater than 98% sequence identity at the amino acid level to such peptidases, more usually excluded are enzymes having greater than 90% sequence identity at the amino acid level to such peptidases, and preferably excluded are enzymes having greater than 70% sequence identity at the amino acid level to such peptidases.

Among gluten proteins with potential harmful effect to Celiac Sprue patients are included the storage proteins of wheat, species of which include Triticum aestivum; Triticum aethiopicum; Triticum baeoticum; Triticum militinae; Triticum monococcum; Triticum sinskajae; Triticum timopheevii; Triticum turgidum; Triticum urartu, Triticum vavilovii; Triticum zhukovskyi; etc. A review of the genes encoding wheat storage proteins may be found in Colot (1990) Genet Eng (N Y) 12:225-41. Gliadin is the alcohol-soluble protein fraction of wheat gluten. Gliadins are typically rich in glutamine and proline, particularly in the N-terminal part. For example, the first 100 amino acids of .alpha.- and .gamma.-gliadins contain .about.35% and .about.20% of glutamine and proline residues, respectively. Many wheat gliadins have been characterized, and as there are many strains of wheat and other cereals, it is anticipated that many more sequences will be identified using routine methods of molecular biology. In one aspect of the present invention, genetically modified plants are provided that differ from their naturally occurring counterparts by having gliadin proteins that contain a reduced content of glutamine and proline residues.

Examples of gliadin sequences include but are not limited to wheat alpha gliadin sequences, for example as provided in Genbank, accession numbers AJ133612; AJ133611; AJ133610; AJ133609; AJ133608; AJ133607; AJ133606; AJ133605; AJ133604; AJ133603; AJ133602; D84341.1; U51307; U51306; U51304; U51303; U50984; and U08287. A sequence of wheat omega gliadin is set forth in Genbank accession number AF280605.

For the purposes of the present invention, toxic gliadin oligopeptides are peptides derived during normal human digestion of gliadins and related storage proteins as described above, from dietary cereals, e.g. wheat, rye, barley, and the like. Such oligopeptides are believed to act as antigens for T cells in Celiac Sprue. For binding to Class II MHC proteins, immunogenic peptides are usually from about 8 to 20 amino acids in length, more usually from about 10 to 18 amino acids. Such peptides may include PXP motifs, such as the motif PQPQLP (SEQ ID NO:8). Determination of whether an oligopeptide is immunogenic for a particular patient is readily determined by standard T cell activation and other assays known to those of skill in the art.

As demonstrated herein, during digestion, peptidase resistant oligopeptides remain after exposure of glutens, e.g. gliadin, to normal digestive enzymes. Examples of peptidase resistant oligopeptides are provided, for example, as set forth in SEQ ID NO:5, 6, 7 and 10. Other examples of immunogenic gliadin oligopeptides are described in Wieser (1995) Baillieres Clin Gastroenterol 9(2):191-207, incorporated herein by reference.

Determination of whether a candidate enzyme will digest a toxic gluten oligopeptide, as discussed above, can be empirically determined. For example, a candidate may be combined with an oligopeptide comprising one or more Gly-Pro-p-nitroanilide, Z-Gly-Pro-p-nitroanilide, Hip-His-Leu, SEQ ID NO:29 Abz-QLP-Tyr(NO.sub.2)-PQ, SEQ ID NO:30 Abz-PYPQPQ-Tyr(NO.sub.2), SEQ ID NO:31 PQP-Lys(Abz)-LP-Tyr(NO.sub.2)-PQPQLP, SEQ ID NO:32 PQPQLP-Tyr(NO.sub.2)-PQP-Lys(Abz)-LP motifs; with one or more of the oligopeptides (SEQ ID NO:1) QLQPFPQPQLPY, (SEQ ID NO:3) PQPQLPYPQPQLPY, (SEQ ID NO:13) QPQQSFPQQQ, (SEQ ID NO:14) QLQPFPQPELPY, (SEQ ID NO:15) PQPELPYPQPELPY, (SEQ ID NO:16) QPQQSFPEQQ or (SEQ ID NO:12) LQLQPFPQPQLPYPQPQLPYPQPQLPYPQPQPF; or with a pretreated substrate comprising one or more of gliadin, hordein, secalin or avenin proteins that have been treated with physiological quantities of gastric and pancreatic proteases. In each instance, the candidate is determined to be a glutenase of the invention if it is capable of cleaving the oligopeptide. Glutenases that have a low toxicity for human cells and are active in the physiologic conditions present in the intestinal brush border are preferred for use in some applications of the invention, and therefore it may be useful to screen for such properties in candidate glutenases.

