WO2005037226A2 - Genetically engineered enteroendocrine cells for treating glucose-related metabolic disorders - Google Patents

Abstract

Methods and compositions for restoration of regulated insulin release in response to blood glucose levels in an individual in need thereof are disclosed. A recombinant adeno-associated virus expression vector expressing preproinsulin or insulin is used for selective transduction of enteroendocrine cells. Cells can be transfected with vectors where the genes of interest are under the control of tissue-specific promoters. Other appropriate enhancers or transcriptional regulators may be included in the vector to modulate expression. Cells can be transduced in vivo or manipulated ex vivo and transplanted into an individual in need of treatment. A selection gene or reporter gene can optionally be included in the vector for selection of transduced cells after expression of the vector. Genes encoding luminescent markers can optionally be included in the vector to allow for selection of transduced cells using fluorescence-based selection procedures.

Description

GENETICALLY ENGINEERED ENTEROENDOCRINE CELLS FOR TREATING GLUCOSE-RELATED METABOLIC DISORDERS FIELD OF THE INVENTION This invention relates to compositions and methods of genetically engineering enteroendocrine cells for treating disorders of glucose metabolism. More specifically, this invention relates to viral transduction of enteroendocrine cells using an adeno-associated virus for treating disorders of glucose-metabolism.

BACKGROUND Disorders of glucose metabolism are prevalent and have a significant impact on the population. Insulin-dependent diabetes (IDD) for example, is a serious pathological disease affecting more than 4 million people in the United States alone with an overall annual cost in excess of 20 billion dollars. This cost involves both expenses for direct treatment of the disease, via blood glucose monitoring and daily insulin injections as well as addressing the long- term complications of diabetes, work loss, etc. Diabetes can be juvenile, or type I, diabetes and adult onset, or type II, diabetes. Type I diabetes is caused by autoimmune-mediated destruction of the insulin-producing pancreatic beta cells. Type II diabetes is caused by impaired receptor binding at the insulin receptor. Cell-based therapies for treating insulin-dependent diabetes (IDD) can provide a physiologic regulation of blood glucose levels that is less invasive than insulin injections. Surrogate pancreatic beta-cells that are generated by genetic engineering of non-beta-cells to produce insulin provide an alternative to islet transplantation in cell-based therapies for treating insulin-dependent diabetes (Lee et al. Nature (2000) 408:483-488, Cheung et al. Science 2000 290:1959-1962, Thule et al, Gene Therapy (2000) 7:205-214). Engineered β- cell surrogates are potentially autologous, targeted by gene transfer vehicles in vivo or obtained as a biopsy from the patient and genetically modified ex vivo, and thus greatly relax the immune acceptance problems posed by allogeneic and, more so, xenogeneic islet transplantation. The advantages of targeted intestinal enteroendocrine cells have also received notable attention during the development of recombinant beta-cell surrogates (Cheung et al. Science 2000 290:1959-1962, Tang and Sambanis, Biochem Biophys Res Common 2003 303:645-652, Ramshur et al, J Cell Physiol 2002 192:339-350). Enteroendocrine cell families are naturally found scattered in the crypts of gut mucosa; they release incretin hormones such as glucagon-like peρtide-1 (GLP-1 from intestinal L-cells) and glucose- dependent insulinotropic peptide (GIP, from gut K-cells) after a meal to potentiate insulin production from pancreas. Both incretin hormone and insulin secretion are closely related to nutrient ingestion and digestion for normalization of postprandial glycemia. Although promising results from in vitro and in vivo models have demonstrated the potential of using the engineered enteroendocrine cells to correct IDD, the targeting of enteroendocrine cells in vivo for insulin production remains a big hurdle. This is because only approximately 1% of the intestinal epithelial population consists of enteroendocrine cells. Enteroendocrine cells provide a desirable cell source for cell-based treatment of IDD because their cell surface signature is different from pancreatic beta cells and thus would avoid the autoimmune attack that occurs with beta cells. Unfortunately, it is difficult to isolate a pure enteroendocrine population from intestinal biopsy and perform ex-vivo somatic cell gene delivery. Along the digestive tract, the intestinal epithelium consists of four major cell types: enterocytes, goblet cells, Paneth cells and enteroendocrine cells. Among these cells, the enterocytes, which account for digestion and absorption of lummal nutrients, are the predominant type. Because of the prevailing enterocytes in the gut epithelium, any method intending to modify enteroendocrine cells will inevitably interact with the surrounding enterocytes. Enteroendocrine cells can be genetically engineered to express insulin and used either by themselves or, possibly, in a combination approach with other cells engineered to secrete insulin constitutively or under transcriptional glucose regulation. The unique connection between incretins and insulin permits engineering of enteroendocrine cells for regulated insulin secretion and constitutes a feasible approach for IDD treatment in terms of the dynamic release of insulin as well as the compatibility of incretins and insulin in glycemic normalization. In type II diabetes, the function of insulin receptors in the body is impaired and normal amounts of insulin generated from pancreas after each meal cannot efficiently metabolize the elevated postprandial glucose. In this cause, extra dosages of insulin are needed to overcome the inefficient binding between insulin and its receptor and maintain normal glycemia. Methods used to increase insulin levels in the circulation include insulin injections, as well as uptake of chemicals to boost insulin secretion from the pancreas. Since GLP-1 is a potent insulin secretagogue released normally from enteroendocrine L-cells to stimulate insulin secretion, the application of GLP-1 in normalizing hyperglycemia has been intensively studied (D'Alessio et al. Am J Physiol Endocrinol Metab 286: E882-890,

2004; Drucker, Diabetes Care 26: 2929-2940, 2003; Hoist Diabetes Metab Res Rev 18: 430-441, 2002). In fact, human clinical studies have demonstrated

GLP-1' s therapeutic effects in reducing plasma glucose in type 2 diabetic patients (Nauck Diabetologia 39: 1546-1553, 1996). However, the difficulty of applying GLP-1 to patients is the short half-life of GLP-1, which is eliminated relatively rapidly from plasma, with a half-life of approximately 5 minutes in humans. Therefore, compositions and methods are needed for maintaining appropriate physiological insulin levels, and specifically for restoring glucose- dependent insulin release for treating types I and II diabetes. Also needed are methods of achieving selective expression of insulin in enteroendocrine cells and long-term expression of the gene products.

SUMMARY OF THE INVENTION The present invention addresses the problems described above by providing compositions and methods for maintaining and restoring appropriate physiological insulin levels in individuals with a glucose-related metabolic disorder. More specifically, the present invention addresses the above- identified problems by achieving expression of insulin targeted specifically to cells of the intestine such as the enteroendocrine cells. Also provided are the methods and compositions for restoration of regulated insulin release in response to blood glucose levels. Expression vectors, recombinant viral particles and transformed enteroendocrine cells are described herein for use in the treatment for disorders of glucose metabolism. Adeno-associated vectors are one preferred method for delivering an expression vector. A recombinant adeno-associated virus serotype 2 (rAAV2) expression vector expressing preproinsulin is another preferred vector. The gene encoding preproinsulin may be under the control or a constitutive of tissue-specific promoter with appropriate enhancers or transcriptional regulators. Preferably, a preproinsulin-expressing recombinant adeno-associated virus serotype 2 expression vector is used to transduce target enteroendocrine cells of the intestinal epithelium. Preferably the expression vector encodes at least preproinsulin. A selection gene or reporter gene can optionally be included in the vector for selection of transduced cells after expression of the vector. Genes encoding luminescent markers can optionally be included in the vector to allow for selection of transduced cells using fluorescence activated cell sorting (FACS). In one embodiment, the vector is administered locally to the intestine to transduce enteroendocrine cells. The rAAV2 has a selective tropism for enteroendocrine cells of the intestinal epithelium over enterocytes. Preproinsulin is expressed in enteroendocrine L cells and co-localized in vesicles with glucagon-like peptide 1 (GLP-1). Stimulation of enteroendocrine cells causes regulated secretion of exogenous insulin into the circulation with. GLP-1. In another embodiment, cells are transfected with a construct where the insulin or proinsulin gene is driven by a tissue specific promoter for selective expression in glucose-responsive enteroendocrine cells. In another embodiment, cells are harvested from a donor and manipulated ex vivo using the rAAV2 vector expressing preproinsulin and then transplanted into a recipient with a disorder of glucose metabolism. The donor cells may be xenogeneic, allogeneic, or autologous and are transduced in culture. Some of the cultured donor cells may be transplanted into the recipient or preserved for future transplantation. Accordingly, it is an object of the present invention to provide expression vectors for genetically modifying intestinal cells such as enteroendocrine cells to express insulin for treating disorders of glucose metabolism. It is a further object of the invention to provide transformed cells for cell-based treatment of disorders of glucose metabolism. It is another object of the invention to provide methods of achieving long-term gene expression by transducing enteric stem cells. It is another object of the invention to provide methods for treating type I diabetes. It is another object of the invention to provide methods for improving the glucagon-like peptide 1 production for treatment of type II diabetes. It is a further object of the present invention to provide compositions and methods that modulate physiologic insulin levels for treating juvenile diabetes, type I diabetes or type II diabetes. Yet another object of the present invention is to provide compositions and methods that modulate physiologic insulin levels for treatment of the disorders of glucose metabolism. With the foregoing and other advantages and features of the invention that will become hereinafter apparent, the nature of the invention may be more clearly understood by reference to the folliwing non-limiting detailed description of the invention and the several views illustrated in the drawings.

BRIEF DESCRIPTION OF DRAWINGS Figure 1 provides structures of rAAV vector plasmids for expression of insulin and EGFP (a), and insulin-EGFP fusion protein (b). (c), DNA sequence at the junction of the preproinsulin-EGFP fusion cDNA in (b). Pvul restriction endonuclease was used to generate a preproinsulin cDNA fragment with a 3 '-blunt end. Smal restriction endonuclease was used to generate an EGFP cDNA fragment from plasmid pEGFP-N2 with a 5'-blunt end. The two blunt ends were then ligated to generate a chimeric fusion cDNA encoding insulin-EGFP fusion protein. PPI: preproinsulin. Figure 2 provides a graph showing data generated from a secretion study of engineered NCI-H716 cells against MH stimulation. Solid bars (test) are for monolayers incubated in the basal medium for 1 h, exposed to meat hydrolysate (MH) for 1 h, then switched back to the basal medium for another 4 h. Empty bars (control) are for monolayers treated with basal medium throughout the test. In each independent test of (a) and (b), the GLP-1 and the insulin secretion rates were normalized against the 1-h sample, which was set at 100%. (c), conversion of proinsulin to insulin. During each 1-h period of the secretion study, proinsulin and insulin concentrations in the samples were determined by proinsulin and the msulin radioimmunoassays each with very low cross-reactivity against the other species (see Materials and Methods, Example I). The percent conversion of proinsulin to insulin was calculated as (insulin)xl00%/(insulin+proinsulin). Each experiment involved 4 independent tests. Bars indicate standard deviations.

