Lentiviral vectors that express UGT1A1 in liver and contain miR-142 target sequences normalize hyperbilirubinemia in Gunn rats

Arginine attenuates chronic mountain sickness in rats via microRNA-144-5p

Hypobaric hypoxia is an environmental stress leading to high-altitude pulmonary hypertension. While high-altitude pulmonary hypertension has been linked to high hematocrit findings (chronic mountain sickness; CMS). The present study is designed to investigate the effect of arginine (ARG) on hypobaric hypoxia-induced CMS of rats. Hypobaric hypoxia resulted in lower body weight, decreased appetite, increased pulmonary artery pressure, and deteriorated lung tissue damage in rats. Red blood cells (RBC), hemoglobin, hematocrit, mean corpuscular volume, and mean corpuscular hemoglobin values and blood viscosity were increased in rats, which were alleviated by ARG. microRNA (miRNA) microarray analysis was used to filter differentially expressed miRNAs after ARG in rats. miR-144-5p was reduced under hypobaric hypoxia and upregulated by ARG. miR-144-5p silencing aggravated the erythrocytosis and hyperviscosity in rats, and also accentuated tissue damage and excessive accumulation of RBC. The role of miR-144-5p in rats with CMS was achieved by blocking erythropoietin (EPO)/erythropoietin receptor (EPOR). In conclusion, ARG alleviated CMS symptoms in rodents exposed to hypobaric hypoxia by decreasing EPO/EPOR via miR-144-5p.

Delivering genes with human immunodeficiency virus-derived vehicles: still state-of-the-art after 25 years

Viruses are naturally endowed with the capacity to transfer genetic material between cells. Following early skepticism, engineered viruses have been used to transfer genetic information into thousands of patients, and genetic therapies are currently attracting large investments. Despite challenges and severe adverse effects along the way, optimized technologies and improved manufacturing processes are driving gene therapy toward clinical translation. Fueled by the outbreak of AIDS in the 1980s and the accompanying focus on human immunodeficiency virus (HIV), lentiviral vectors derived from HIV have grown to become one of the most successful and widely used vector technologies. In 2022, this vector technology has been around for more than 25 years. Here, we celebrate the anniversary by portraying the vector system and its intriguing properties. We dive into the technology itself and recapitulate the use of lentiviral vectors for ex vivo gene transfer to hematopoietic stem cells and for production of CAR T-cells. Furthermore, we describe the adaptation of lentiviral vectors for in vivo gene delivery and cover the important contribution of lentiviral vectors to basic molecular research including their role as carriers of CRISPR genome editing technologies. Last, we dwell on the emerging capacity of lentiviral particles to package and transfer foreign proteins.

Designing Lentiviral Vectors for Gene Therapy of Genetic Diseases

Lentiviral vectors are the most frequently used tool to stably transfer and express genes in the context of gene therapy for monogenic diseases. The vast majority of clinical applications involves an ex vivo modality whereby lentiviral vectors are used to transduce autologous somatic cells, obtained from patients and re-delivered to patients after transduction. Examples are hematopoietic stem cells used in gene therapy for hematological or neurometabolic diseases or T cells for immunotherapy of cancer. We review the design and use of lentiviral vectors in gene therapy of monogenic diseases, with a focus on controlling gene expression by transcriptional or post-transcriptional mechanisms in the context of vectors that have already entered a clinical development phase.

Epigenetics and microRNAs in UGT1As

UDP-glucuronosyltransferases (UGTs) are the main phase II drug-metabolizing enzymes mediating the most extensive glucuronidation-binding reaction in the human body. The UGT1A family is involved in more than half of glucuronidation reactions. However, significant differences exist in the distribution of UGT1As in vivo and the expression of UGT1As among individuals, and these differences are related to the occurrence of disease and differences in metabolism. In addition to genetic polymorphisms, there is now interest in the contribution of epigenetics and noncoding RNAs (especially miRNAs) to this differential change. Epigenetics regulates UGT1As pretranscriptionally through DNA methylation and histone modification, and miRNAs are considered the key mechanism of posttranscriptional regulation of UGT1As. Both epigenetic inheritance and miRNAs are involved in the differences in sex expression and in vivo distribution of UGT1As. Moreover, epigenetic changes early in life have been shown to affect gene expression throughout life. Here, we review and summarize the current regulatory role of epigenetics in the UGT1A family and discuss the relationship among epigenetics and UGT1A-related diseases and treatment, with references for future research.