The oligopeptide or protein substrates for such assays may be prepared in accordance with conventional techniques, such as synthesis, recombinant techniques, isolation from natural sources, or the like. For example, solid-phase peptide synthesis involves the successive addition of amino acids to create a linear peptide chain (see Merrifield (1963) J. Am. Chem. Soc. 85:2149-2154). Recombinant DNA technology can also be used to produce the peptide.

Candidate glutenases for use in the practice of the present invention can be obtained from a wide variety of sources, including libraries of natural and synthetic proteins. For example, numerous means are available for random and directed mutation of proteins. Alternatively, libraries of natural proteins in the form of bacterial, fungal, plant and animal extracts are available or readily produced. Extracts of germinating wheat and other grasses is of interest as a source of candidate enzymes. Natural or synthetically produced libraries and compounds are readily modified through conventional chemical, physical and biochemical means, and such means can be used to produce combinatorial libraries. Known pharmacological agents may be subjected to directed or random chemical modifications, such as acylation, alkylation, esterification, and amidification, to produce structural analogs of proteins.

Generally, a variety of assay mixtures are run in parallel with different peptidase concentrations to obtain a differential response to the various concentrations. Typically, one of these concentrations serves as a negative control, i.e. at zero concentration or below the level of detection. A variety of other reagents may be included in a screening assay. These include reagents like salts, detergents, and the like that are used to facilitate optimal activity and/or reduce non-specific or background interactions. Reagents that improve the efficiency of the assay may be used. The mixture of components is added in any order that provides for the requisite activity. Incubations are performed at any suitable temperature, typically between 4 and 40.degree. C. Incubation periods are selected for optimum activity but can also be optimized to facilitate rapid high-throughput screening or other purposes. Typically, between 0.1 and 1 hours will be sufficient.

The level of digestion of the toxic oligopeptide can be compared to a baseline value. The disappearance of the starting material and/or the presence of digestion products can be monitored by conventional methods. For example, a detectable marker can be conjugated to a peptide, and the change in molecular weight associated with the marker is then determined, e.g. acid precipitation, molecular weight exclusion, and the like. The baseline value can be a value for a control sample or a statistical value that is representative a control population. Various controls can be conducted to ensure that an observed activity is authentic, including running parallel reactions, positive and negative controls, dose response, and the like.

Active glutenases identified by the screening methods described herein can serve as lead compounds for the synthesis of analog compounds to identify glutenases with improved properties. Identification of analog compounds can be performed through use of techniques such as self-consistent field (SCF) analysis, configuration interaction (CI) analysis, and normal mode dynamics analysis.

In one embodiment of the invention, the glutenase is a prolyl endopeptidase (PEP, EC 3.4.21.26). Prolyl endopeptidases are widely distributed in microorganisms, plants and animals, and have been cloned from Flavobacterium meningosepticum, (Yoshimoto et al. (1991) J. Biochem. 110, 873-8); Aeromonas hydrophyla (Kanatani et al. (1993) J. Biochem. 113, 790-6); Sphingomonas capsulata (Kabashima et al. (1998) Arch. Biochem. Biophys. 358, 141-148), Pyrococcus furious (Robinson et al. (1995) Gene 152, 103-6); pig (Rennex et al., (1991) Biochemistry 30, 2195-2030); and the like. The suitability of a particular enzyme is readily determined by the assays described above, by clinical testing, determination of stability in formulations, and the like. Other sources of PEP include Lactobacilli (Habibi-Najafi et al. (1994) J. Dairy Sci. 77, 385-392), from where the gene of interest can be readily cloned based on sequence homology to the above PEP's or via standard reverse genetic procedures involving purification, amino-acid sequencing, reverse translation, and cloning of the gene encoding the target extracellular enzyme.

