Antonio Fontanellas

Effect of Adeno-Associated Virus Serotype and Genomic Structure on Liver Transduction and Biodistribution in Mice of Both Genders

Recombinant adeno-associated viral (AAV) vectors have unique properties, which make them suitable vectors for gene transfer. Here we assess the liver transduction efficiency and biodistribution of AAV-pseudotyped capsids (serotypes) 1, 5, 6, and 8, combined with single-stranded and double-stranded genomic AAV2 structures carrying the luciferase reporter gene after systemic administration. The analysis was performed in vivo and ex vivo, in male and female mice. Gender-related differences in AAV-mediated transduction and biodistribution were shown for the four serotypes. Our data confirm the superiority of AAV8 over the rest of the serotypes, as well as a significant advantage of double-stranded genomes in terms of liver transduction efficiency, particularly in females. Regarding biodistribution, AAV5 displayed a narrower tropism than the other serotypes tested, transducing, almost exclusively, the liver. Interestingly, AAV1 and AAV8, in particular those having single-stranded genomes, showed high transduction efficiency of female gonads. However, no inadvertent germ line transmission of AAV genomes was observed after breeding single-stranded AAV8-injected female mice with untreated males. In conclusion, double-stranded AAV8 vectors led to the highest levels of liver transduction in mice, as demonstrated by luciferase expression. Nevertheless, the transduction of other organs with AAV8 vectors could favor the use of less efficient serotypes, such as AAV5, which display a narrow tropism.

Safety and Liver Transduction Efficacy of rAAV5-cohPBGD in Nonhuman Primates: A Potential Therapy for Acute Intermittent Porphyria

Acute intermittent porphyria (AIP) results from haplo-insufficient activity of porphobilinogen deaminase (PBGD) and is characterized clinically by life-threatening, acute neurovisceral attacks. To date, liver transplantation is the only curative option for AIP. The aim of the present preclinical nonhuman primate study was to determine the safety and transduction efficacy of an adeno-associated viral vector encoding PBGD (recombinant AAV serotype 5-codon-optimized human porphobilinogen deaminase, rAAV5-cohPBGD) administered intravenously as part of a safety program to start a clinical study in patients with AIP. Macaques injected with either 1 × 10(13) or 5 × 10(13) vector genomes/kg of clinical-grade rAAV5-cohPBGD were monitored by standardized clinical parameters, and vector shedding was analyzed. Liver transduction efficacy, biodistribution, vector integration, and histopathology at day 30 postvector administration were determined. There was no evidence of acute toxicity, and no adverse effects were observed. The vector achieved efficient and homogenous hepatocellular transduction, reaching transgenic PBGD expression levels equivalent to 50% of the naturally expressed PBGD mRNA. No cellular immune response was detected against the human PBGD or AAV capsid proteins. Integration site analysis in transduced liver cells revealed an almost random integration pattern supporting the good safety profile of rAAV5-cohPBGD. Together, data obtained in nonhuman primates indicate that rAAV5-cohPBGD represents a safe therapy to correct the metabolic defect present in AIP patients.

Phase I open label liver-directed gene therapy clinical trial for acute intermittent porphyria

BACKGROUND & AIMS Acute intermittent porphyria (AIP) results from porphobilinogen deaminase (PBGD) haploinsufficiency, which leads to hepatic over-production of the neurotoxic heme precursors porphobilinogen (PBG) and delta-aminolevulinic acid (ALA) and the occurrence of neurovisceral attacks. Severe AIP is a devastating disease that can only be corrected by liver transplantation. Gene therapy represents a promising curative option. The objective of this study was to investigate the safety of a recombinant adeno-associated vector expressing PBGD (rAAV2/5-PBGD) administered for the first time in humans for the treatment of AIP. METHODS In this phase I, open label, dose-escalation, multicenter clinical trial, four cohorts of 2 patients each received a single intravenous injection of the vector ranging from 5×10(11) to 1.8×10(13) genome copies/kg. Adverse events and changes in urinary PBG and ALA and in the clinical course of the disease were periodically evaluated prior and after treatment. Viral shedding, immune response against the vector and vector persistence in the liver were investigated. RESULTS Treatment was safe in all cases. All patients developed anti-AAV5 neutralizing antibodies but no cellular responses against AAV5 or PBGD were observed. There was a trend towards a reduction of hospitalizations and heme treatments, although ALA and PBG levels remained unchanged. Vector genomes and transgene expression could be detected in the liver one year after therapy. CONCLUSIONS rAAV2/5-PBGD administration is safe but AIP metabolic correction was not achieved at the doses tested in this trial. Notwithstanding, the treatment had a positive impact in clinical outcomes in most patients. LAY SUMMARY Studies in an acute intermittent porphyria (AIP) animal model have shown that gene delivery of PBGD to hepatocytes using an adeno-associated virus vector (rAAV2/5-PBG) prevent mice from suffering porphyria acute attacks. In this phase I, open label, dose-escalation, multicenter clinical trial we show that the administration of rAAV2/5-PBGD to patients with severe AIP is safe but metabolic correction was not achieved at the doses tested; the treatment, however, had a positive but heterogeneous impact on clinical outcomes among treated patients and 2 out of 8 patients have stopped hematin treatment. CLINICAL TRIAL NUMBER The observational phase was registered at Clinicaltrial.gov as NCT 02076763. The interventional phase study was registered at EudraCT as n° 2011-005590-23 and at Clinicaltrial.gov as NCT02082860.