Generation of induced pluripotent stem cells-derived hepatocyte-like cells for ex vivo gene therapy of primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disorder of the liver metabolism due to functional deficiency of the peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT). AGT deficiency results in overproduction of oxalate which complexes with calcium to form insoluble calcium-oxalate salts in urinary tracts, ultimately leading to end-stage renal disease. Currently, the only curative treatment for PH1 is combined liver-kidney transplantation, which is limited by donor organ shortage and lifelong requirement for immunosuppression. Transplantation of genetically modified autologous hepatocytes is an attractive therapeutic option for PH1. However, the use of fresh primary hepatocytes suffers from limitations such as organ availability, insufficient cell proliferation, loss of function, and the risk of immune rejection. We developed patient-specific induced pluripotent stem cells (PH1-iPSCs) free of reprogramming factors as a source of renewable and genetically defined autologous PH1-hepatocytes. We then investigated additive gene therapy using a lentiviral vector encoding wild-type AGT under the control of the liver-specific transthyretin promoter. Genetically modified PH1-iPSCs successfully provided hepatocyte-like cells (HLCs) that exhibited significant AGT expression at both RNA and protein levels after liver-specific differentiation process. These results pave the way for cell-based therapy of PH1 by transplantation of genetically modified autologous HLCs derived from patient-specific iPSCs.

Repeated AAV-mediated gene transfer by serotype switching enables long-lasting therapeutic levels of hUgt1a1 enzyme in a mouse model of Crigler-Najjar Syndrome Type I

Adeno-associated virus (AAV) -mediated gene therapy is a promising strategy to treat liver-based monogenic diseases. However, two major obstacles limit its success: first, vector dilution in actively dividing cells, such as hepatocytes in neonates/children, due to the non-integrating nature of the vector; second, development of an immune response against the transgene and/or viral vector. Crigler-Najjar Syndrome Type I is a rare monogenic disease with neonatal onset, caused by mutations in the liver-specific UGT1 gene, with toxic accumulation of unconjugated bilirubin in plasma, tissues and brain. To establish an effective and long lasting cure, we applied AAV-mediated liver gene therapy to a relevant mouse model of the disease. Repeated gene transfer to adults by AAV-serotype switching, upon neonatal administration, resulted in lifelong correction of total bilirubin (TB) levels in both genders. In contrast, vector loss over time was observed after a single neonatal administration. Adult administration resulted in lifelong TB levels correction in male, but not female Ugt1^-/- mice. Our findings demonstrate that neonatal AAV-mediated gene transfer to the liver supports a second transfer of the therapeutic vector, by preventing the induction of an immune response and supporting the possibility to improve AAV-therapeutic efficacy by repeated administration.

mRNA destabilization improves glycemic responsiveness of transcriptionally regulated hepatic insulin gene therapy in vitro and in vivo

BACKGROUND

Hepatic insulin gene therapy (HIGT) employing a glucose and insulin sensitive promoter to direct insulin transcription can lower blood sugars within 2 h of an intraperitoneal glucose challenge. However, post-challenge blood sugars frequently decline to below baseline. We hypothesize that this 'over-shoot' hypoglycemia results from sustained translation of long-lived transgene message, and that reducing pro-insulin message half-life will ameliorate post-challenge hypoglycemia.

METHODS

We compared pro-insulin message content and insulin secretion from primary rat hepatocytes expressing insulin from either a standard construct (2xfur), or a construct producing a destabilized pro-insulin message (InsTail), following exposure to stimulating or inhibitory conditions.