Figure 3 provides a table comparing the insulin secretion rates from engineered NCI-H716 cells, mouse β-TC3 insulinomas and engineered insulin-secreting mouse pituitary AtT-20 tumor cells. Figure 4 provides a graph showing insulin secretion from engineered co-cultures against MH stimulation. Empty and solid bars are for monolayers treated with basal medium and 2% MH medium, respectively. Monolayers were treated with basal medium for 2 h (empty bar), exposed to MH for 2 h (solid bar), and then switched back to the basal medium for another 2 h (empty bar). (A) and (B) Insulin secretion rates averaged over 2-hour periods. In each independent test, secretion rates were normalized against the first 2-h sample, which was set at 100%. Below sensitivity means the insulin concentration in the sample was lower than the sensitivity of the assay (2 μU/ml, i.e. 12 pM). (C) and (D) Conversion of proinsulin to insulin. During each 2-h period of the secretion study, proinsulin and insulin concentrations in the samples were determined by proinsulin and insulin radioimmunoassay, each with very low cross-reactivity against the other species. The percent conversion of proinsulin to insulin was calculated as (insulin)xlOO%/(insulin+ρroinsulin). Each experiment involved 4 independent tests. Error bars indicate standard deviations. *(asterisk), • (round dot), # (pound/number sign), and ♦ (solid black diamond) indicate pair-wise statistical comparisons using a one-tailed t-test, assuming unequal variances. * and • : P < 0.01; # : P = 0.40; and ♦: P = 0.10. There were no statistical differences between the proinsulin-to-insulin conversion ratio during each induced period and the ratio during the corresponding prior and subsequent basal period. DETAILED DESCRIPTION OF THE INVENTION The present invention provides compositions and methods for the treatment of disorders of glucose metabolism. The present invention includes methods and compositions for the treatment of disorders including, but not limited to, juvenile diabetes, type I diabetes or type II diabetes. More specifically the present invention provides novel methods for the administration of transformed cells for cell-based treatment of modulating physiological insulin levels. Reference is made below to specific embodiments of the present invention. Each embodiment is provided by way of explanation of the invention, not as a limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment may be incorporated into another embodiment to yield a further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. All cited references including U.S. provisional patent application 60/512,044 are hereby incorporated by reference. For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities of ingredients, reaction conditions, and so forth used in the specification are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification are approximations that can vary, depending upon the desired properties sought to be obtained with the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Disorders related to glucose metabolism continue to be prevalent in most of today's societies. With higher rates of obesity due to a variety of factors such as poor nutrition and/or lack of physical exertion, disorders such as diabetes continues to escalate at alarming rates. Individuals with insulin- dependent diabetes continue to use daily insulin injections to maintain normoglycemia. There exists a desperate and compelling need for effective therapeutics that enable modulation and restoration of regulated insulin release and appropriate physiological insulin levels. As used herein, the term "glucose-related metabolic disorder" is defined as a disorder where the metabolism of glucose by the body is impaired. Examples of such disorders include, but are not limited to, juvenile diabetes, type I diabetes and type II diabetes. Pancreatic substitute combination approaches are desirable for restoring regulated insulin release and supplying engineered cells to restore regulated msulin release to treat diabetes. Surrogate beta cells of the pancreas can be engineered to contribute insulin to an individual in need. An intestinal component of insulin release will be one part of a two-component pancreatic substitute, the other being a hepatic component providing the more basal type of msulin release. Intestinal cells such as enteroendocrine cells are used to provide the acute phase of insulin secretion. The present invention contemplates methods and compositions for expressing insulin in intestinal cells, including but not limited to, enteroendocrine cells. Enteroendocrine cells comprise two subtypes that are distinguished by the hormone they synthesize. L type enteroendocrine cells ("L cells") release GLP-1 in response to a meal while K type enteroendocrine cells ("K cells") release glucose- dependent insulinotropic polypeptide (GIP). Both L and K cells may be engineered to co-express insulin with their endogenous product. I. Vector and Cell Compositions The present invention provides vectors for genetically engineering enteroendocrine cells and genetically modified enteroendocrine cells for selection and transplantation. The term "vector" is used interchangeably with the terms "construct",

"DNA construct" and "genetic construct" to denote synthetic nucleotide sequences used for manipulation of genetic material, including but not limited to cloning, subcloning, sequencing, or introduction of exogenous genetic material into cells, tissues or organisms, such as birds. It is understood by one skilled in the art that vectors may contain synthetic DNA sequences, naturally occurring DNA sequences, or both. The vectors of the present invention are transposon-based vectors as described herein. When referring to two nucleotide sequences, one being a regulatory sequence, the term "operably-linked" indicates that the two sequences are associated in a manner that allows the regulatory sequence to affect expression of the other nucleotide sequence. It is not required that the operably-linked sequences be directly adjacent to one another with no intervening sequence(s). The term "regulatory sequence" is includes promoters, enhancers and other expression control elements such as polyadenylation sequences, matrix attachment sites, insulator regions for expression of multiple genes on a single construct, ribosome entry/attachment sites, introns that are able to enhance expression, and silencers. It is to be understood that as used in the specification and in the claims, "a" or "an" can mean one or more, depending upon the context in which it is used. Thus, for example, reference to "a cell" can mean that at least one cell can be utilized. Target cells The term "enteroendocrine cell" is used to denote endocrine cells of the intestine that are responsible for secreting hormones in the systemic circulation after stimulation by chemical cues in the intestine. This term encompasses both L cell and K cell subtypes that synthesize and release GLP-

1 and GIP respectively. In one embodiment enteroendocrine cells are the preferred target cells. Enteroendocrine form a minority of approximately 1% of intestinal cells. The remaining 99% form the vast majority of other cell types in the intestine. Enteroendocrine are polarized cells with receptors facing the intestinal lumen and specialized secretory mechanisms for secretion to the circulatory system. Stimulation by post-prandial signals results in basal secretion of hormone from secretory vesicles. L cells endogenously produce glucagon-like peptide 1 (GLP-1). Exogenous insulin expressed in transduced L cells is co-localized in vesicles with GLP-1 and displays the same secretion kinetics after stimulus with a meat hydrolysate. L cells also normally express PC 1/3 and PC2 endoproteases. The presence of these endoproteases in this cell type permits the cleavage of proinsulin into insulin. K cells are a subpopulation of enteroendocrine cells that secrete glucose-dependent insulinotropic polypeptide (GIP), a hormone that promotes glucose homeostasis. Insulin may be co-expressed with GIP in K cells for regulation of glucose levels as described in Cheung et al. Science 2000, 290:1959-1962 and Ramshur et al. J Cell Physiol 2002, 192:339-350. In another embodiment, enteric stem or progenitor cells are the preferred target cell. Enteric stem or progenitor cells are localized in the base of crypts of the intestinal villi. These cells generally move upward along the villi toward the lumen of the gut as they mature. Hence, the differentiated, functional cells are found mainly on the villi (small intestine) or toward the top of the colonic crypt (large intestine). During the latter stages of the process, these mature epithelial cells become senescent and are shed intact into the lumen. Stably transduced stem cells permit the transfer of the vector to all daughter cells while maintaining a multipotent state. This permits long-term expression of the gene product despite the high turnover of cells in the intestine. Use of a tissue specific promoter as described herein ensures that the vector is only expressed in daughter cells of the committed L cell lineage. Intestinal stem cells are described in further detail in Booth and Potten (J Clin Invest. 2000 June 1; 105 (11): 1493-1499) and Stelzner et al. (J Gastrointest Surg. 2003 May-Jun;7(4):516-22). Methods of transducing intestinal stem cells are decribed in United States Patent No. 5,786,340 incorporated by reference herein. Expression vectors Adeno-associated virus vector plasmids Recombinant adeno-associated virus (rAAV) has recently been recognized as an extremely attractive vehicle for gene delivery (Muzyczka, 1992) efficiently infect both non-dividing and dividing cells, integrate into a single chromosomal site in the human genome, and pose relatively low pathogenic risk to humans. As discovered by the present inventors, rAAV serotype 2 (rAAV2) displays a selective tropism for L cells of the intestinal epithelium. The expression vector is associated with rAAV particles and administered to the host cells. Administration of a gene construct using rAAN2 allows for selective targeting of L cells. Adeno-associated virus serotype 2 has never been associated with any known human disease and is less likely to become replication-proficient compared to other viral-based gene delivery vectors. Recombinant AAV-2 can be maintained in the human host cell by integration into the host genome, establishing long-term gene expression. In view of these advantages, recombinant adeno-associated virus (rAAV) presently is being used in gene therapy clinical trials for hemophilia B, malignant melanoma, cystic fibrosis, and other diseases. rAAV has also been used for gene delivery in muscle cells (see U.S. Pat. No. 6,461,606). Most commonly, rAAV is produced in 293 cells, COS cells, HeLa cells, KB cells, and other mammalian cell lines. See, e.g., U.S. Pat. Nos. 6,156,303, 5,387,484, 5,741,683, 5,691,176, and 5,688,676; U.S. patent application 2002/0081721, and International Patent Applications WO 00/47757, WO 00/24916, and WO 96/17947.r^ 4F vectors have been developed by substituting all viral open reading frames with a therapeutic minigene, while retaining the cis elements contained in two inverted terminal repeats (ITRs) (Samulski et al, 1987; Samulski et al., 1989). Following transduction, rAAV genomes can persist as episomes (Flotte et al., 1994; Afione et al., 1996; Duan et al., 1998), or alternatively can integrate randomly into the cellular genome (Berns et al., 1996; McLaughlin et al., 1988; Duan et al., 1997; Fisher-Adams et al., 1996; Kearns et al., 1996; Ponnazhagan et al., 1997). Transduction of rAAV has been demonstrated in vitro in cell culture (Muzyczka, 1992) and in vivo in various organs (Kaplitt et al., 1994; Walsh et al., 1994; Conrad et al., 1996; Herzog et al., 1997; Snyder et al., 1997). The selective tropism for enteroendocrine cells was previously unknown and provides a novel method to selectively transduce the small proportion of intestinal cells that make up the enteroendocrine population. The selective tropism for enteroendocrine cells could not have been predicted based on earlier studies. The genus Dependovirus includes adeno-associated virus (AAV), which normally infects humans (e.g., serotypes 2, 3A, 3B, 5, and 6) or primates (e.g., serotypes 1 and 4), and related viruses that infect other warmblooded animals (e.g., bovine, canine, equine, and ovine adeno-associated viruses). Generally, the AAV serotypes have genomic sequences of significant homology at the amino acid and the nucleic acid levels, provide an identical set of genetic functions, produce virions which are essentially physically and functionally equivalent, and replicate and assemble by practically identical mechanisms. For the genomic sequence of AAV serotypes and a discussion of the genomic similarities see, for example, GenBank Accession number U89790; GenBank Accession number JO 1901; GenBank Accession number AF043303; GenBank Accession number AF085716; Chiorini et al., J. Vir. 71: 6823-33(1997); Srivastava et al., J. Vir. 45:555-64 (1983); Chiorini et al., J. Vir. 73:1309-1319 (1999); Rutledge et al., J. Vir. 72:309-319 (1998); and Wu et al., J. Vir. 74: 8635-47 (2000). In one embodiment, a recombinant polynucleotide vector of the present invention is derived from adeno-associated virus (AAV) and comprises a constitutive or regulatable promoter capable of driving sufficient levels of expression of the heterologous DNA in the viral vector. Preferably, a recombinant vector of the invention comprises inverted terminal repeat sequences of AAV, such as those described in WO 93/24641. The nucleotide sequences of AAV ITR regions are known. See, e.g., Kotin, R. M. (1994) Human Gene Therapy 5:793-801; Berns, K. I. "Parvoviridae and their Replication" in Fundamental Virology, 2nd Edition, (B. N. Fields and D. M. Knipe, eds.) for the AAV-2 sequence. AAV ITRs used in the vectors of the invention need not have a wild-type nucleotide sequence, and may be altered, e.g., by the insertion, deletion or substitution of nucleotides. Additionally, AAV ITRs may be derived from any of several AAV serotypes, including without limitation, AAV-1, AAV-2, AAV-3, AAV-4, AAV-5, AAVX7, etc. Genes of Interest This invention provides polynucleotide cassettes containing at least one gene of interest. Suitable DNA molecules for use in AAV vectors will generally be less than about 5 kilobases (kb) in size. Preferably between 1-3 kb in size. Genes encoding protein and peptide hormones are a preferred class of genes of interest in the present invention. In a preferred embodiment of the present invention, the gene of interest is a proinsulin gene and the desired molecule is insulin. Proinsulin consists of three parts: a C-peptide and two strands of amino acids (the alpha and beta chains) that form the insulin molecule. In one embodiment, proinsulin is expressed in L cells that have been transduced with the rAAV2 vector encoding preproinsulin. One example of a proinsulin polynucleotide sequence is shown in SEQ ID NO:l, wherein the C-peptide cleavage site spans from Arg at position 31 to Arg at position 65. The vector may encode proinsulin or alternatively insulin mutants that require no cleavage for activation. Furthermore, one of skill will recognize that, as mentioned above, individual substitutions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids (typically less than about 5%, more typically less than about 1%) in an encoded sequence are conservatively modified variations where the alterations result in the substitution of an amino acid with a chemically similar amino acid. It is to be understood that codons in the polynucleotide sequences associated with the genes of interest may be substituted with other codons that encode for such conservative amino acid substitutions. Conservative substitution tables providing functionally similar amino acids are well known in the art. The following six groups each contain amino acids that are conservative substitutions for one another:

1) Alanine (A), Serine (S), Threonine (T);

2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q);

4) Arginine (R), Lysine (K);

5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and

6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W). A conservative substitution is a substitution in which the substituting amino acid (naturally occurring or modified) is structurally related to the amino acid being substituted, i.e., has about the same size and electronic properties as the amino acid being substituted. Thus, the substituting amino acid would have the same or a similar functional group in the side chain as the original amino acid. A "conservative substitution" also refers to utilizing a substituting amino acid which is identical to the amino acid being substituted except that a functional group in the side chain is protected with a suitable protecting group. Suitable protecting groups are described in Green and Wuts,

"Protecting Groups in Organic Synthesis", John Wiley and Sons, Chapters 5 and 7, 1991, the teachings of which are incorporated herein by reference. Preferred protecting groups are those which facilitate transport of the peptide through membranes, for example, by reducing the hydrophilicity and increasing the lipophilicity of the peptide, and which can be cleaved, either by hydrolysis or enzymatically (Ditter et al., 1968. J. Pharm. Sci. 57:783; Ditter et al., 1968. J. Pharm. Sci. 57:828; Ditter et al., 1969. J. Pharm. Sci. 58:557; King et al., 1987. Biochemistry 26:2294; Lindberg et al., 1989. Drug Metabolism and Disposition 17:311; Tunek et al., 1988. Biochem. Pharm. 37:3867; Anderson et al., 1985 Arch. Biochem. Biophys. 239:538; and Singhal et al., 1987. FASEB J. 1:220). Suitable hydroxyl protecting groups include ester, carbonate and carbamate protecting groups. Suitable amine protecting groups include acyl groups and alkoxy or aryloxy carbonyl groups, as described above for N-terminal protecting groups. Suitable carboxylic acid protecting groups include aliphatic, benzyl and aryl esters, as described below for C-terminal protecting groups. In one embodiment, the carboxylic acid group in the side chain of one or more glutamic acid or aspartic acid residues in a peptide of the present invention is protected, preferably as a methyl, ethyl, benzyl or substituted benzyl ester, more preferably as a benzyl ester. Promoters The first promoter operably-linked to a first gene of interest and the second promoter operably-linked to a second gene of interest can be a constitutive promoter or tissue specific promoter. Constitutive promoters include, but are not limited to, immediate early cytomegalovirus (CMV) promoter, herpes simplex virus 1 (HSV1) immediate early promoter, SV40 promoter, lysozyme promoter, early and late CMV promoters, early and late HSV promoters, /J-actin promoter, tubulin promoter, Rous-Sarcoma virus (RSV) promoter, and heat-shock protein (HSP) promoter. Inducible promoters include tissue-specific promoters, developmentally-regulated promoters and chemically inducible promoters. Examples of L-cell tissue-specific promoters include the proglucagon promoter. The proglucagon promoter is silent in enterocytes but is expressed specifically in L cells. Properties and structural elements for the proglucagon promoter have been described in Nian et al (Am J Physiol Regul Integr Comp Physiol 2002 282:R173-183); Wang et al. (J Biol Chem 2003. -278(35):32899- 32904); Wang and Drucker (J Biol Chem 1995; 270(21): 12646-12652); and Jin and Drucker (Mol Cell Biol 1996; 16(1): 19-28). The proglucagon promoter is regulated by cAMP-response element binding (CREB), islet- 1 protein binding. Cell specificity is mediated by proteins that interact with the proximal Gl promoter element. Elements or fragments of the proglucagon promoter may be conjugated with constitutive promoters or enhancers for improved gene expression. Examples of K-cell tissue-specific promoters include the glucose- dependent insulinorropic polypeptide (GIP) promoter. Properties and structural elements for the GIP promoter have been described in Boylan et al. J Biol Chem 1997 272(28):17438-43, Cheung et al. Science, 2000, 290:1959-1962, Ramshur et al. J Cell Physiol 2002, 192:339-350). Elements or fragments of the GIP promoter may be conjugated with constitutive promoters or enhancers for enhanced gene expression. Other promoters that have specific expression in L cells or K cells may be used in the present expression vectors. Tissue specific promoters may be strong or weak promoters as long as expression is specific to enteroendocrine cells. Appropriate enhancers can be conjugated to the tissue-specific promoters to enhance expression of the gene of interest or else sequences from the tissue-specific promoter that convey tissue specificity can be conjugated to constitutive promoters to result in modulation of the gene expression in L cells. Tissue-specific expression to the enteroendocrine cells prevents blanket expression of the gene of interest to all intestinal cells. Poly-adenylation sequences As used herein an "effective polyA sequence" refers to either a synthetic or non-synthetic sequence that contains multiple and sequential nucleotides containing an adenine base (an A polynucleotide string) and that increases expression of the gene to which it is operably-linked. A polyA sequence may be operably-linked to any gene in the expression vector. A preferred polyA sequence is optimized for use in the host animal or human. Examples of preferred polyA sequences include but are not limited to SV40 polyA sequence, the human growth hormone polyA sequence, bovine growth hormone polyA sequence, and HSV-TK polyA sequence. Enhancers Enhancers also consist of composite elements and/or single binding sites. They modulate the level of transcription depending on the type of tissue, developmental stage, stage of the cell cycle, induction by hormones or other molecular signals. An enhancer can act over many kb 3' or 5' from the transcription start site, possibly from within an intron, and its activity does not depend on its orientation. Enhancers can generally be placed in either orientation, 3' or 5', with respect to promoter sequences. In addition to the natural enhancers, synthetic enhancers can be used in the present invention. These enhancers may or may not be operably-linked to their native promoter and may be located at any distance from their operably-linked promoter. A promoter operably-linked to an enhancer is referred to herein as an "enhanced promoter." In one embodiment, the insulin gene enhancer located within the 5'-flanking region of the insulin gene is used. In another embodiment, the Simian Virus 40 enhancer is used. Other enhancers that enhance gene expression in enteroendocrine cells are contemplated herein. Introns The vectors can also include introns inserted into the polynucleotide sequence of the vector as a means for increasing expression of heterologous DNA encoding a protein of interest. For example, an intron can be inserted between a promoter sequence and the region coding for the protein of interest on the vector. Introns can also be inserted in the coding regions. Exemplified in the present invention is the use of a chimeric intron from plasmid pRL/Null (Promega, Madison, WI). Reporters Reporters are genes that encode proteins whose presence can be easily be determined and quantified or used for selection. As used herein, the term "reporters" is understood to be, and can be used interchangeably herewith, a detectable marker or detectable label. For optimal use, the reporter proteins must: 1) have an easy and very sensitive assay to detect their presence. 2) be very stable in the cell and 3) not be present in the cell prior to transduction. Examples of reporter genes include but are not limited to Firefly luciferase, Renilla luciferase, green fluorescent protein (GFP), enhanced green fluorescent protein (EGFP), Red fluorescent protein (RFP) and blue fluorescent protein (BFP). A reporter protein can be expressed as a fusion protein with the gene of interest or expressed as a separate protein in the host cell. Expression of the reporter proteins provides means to select out transduced cells using reporter-dependent sorting methods such as fluorescence activated cell sorting (FACS). Other reporters are contemplated where luminescence can be captured by the luminometer or by charged coupled device (CCD) camera. Formulations The expression vectors and delivery vehicles of the present invention may include classic pharmaceutical preparations. One of ordinary skill will employ appropriate salts and buffers to render delivery vectors stable and allow for uptake by target cells. Buffers also will be employed when recombinant cells are introduced into a patient. Aqueous compositions of the present invention comprise an effective amount of the vector to cells, dissolved or dispersed in a pharmaceutically acceptable carrier or aqueous medium. The phrase "pharmaceutically or pharmacologically acceptable" refer to molecular entities and compositions that do not produce adverse, allergic, or other untoward reactions when administered to an animal or a human. As used herein, "pharmaceutically acceptable carrier" includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutically active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the vectors or cells of the present invention, its use in therapeutic compositions is contemplated. Supplementary active ingredients also can be incorporated into the compositions. Under ordinary conditions of storage and use, these preparations contain a preservative to prevent growth of microorganisms. Administration of these compositions according to the present invention will be via any common route so long as the target tissue is available via that route. This includes oral, intestinal, intraperitoneal or intravenous injection. Such compositions would normally be administered as pharmaceutically acceptable compositions, described supra. Additional formulations are suitable for oral administration in liquid or solid form. Oral formulations include such typical excipients as, for example, pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate and the like. The compositions take the form of solutions, suspensions, tablets, pills, capsules, sustained release formulations or powders. Enteric formulations are often used to protect an active ingredient from the strongly acidic contents of the stomach. Such formulations are created by coating a solid dosage form with a film of a polymer which is insoluble in acidic environments, and soluble in basic environments. Exemplary films include but are not limited to cellulose acetate phthalate, polyvinyl acetate phthalate, hydroxypropyl methylcellulose phthalate and hydroxypropyl methylcellulose acetate succinate. An effective amount of the therapeutic agent is determined based on the intended goal. The term "unit dose" refers to a physically discrete unit suitable for use in a subject, each unit containing a predetermined quantity of the therapeutic composition calculated to produce the desired response in association with its administration, i.e., the appropriate route and treatment regimen. The quantity to be administered, both according to number of treatments and unit dose, depends on the subject to be treated, the state of the subject, and the protection desired. Precise amounts of the therapeutic composition also depend on the judgment of the practitioner and are peculiar to each individual. An effective amount of insulin-producing enteroendocrine cells that are required to restore effective insulin release can be calculated as follows. Since an average person releases about 0.5 - 0.7 units of insulin per kg per day (American Association of Diabetes Educators, A core curriculum for diabetes education, (2001), 4th Edition, Chicago), the number of engineered enteroendocrine cells needed to produce the same amount of insulin is preferably between 1 x 10¹¹ and 2 x 10^π cells and more preferably between 1.1 x 10¹¹ and 1.6 x 10^π cells for a 70-kg person. These values are derived from doing the following calculation:

cells,

where 79 fmole/(10⁶cellsxh) is the basal insulin secretion rate of recombinant NCI-H716 cells. In another calculation to estimate the number of engineered enteroendocrine cells to maintain the basal insulin level in the body, the dynamic insulin balance can be written as:

Δ(Vc) / Δt = N x q- k x Vc, where Δ(Nc) is the change of insulin amount in the body over time period Δt; Ν is the number of cells; q is the specific insulin secretion rate; and k is the reaction constant of insulin degradation. First order degradation of insulin in the body is assumed. We also assume 150 fmole/ml of basal insulin level in the circulation, 5 L of blood and 5-min half-life of insulin(J. Schirra et al. J

Clin Invest 97 (1996) 92-103; American Association of Diabetes Educators, A core curriculum for diabetes education, (2001), 4th Edition, Chicago). To obtain the reaction constant k of insulin degradation, we do the following calculation:

Δ(Vc) / Δt = - k x Vc, where zero generation of insulin and only insulin degradation occurs. Integrating, we obtain ln(Vc/Vco) = -k x t, where VcNco is 1/2 when t = 5 min; therefore, k is 0.139 min^"1 or 8.34 h^"1. Assuming insulin concentration reaches steady state at the basal level, the number of required engineered L- cells to maintain the basal insulin level is: N = k x Vc / q = (8.34 h^"1 x 5 L x 150 fmole/ml x 1000 ml/L) / 79 fmole/(10⁶cellsxh) = 7.9 x 10¹⁰ cells. The result is within the range of the first estimation, thus validating the approximate equivalence of the two approaches. Following the second approach, we estimate the number of enteroendocrine L-cells in the body by doing the following calculation: ln(Vc/Vco) = -k' x t = k' = 8.34 h^"1, where k' is the reaction constant of GLP-1 degradation and we assume 5-min half-life of GLP-1 in the circulation (Kieffer et al. Endocr Rev 20 (1999) 876-913), and N' (the number of L-cells in the body) = k' x Vc' / q' = (8.34 h^"1 x 5 L x 1 pmole/L) / 9.5 pmole/(10⁶cellsxh) = 4.4 x 10⁹ cells (assuming 1 pmole/L of the basal GLP-1 level, 5 L of blood (J. Schirra, et al. J Clin Invest 97 (1996) 92-103.) and the averaged basal GLP-1 secretion rate, 9.5xl0^"3 pmole/(10⁶ cellsxh), obtained via the secretion study of NCI-H716 cells in the result section), which is less than the number required to maintain the basal insulin level by a factor of 25 - 36. Thus, to overcome the deficiency, a higher insulin secretion rate from the engineered L-cells is necessary to reduce the required L-cell number. This is done by improving the transduction efficiency, such as using a higher viral titer as well as multiple transductions, which would increase the percentage of transduced cells and the gene dosage per cell.