Sustained Enzymatic Correction by rAAV-Mediated Liver Gene Therapy Protects Against Induced Motor Neuropathy in Acute Porphyria Mice

Acute intermittent porphyria (AIP) is characterized by a hereditary deficiency of hepatic porphobilinogen deaminase (PBGD) activity. Clinical features are acute neurovisceral attacks accompanied by overproduction of porphyrin precursors in the liver. Recurrent life-threatening attacks can be cured only by liver transplantation. We developed recombinant adeno-associated virus (rAAV) vectors expressing human PBGD protein driven by a liver-specific promoter to provide sustained protection against induced attacks in a predictive model for AIP. Phenobarbital injections in AIP mice induced porphyrin precursor accumulation, functional block of nerve conduction, and progressive loss of large-caliber axons in the sciatic nerve. Hepatocyte transduction showed no gender variation after rAAV2/8 injection, while rAAV2/5 showed lower transduction efficiency in females than males. Full protection against induced phenobarbital-attacks was achieved in animals showing over 10% of hepatocytes expressing high amounts of PBGD. More importantly, sustained hepatic expression of hPBGD protected against loss of large-caliber axons in the sciatic nerve and disturbances in nerve conduction velocity as induced by recurrent phenobarbital administrations. These data show for the first time that porphyrin precursors generated in the liver interfere with motor function. rAAV2/5-hPBGD vector can be produced in sufficient quantity for an intended gene therapy trial in patients with recurrent life-threatening porphyria attacks.

Transient and intensive pharmacological immunosuppression fails to improve AAV-based liver gene transfer in non-human primates

BackgroundAdeno-associated vectors (rAAV) have been used to attain long-term liver gene expression. In humans, the cellular immune response poses a serious obstacle for transgene persistence while neutralizing humoral immunity curtails re-administration. Porphobilinogen deaminase (PBGD) haploinsufficiency (acute intermittent porphyria) benefits from liver gene transfer in mouse models and clinical trials are about to begin. In this work, we sought to study in non-human primates the feasibility of repeated gene-transfer with intravenous administration of rAAV5 vectors under the effects of an intensive immunosuppressive regimen and to analyze its ability to circumvent T-cell immunity and thereby prolong transgene expression.MethodsThree female Macaca fascicularis were intravenously injected with 1x1013 genome copies/kg of rAAV5 encoding the human PBGD. Mycophenolate mofetil (MMF), anti-thymocyte immunoglobulin, methylprednisolone, tacrolimus and rituximab were given in combination during 12 weeks to block T- and B-cell mediated adaptive immune responses in two macaques. Immunodeficient and immunocompetent mice were intravenously injected with 5x1012 genome copies/kg of rAAV5-encoding luciferase protein. Forty days later MMF, tacrolimus and rituximab were daily administrated to ascertain whether the immunosuppressants or their metabolites could interfere with transgene expression.ResultsMacaques given a rAAV5 vector encoding human PBGD developed cellular and humoral immunity against viral capsids but not towards the transgene. Anti-AAV humoral responses were attenuated during 12 weeks but intensely rebounded following cessation of the immunosuppressants. Accordingly, subsequent gene transfer with a rAAV5 vector encoding green fluorescent protein was impossible. One macaque showed enhanced PBGD expression 25 weeks after rAAV5-pbgd administration but overexpression had not been detected while the animal was under immunosuppression. As a potential explanation, MMF decreases transgene expression in mouse livers that had been successfully transduced by a rAAV5 several weeks before MMF onset. Such a silencing effect was independent of AAV complementary strand synthesis and requires an adaptive immune system.ConclusionsThese results indicate that our transient and intensive pharmacological immunosuppression fails to improve AAV5-based liver gene transfer in non-human primates. The reasons include an incomplete restraint of humoral immune responses to viral capsids that interfere with repeated gene transfer in addition to an intriguing MMF-dependent drug-mediated interference with liver transgene expression.