RESULTS

Hepatocytes transduced with a 2xfur construct accumulated pro-insulin message, and exhibited increased insulin secretion, under conditions that both inhibit or stimulate transcription. By contrast, pro-insulin message content remained stable in InsTail expressing cells, and insulin secretion increased less than 2xfur during prolonged stimulation. During transitions from stimulatory to inhibitory conditions, or vice versa, amounts of pro-insulin message changed more rapidly in InsTail expressing cells than 2xfur expressing cells. Importantly, insulin secretion increased during the transition from stimulation to inhibition in 2xfur expressing cells, although it remained unchanged in InsTail expressing cells. Use of the InsTail destabilized insulin message tended to more rapidly reduce glucose induced glycemic excursions, and limit post-load hypoglycemia in STZ-diabetic mice in vivo.

CONCLUSIONS

The data obtained in the present study suggest that combining transcriptional and post-transcriptional regulatory strategies may reduce undesirable glycemic excursion in models of HIGT.

A translationally optimized AAV-UGT1A1 vector drives safe and long-lasting correction of Crigler-Najjar syndrome

Crigler-Najjar syndrome is a severe metabolic disease of the liver due to a reduced activity of the UDP Glucuronosyltransferase 1A1 (UGT1A1) enzyme. In an effort to translate to the clinic an adeno-associated virus vector mediated liver gene transfer approach to treat Crigler-Najjar syndrome, we developed and optimized a vector expressing the UGT1A1 transgene. For this purpose, we designed and tested in vitro and in vivo multiple codon-optimized UGT1A1 transgene cDNAs. We also optimized noncoding sequences in the transgene expression cassette. Our results indicate that transgene codon-optimization is a strategy that can improve efficacy of gene transfer but needs to be carefully tested in vitro and in vivo. Additionally, while inclusion of introns can enhance gene expression, optimization of these introns, and in particular removal of cryptic ATGs and splice sites, is an important maneuver to enhance safety and efficacy of gene transfer. Finally, using a translationally optimized adeno-associated virus vector expressing the UGT1A1 transgene, we demonstrated rescue of the phenotype of Crigler-Najjar syndrome in two animal models of the disease, Gunn rats and Ugt1a1^-/- mice. We also showed long-term (>1 year) correction of the disease in Gunn rats. These results support further translation of the approach to humans.

MicroRNAs in the Evaluation and Potential Treatment of Liver Diseases

Acute and chronic liver disease continue to result in significant morbidity and mortality of patients, along with increasing burden on their families, society and the health care system. This in part is due to increased incidence of liver disease associated factors such as metabolic syndrome; improved survival of patients with chronic predisposing conditions such as HIV; as well as advances in the field of transplantation and associated care leading to improved survival. The fact that one disease can result in different manifestations and outcomes highlights the need for improved understanding of not just genetic phenomenon predisposing to a condition, but additionally the role of epigenetic and environmental factors leading to the phenotype of the disease. It is not surprising that providers continue to face daily challenges pertaining to diagnostic accuracy, prognostication of disease severity, progression, and response to therapies. A number of these challenges can be addressed by incorporating a personalized approach of management to the current paradigm of care. Recent advances in the fields of molecular biology and genetics have paved the way to more accurate, individualized and precise approach to caring for liver disease. The study of microRNAs and their role in both healthy and diseased livers is one example of such advances. As these small, non-coding RNAs work on fine-tuning of cellular activities and organ function in a dynamic and precise fashion, they provide us a golden opportunity to advance the field of hepatology. The study of microRNAs in liver disease promises tremendous improvement in hepatology and is likely to lay the foundation towards a personalized approach in liver disease.

Liver-directed lentiviral gene therapy in a dog model of hemophilia B

We investigated the efficacy of liver-directed gene therapy using lentiviral vectors in a large animal model of hemophilia B and evaluated the risk of insertional mutagenesis in tumor-prone mouse models. We showed that gene therapy using lentiviral vectors targeting the expression of a canine factor IX transgene in hepatocytes was well tolerated and provided a stable long-term production of coagulation factor IX in dogs with hemophilia B. By exploiting three different mouse models designed to amplify the consequences of insertional mutagenesis, we showed that no genotoxicity was detected with these lentiviral vectors. Our findings suggest that lentiviral vectors may be an attractive candidate for gene therapy targeted to the liver and may be potentially useful for the treatment of hemophilia.