II. Methods of Use The present method provides a means to selectively engineer insulin- secreting enteroendocrine cells from a majority of enterocytes in the intestinal epithelium. In Vivo Administration of Viral Vector The vectors and cells of the present invention are advantageously administered in the form of injectable compositions either as liquid solutions or suspensions; solid forms suitable for solution in, or suspension in, liquid prior to injection also may be prepared. These preparations also may be emulsified. A typical composition for such purposes comprises a 50 mg or up to about 100 mg of human serum albumin per milliliter of phosphate-buffered saline. Other pharmaceutically acceptable carriers include aqueous solutions, non-toxic excipients, including salts, preservatives, buffers and the like. Examples of non-aqueous solvents are propylene glycol, polyethylene glycol, vegetable oil and injectable organic esters, such as ethyloleate. Aqueous carriers include water, alcoholic/aqueous solutions, saline solutions, parenteral vehicles such as sodium chloride, Ringer's dextrose, etc. Intravenous vehicles include fluid and nutrient replenishers. Preservatives include antimicrobial agents, anti-oxidants, chelating agents and inert gases. The pH and exact concentration of the various components in the pharmaceutical are adjusted according to well-known parameters. The dosage of recombinant vector or the virus to be administered to an animal in need of such treatment can be determined by the ordinarily skilled clinician based on various parameters such as mode of administration, duration of treatment, the disease state or condition involved, and the like. Typically, recombinant virus of the invention is administered in doses between 10⁵ and 10¹⁴ infectious units. The recombinant vectors and virus of the present invention can be prepared in formulations using methods and materials known in the art. Numerous formulations can be found in Remington's Pharmaceutical Sciences, 15^th Edition (1975). Ex Vivo Transduction Harvesting Cells Mature enteroendocrine cells may be harvested from intestinal biopsies for ex vivo amplification and manipulation. Xenogeneic tissue may be harvested from a donor animal and subjected to cell dissociation and culture procedures. Preferable donor animals for intestinal tissue are primates, pigs, or any animals with intestinal tissue that is histocompatible with the human intestine. Allogeneic tissue is preferably harvested from organ donors and subjected to similar cell dissociation and culture procedures. Autologous cells are preferably harvested from a live donor by biopsy and subjected to cell dissociation and culture. Intestinal cells are preferably isolated using methods based on

Perreault and Beaulieu (Exp Cell Res 1998 245:34-42) to provide cultures of intestinal epithelial cells and provide isolation of intestinal stem cells. The intestine is isolated from the donor and opened longitudinally, washed in phosphate buffered saline and cut into small pieces. The tissue pieces are inclubated in ice-cold Matrisperse™ (Collaborative Biomedical Products, Bedford, MA) for 8-10 hours at 4°C without agitation. Matrisperse™ allows the isolation of a large proportion of the epithelium free of mesenchymal cells. It is within the capability of the skilled artisan to determine optimal incubation times and temperatures for separating the intestinal epithelium as crypts from the mucosal wall. Incubation times and temperatures will be adjusted accordingly for a given species to optimize separation of the tissue layers and increase cell viability or decrease incubation time. It is desirable to reduce separation of single cells and contamination from other cell types, such as fibroblasts, unless additional efforts are made to eliminate contaminating cell types. Each dish is gently shaken to separate the epithlieum from the underlying submucosa. Epithelial fragments are collected, washed in PBS, resuspended in culture medium and dissociated by gentle trituration and filtering through an 80 μm nylon mesh. The mesh is rinsed in growth medium and backwashed with complete serum-free growth medium containing antibiotics. Aliquots of cell suspension are plated on compatible culture substrata in appropriate growth media. Growth of stem cells in the cultures can be promoted by treating cultures with mitogenic growth factors known to promote proliferation of stem cells and progenitor cells. Such growth factors include but are not limited to bFGF, EGF, TGF beta, TGF alpha or stem cell factor. These proliferation factors can be added to cultures to maintain the stem cells in an actively proliferating state and prevent differentiation of stem cells into committed intestinal cell lineages until such a time as differentiation is desired. Gene Introduction into Target Cells Various procedures may be used to introduce an expression vector into a target cell type of the present invention. General methods of gene transfection are routine in the art and are described in "Current Protocols in Molecular Biology" Chapter 9. (Eds. Ausubel, F.M. et al.) John Wiley & Sons. Transfection reagents are commercially available and include but are not limited to DAC-30™, DC-30™, Lipofectin™, LipofectAMINE PLUS™, Effectene™, FuGene 6™ and Superfect™. General transfection methods are preferably used for ex-vivo manipulation of cells using tissue-specific promoters for selective expression of the gene construct in enteroendocrine cells. In another embodiment of the present invention, an rAAV is used to selectively transduce enteroendocrine cells of the intestinal epithelium. The rAAV displays selective tropism for enteroendocrine cells avoiding infection of enterocytes. Cells can be manipulated ex-vivo by adding the rAAV to a adherent cells or cells in suspension. Cells can also be transduced by administering a suspension of rAAV in solution in the vicinity of the enteroendocrine cells. Selecting Cells Various procedures may be employed to separate transduced cells from untransduced contaminating cells. These include physical separation, magnetic separation using antibody-coated magnetic beads, affinity chromatography, and cytotoxic agents joined to a monoclonal antibody or used in conjunction with a monoclonal antibody. Also included is the use of fluorescence activated cell sorters (FACS) wherein the cells can be separated on the basis of the level of fluorescence. All of these techniques are well known to those skilled in the art and are described in various references including U.S. Pat. Nos. 5,061,620; 5,409,8213; 5,677,136; and 5,750,397; and Yau et al., Exp. Hematol. 18:219- 222 (1990). More recently, selectable markers that are combined with fluorescence activated cell sorting (FACS) have been used, for example, green fluorescent protein (GFP). EGFP-expressing cells are analyzed by flow cytometry using FACSVantage or FACSstar Plus (Becton Dickinson Immunocytometry Group) at an excitation wavelength of 488 nm and an emission wavelength of 515-545 nm according to manufacturer's protocol. Buoyancy based separation may also be used to select the target cell population based on their different cellular densities ( See U.S. Pat 6,767,738). Density gradients can be created using any suitable media, including, PERCOLL.TM. (polyvmylpyrrolidone-coated silica colloids), FICOLL.TM. (copolymers of sucrose and epichlorohydrin), sucrose, and the like. In an even more preferred embodiment of the present invention, a PERCOLL.TM. (polyvmylpyrrolidone-coated silica colloids) gradient is employed. Engineered cells may be cryopreserved for future use. Alternatively cells may be harvested and cryopreserved and transduced or transfected at a future time. Methods of cryopreservation are well known in the art. In general terms, cryopreservation of animal cells involves freezing the cells in a mixture of a growth medium and another liquid that prevents water from forming ice crystals, and then storing the cells at liquid nitrogen temperatures (e.g., from about -80 to about -196°C). Insulin Expression Assay Cultured cells may be stimulated with meat hydroslysate and assayed for the presence of insulin secreted into the culture. The secretion test is initiated by incubating stabilized monolayers in basal medium for 2 hours to determine basal secretion rate and then exposing to medium supplemented with meat hydrolysate to stimulate insulin secretion for 2 hours and then washed three times and incubated in basal medium for another 2 hours. All samples are collected for insulin and proinsulin detection. Conventional ELISA methods, immunohistochemistry, radioimmunoassay, fluorescence detection or luciferase assays are used to detect proinsulin and insulin in the culture media after the stimulus. Alternatively, GLP-1 or GIP can be assayed using ELISA because of the similar secretion kinetics as expressed insulin and provides an indirect method to measure insulin secretion. For in vivo transduction, blood glucose levels can be monitored using conventional blood glucose monitoring methods and apparati to evaluate the effects of viral transduction on circulating insulin levels. Transplantation of Cells The engineered cells of the present invention may be introduced into animals with certain needs, such as animals with insulin-dependent diabetes. In the diabetic treatment aspects, ideally cells are engineered to achieve glucose dose responsiveness closely resembling that of islets in the pancreas. However, other cells will also achieve advantages in accordance with the invention. Previous studies have shown that implantation of poorly differentiated insulin-secreting rat tumor cells into animals results in a return to a more differentiated state, marked by enhanced insulin secretion in response to metabolic fuels (Madsen et al., Proc Natl Acad Sci U S A. 1988 85(18):6652-6). Although related to the present invention and not generally predictive of the behavior of the present engineered cells, exposure of engineered cell lines or intestinal stem cells to the in vivo milieu may have some effects on their response(s) to secretagogues resulting in enhanced secretion. Engineered cells may be transplanted into an individual by engineering a segment of gut containing the modified cells and transplanting the engineered segment of intestine. In one embodiment, genetically engineered intestine is made using an approach based on the work of Dr. Matthias Stelzner (University of Washington, Annual Research Report Archives Website). The engineered segment of gut may be produced by seeding ileal mucosal stem cells into jejunum that had its inner lining, the "mucosal layer", removed. The stem cells give rise to a layer of ileal mucosal cells that is integrated into the normal jejunum mucosa. The new cells, the "neo-ileal intestine", can actively absorb bile acids while normal jejunal cells do not have this special property. Similar stem cell differentiation into endocrine cells and integration of the latter with the mucosa can be applied in the present invention. In another embodiment, genetically engineered intestine is made using an approach is based on the work of Dr. Joseph Vacanti in tissue engineering neointestine. This approach comprises seeding intestinal organoids onto a scaffold made of biomaterials such as, but not limited to, polyglycolic acid and polylactic acid. The cell-scaffold constructs are implanted where they develop into vascularized cystic structures resembling neointestine. The biomaterials are completely absorbed over time. Histologically, such developed neomucosa is characterized by a columnar epithelium containing goblet cells, Paneth cells and Crypt-like invaginations that resemble crypt-villus structures. The neomucosa has been anastomosed to the native bowel without causing feeding problems. Brush-border enzymes, basement membrane components, and electrophysiologic properties similar to those of normal small bowel are present (Chen & Beirele, Biomaterials 25 (2004) 1675-1681). These methods are described in U.S. Patent Publication 2003/0129751, and United States Patents 6,348,069, 6,455,311 all of which are incoφorated by reference herein. The invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes, and are intended neither to limit nor define the invention in any manner. EXAMPLE I Development of Genetically Engineered Human Intestinal Cells for Regulated Insulin Secretion Using rAAV-mediated Gene Transfer rAAV-mediated insulin gene transfer was used to genetically modify a model cell type, the human NCI-H716 intestinal cell line, for regulated insulin release. This line was derived from a poorly differentiated caecal adenocarcinoma (Park et al. Cancer Res 47 (1987) 6710-6718), and has been described to exhibit enteroendocrine L-cell-like characteristics, in particular formation of secretory granules and regulated GLP-1 secretion after differentiation (Reimer et al, Endocrinology 142 (2001) 4522-4528, deBruine et al Arch B Cell Pathol Incl Mol Pathol 62 (1992) 311-320, and deBruine et al Am J Pathol 142 (1993) 773-782). This cell line acts as a human cellular model to demonstrate that insulin release from the engineered GLP-1 - secreting intestinal cells responds to physiologic stimuli.

