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To address complications of pathogenic antibody or life-threatening anaphylactic reactions in protein replacement therapy for patients with hemophilia or other inherited protein deficiencies, we have developed a prophylactic protocol using a murine hemophilia 8 model. Oral delivery of coagulation factor IX fused with cholera toxin [beta]-subunit (with or without a furin cleavage site; CTB-FFIX or CTB-FIX), expressed in chloroplasts (up to 3.8% soluble protein or 0.4 mg/g leaf tissue), bioencapsulated in plant cells, effectively blocked formation of inhibitory antibodies (undetectable or up to 100-fold less than controls). Moreover, this treatment eliminated fatal anaphylactic reactions that occurred after four to six exposures to intravenous F.IX. Whereas only 20-25% of control animals survived after six to eight F.IX doses, 90-93% of F.IX-fed mice survived 12 injections without signs of allergy or anaphylaxis. Immunostaining confirmed delivery of F.IX to Peyer's patches in the ileum. Within 2-5 h, feeding of CTB-FFIX additionally resulted in systemic delivery of F.IX antigen. This high-responder strain of hemophilia B mice represents a new animal model to study anaphylactic reactions. The protocol was effective over a range of oral antigen doses (equivalent to 5-80 [micro]g recombinant F.IX/kg), and controlled inhibitor formation and anaphylaxis long-term, up to 7 months (~40% life span of this mouse strain). Oral antigen administration caused a deviant immune response that suppressed formation of IgE and inhibitory antibodies. This cost-effective and efficient approach of antigen delivery to the gut should be applicable to several genetic diseases that are prone to pathogenic antibody responses during treatment. allergy | chloroplast | genetic disorders | oral tolerance | plant-made therapeutics doi/ 10.1073/pnas.0912181107

Recombinant adeno-associated virus 2 (AAV2) vectors are in use in several Phase I/II clinical trials, but relatively large vector doses are needed to achieve therapeutic benefits. Large vector doses also trigger an immune response as a significant fraction of the vectors fails to traffic efficiently to the nucleus and is targeted for degradation by the host cell proteasome machinery. We have reported that epidermal growth factor receptor protein tyrosine kinase (EGFR-PTK) signaling negatively affects transduction by AAV2 vectors by impairing nuclear transport of the vectors. We have also observed that EGFR-PTK can phosphorylate AAV2 capsids at tyrosine residues. Tyrosine-phosphorylated AAV2 vectors enter cells efficiently but fail to transduce effectively, in part because of ubiquitination of AAV capsids followed by proteasome-mediated degradation. We reasoned that mutations of the surface-exposed tyrosine residues might allow the vectors to evade phosphorylation and subsequent ubiquitination and, thus, prevent proteasome-mediated degradation. Here, we document that site-directed mutagenesis of surface-exposed tyrosine residues leads to production of vectors that transduce HeLa cells [approximately equal to] 10-fold more efficiently in vitro and murine hepatocytes nearly 30-fold more efficiently in vivo at a log lower vector dose. Therapeutic levels of human Factor IX (F.IX) are also produced at an [approximately equal to] 10-fold reduced vector dose. The increased transduction efficiency of tyrosine-mutant vectors is due to lack of capsid ubiquitination and improved intracellular trafficking to the nucleus. These studies have led to the development of AAV vectors that are capable of high-efficiency transduction at lower doses, which has important implications in their use in human gene therapy. AAV vectors | capsid mutations | gene expression | gene therapy | gene transfer

Treatment of genetic disease such as the bleeding disorder hemophilia B [deficiency in blood coagulation factor IX (F.IX)] by gene replacement therapy is hampered by the risk of immune responses to the therapeutic gene product and to the gene transfer vector. Immune competent mice of two different strains were tolerized to human F.IX by hepatic gene transfer mediated by adenoassociated viral vector. These animals were subsequently challenged by systemic administration of an E1/E3-deleted adenoviral vector, which is known to induce a cytotoxic T lymphocyte response to the transgene product. Immune tolerance prevented cytotoxic T lymphocyte activation to F.IX and CD[8.sup.+] cellular infiltrates in the liver. Moreover, a sustained and substantial increase in hepatic F.IX expression from the adenoviral vector was achieved despite in vitro T cell responses to adenoviral antigens. Cytolytic responses to therapeutic and to viral vector-derived antigens had been prevented in vivo by activation of regulatory CD[4.sup.+] T cells, which mediated suppression of inflammatory lymphocyte responses to the liver. This result suggests that augmentation of regulatory T cell activation should provide new means to avoid destructive immune responses in gene transfer. adenoassociated virus | gene therapy | tolerance | hemophilia