Gene therapies for hepatitis C virus

Hepatitis C virus (HCV) is a leading cause of chronic hepatitis and infects approximately three to four million people per year, about 170 million infected people in total, making it one of the major global health problems. In a minority of cases HCV is cleared spontaneously, but in most of the infected individuals infection progresses to a chronic state associated with high risk to develop liver cirrhosis, hepatocellular cancer, or liver failure. The treatment of HCV infection has evolved over the years. Interferon (IFN)-α in combination with ribavirin has been used for decades as standard therapy. More recently, a new standard-of-care treatment has been approved based on a triple combination with either HCV protease inhibitor telaprevir or boceprevir. In addition, various options for all-oral, IFN-free regimens are currently being evaluated. Despite substantial improvement of sustained virological response rates, some intrinsic limitations of these new direct-acting antivirals, including serious side effects, the risk of resistance development and high cost, urge the development of alternative or additional therapeutic strategies. Gene therapy represents a feasible alternative treatment. Small RNA technology, including RNA interference (RNAi) techniques and antisense approaches, is one of the potentially promising ways to investigate viral and host cell factors that are involved in HCV infection and replication. With this, newly developed gene therapy regimens will be provided to treat HCV. In this chapter, a comprehensive overview guides you through the current developments and applications of RNAi and microRNA-based gene therapy strategies in HCV treatment.

Dysregulated miR-124 and miR-200 expression contribute to cholangiocyte proliferation in the cholestatic liver by targeting IL-6/STAT3 signalling

BACKGROUND & AIMS

Cholestatic liver disease is associated with dysregulated expression of microRNAs (miRNAs). However, it remains unknown whether miRNAs are involved in the cholestasis-induced proliferation of cholangiocytes. In this study, we tested the hypothesis that miRNAs modulate cholangiocyte proliferation through effects on the IL-6 pathway, a known regulator of cholangiocyte proliferation.

METHODS

Expression of IL-6, Foxa2, and phosphorylated signal transducer activator of transcription 3 (STAT3) was investigated in patients with biliary atresia (BA) and in rats subjected to bile duct ligation (BDL). miRNA expression was determined in BA patients and BDL rats, with miRNA array and quantitative real-time PCR. Biological functions of miRNAs were studied using immunoblot, immunohistochemical and proliferation assays. Luciferase reporter assays and Western blots were performed to identify miRNA targets.

RESULTS

Hepatic interleukin-6 (IL-6) expression was significantly elevated in BA patients and BDL rats, while the expression of miR-124 was dramatically decreased in comparison to controls. Moreover, mRNA levels of STAT3 and IL-6 receptor (IL-6R) were inversely correlated with those of miR-124. Ectopic expression of miR-124 inhibited IL-6-mediated cholangiocyte proliferation in vitro and cholangiocyte hyperplasia in vivo, through a mechanism involving direct targeting of the 3'-untranslated region of STAT3 and IL-6R. We further demonstrated that miR-200 family members were significantly upregulated in cholestasis and inhibited FOXA2 expression in cholangiocytes, which further enhanced the expression of IL-6.

CONCLUSIONS

Our findings suggest that downregulation of miR-124 and upregulation of miR-200 collaboratively promote bile duct proliferation through the IL-6/STAT3 pathway.

Rosuvastatin alleviates diabetic cardiomyopathy by inhibiting NLRP3 inflammasome and MAPK pathways in a type 2 diabetes rat model

PURPOSE

Nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome is important in inflammation of several diabetic complications. However, the potential role of NLRP3 inflammasome in the inflammatory process of diabetic cardiomyopathy (DCM) remains unclear. Although rosuvastatin (RSV) has an anti-inflammatory effect on some cardiovascular diseases, its influence on DCM is incompletely understood. We aimed to explore the effect on and underlying mechanism of RSV in DCM, and whether NLRP3 is a target for RSV.