Materials and methods Cell culture. Human NCI-H716 cells (ATCC, Manassas, VA) were grown in suspension in RPMI 1640 medium supplemented with 10% fetal bovine serum, 100 units/ml penicillin and 100 μg/ml streptomycin. Adhesion and endocrine differentiation were initiated by growing the cells on Matrigel (Becton Dickinson, Bedford, MA)-coated tissue culture surfaces in differentiation medium (DMEM supplemented with 10% fetal bovine serum). Human embryonic kidney 293 (HEK293) cells (ATCC) used for AAV production and human HT-1080 fibrosarcoma cells (ATCC) used for AAV titer determination were grown in DMEM supplemented with 10% heat- inactivated fetal bovine serum and 100 units/ml penicillin/streptomycin. Cell cultures were all maintained at 37°C in a 5% CO₂ / 95% air humidified atmosphere. rAA V vector plasmid. Figure la shows the structure of the rAAV vector plasmid constructed for insulin and EGFP expression. The backbone of the plasmid originated from plasmid pAAV-MCS (Stratagene, La Jolla, CA), which contains inverted terminal repeats (ITRs) of AAV serotype 2 (AAV2) (SEQ ID NO:2 and 12). Human preproinsulin cDNA with the His BlO-to-Asp mutation (BIO mutation) was a generous gift from Genentech, Inc (San Francisco, CA) (Grodkreutz et al, J Biol Chem 269 (1994) 6241-6245). The 5'-end of this gene was connected to a chimeric intron obtained from plasmid pRL/Null (Promega, Madison, WI) for optimal splicing (SEQ ID NO:4). The 3'-end of this gene was connected to a fragment originated from plasmid pGL3 -control (Promega) containing Simian Virus 40 (SV40) late polyadenylation signal for transcription termination and SV40 enhancer to elevate gene expression (SEQ ID NO:6). The human cytomegalovirus (CMV) promoter (SEQ ID NO:3) provided by the backbone plasmid pAAV-MCS was used to constitutively drive the insulin gene expression. To include an EGFP expression cassette for reporter assays, a gene fragment containing EGFP cDNA (SEQ ID NO: 8) and a synthetic intron from plasmid pEGFP-IRESpuro (SEQ ID NO: 9) (Clontech, Palo Alto, CA) was connected to the SV40 promoter (SEQ ID NO:7) (originated from plasmid pGL3-control) then inserted to the 3'-end of the insulin expression cassette. The human growth hormone (hGH) polyadenylation signal (SEQ ID NO: 10) provided by the backbone plasmid pAAV-MCS supported transcription termination of EGFP expression. The finished construct contained insulin and EGFP expression cassettes flanked by AAV2 ITRs. rAAV vector production, purification, titration and transduction. Production of the rAAV vector, AAV/insulin/EGFP, encoding insulin and EGFP expression cassettes was accomplished using the AAV Helper-Free System (Stratagene) as described in the manufacture's protocol. Briefly, sixty 100-mm dishes of approximately 70% confluent, low-passage HEK293 cells were co-transfected with the constructed insulin and EGFP expression plasmid (Figure IA), plasmid pAAV-RC (Stratagene) and plasmid pHelper (Stratagene). Transfections were carried out with FUGENE 6 reagent (Roche, Indianapolis, IN) following the manufacturer's directions. Plasmid plnsulin-EGFP is made of the following polynucleotide elements operably linked so as to form a functioning expression construct. Left AAV2 ITR (SEQ ID NO:2); CMV promoter (SEQ ID NO:3); Intron (SEQ ID NO:4); PPI cDNA (SEQ ID NO:5); SV40 polyA/SV40 enhancer (SEQ ID NO:6); SV40 Promoter (SEQ ID NO:7); EGFP cDNA (SEQ ID NO:8); Intron (SEQ ID NO:9); hGH polyA (SEQ ID NO: 10); Right AAV2 ITR (SEQ ID NO: 11). For each 100-mm dish, HEK293 cells were transfected with 2.5 μg of each of the three plasmids and 15 μl of FUGENE 6 reagent. Transfected cells were harvested 3 days after transfection. Purification of rAAV particles followed the protocol developed by Auricchio et al. (Hum Gene Ther 12 (2001) 71-76) using a single-step heparin column chromatography. Titration of infectious rAAV particles (infectious units) was performed by fluorescence- activated cell sorting (FACS) following the protocol offered by Stratagene (Instruction Manual of AAV Helper-Free System) using HT-1080 cells as targets for transduction. FACS analysis was carried out using a Becton Dickinson LSR benchtop flow cytometer (BD Bioscience, Lexington, KY). The number of infectious units per ml of viral stock was approximately 7xl0⁷. Transduction of NCI-H716 cells was performed in suspension using a multiplicity of infection (MOI) of 10 infectious units per cell in a 6-well-plate with 10⁶ cells/well. Prior to transduction, NCI-H716 cells were centrifuged, washed with L-RPMI (RPMI supplemented with 2% FBS) then centrifuged again. A viral suspension prepared in L-RPMI was added to the cell pellet, mixed, then passed through a 21G needle several times. The cell-virus suspension was transferred to a 6-well-plate with 1.5-ml suspension per well. After 2-h incubation at 37°C, 1.5 ml of H-RPMI (RPMI supplemented with 18% FBS) were added to each well. Images of EGFP expression in NCI-H716 cells were taken 3 days after transduction using OLYMPUS 1X70 fluorescence microscope (Lake Success, NY). Transduction efficiencies were determined at the same time using FACS with EGFP as the reporter. Immunochemical staining ofinsulin/proinsidin. AAV/insulin/EGFP transduced NCI-H716 cells were examined by immunochemical staining for insulin expression 3 days after transduction. Prior to the staining procedure, aggregates of transduced cells were disrupted by passing the cell suspension through a 21 G needle several times. Cells were then seeded on a poly-L-lysine coated 4-chamber slide, fixed with 4% paraformaldehyde and permeabilized with 0.5% Triton X-100 in PBS. The