We sought to determine whether intramuscular injection of a recombinant adeno-associated virus (rAAV) vector expressing human factor IX (hF.IX) could direct expression of therapeutic levels of the transgene in experimental animals. High titer ([10.sup.12]-[10.sup.13] vector genomes/ ml) rAAV expressing hF.IX was prepared, purified, and injected into hindlimb muscles of C57BL/6 mice and Rag 1 mice. In the immunocompetent C57BL/6 mice, immunofluorescence staining of muscle harvested 3 months after injection demonstrated the presence of hF.IX protein, and PCR analysis of muscle DNA was positive for AAV DNA, but no hF.IX was detected in mouse plasma. Further studies showed that these mice had developed circulating antibodies to hF.IX. In follow-up experiments in Rag 1 mice, which carry a mutation in the recombinase activating gene-1 and thus lack functional B and T cells, similar results were seen on DNA analysis of muscle, but these mice also demonstrated therapeutic levels (200-350 ng/ml) of F.IX in the plasma. The time course of F.IX expression demonstrates that levels gradually increase over a period of several weeks before reaching a plateau that is stable 6 months after injection. In other experiments we demonstrate colocalization of hF.IX and collagen IV in intersitial spaces between muscle fibers. Collagen IV has recently been identified as a F.IX-binding protein; this finding explains the unusual pattern of immunofluorescent staining for F.IX shown in these experiments. Thus rAAV can be used to direct stable expression of therapeutic levels of F.IX after intramuscular injection and is a feasible strategy for treatment of patients with hemophilia B.

Primary human hepatocytes (PHHs) are an essential tool for modeling drug metabolism and liver disease. However, variable plating efficiencies, short lifespan in culture, and resistance to genetic manipulation have limited their use. Here, we show that the pyrrolizidine alkaloid retrorsine improves PHH repopulation of chimeric mice on average 10-fold and rescues the ability of even poorly plateable donor hepatocytes to provide cells for subsequent ex vivo cultures. These mouse-passaged (mp) PHH cultures overcome the marked donor-to-donor variability of cryopreserved PHH and remain functional for months as demonstrated by metabolic assays and infection with hepatitis B virus and Plasmodium falciparum. mpPHH can be efficiently genetically modified in culture, mobilized, and then recultured as spheroids or retransplanted to create highly humanized mice that carry a genetically altered hepatocyte graft. Together, these advances provide flexible tools for the study of human liver disease and evaluation of hepatocyte-targeted gene therapy approaches. [ABSTRACT FROM AUTHOR]

Because our in silico analysis with a human transcription factor database demonstrated the presence of several binding sites for NF-κB, a central regulator of cellular immune and inflammatory responses, in the adeno-associated virus (AAV) genome, we investigated whether AAV uses NF-κB during its life cycle. We used small molecule modulators of NF-κB in HeLa cells transduced with recombinant AAV vectors. VP16, an NF-κB activator, augmented AAV vector-mediated transgene expression up to 25-fold. Of the two NF-κB inhibitors, Bay11, which blocks both the canonical and the alternative NF-κB pathways, totally ablated transgene expression, whereas pyrrolidone dithiocarbamate, which interferes with the classical NF-κB pathway, had no effect. Western blot analyses confirmed the abundance of the nuclear p52 protein component of the alternative NF-κB pathway in the presence of VP16, which was ablated by Bay11, suggesting that AAV transduction activates the alternative NF-κB pathway. In vivo, hepatic AAV gene transfer activated the canonical NF-κB pathway within 2 h, resulting in expression of proinflammatory cytokines and chemokines (likely reflecting the sensing of viral particles by antigen-presenting cells), whereas the alternative pathway was activated by 9 h. Bay11 effectively blocked activation of both pathways without interfering with long-term transgene expression while eliminating proinflammatory cytokine expression. These studies suggest that transient immunosuppression with NF-κB inhibitors before transduction with AAV vectors should lead to a dampened immune response, which has significant implications in the optimal use of AAV vectors in human gene therapy. [ABSTRACT FROM AUTHOR]

Recombinant adeno-associated virus 2 (AAV2) vectors are in use in several Phase I/II clinical trials, but relatively large vector doses are needed to achieve therapeutic benefits. Large vector doses also trigger an immune response as a significant fraction of the vectors fails to traffic efficiently to the nucleus and is targeted for degradation by the host cell proteasome machinery. We have reported that epidermal growth factor receptor protein tyrosine kinase (EGFR-PTK) signaling negatively affects transduction by AAV2 vectors by impairing nuclear transport of the vectors. We have also observed that EGFR-PTK can phosphorylate AAV2 capsids at tyrosine residues. Tyrosine-phosphorylated AAV2 vectors enter cells efficiently but fail to transduce effectively, in part because of ubiquitination of AAV capsids followed by proteasome-mediated degradation. We reasoned that mutations of the surface-exposed tyrosine residues might allow the vectors to evade phosphorylation and subsequent ubiquitination and, thus, prevent proteasome-mediated degradation. Here, we document that site-directed mutagenesis of surface-exposed tyrosine residues leads to production of vectors that transduce HeLa cells ≈10-fold more efficiently in vitro and murine hepatocytes nearly 30-fold more efficiently in vivo at a log lower vector dose. Therapeutic levels of human Factor IX (F.IX) are also produced at an ≈10-fold reduced vector dose. The increased transduction efficiency of tyrosine-mutant vectors is due to lack of capsid ubiquitination and improved intracellular trafficking to the nucleus. These studies have led to the development of AAV vectors that are capable of high-efficiency transduction at lower doses, which has important implications in their use in human gene therapy. [ABSTRACT FROM AUTHOR]