METHODS

Type 2 diabetes was induced in rat. The characteristics of type 2 DCM were evaluated by metabolic tests, echocardiography and histopathology. The expression of factors was determined by real-time RT-PCR and western blot. Eight-week RSV treatment and NLRP3 gene silencing were used to investigate the effect and underlying target of RSV in DCM.

RESULTS

Compared with controls, diabetic rats showed severe metabolic disorder, cardiac dysfunction, fibrosis, disorganized ultrastructure, and excessive activation of thioredoxin interacting/inhibiting protein (TXNIP, p < 0.05), NLRP3 inflammasome (NLRP3, p < 0.01; apoptosis-associated speck-like protein containing a caspase recruitment domain [ASC], p < 0.05; caspase-1, p < 0.01), interleukin-1β (p < 0.01) and mitogen-activated protein kinases (MAPKs, all p < 0.01). Compared with diabetes alone, RSV ameliorated the overexpression of NLRP3 inflammasome (NLRP3, p < 0.05; ASC, p < 0.05; pro-caspase-1 p < 0.05, caspase-1 p20, p < 0.01) and MAPKs (all p < 0.05), which paralleled the cardiac protection of RSV. Silencing NLRP3 ameliorated cardiac remodeling and dysfunction. The beneficial effects of RSV in vehicle-treated rats were all abrogated in NLRP3-silenced rats.

CONCLUSIONS

The beneficial effect of RSV on DCM depended on inhibited NLRP3 inflammasome, and correlated with suppression of the MAPKs.

Prolonged gene expression in muscle is achieved without active immune tolerance using microrRNA 142.3p-regulated rAAV gene transfer

Gene transfer efficacy is limited by unwanted immunization against transgene products. In some models, immunization may be avoided by regulating transgene expression with mir142.3p target sequences. Yet, it is unclear if such a strategy controls T-cell responses following recombinant adeno-associated viral vector (rAAV)-mediated gene transfer, particularly in muscle. In mice, intramuscular rAAV1 gene delivery of a tagged human sarcoglycan muscle protein is robustly immunogenic and leads to muscle destruction. In this model, the simple insertion of mir142.3p-target sequences in the transgene expression cassette modifies the outcome of gene transfer, providing high and persistent levels of muscle transduction in C57Bl/6 mice. Such regulated vector fails to prime specific CD4 and CD8 T cells; although, transgene tolerance seems to result from ignorance and could be broken by a robust antigenic challenge. While effective in normal mice, the mir142.3p-regulated transgene remains immunogenic in sarcoglycan-deficient dystrophic mice. In these mice, transgene expression is only prolonged but does not persist as effector CD4 and CD8 T-cell responses develop. Thus, using a mir142.3p-regulated transgene can improve rAAV muscle gene transfer results, but the level of efficacy depends on the context of application. In normal muscle, this strategy is sufficient to prevent immunization and functions even more effectively than tissue-specific promoters. In dystrophic models, additional strategies are required to fully control T-cell responses.

Immune responses in liver-directed lentiviral gene therapy

The use of lentiviral vectors (LV)s for in vivo gene therapy is an ideal platform for treating many types of disease. Since LVs can transduce a wide array of cells, support long-term gene expression, and be modified to enhance cell targeting, LVs are a powerful modality to deliver life-long therapeutic proteins. A major limitation facing the use of LVs for in vivo gene therapy is the induction of immune responses, which can reduce the transduction efficiency of LV, eliminate the transduced cells, and inhibit the effect of the therapeutic protein. LV strategies designed to restrict transgene expression to the liver to exploit its naturally tolerogenic properties have proven to significantly reduce the induction of pathogenic immune responses and increase therapeutic efficacy. In this review, we outline the immunological hurdles facing in vivo LV gene therapy and highlight the advantages and limitations of using liver-directed LV gene therapy.