DAKO ARK kit (DAKO, Carpinteria, CA) and mouse monoclonal anti-human insulin/proinsulin antibody (Sigma, cat # 1-2018; diluted 1:1000) were applied to detect the presence of insulin/proinsulin in the fixed monolayer following the manufacturer's directions. This kit incorporates the avidin-biotin complex with peroxidase and uses diaminobenzidine as the chromogen. Secretion studies. Three million of AAV/insulin/EGFP transduced NCI-H716 cells were differentiated by growing on Matrigel-coated, 60-mm culture wells in 4 ml differentiation medium for two days. The culture medium was then switched to basal medium [DMEM (GIBCO, cat.# 23800-022, Grand Island, NY) supplemented with 5 mM glucose and 1% fetal bovine serum] overnight before secretion studies. On the day of the experiment, parallel cultures were washed and incubated in basal medium for two consecutive 1-h periods to stabilize the basal secretions of insulin and GLP-1. The secretion test was initiated by incubating stabilized monolayers in basal medium for one hour to determine the basal secretion rate. Monolayers were then exposed to 2% (w/v) meat hydrolysate (Sigma, cat. # P-7750, supplemented in basal medium) to stimulate GLP-1 and insulin secretion (test) or maintained in basal medium (control) for one hour. Cultures were then washed three times with basal medium and maintained in basal medium for another four hours. Every hour, the culture medium was renewed and samples were collected for insulin, proinsulin and GLP-1 assays. Assays. Insulin and proinsulin concentrations were measured by human insulin specific radioimmunoassay (RIA) kit (LINCO Research, St. Charles, MI, cat. # HI-14K) and human proinsulin RIA kit (LINCO research, cat. # HPI-15K), respectively, according to the manufacturer's protocols. The human insulin specific RIA kit cross-reacts with proinsulin at less than 0.2%. The human proinsulin RIA cross-reacts with human insulin at less than 0.1% (manufacturer's specifications). Radioactivities were determined in Auto- Gamma Counting System, Cobra II (Packard, Meriden, CT). GLP-1 concentration was measured by GLP-1 ELISA kit (LINCO research, cat. # EGLP-35K). This kit measures only active forms of GLP-1, i.e., GLP-1 (7- 36) and GLP-1 (7-37), and does not cross-react with other forms of GLP-1, including GLP-1 (1-36), GLP-1 (1-37), GLP-1 (9-36) and GLP-1 (9-37) (manufacturer's specifications). The fluorochrome generated from the ELISA assay was quantified using a Spectra Max Gemini plate reader (Molecular Devices, Sunnyvale, CA). Expression of insulin-EGFP fusion protein. Figure lb shows schematically the rAAV vector plasmid designed for the expression of insulin-EGFP fusion protein. The backbone of the plasmid is the same as the plasmid in Figure la except the gene of interest is insulin- EGFP fusion protein (SEQ ID NO: 13). EGFP encoded from the plasmid pEGFP-N2 (Clontech) is located at the C terminus of preproinsulin. Figure lc shows the DNA sequence at the junction of preproinsulin-EGFP cDNA fusion and the restriction enzymes used for the connection of preproinsulin cDNA and EGFP cDNA. Production, purification and titration of the rAAV vector, AAV/FUSION, encoding the insulin-EGFP fusion protein for infecting NCI- H716 cells followed the same procedure as previously described for preparation of AAV/insulin/EGFP. Plasmid plnsulin-EGFP-fusion-protein is made of the following polynucleotide elements operably linked so as to form a functioning expression construct. Left AAV2 ITR (SEQ ID NO:2); CMV promoter (SEQ ID NO:3); Intron (SEQ ID NO:4); PPI-EGFP fusion cDNA (SEQ ID NO: 13); SV40 polyA/SV40 enhancer (SEQ ID NO:6); hGH polyA (SEQ ID NO: 10); Right AAV2 ITR (SEQ ID NO: 11). Fluorescence microscopy of insulin-EGFP fusion protein and GLP-1 staining. AAV/FUSION transduced then differentiated NCI-H716 cells were detached and seeded on a poly-L-lysine coated 4-chamber glass slide. Seeded cells were imaged immediately by the OLYMPUS 1X70 fluorescence microscope, or fixed (4% paraformaldehyde in PBS) for confocal microscopy, or fixed and permeabilized (0.5% Triton X-100 in PBS) for GLP-1 staining. GLP-1 staining was achieved by incubating the monolayer with primary antibody, rabbit-anti-GLP-1 (A viva, San Diego, CA; diluted 1:50), at 4°C overnight then revealed with TRITC-conjugated anti-rabbit IgG (Sigma; diluted 1:160). Localization of the insulin-EGFP fusion protein and GLP-1 immunofluorescence staining were performed using a Zeiss LSM510 laser- scanning confocal microscope (Carl Zeiss, Thornwood, NY). An argon laser at 488-nm and a 505-530-nm filter were used for detecting insulin-EGFP fusion protein. A helium neon laser at 543-nm and a long pass 585-nm filter were used for TRITC detection. Results AAV/insulin/EGFP transduction ofNCI-H716 cells Human intestinal NCI-H716 cells grown in suspension as floating aggregates were transduced with the rAAV vector, AAV/insulin/EGFP, before differentiation. Twenty-four hours after transduction, some EGFP-positive cells could be identified under the fluorescence microscope. To quantify the transduction efficiency, fluorescence-activated cell sorting (FACS) was applied to detect EGFP-positive cells. FACS analysis indicated that the percentage of EGFP-positive cells in a pool of transduced cells was 31% - 43% with an average of 37 + 5% (n=4); the latter can be considered as the average transduction efficiency. To further characterize the insulin expression, insulin and proinsulin in transduced cells were immunochemically stained. A brown-colored precipitate indicates the mtracellular presence of insulin and/or proinsulin antigens. These results show that the insulin and EGFP genes were successfully expressed in NCI-H716 cells via rAAV- mediated gene transfer. Regulated GLP-1 and insulin secretion from the AAV/insulin/EGFP transduced and differentiated NCTH716 cells Endogenous GLP-1 and recombinant insulin secretion was studied from transduced, differentiated cells by exposing them to a square wave of 2% meat hydrolysate (MH) for 1 hour. MH has previously been shown to induce a 5-fold increase of GLP-1 release over a 2-h period (Reimer et al, Endocrinology 142 (2001) 4522-4528). Figure 2 shows the MH profile and the GLP-1 and insulin secretion rates, averaged over 1-h periods. GLP-1, msulin and proinsulin assays were all performed on the same samples collected during the secretion study. A 4.2-fold (± 1.1, n=4) increase of the GLP-1 secretion rate was achieved with MH stimulation. Upon removal of MH, the GLP-1 secretion rate quickly decreased toward the basal level. The insulin release exhibited similar kinetics as the GLP-1, with a 2.7-fold (± 0.4, n=4) increase after the stimulation (Figure 2b). Since the radioimmunoassays used to measure the concentrations of insulin and proinsulin are highly specific (see Materials and Methods for cross-reactivities), it was possible to estimate the conversion of proinsulin to insulin by calculating the ratio (insulin)xlOO%/(insulin+proinsulin) using the amounts of secreted polypeptides. An approximately 80% conversion of proinsulin to insulin was consistently maintained throughout the test (Figure 2c), indicating that the engineered NCI-H716 cells possess the necessary proteolytic enzymes to process proinsulin to immunoreactive insulin. Figure 3 compares the msulin secretion rates from engineered NCI-H716 cells, mouse β-TC3 insulinomas, and engineered, insulin-secreting mouse pituitary AtT-20 tumor cells. Both the basal and stimulated insulin secretion rates from recombinant NCI-H716 cells are lower by roughly an order of magnitude than those from β-TC3 cells, but they are comparable to the msulin secretion rates from engineered AtT-20 cells. Intracellular localization of insulin-EGFP fusion protein and of GLP-1 A control experiment was performed to reveal the secretory granules in the engineered NCI-H716 cells using the insulin-EGFP fusion protein. The plasmid constructed for the production of the rAAV vector, AAV/FUSION, encoding the insulin-EGFP fusion chimera is shown schematically in Figure lb. This plasmid was designed to tag EGFP at the C terminus of preproinsulin by fusing the 3' end of the preproinsulin cDNA with the 5' end of the EGFP cDNA (Figure lc). By this design, the secretory signal peptide from preproinsulin will direct the intracellular traffic of the fusion protein to the secretory granules, and the EGFP will reveal the localization of the fusion protein. The AAV/FUSION transduced and differentiated cells were first examined by a conventional fluorescence microscope after being seeded on a poly-L- lysine coated glass slide. In cells expressing insulin-EGFP fusion protein, small vesicular structures inside the cells were visualized. Granule-like compartments were clearly revealed inside the cell. This kind of compartment cannot be visualized in the AAV/insulin EGFP transduced then differentiated cells, which express separately insulin and EGFP. This is because EGFP naturally does not include any secretory peptide signal in its protein sequence; thus EGFP was homogenously distributed in the cytosol. Confocal laser- scanning microscopy is used to examine co-expression of insulin-EGFP and GLP-1 labeled with green and red labels respectively. The co-localization of green and red fluorescence demonstrates the co-localization of recombinant insulin-EGFP fusion protein and endogenous GLP-1 in the granule-like compartments. These findings show that the engineered NCI-H716 cells possess secretory granules after differentiation, and that these granules are available for storage of endogenous GLP-1 as well as recombinant insulin. This is consistent with the similarity of GLP-1 and insulin secretory responses against MH (Figure 2). rAAV can transduce and express the msulin gene in these cells which, after differentiation, secrete endogenous GLP-1 and recombinant msulin with the same acute dynamics following stimulation by MH. In accord with this, a fusion insulin EGFP chimera was found to co-localize with endogenous GLP- 1 in the same granule-like compartments displaying the endocrine features of the cells. After meals, dietary nutrients stimulate GLP-1 secretion mainly from the lower gut (jejunum, ileum, colon and rectum) where L cells are relatively abundant (Herrmann et al Digestion 56 (1995) 117-126, Elliot et al J Endocrinol 138 (1993) 159-166, Eissele et al Eur J Clin Invest 22 (1992) 283- 291). Specifically, oral administration of glucose has shown a dose-dependent effect on circulative GLP-1 levels and parallel secretions of GLP-1 and insulin in humans. Both hormones rise within a few minutes after glucose ingestion, and return to the basal levels in 2 to 3 h depending on the glucose dosage (Schirra et al. J Clin Invest 97 (1996) 92-103). In this study, the engineered L- cell model demonstrated an acute release of both the recombinant insulin and the endogenous GLP-1 against stimulation. Cultures promptly responded to MH stimulation and up-regulated insulin and GLP-1 release within 1 h; once MH was removed, insulin and GLP-1 release decreased to essentially basal levels also within 1 h. Interestingly, the proinsulin conversion to insulin remained consistently high at 80%, indicating that there is a sufficient concentration of proteolytic enzymes recognizing proinsulin in the vesicular structures where proinsulin localizes. In the enterondocrine cell model of this study, the correspondence of GLP-1 and insulin release against MH stimulation actually resembles the parallel secretion of postprandial GLP-1 and insulin in healthy humans. Thus, for IDD treatment, the engineered L cells will quickly adjust between pre- and postprandial conditions to meet the different insulin demands. To genetically modify gut epithelia, viral vectors have shown significant potential in targeting cells lining the gastrointestinal tract(Croyle et al. Gene Ther 5 (1998) 645-654, Lau et al, Hum Gene Ther 6 (1995) 1145- 1151, During Nat Med 4 (1998) 1131-1135). In particular, rAAV vectors have been used to infect gut epithelia through oral gavage administration resulting in phenotypic change in a rat model over a 6 month period (During Nat Med 4 (1998) 1131-1135). L cells face the gut lumen, so it is expected that they could be directly accessed via noninvasive administrations in the gastrointestinal tract. However, since only about 1% of the intestinal epithelial population consists of enteroendocrine cells, there exists a significant challenge in selectively targeting L cells to express insulin. Recent work by Nian et al. (Am J Physiol Regul Integr Comp Physiol 282 (2002) R173-183) using a transgenic mouse model to demonstrate that the human proglucagon promoter regulates tissue-specific gene expression in L cells opens the possibility that recombinant insulin expression can be limited specifically in L cells via the selective activity of the proglucagon promoter. In parallel with the engineering of enteroendocrine cells for regulated insulin release, other investigators are using promoters up-regulated by glucose and possibly down-regulated by insulin to drive insulin expression in liver or muscle cells (Thule et al. Gene Ther 7 (2000) 205-214, Thule et al. Gene Ther 7 (2000) 1744-1752, Lee et al. Nature 408 (2000) 483-488, Nature 408 (2000) 483-488, Barry et al Hum Gene Ther 12 (2001) 131-139, Chen et al. Mol Ther 3 (2001) 584-590). Using these glucose-regulated trangenes, insulin expression has been achieved in streptozotocin (STZ)-induced diabetic rodents with promising results. However, transcriptional regulation of insulin expression results in sluggish secretion dynamics which may not be appropriate for glycemic regulation in higher animals and, eventually, humans. Destabilization of preproinsulin rnRNA by nonsense-mediated decay improves the secretion dynamics from transcriptionally regulated cells but not to the point of achieving an acute secretory response (Tang et al. FEBS Letters (2003)). In a different approach, investigators are engineering insulin expression in other endocrine cells, such as pituitary cells, which possess the regulated secretion pathway; this is done in both transgenic mouse models and cell lines (Lipes et al, Proc Natl Acad Sci U S A 93 (1996) 8595-8600, Motoyoshi et al. Diabetologia 41 (1998) 1492-1501, Meoni et al, Cell Transplant 9 (2000) 829-840, Davalli et al Cell Transplant 9 (2000) 841-851). Recombinant pituitary cells respond to secretagogues with acute release of the insulin through exocytosis. Since pituitary cells lack responsiveness to postprandial stimuli, attempts have been made to engineer glucose responsiveness by expressing glucokinase (GK), or the type II glucose transporter GLUT2, or both, in these cells (Motoyoshi et al. Diabetologia 41 (1998) 1492-1501). However, recent data have shown that this approach may lead to glucose-induced toxicity and result in glucose-dependent apoptotic cell loss (Faradji et al, J Biol Chem 276 (2001) 36695-36702). In addition, recombinant pituitary cells secrete not only msulin but also their endogenous hormones, and serious disorders may result if these hormones are abnormally up-regulated after meals. A regulated insulin-secreting cellular model has been established by rAAV-mediated insulin gene transfer to a human GLP-1 -secreting intestinal cell line. Results demonstrated similar secretion dynamics of recombinant insulin and endogenous GLP-1. Engineering intestinal L cells to produce insulin may constitute a feasible approach for IDD treatment in terms of the dynamic response and the compatibility of GLP-1 and insulin in glycemic normalization. Example 2: Differential rAAV2 Transduction in Pure and Co-Culture Models of Human Enteroendocrine L Cells and Enterocytes. The efficiency and specificity of rAAV2-mediated transduction in co- cultures of human enterocyte and enteroendocrine L cell lines was studied to observe the specificity of rAAV2 to enteroendocrine L cells. The uptake and expression of the insulin gene, as well as the conversion of proinsulin to insulin and the dynamics of insulin secretion were characterized. Materials and methods