In another embodiment of the invention, glutenases are peptidases present in the brush border, which are supplemented. Formulations of interest may comprise such enzymes in combination with other peptidases. Peptidases present in brush border include dipeptidyl peptidase IV (DPP IV, EC 3.4.14.5), and dipeptidyl carboxypeptidase (DCP, EC 3.4.15.1). The human form of these proteins may be used, or modified forms may be isolated from other suitable sources. Example of DPP IV enzymes include Aspergillus spp. (e.g. Byun et al., (2001) J. Agric. Food Chem. 49, 2061-2063), ruminant bacteria such as Prevotella albensis M384 (NCBI protein database Locus # CAC42932), dental bacteria such as Porphyromonas gingivalis W83 (Kumugai et al., (2000) Infect. Immun. 68, 716-724), lactobacilli such as Lactobacillus helveticus (e.g. Vesanto, et al, (1995) Microbiol. 141, 3067-3075), and Lactococcus lactis (Mayo et al., (1991) Appl. Environ. Microbiol. 57, 38-44). Other DPP IV candidates can readily be recognized based on homology to the above enzymes, preferably >30% sequence identity. Similarly, secreted dipeptidyl carboxypeptidases that cleave C-terminal X-Pro sequences are found in many microbial sources including Pseudomonas spp (e.g. Ogasawara et al, (1997) Biosci. Biotechnol. Biochem. 61, 858-863), Streptomyces spp. (e.g. Miyoshi et al., (1992) J. Biochem. 112, 253-257) and Aspergilli spp. (e.g. Ichishima et al., (1977) J. Biochem. 81, 1733-1737). Of particular interest is the enzyme from Aspergillus saitoi (Ichishima), due to its high activity at acidic pH values. Although the genes encoding many of these enzymes have not yet been cloned, they can be readily cloned by standard reverse genetic procedures. The DCP I enzymes can be purified from the extracellular medium based on their ability to hydrolyze (SEQ ID NO:19) Z-Giy-Pro-Leu-Gly-Pro, Z-Gly-Pro, or Hip-Gly-Pro. Alternatively, putative DCP I genes can be identified based on homology to the E. coli enzyme (NCBI protein database Locus CAA41014.)

In another embodiment of the invention, glutenases are endoproteases found in developing grains of toxic cereals such as wheat, barley and rye. For example, Dominguez and Cejudo (Plant Physiol. 112, 1211-1217, 1996) have shown that the endosperm of wheat (i.e. the part of the grain that contains gliadin and glutenin) contains a variety of neutral and acid proteases. Although these proteases have not been individually characterized, they are expected to be an especially rich source of glutenases. Moreover, although the genes encoding these proteases have not yet been cloned, Dominguez and Cejudo have established a convenient SDS-PAGE assay for identification and separation of these proteases. After excision of the corresponding protein bands from the gel, limited sequence information can be obtained. The cDNA encoding these proteases can therefore be readily cloned from this information using established reverse genetic procedures, and expressed in heterologous bacterial or fungal hosts. Of particular interest are proteases that hydrolyze .alpha.2-gliadin within the 33-mer amino acid sequence identified in Example 2 below. Of further interest are the subset of these proteases that retain activity at acidic pH values (pH2-5) encountered in the stomach.

The amino acid sequence of a glutenase, e.g. a naturally occurring glutenase, can be altered in various ways known in the art to generate targeted changes in sequence and additional glutenase enzymes useful in the formulations and compositions of the invention. Such variants will typically be functionally-preserved variants, which differ, usually in sequence, from the corresponding native or parent protein but still retain the desired biological activity. Variants also include fragments of a glutenase that retain enzymatic activity. Various methods known in the art can be used to generate targeted changes, e.g. phage display in combination with random and targeted mutations, introduction of scanning mutations, and the like.