Polyploidization without mitosis improves in vivo liver transduction with lentiviral vectors

Lentiviral vectors are efficient gene delivery vehicles for therapeutic and research applications. In contrast to oncoretroviral vectors, they are able to infect most nonproliferating cells. In the liver, induction of cell proliferation dramatically improved hepatocyte transduction using all types of retroviral vectors. However, the precise relationship between hepatocyte division and transduction efficiency has not been determined yet. Here we compared gene transfer efficiency in the liver after in vivo injection of recombinant lentiviral or Moloney murine leukemia viral (MoMuLV) vectors in hepatectomized rats treated or not with retrorsine, an alkaloid that blocks hepatocyte division and induces megalocytosis. Partial hepatectomy alone resulted in a similar increase in hepatocyte transduction using either vector. In retrorsine-treated and partially hepatectomized rats, transduction with MoMuLV vectors dropped dramatically. In contrast, we observed that retrorsine treatment combined with partial hepatectomy increased lentiviral transduction to higher levels than hepatectomy alone. Analysis of nuclear ploidy in single cells showed that a high level of transduction was associated with polyploidization. In conclusion, endoreplication could be exploited to improve the efficiency of liver-directed lentiviral gene therapy.

Priming of hepatocytes enhances in vivo liver transduction with lentiviral vectors in adult mice

Lentiviral vectors are promising tools for liver disease gene therapy, because they can achieve protracted expression of transgenes in hepatocytes. However, the question as to whether cell division is required for optimal hepatocyte transduction has still not been completely answered. Liver gene-transfer efficiency after in vivo administration of recombinant lentiviral vectors carrying a green fluorescent protein reporter gene under the control of a liver-specific promoter in mice that were either hepatectomized or treated with cholic acid or phenobarbital was compared. Phenobarbital is known as a weak inducer of hepatocyte proliferation, whereas cholic acid has no direct effect on the cell cycle. This study shows that cholic acid is able to prime hepatocytes without mitosis induction. Both phenobarbital and cholic acid significantly increased hepatocyte transduction six- to ninefold, although cholic acid did not modify the mitotic index or cell-cycle entry. However, the effect of either compound was weaker than that observed after partial hepatectomy. In no cases was there a correlation between the expression of cell-cycle marker and transduction efficiency. We conclude that priming of hepatocytes should be considered a clinically applicable strategy to enhance in vivo liver gene therapy with lentiviral vectors.

Specific micro RNA-regulated TetR-KRAB transcriptional control of transgene expression in viral vector-transduced cells

Precise control of transgene expression in a tissue-specific and temporally regulated manner is desirable for many basic and applied investigations gene therapy applications. This is important to regulate dose of transgene products and minimize unwanted effects. Previously described methods have employed tissue specific promoters, miRNA-based transgene silencing or tetR-KRAB-mediated suppression of transgene promoters. To improve on versatility of transgene expression control, we have developed expression systems that use combinations of a tetR-KRAB artificial transgene-repressor, endogenous miRNA silencing machinery and tissue specific promoters. Precise control of transgene expression was demonstrated in liver-, macrophage- and muscle-derived cells. Efficiency was also demonstrated in vivo in murine muscle. This multicomponent and modular regulatory system provides a robust and easily adaptable method for achieving regulated transgene expression in different tissue types. The improved precision of regulation will be useful for many gene therapy applications requiring specific spatiotemporal transgene regulation.

Sustained reduction of hyperbilirubinemia in Gunn rats after adeno-associated virus-mediated gene transfer of bilirubin UDP-glucuronosyltransferase isozyme 1A1 to skeletal muscle