Cell lines and culture conditions Human Caco-2 cells (ATCC, Manassas, VA; an enterocyte model Pageot et al. Microsc Res Tech 2000; 49:394-406) and Human HT-1080 fibroblasts (ATCC) were cultured in Dulbecco's modification of Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 1% nonessential amino acids. Human T84 cells (ATCC; an enterocyte model (Dharmsathaphorn et al. Am J Physiol 1984; 246:G204-20818) were cultured in a 1:1 mixture of Ham's F12 medium and DMEM supplemented with 5% of FBS. Human NCI-H716 cells (ATCC) as the enteroendocrine L-cell model (Reime et al. Endocrinology 2001; 142:4522-4528; Anini et al. Endocrinology 2003; 144: 3244-3250) were grown in suspension in RPMI medium supplemented with 10% FBS. Adhesion and endocrine differentiation of NCI- H716 cells were initiated by growing the cells on Matrigel (Becton Dickinson, Bedford, MA)-coated surfaces in DMEM supplemented with 10% fetal bovine serum (de Bruine et al. Am J Pathol 1993; 142:773-782). Human embryonic kidney 293 (HEK293) cells (ATCC) used for rAAV2 production were grown in DMEM supplemented with 10% heat-inactivated FBS. Co-cultures of NCI- H716 cells and Caco-2 cells were grown in the Caco-2 culture medium; co- cultures of NCI-H716 cells and T84 cells were grown in the T84 culture medium. Growth media were all supplemented with 100 U/ml penicillin and 100 μg/ml streptomycin. Cell cultures were all maintained at 37°C in a 5% CO₂ / 95% air humidified atmosphere. Plasmids and Virus The rAAV vector plasmid, plnsulin-EGFP (Figure IA), carrying the expression cassettes of insulin (CMV-driven) and EGFP (SV40-driven), was constructed as previously described (Tang and Sambanis Biochem Biophys Res Commun 2003; 303:645-652). This plasmid was used with two other plasmids, pAAV-RC (Stratagene, La Jolla, CA) and pHelper (Stratagene), for rAAV2 production following the manufacturer's protocol (AAV Helper-Free System, Stratagene). Purification and titration of rAAV2 were performed as previously described (Tang and Sambanis Biochem Biophys Res Commun 2003; 303:645-652.). Plasmid plnsulin-EGFP, alone, was also used in FUGENE6 (Roche, Indianapolis, IN)-mediated transfection as a control. Plasmid plnsulin-EGFP is made of the following polynucleotide elements operably linked so as to foπn a functioning expression construct. Left AAV2 ITR (SEQ ID NO:2); CMV promoter (SEQ ID NO:3); Intron (SEQ ID NO:4); PPI cDNA (SEQ ID NO:5); SV40 polyA/SV40 enhancer (SEQ ID NO:6); SV40 Promoter (SEQ ID NO:7); EGFP cDNA (SEQ ID NO:8); Intron (SEQ ID NO:9); hGH polyA (SEQ ID NO: 10); Right AAV2 ITR (SEQ ID NO: 11). Co-culture systems Two co-culture systems of enterocyte and enteroendocrine L cell lines were applied. In the first co-culture system, a total of 2.5 million NCI-H716 L-cells and enterocytes (Caco-2 cells or T84 cells), were mixed in a ratio of 1:10 and seeded onto a 35-mm tissue-culture dish. One day later, the co- culture was washed twice using culture medium. Unlike enterocytes, NCI- H716 cells attached poorly to tissue culture plastic; therefore, after the washing step, more than 80% of NCI-H716 cells were detached and removed. The remaining NCI-H716 cells with enterocytes were then subjected to transduction or transfection as described below. In the second co-culture system, serial seeding of Caco-2 enterocytes and NCI-H716 cells to a 35-mm tissue-culture dish was applied. First, a 5- mm cloning disc (Scienceware, Pequannock, NJ) was used to transfer Matrigel to the center of a 35-mm dish. This created a Matrigel-coated circular area for the adhesion of NCI-H716 cells (de Bruine et al. Am J Pathol 1993; 142:773- 782); the ratio of the Matrigel-coated region to the surface area of a 35-mm dish was 1/49. The dish was then placed in a 37°C incubator for 1 h. One ml of the Caco-2 culture medium was carefully added to the dish, and surface tension effects were used to ensure that medium did not wet the cloning disc. One hour later, the culture medium was replaced by a suspension of 2.5 million Caco-2 cells in 1 ml culture medium. Again, surface tension was carefully used to prevent wetting the disc region. Thus, Caco-2 cells grew around the Matrigel disc, but not into the disc region. Twelve hours later, the disc was removed and a suspension of 2 million NCI-H716 cells in 1.5 ml medium was added to the dish and covered the entire surface. The dish was then placed in a 37°C incubator for settling and adhesion of NCI-H716 cells to the Matrigel. Ten minutes later, unattached cells were re-suspended by tapping and swirling the dish. After another 10 min of settling and adhesion, unattached cells were removed by washing with culture medium twice. Approximately 0.5 - 1x10^s NCI-H716 cells adhered to the center, as determined from pure culture controls prepared by seeding NCI-H716 cells to the Matrigel-coated dish without Caco-2 cells. The two domains in the co- culture system were clearly delineated, as seen under the microscope one day after the seeding process. Pure culture controls were prepared in the same way, i.e., NCI-H716 cells were seeded on the same 5-mm central Matrigel region (without any surrounding Caco-2 cells), and Caco-2 cells in the same area of the dish with a 5-mm diameter cell-free Matrigel area at the center. Thus, the co-culture and each pure culture control involved the same culture area covered by each type of cells. Transduction and transfection of the co- cultures and of the pure culture controls were performed one day later. Transduction and transfection Recombinant AAV2 transduction of the pure cultures of Caco-2 cells, T84 cells or HT-1080 cells was done in a 35-mm tissue culture dish at 60% to 80%) of confluency using a multiplicity of infection (MOI) of 10 infectious units per cell. Transduction followed the procedure suggested by the Instruction Manual of AAV Helper-Free System (Stratagene) for HT-1080 transduction, except that genotoxic agents, hydroxyurea and sodium byruvate were not added. Transduction of the pure culture of NCI-H716 cells in suspension used a MOI of 10 as previously described (de Bruine et al. Am J Pathol 1993; 142: 773-782). Transduction of the co-culture of enterocytes and NCI-H716 cells followed the same procedure as that for the pure cultures of enterocytes. Plasmid transfection was carried out with FUGENE6 reagent (Roche) following the manufacture's directions for adherent cells (Caco-2, T84, HT- 1080 cells and the co-cultures) or suspension cells (NCI-H716 cells). For each transfection of cells in a 35-mm dish, 5 μg of the plasmid DNA and 12 μl of FUGENE6 reagent were used. Immunofluorescent staining Double immunofluorescent staining was used to detect AAV2 whole particle in transduced cells. Caco-2 cells and HT-1080 cells were seeded on 2- well chamber slides and cultured overnight. NCI-H716 cells were seeded to poly-L-lysine-coated 2-well chamber slides right before the experiment. Recombinant AAV2 transduction of cells on the slides was performed at a 37°C incubator for 2.5 h. Cells were then washed with culture medium, fixed with 4% paraformaldehyde in PBS for 15 min, permeabilized with 0.5% Triton X-100 in PBS for 10 min, and blocked in 10% horse-serum PBS for 1 h. Mouse A20 monoclonal antibody against the intact particle of AAV2 (Maine Biotechnology Services, Portland, ME; diluted 1:5) was incubated with the monolayer at 4°C overnight, then revealed with TRITC-conjugated goat-anti-mouse IgG (Sigma; diluted 1:30). Visualization of the AAV2 immunofluorescent staining was performed using a Zeiss LSM510 laser- scanning confocal microscope (Carl Zeiss, Thornwood, NY). A helium/neon laser at 543-nm and a long-pass 560-nm filter were used for TRITC detection. For detection of prohormone convertases PC 1/3 and PC2 in the co- culture of NCI-H716 cells and Caco-2 enterocytes, co-culture monolayers were fixed, permeabilized and blocked as described in the previous paragraph. Rabbit-anti-human PC 1/3 (United States Biological, Swampscott, MA; diluted 1:25) and PC2 (United States Biological; diluted 1:50) polyclonal antibodies were incubated with monolayers at 4°C overnight, then revealed with TRITC- conjugated goat-anti-rabbit IgG (Sigma; diluted 1:100). Visualization of the immunofluorescent signals was performed in the same way as for AAV2 immunostaining. Secretion study The co-culture prepared by serial seeding of Caco-2 cells and NCI- H716 cells, as well as the corresponding pure culture controls were subjected to rAAV2 transduction or FUGENE6-mediated transfection for insulin expression. Two days later, the culture medium was switched to basal medium (DMEM (GIBCO, cat.# 23800-022, Grand Island, NY) supplemented with 5 mM glucose and 1% fetal bovine serum), and cultures were incubated overnight. On the day of the experiment, parallel cultures were washed and incubated in basal medium for two hours to stabilize the basal secretion of insulin. The secretion test was initiated by incubating stabilized monolayers in basal medium for two hours to determine the basal secretion rate. Monolayers were then exposed to basal medium supplemented with 2% (w/v) meat hydrolysate (Sigma, cat. # P-7750) to stimulate insulin secretion for two hours. Cultures were finally washed three times with basal medium and incubated in basal medium for another two hours. When switching medium from one type to another, samples were collected for insulin and proinsulin assays. Insulin and proinsulin secretion rates of the first two-hour basal exposure were used to normalize the rest of the data, thereby accounting for differences in transduction and transfection efficiency between individual experiments. Analytical techniques EGFP expression was visualized using a Zeiss LSM510 laser-scanning confocal microscope (Carl Zeiss) with an argon laser at 488 nm and a bandpass 500-550-nm filter. Fluorescence-activated cell sorting (FACS) analysis was carried out using a Becton Dickinson LSR benchtop flow cytometer (BD Bioscience, Lexington, KY) with an argon laser at 488 nm and a FITC window to detect EGFP. Insulin and proinsulin concentrations were measured by human insulin-specific radioimmunoassay (RIA) (LINCO Research, St. Charles, MI, cat. # HI-14K) and human proinsulin RIA (LINCO research, cat. # HPI-15K), respectively, according to the manufacturer's protocols. The human insulin-specific RIA cross-reacts with human proinsulin at less than 0.2%, whereas the human proinsulin RIA cross-reacts with human insulin at less than 0.1% (Manufacturer's specifications). Radioactivities were determined in Auto-Gamma Counting System, Cobra II (Packard, Meriden, CT). Results Recombinant AAV2 transduction in pure cultures The ability to transduce NCI-H716, Caco-2 and T84 cells by AAV2 was first investigated in pure cultures using the viral vector derived from plasmid plnsulin-EGFP (Figure IA). Human HT-1080 fibroblasts, known for their permissiveness to AAV2 transduction, were used as positive controls. The transduction efficiency, indicated by EGFP expression, was visualized by confocal microscopy and quantified by FACS. As seen in Figure 2, NCI- H716 and HT-1080 cells expressed EGFP strongly, indicating permissiveness to rAAN2 transduction. On the other hand, the Caco-2 and T84 cell cultures exhibited only sparse green fluorescence, indicating low transduction efficiencies. FACS analysis showed that enterocytes were transduced at less than 1% on average (0.9 ± 0.5% for Caco-2 and 0.7 + 0.3% for T84, n = 3), whereas ΝCI-H716 cells were transduced at approximately 37% (+ 5%, n = 4). Chemical reagent (FUGENEό)-mediated transfection in pure cultures In parallel with rAAV2-mediated transduction, FUGENE6-mediated transfection with plasmid plnsulin-EGFP (Figure IA) was used as control. Results are shown in Figure 3. NCI-H716 L-cells exhibited little permissiveness to FUGENE6 transfection, lower than to rAAV2 transduction. On the other hand, Caco-2 and T84 enterocytes were both efficiently transfected and expressed EGFP. This finding shows that the low EGFP expression in enterocytes after rAAN2 transduction was caused by the low permissiveness of these cells to rAAV2, and not by the low expression of the EGFP cassette. HT-1080 cells were transfected efficiently with FUGEΝE6, similar to rAAV2. Immunofluorescent staining of transduced monolayers The staining of AAV2 particles in transduced monolayers supported the hypothesis that AAV2 has different entry efficiencies in Caco-2 relative to permissive cells. Figures 4A and 4B show that, in permissive NCI-H716 L- cells and HT-1080 fibroblasts, entry, endocytosis and aggregation of AAV2 have taken place 2.5 h post-transduction. In comparison, in the transduced Caco-2 monolayer, the fluorescence signals of AAV2 capsids did not reveal similar aggregation; in fact, the immunofluorescent staining of transduced Caco-2 cells was indistinguishable from that of untransduced controls.