A variant can be substantially similar to a native sequence, i.e. differing by at least one amino acid, and can differ by at least two but usually not more than about ten amino acids (the number of differences depending on the size of the native sequence). The sequence changes may be substitutions, insertions or deletions. Scanning mutations that systematically introduce alanine, or other residues, may be used to determine key amino acids. Conservative amino acid substitutions typically include substitutions within the following groups: (glycine, alanine); (valine, isoleucine, leucine); (aspartic acid, glutamic acid); (asparagine, glutamine); (serine, threonine); (lysine, arginine); and (phenylalanine, tyrosine).

Glutenase fragments of interest include fragments of at least about 20 contiguous amino acids, more usually at least about 50 contiguous amino acids, and may comprise 100 or more amino acids, up to the complete protein, and may extend further to comprise additional sequences. In each case, the key criterion is whether the fragment retains the ability to digest the toxic oligopeptides that contribute to the symptoms of Celiac Sprue.

Modifications of interest that do not alter primary sequence include chemical derivatization of proteins, e.g., acetylation or carboxylation. Also included are modifications of glycosylation, e.g. those made by modifying the glycosylation patterns of a protein during its synthesis and processing or in further processing steps; e.g. by exposing the protein to enzymes that affect glycosylation, such as mammalian glycosylating or deglycosylating enzymes. Also embraced are sequences that have phosphorylated amino acid residues, e.g. phosphotyrosine, phosphoserine, or phosphothreonine.

Also useful in the practice of the present invention are proteins that have been modified using molecular biological techniques and/or chemistry so as to improve their resistance to proteolytic degradation and/or to acidic conditions such as those found in the stomach, and to optimize solubility properties or to render them more suitable as a therapeutic agent. For example, the backbone of the peptidase can be cyclized to enhance stability (see Friedler et al. (2000) J. Biol. Chem. 275:23783-23789). Analogs of such proteins include those containing residues other than naturally occurring L-amino acids, e.g. D-amino acids or non-naturally occurring synthetic amino acids.

The glutenase proteins of the present invention may be prepared by in vitro synthesis, using conventional methods as known in the art. Various commercial synthetic apparatuses are available, for example, automated synthesizers by Applied Biosystems, Inc., Foster City, Calif., Beckman, and other manufacturers. Using synthesizers, one can readily substitute for the naturally occurring amino acids one or more unnatural amino acids. The particular sequence and the manner of preparation will be determined by convenience, economics, purity required, and the like. If desired, various groups can be introduced into the protein during synthesis that allow for linking to other molecules or to a surface. For example, cysteines can be used to make thioethers, histidines can be used for linking to a metal ion complex, carboxyl groups can be used for forming amides or esters, amino groups can be used for forming amides, and the like.

The glutenase proteins useful in the practice of the present invention may also be isolated and purified in accordance with conventional methods from recombinant production systems and from natural sources. A lysate can be prepared from the expression host and the lysate purified using HPLC, exclusion chromatography, gel electrophoresis, affinity chromatography, and/or other purification techniques. Typically, the compositions used in the practice of the invention will comprise at least 20% by weight of the desired product, more usually at least about 75% by weight, preferably at least about 95% by weight, and for therapeutic purposes, usually at least about 99.5% by weight, in relation to contaminants related to the method of preparation of the product and its purification. Usually, the percentages will be based upon total protein.

In one aspect, the present invention provides a purified preparation of a glutenase. Prior to the present invention, there was no need for a glutenase that could be ingested by a human or mixed with a foodstuff. Thus, prior to the present invention most glutenases did not exist in a form free of contaminants that could be deleterious to a human if ingested. The present invention creates a need for such glutenase preparations and provides them and methods for preparing them. In a related embodiment, the present invention provides novel foodstuffs that are derived from gluten-containing foodstuffs but have been treated to reduce the concentration and amount of the oligopeptides and oligopeptide sequences discovered to be toxic to Celiac Sprue patients. While gluten-free or reduced-gluten content foods have been made, the foodstuffs of the present invention differ from such foodstuffs not only by the manner in which they are prepared, by treatment of the foodstuff with a glutenase, but also by their content, as the methods of the prior art result in alteration of non-toxic (to Celiac Sprue patients) components of the foodstuff, resulting in a different taste and composition. Prior art foodstuffs include, for example, Codex Alimentarius wheat starch, which is available in Europe and has <100 ppm gluten. The starch is usually prepared by processes that take advantage of the fact that gluten is insoluble in water whereas starch is soluble.