Crigler-Najjar syndrome is an autosomal recessive disorder with severe unconjugated hyperbilirubinemia due to deficiency of bilirubin UDP-glucuronosyltransferase isozyme 1A1 (UGT1A1) encoded by the UGT1A1 gene. Current therapy relies on phototherapy to prevent life-threatening elevations of serum bilirubin levels, but liver transplantation is the only permanent treatment. Muscle-directed gene therapy has several advantages, including easy and safe access through simple intramuscular injections, and has been investigated in human clinical trials. In this study, we have investigated the efficacy of adeno-associated viral (AAV) vector-mediated muscle-directed gene therapy in the preclinical animal model of Crigler-Najjar syndrome, that is the Gunn rat. Serotype 1 AAV vector expressing rat UGT1A1 under the control of muscle-specific creatine kinase promoter was injected at a dose of 3×10(12) genome copies/kg into the muscles of Gunn rats and resulted in expression of UGT1A1 protein and functionally active enzyme in injected muscles. AAV-injected Gunn rats showed an approximately 50% reduction in serum bilirubin levels as compared with saline-treated controls, and this reduction was sustained for at least 1 year postinjection. Increased excretion of alkali-labile metabolites of bilirubin in bile and urine was detected in AAV-injected animals. High-performance liquid chromatography analysis of bile from AAV-injected Gunn rats showed a metabolite with retention time close to that of bilirubin diglucuronide. Taken together, these data show that clinically relevant and sustained reduction of serum bilirubin levels can be achieved by simple and safe intramuscular injections in Gunn rats. AAV-mediated muscle directed gene therapy has potential for the treatment of patients with Crigler-Najjar syndrome type 1.

A TLR and non-TLR mediated innate response to lentiviruses restricts hepatocyte entry and can be ameliorated by pharmacological blockade

Lentiviral vector (LV)-mediated gene transfer is a promising method of gene therapy. We previously reported that systemic injection of HIV-based LV triggers a transient inflammatory response. Here, we carried out studies to better characterize this response, and to develop a strategy to overcome the adverse effects of interferon (IFN) on LV-mediated gene transfer. We profiled gene expression in the liver after LV administration using deep-sequencing (RNA-seq), and identified several innate response pathways. We examined the response to LV in MyD88-TRIF knockout mice, which are incapable of toll-like receptor (TLR) signaling. Unexpectedly, the IFN response to LV was not reduced in the liver indicating that a non-TLR pathway can recognize LV in this organ. Indeed, blocking reverse transcription with azidothymidine (AZT) reduced the IFN response only in the liver, suggesting that proviral DNA can be a trigger. To block the inflammatory response, we pretreated mice with a short course of dexamethasone (Dex). At 4 hours post-treatment, all the IFN-induced genes were normalized. By blocking the inflammatory response, hepatocyte transduction was dramatically increased, which in turn doubled the level of human factor IX (FIX) produced by a hepatocyte-specific LV. Our studies uncover new insights into LV-induced immune responses in the liver, and provide a means to increase the safety and efficiency of LV-mediated gene transfer.

Gene therapy of liver diseases: a 2011 perspective

Liver diseases including inherited metabolic disorders, chronic viral hepatitis, liver cirrhosis and primary and metastatic liver cancer constitute a formidable health problem because of their high prevalence and the important limitations of current therapies. Gene therapy, a procedure based on the transfer of therapeutic genes to tissues, has been used since the 1990s as a new approach to treating a number of incurable conditions. After a period of lights and shades recent success in treating several devastating diseases like inherited immune deficiency disorders, beta-thalassemia, or inherited blindness appear to herald a new era where gene therapy can be listed among standard therapy options for a wide variety of human conditions. In this review, we provide information illustrating the potentiality of gene therapy in the management of liver diseases lacking other effective therapies.

Paediatric liver transplantation for metabolic disorders. Part 1: Liver-based metabolic disorders without liver lesions

Liver-based metabolic disorders account for 10 to 15% of the indications for paediatric liver transplantation. In the last three decades, important progress has been made in the understanding of these diseases, and new therapies have emerged. Concomitantly, medical and surgical innovations have lead to improved results of paediatric liver transplantation, patient survival nowadays exceeding 80% 10-year after surgery with close to normal quality of life in most survivors. This review is a practical update on medical therapy, indications and results of liver transplantation, and potential future therapies, for the main liver-based metabolic disorders in which paediatric liver transplantation may be considered. Part 1 focuses on metabolic based liver disorders without liver lesions, and part 2 on metabolic liver diseases with liver lesions.