Recombinant AAV2 transduction andFUGENEό transfection in co-cultures Although NCI-H716 L-cells are permissive to rAAV2 transduction in the pure-culture condition, it is unclear whether L-cells can be effectively transduced when surrounded by a large number of low-permissive enterocytes. To test this, the two in vitro co-culture systems described in Materials and Methods were used. The first system, consisting of a monolayer of NCI-H716 cells and Caco-2 or T84 enterocytes randomly dispersed at a ratio of 1:50 to 1:100, was transduced by rAAV2 in experiments and was transfected by FUGENE6 in parallel controls. Two different patterns of EGFP expression occur in rAAV2-transduced and FUGENE6-transfected cultures. In the rAAV2-mediated transduction, only a limited number of cells were transduced to exhibit green fluorescence; most of them were spherical, identifiable as NCI-H716 L-cells. On the other hand, in the FUGENEό-transfected cultures, a greater number of cells expressed EGFP, and these cell clusters appeared morphologically similar to enterocytes transfected under pure-culture conditions. These findings indeed indicate that rAAV2-mediated gene transfer avoids the low-permissive enterocytes and selectively targets NCI-H716 L- cells in this co-culture system, whereas specific targeting of L-cells cannot be achieved with the non-viral, FUGENE6-mediated gene transfer. The second co-culture system consisted of a 5-mm island of NCI-H716 L-cells on Matrigel in a 35-mm dish surrounded by enterocytes. In this system, the L-cells were strongly attached and easily withstood the washing and mixing steps in the insulin secretion studies. Figure 1C shows this co- culture system one day after the seeding was completed. NCI-H716 cells attached primarily to the central Matrigel area; only few of these cells attached to the Caco-2 area of the co-culture, appearing under the optical microscope as bright dots in this area. This sparse presence of NCI-H716 cells in the Caco-2 area did not in any way compromise the objectives of this study. Results from transduction by rAAV2 and transfection via FUGENE6, visualized using confocal microscopy, are shown in Figure 6. Similar to what was found with the previous co-culture system, rAAV2 transduction was able to preferentially modify NCI-H716 L-cells at the central island, whereas FUGENE6-mediated transfection mainly modified Caco-2 enterocytes in the surrounding area with very low efficiency towards the L-cells. Since individual populations of the co-culture could not be specifically detached and analyzed, the gene transfer efficiencies towards NCI-H716 and Caco-2 cells were not quantified. However, fluorescent microscopy clearly indicated that the AAV2 transduction towards L-cells was similar in the co-culture as in the pure culture controls. Insulin secretion profiles of transduced and transfected co-cultures Recombinant insulin secretion was studied from rAAV2-transduced co- cultures and pure cultures, as well as from FUGENE6-transfected co-cultures and pure cultures. Monolayers were exposed to basal medium for 2 hours, followed by medium with 2% meat hydrolysate (MH) for 2 hours to stimulate insulin secretion, followed by 2 hours of basal medium. MH has been shown to be a secretagogue to parental and recombinant NCI-H716 L-cells and induce acute release of endogenous glucagon-like peptide- 1 (GLP-1) and recombinant msulin (Tang and Sambanis Biochem Biophys Res Commun 2003; 303:645-652.; Reimer et al. Endocrinology 2001; 142:4522-4528). In our previously published work, expression of a fusion protein of recombinant insulin tagged with EGFP has been used to directly visualize the secretory granules of engineered NCI-H716 L-cells and access its co-localization with endogenous GLP-1, suggesting that these granules are available for the storage of GLP-1 as well as recombinant insulin (Tang SC, Sambanis A. Development of genetically engineered human intestinal cells for regulated insulin secretion using rAAV-mediated gene transfer. Biochem Biophys Res Commun 2003; 303: 645-652). Figure 4 shows the insulin secretion rates and the conversion ratio of proinsulin to insulin, averaged over each 2-h period for both the co- cultures and the pure culture controls. Measurements of insulin and proinsulin were both performed on the same samples collected during the secretion study. To account for differences in transduction efficiency among independent experiments, secretion rates were normalized against the initial 2-h sample, which was set at 100%. MH exposure increased the insulin secretion rate to (1.73 + 0.22)-fold and (1.99 ± 0.38)-fold of the basal rate for the rAAV2- transduced NCI-H716 L-cells and the co-culture, respectively. On the other hand, the insulin released from rAAV2-transduced Caco-2 cells was too low to be detected (Figure 4A). In comparison, FUGENE6-transfected Caco-2 cells and the co-culture failed to respond to MH stimulation, and the insulin released from the transfected NCI-H716 L-cells was too low to be quantified (Figure 4B). Since the radioimmunoassays used to determine the insulin and proinsulin concentrations are highly specific (see Materials and Methods for cross-reactivities), it was possible to estimate the conversion of proinsulin to insulin by calculating the ratio (insulin)xl00%o/(msulm+proinsulin). NCI- H716 L-cells have previously been shown to possess the necessary proteolytic enzymes to process proinsulin to immunoreactive insulin. rAAV2-mediated insulin delivery can target NCI-H716 L-cells in the co-culture and achieve an average of 66 + 12 % conversion of proinsulin to insulin over the 6-h secretion study, similar to the conversion achieved in pure NCI-H716 cell cultures (76 ± 6 %, Figure 4C). In comparison, FUGENE6-mediated transfection only generated an average of 25 ± 3 % and 28 + 3% of proinsulin conversion over the same period of study from the transfected Caco-2 pure culture and co- culture systems, respectively (Figure 4D). To assess expression of PCI/3 and PC2 convertases, double immunofluorescent staining against PC 1/3 and PC2 was applied to the co- culture monolayers of NCI-H716 and Caco-2 cells. Results show that both endoproteases were abundant in NCI-H716 cells as opposed to Caco-2 cells, thus explaining the discrepancy in converting recombinant proinsulin to insulin between these two cell types in the secretion study. These results demonstrated that rAAV2 can genetically modify NCI-

H716 L-cells in the co-culture environment in spite of a prevailing number of Caco-2 or T84 enterocytes. The rAAV2-transduced co-culture achieved regulated insulin release in response to stimulation; on the other hand, the co- culture subjected to non-viral chemical-mediated transfection failed to generate such a response. Recombinant AAV2 is capable of transgene delivery to a broad spectrum of host cells, but the transduction efficiency may vary widely. The different efficiency towards L-cells and enterocytes identified in this study was not due to the expression cassette, as evidenced by the results from the chemical transfection. Rather, by comparing the virus immunostaining in transduced monolayers of enterocytes and permissive cells, the different efficiency appears to be due to an inefficient binding and/or endocytosis of rAAV2 in enterocytes. Example 3: In Vivo Administration ofrAAV2 Vector Encoding Preproinsulin. A recombinant adeno-associated viral vector is used for in vivo administration to transduce enteroendocrine L cells to produce insulin in response to a food stimulus. The rAAV2 vector plasmid, plnsulin-EGFP (Figure IA), is constructed as described above. This vector carries the expression cassettes of insulin under a CMV promoter and EGFP under the control of an SN40 promoter. Infectious viral particles carrying the vector are prepared using the AAV Helper-Free System (Stratagene). The vector is transfected using calcium phosphate into a cell line to produce adeno-associated virus containing the vector. HEK293 cells are ideal for production of infectious viral particles because HEK293 cells produce the El gene for the AAV to replicate. To produce a more concentrated viral stock, the protocol of Matsuhita et al is used (Gene Therapy 1998 5:938-945). The rAAV2 with vector is administered in an oral dose as liquid solutions or suspensions in liquid made prior to administration. These preparations also may be emulsified. The viral stock is diluted in 50 mg to 100 mg of human serum albumin per milliliter of phosphate-buffered saline. The pH and exact concentration of the various components in the pharmaceutical are adjusted according to well-known parameters to promote transduction efficiency of the virus. The dosage of recombinant vector or the virus to be administered to an animal in need of such treatment is determined by the ordinarily skilled clinician by routine titration based on various parameters such as mode of administration, duration of treatment, the disease state or condition involved, and the like. rAAV2 is administered in a dosage equivalent to the titer of rAAV2 required in transducing 100% confluent Caco-2 enterocytes on a similar surface area with a multiplicity of infection (M.O.I.) at 10. Recombinant virus of the invention may also be administered in doses between 10⁵ and 10¹⁴ infectious units. After 2.5 hours blood samples are withdrawn and assayed for GLP-1 and insulin expression by ELISA. Biopsies are also removed to visualize expression of the EGFP reporter under a fluorescent microscope. Intracellular insulin is also visualized by double antibody immunostaining, as demonstrated in Tang and Sambanis, Biochem. Biophys. Res. Commun., 303: 645-652 (2003). Example 4: Ex Vivo Gene Manipulation of Enteroendocrine L-cells with rAAV2 Vector Encoding Preproinsulin Donor tissue is removed from xenogeneic, allogeneic or autologous donors using methods based on Perreault and Beaulieu (Exp Cell Res 1998 245:34-42) to provide cultures of intestinal epithelial cells and provide isolation of intestinal stem cells. The intestine is isolated from the donor in Hank's Balanced Salt Solution and placed in a petri dish containing 0.04% cold sodium hypochlorate in phosphate buffered saline to disinfect the tissue. The intestine sample is opened longitudinally and debris is cleaned away thoroughly. The tissue is inclubated in ice-cold Matrisperse™ (Collaborative Biomedical Products, Bedford, MA) for 8-10 hours at 4°C without agitation. Each dish is tapped several times to separate the epithlieum from the underlying submucosa. Epithelial fragments are collected with 5 ml pipette, pooled in a 50 ml centrifuge tube and gently pipetted up and down a few times. Tissue is filtered through an 80 μm nylon mesh. The mesh is rinsed in 20 ml Dulbecco's modified eagle medium (DMEM). Purified crypts are backwashed with 15 ml complete serum-free growth medium supplemented with 2.5%) penicillin/streptomycin and 1% gentamicin. The cell suspension is seeded on type I collagen-coated surfaces. Cultures of cells are transduced as described above using the vector shown in Figure la. Gene expression is confirmed visually by expression of EGFP and cells are subjected to fluorescence activated cell sorting (FACS) using FACSstar Plus (Becton Dickinson Immunocytometry Group) at an excitation wavelength of 488 nm and an emission wavelength of 515-545 nm according to manufacturer's protocol. Purified cultures are assayed for glucose responsiveness and insulin expression as described above. Cells are maintained in culture for transplantation and an aliquot is cryopreserved in 10% DMSO/ with fetal bovine serum and stored in liquid nitrogen for future use. Example 5: Transplantation of Genetically Engineered

Enteroendocrine Cells. Genetically engineered enteroendocrine cells are manipulated in culture and grown as intestinal organoids. These intestinal organoids are seeded onto a biodegradable polymer scaffold made of biomaterials such as, polyglycolic acid (PGA) and polylactic acid(PLA) or a combination of both poly-lactic-co-glycolic acid (PLGA). The cell-scaffold constructs are implanted into an individual in need thereof and develop into vascularized cystic structures resembling neointestine. The biomaterials progressively degrade over time as the body vascularizes and innervates the tissue graft and endogenous proteins and connective tissues begin to support the construct. Histologically, such developed neomucosa is characterized by a columnar epithelium containing goblet cells, Paneth cells and Crypt-like invaginations that resemble crypt-villus structures. The manipulated enteroendocrine cells of the neointestine produce insulin co-localized with GLP-1 or GIP and secrete insulin in response to post-prandial stimuli. All patents, publications and abstracts cited above are incorporated herein by reference in their entirety. It should be understood that the foregoing relates only to preferred embodiments of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the present invention as defined in the following claims.

Claims

Claims

We claim:

1. A composition comprising an adeno-associated vector wherein the vector comprises a nucleotide sequence encoding preproinsulin or a conservative substitution thereof and further comprising a sequence encoding a detectable label.

2. The composition of claim 1 further comprising a tissue specific promoter wherein the tissue specific promoter controls expression of the gene of interest.

3. The composition of claim 1 wherein the tissue specific promoter is specific for L cells.

4. The composition of claim 3 wherein the tissue-specific promoter is the proglucagon promoter.

5. The composition of claim 1 wherein the tissue specific promoter is specific for K cells.

6. The composition of claim 5 wherein the tissue specific promoter is the GIP promoter.

7. The composition of any of claims 1-6 further comprising a pharmaceutically acceptable carrier.

8. An intestinal host cell comprising a vector comprising a nucleotide sequence encoding preproinsulin or a conservative substitution thereof.

9. The cell of claim 8 wherein the cell is an intestinal stem cell.

10. The cell of claim 8 wherein the cell is an enteroendocrine cell.

11. The cell of claim 10 wherein the cell is a L cell.

12. The cell of claim 10 wherein the cell is a K cell.

13. The cell of claim 8 further comprising a biodegradable polymer scaffold.

14. The cell of claim 13 wherein the biodegradable polymer scaffold is selected from the group consisting of PLA, PGA, and PLGA.

15. A method for introducing a vector into an intestinal cell comprising associating the vector in recombinant adeno-associated virus particles and transducing host cells with the virus particles.

16. The method of claim 15 wherein the recombinant adeno- associated virus particle is rAAV2.

17. The method of claim 15 wherein the vector is introduced ex- vivo.

18. The method of claim 15 wherein the recombinant adeno- associated virus viral particles display a selective tropism for enteroendocrine cells.

19. The method of claim 18 wherein the enteroendocrine cells are L cells.

20. The method of claim 18 wherein the enteroendocrine cells are K cells.

21. The method of claim 15 wherein the vector is introduced hi vivo.

22. A method for introducing a vector into an intestinal cell comprising transfecting the vector with a transfection reagent into intestinal cells.

23. The method of claim 22 wherein the cell is an intestinal stem cell. 24. The method of claim 22 wherein the cell is an enteroendocrine cell. 25. The method of claim 24 wherein the cell is an L cell.

26. The method of claim 24 wherein the cell is a K cell.

27. A method for treating symptoms of a glucose-related metabolic disorder comprising introducing an effective amount of a vector into an intestinal host cell wherein the intestinal host cell is an enteroendocrine cell expressing a protein encoded by the vector.

28. The method of claim 27 wherein the protein is preproinsulin.

29. The method of claim 27 wherein the protein is insulin.

30. The method of claim 27 wherein the glucose-related metabolic disorder is juvenile diabetes, type I diabetes or type II diabetes.

31. The method of claim 27 wherein the vector is administered perorally.

32. The method of claim 27 wherein the vector is administered systemically.

33. The method of claim 27 wherein the intestinal host cell is transduced ex vivo and then transplanted into the intestine.

35. The method of claim 26 wherein the intestinal host cell is an enteroendocrine cell.

36. The method of claim 35 wherein the intestinal host cell is an L cell. 37. The method of claim 35 wherein the intestinal host cell is a K cell.

36. The method of claim 26 wherein the host cell is an intestinal stem cell.