In one embodiment of the present invention, a Celiac Sprue patient is, in addition to being provided a glutenase or food treated in accordance with the present methods, provided an inhibitor of tissue transglutaminase, an anti-inflammatory agent, an anti-ulcer agent, a mast cell-stabilizing agents, and/or and an-allergy agent. Examples of such agents include HMG-CoA reductase inhibitors with anti-inflammatory properties such as compactin, lovastatin, simvastatin, pravastatin and atorvastatin; anti-allergic histamine H1 receptor antagonists such as acrivastine, cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine and mizolastine; leukotriene receptor antagonists such as montelukast and zafirlukast; COX2 inhibitors such as celecoxib and rofecoxib; p38 MAP kinase inhibitors such as BIRB-796; and mast cell stabilizing agents such as sodium chromoglycate (chromolyn), pemirolast, proxicromil, repirinast, doxantrazole, amlexanox nedocromil and probicromil.

As used herein, compounds which are "commercially available" may be obtained from commercial sources including but not limited to Acros Organics (Pittsburgh Pa.), Aldrich Chemical (Milwaukee Wis., including Sigma Chemical and Fluka), Apin Chemicals Ltd. (Milton Park UK), Avocado Research (Lancashire U.K.), BDH Inc. (Toronto, Canada), Bionet (Cornwall, U.K.), Chemservice Inc. (West Chester Pa.), Crescent Chemical Co. (Hauppauge N.Y.), Eastman Organic Chemicals, Eastman Kodak Company (Rochester N.Y.), Fisher Scientific Co. (Pittsburgh Pa.), Fisons Chemicals (Leicestershire UK), Frontier Scientific (Logan Utah), ICN Biomedicals, Inc. (Costa Mesa Calif.), Key Organics (Cornwall U.K.), Lancaster Synthesis (Windham N.H.), Maybridge Chemical Co. Ltd. (Cornwall U.K.), Parish Chemical Co. (Orem Utah), Pfaltz & Bauer, Inc. (Waterbury Conn.), Polyorganix (Houston Tex.), Pierce Chemical Co. (Rockford Ill.), Riedel de Haen A G (Hannover, Germany), Spectrum Quality Product, Inc. (New Brunswick, N.J.), TCI America (Portland Oreg.), Trans World Chemicals, Inc. (Rockville Md.), Wako Chemicals USA, Inc. (Richmond Va.), Novabiochem and Argonaut Technology.

Compounds useful for co-administration with the glutenases and treated foodstuffs of the invention can also be made by methods known to one of ordinary skill in the art. As used herein, "methods known to one of ordinary skill in the art" may be identified though various reference books and databases. Suitable reference books and treatises that detail the synthesis of reactants useful in the preparation of compounds of the present invention, or provide references to articles that describe the preparation, include for example, "Synthetic Organic Chemistry", John Wiley & Sons, Inc., New York; S. R. Sandler et al., "Organic Functional Group Preparations," 2nd Ed., Academic Press, New York, 1983; H. O. House, "Modern Synthetic Reactions", 2nd Ed., W. A. Benjamin, Inc. Menlo Park, Calif. 1972; T. L. Gilchrist, "Heterocyclic Chemistry", 2nd Ed., John Wiley & Sons, New York, 1992; J. March, "Advanced Organic Chemistry: Reactions, Mechanisms and Structure", 4th Ed., Wiley-Interscience, New York, 1992. Specific and analogous reactants may also be identified through the indices of known chemicals prepared by the Chemical Abstract Service of the American Chemical Society, which are available in most public and university libraries, as well as through on-line databases (the American Chemical Society, Washington, D.C., www.acs.org may be contacted for more details). Chemicals that are known but not commercially available in catalogs may be prepared by custom chemical synthesis houses, where many of the standard chemical supply houses (e.g., those listed above) provide custom synthesis services.

The glutenase proteins of the invention and/or the compounds administered therewith are incorporated into a variety of formulations for therapeutic administration. In one aspect, the agents are formulated into pharmaceutical compositions by combination with appropriate, pharmaceutically acceptable carriers or diluents, and are formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, suppositories, injections, inhalants, gels, microspheres, and aerosols. As such, administration of the glutenase and/or other compounds can be achieved in various ways, usually by oral administration. The glutenase and/or other compounds may be systemic after administration or may be localized by virtue of the formulation, or by the use of an implant that acts to retain the active dose at the site of implantation.

In pharmaceutical dosage forms, the glutenase and/or other compounds may be administered in the form of their pharmaceutically acceptable salts, or they may also be used alone or in appropriate association, as well as in combination with other pharmaceutically active compounds. The agents may be combined, as previously described, to provide a cocktail of activities. The following methods and excipients are exemplary and are not to be construed as limiting the invention.

For oral preparations, the agents can be used alone or in combination with appropriate additives to make tablets, powders, granules or capsules, for example, with conventional additives, such as lactose, mannitol, corn starch or potato starch; with binders, such as crystalline cellulose, cellulose derivatives, acacia, corn starch or gelatins; with disintegrators, such as corn starch, potato starch or sodium carboxymethylcellulose; with lubricants, such as talc or magnesium stearate; and if desired, with diluents, buffering agents, moistening agents, preservatives and flavoring agents.

In one embodiment of the invention, the oral formulations comprise enteric coatings, so that the active agent is delivered to the intestinal tract. Enteric formulations are often used to protect an active ingredient from the strongly acid contents of the stomach. Such formulations are created by coating a solid dosage form with a film of a polymer that is insoluble in acid environments, and soluble in basic environments. Exemplary films are cellulose acetate phthalate, polyvinyl acetate phthalate, hydroxypropyl methylcellulose phthalate and hydroxypropyl methylcellulose acetate succinate, methacrylate copolymers, and cellulose acetate phthalate.

Other enteric formulations comprise engineered polymer microspheres made of biologically erodable polymers, which display strong adhesive interactions with gastrointestinal mucus and cellular linings and can traverse both the mucosal absorptive epithelium and the follicle-associated epithelium covering the lymphoid tissue of Peyer's patches. The polymers maintain contact with intestinal epithelium for extended periods of time and actually penetrate it, through and between cells. See, for example, Mathiowitz et al., (1997) Nature 386 (6623): 410-414. Drug delivery systems can also utilize a core of superporous hydrogels (SPH) and SPH composite (SPHC), as described by Dorkoosh et al., (2001) J Control Release 71(3):307-18.

In another embodiment, a microorganism, for example bacterial or yeast culture, capable of producing glutenase is administered to a patient. Such a culture may be formulated as an enteric capsule; for example, see U.S. Pat. No. 6,008,027, incorporated herein by reference. Alternatively, microorganisms stable to stomach acidity can be administered in a capsule, or admixed with food preparations.

In another embodiment, the glutenase is admixed with food, or used to pre-treat foodstuffs containing glutens. Glutenase present in foods can be enzymatically active prior to or during ingestion, and may be encapsulated or otherwise treated to control the timing of activity. Alternatively, the glutenase may be encapsulated to achieve a timed release after ingestion, e.g. in the intestinal tract.

Formulations are typically provided in a unit dosage form, where the term "unit dosage form," refers to physically discrete units suitable as unitary dosages for human subjects, each unit containing a predetermined quantity of glutenase in an amount calculated sufficient to produce the desired effect in association with a pharmaceutically acceptable diluent, carrier or vehicle. The specifications for the unit dosage forms of the present invention depend on the particular complex employed and the effect to be achieved, and the pharmacodynamics associated with each complex in the host.

The pharmaceutically acceptable excipients, such as vehicles, adjuvants, carriers or diluents, are commercially available. Moreover, pharmaceutically acceptable auxiliary substances, such as pH adjusting and buffering agents, tonicity adjusting agents, stabilizers, wetting agents and the like, are commercially available. Any compound useful in the methods and compositions of the invention can be provided as a pharmaceutically acceptable base addition salt. "Pharmaceutically acceptable base addition salt" refers to those salts which retain the biological effectiveness and properties of the free acids, which are not biologically or otherwise undesirable. These salts are prepared from addition of an inorganic base or an organic base to the free acid. Salts derived from inorganic bases include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Preferred inorganic salts are the ammonium, sodium, potassium, calcium, and magnesium salts. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, methylglucamine, theobromine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Particularly preferred organic bases are isopropylamine, diethylamine, ethanolamine, trimethylamine, dicyclohexylamine, choline and caffeine.

Depending on the patient and condition being treated and on the administration route, the glutenase may be administered in dosages of 0.01 mg to 500 mg/kg body weight per day, e.g. about 20 mg/day for an average person. A typical dose of glutenase in patients will be in at least about 1 mg/adult, more usually at least about 10 mg; and preferably at least about 50 mg; usually not more than about 5 g, more usually not more than about 1 g, and preferably not more than about 500 mg. Dosages will be appropriately adjusted for pediatric formulation. In children the effective dose may be lower, for example at least about 0.1 mg, or 0.5 mg. In combination therapy involving, for example, a PEP+DPP IV or PEP+DCP I, a comparable dose of the two enzymes may be given; however, the ratio will be influenced by the relative stability of the two enzymes toward gastric and duodenal inactivation.

Those of skill will readily appreciate that dose levels can vary as a function of the specific enzyme, the severity of the symptoms and the susceptibility of the subject to side effects. Some of the glutenases are more potent than others. Preferred dosages for a given enzyme are readily determinable by those of skill in the art by a variety of means. A preferred means is to measure the physiological potency of a given compound.

Other formulations of interest include formulations of DNA encoding glutenases of interest, so as to target intestinal cells for genetic modification. For example, see U.S. Pat. No. 6,258,789, herein incorporated by reference, which discloses the genetic alteration of intestinal epithelial cells.

The methods of the invention are used to treat foods to be consumed or that are consumed by individuals suffering from Celiac Sprue and/or dermatitis herpetiformis by delivering an effective dose of glutenase. If the glutenase is administered directly to a human, then the active agent(s) are contained in a pharmaceutical formulation. Alternatively, the desired effects can be obtained by incorporating glutenase into food products or by administering live organisms that express glutenase, and the like. Diagnosis of suitable patients may utilize a variety of criteria known to those of skill in the art. A quantitative increase in antibodies specific for gliadin, and/or tissue transglutaminase is indicative of the disease. Family histories and the presence of the HLA alleles HLA-DQ2 [DQ(a1*0501, b1*02)] and/or DQ8 [DQ(a1*0301, b1*0302)] are indicative of a susceptibility to the disease.

The therapeutic effect can be measured in terms of clinical outcome or can be determined by immunological or biochemical tests. Suppression of the deleterious T-cell activity can be measured by enumeration of reactive Th1 cells, by quantitating the release of cytokines at the sites of lesions, or using other assays for the presence of autoimmune T cells known in the art. Alternatively, one can look for a reduction in symptoms of a disease.

Various methods for administration may be employed, preferably using oral administration, for example with meals. The dosage of the therapeutic formulation will vary widely, depending upon the nature of the disease, the frequency of administration, the manner of administration, the clearance of the agent from the host, and the like. The initial dose can be larger, followed by smaller maintenance doses. The dose can be administered as infrequently as weekly or biweekly, or more often fractionated into smaller doses and administered daily, with meals, semi-weekly, or otherwise as needed to maintain an effective dosage level.
 

Claim 1 of 9 Claims

1. A method of screening a candidate enzyme for glutenase activity, the method comprising contacting a gluten oligopeptide having the amino acid sequence of SEQ ID NO:12 with said enzyme and determining if said oligopeptide is degraded to fragments shorter than 8 amino acids by said contacting step.

 

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