Intensive Pharmacological Immunosuppression Allows for Repetitive Liver Gene Transfer With Recombinant Adenovirus in Nonhuman Primates

Repeated administration of gene therapies is hampered by host immunity toward vectors and transgenes. Attempts to circumvent antivector immunity include pharmacological immunosuppression or alternating different vectors and vector serotypes with the same transgene. Our studies show that B-cell depletion with anti-CD20 monoclonal antibody and concomitant T-cell inhibition with clinically available drugs permits repeated liver gene transfer to a limited number of nonhuman primates with recombinant adenovirus. Adenoviral vector-mediated transfer of the herpes simplex virus type 1 thymidine kinase (HSV1-tk) reporter gene was visualized in vivo with a semiquantitative transgene-specific positron emission tomography (PET) technique, liver immunohistochemistry, and immunoblot for the reporter transgene in needle biopsies. Neutralizing antibody and T cell-mediated responses toward the viral capsids were sequentially monitored and found to be repressed by the drug combinations tested. Repeated liver transfer of the HSV1-tk reporter gene with the same recombinant adenoviral vector was achieved in macaques undergoing a clinically feasible immunosuppressive treatment that ablated humoral and cellular immune responses. This strategy allows measurable gene retransfer to the liver as late as 15 months following the first adenoviral exposure in a macaque, which has undergone a total of four treatments with the same adenoviral vector.

The molecular basis of porphyria cutanea tarda in Chile: Identification and functional characterization of mutations in the uroporphyrinogen decarboxylase gene

Abstract:  The porphyrias are heterogeneous disorders arising from predominantly inherited catalytic deficiencies of specific enzymes in heme biosynthesis. Porphyria cutanea tarda (PCT) results from a decreased activity of uroporphyrinogen decarboxylase, the fifth enzyme in heme biosynthesis. The disorder represents the only porphyria that is not exclusively inherited monogenetically. In PCT, at least two different types can be distinguished: acquired/sporadic (type I) PCT, in which the enzymatic deficiency is limited to the liver and inherited/familial (type II) PCT, which is inherited as an autosomal dominant trait with a decrease of enzymatic activity in all tissues. In an effort to characterize the molecular basis of PCT in Chile, we identified eight mutations in 18 previously unclassified PCT families by polymerase chain reaction, heteroduplex analysis, and automated sequencing. To study the role of these mutations in disease causality, in vitro expression of all novel missense mutations was studied. Our results indicate that the frequency of familial PCT in Chile is approximately 50%, thus, to our knowledge, representing the highest incidence of familial PCT reported to date. The data further emphasize the molecular heterogeneity in type II PCT and demonstrate the advantages of molecular genetic techniques as a diagnostic tool and in the detection of clinically asymptomatic mutation carriers.

Porphobilinogen deaminase over-expression in hepatocytes, but not in erythrocytes, prevents accumulation of toxic porphyrin precursors in a mouse model of acute intermittent porphyria

BACKGROUND & AIMS Acute intermittent porphyria (AIP) is characterized by hepatic porphobilinogen deaminase (PBGD) deficiency resulting in a marked overproduction of presumably toxic porphyrin precursors. Our study aimed to assess the protective effects of bone marrow transplantation or PBGD gene transfer into the liver against phenotypic manifestations of acute porphyria attack induced in an AIP murine model. METHODS Lethally irradiated AIP mice were intravenously injected with 5x10(6) nucleated bone marrow cells from wild type or AIP donor mice. To achieve liver gene transfer, AIP mice received via hydrodynamic injection plasmids expressing human PBGD or luciferase, driven by a liver-specific promoter. RESULTS Erythrocyte PBGD activity increased 2.4-fold in AIP mice receiving bone marrow cells from normal animals. Nevertheless, phenobarbital administration in these mice reproduced key features of acute attacks, such as massively increased urinary porphyrin precursor excretion and decreased motor coordination. Hepatic PBGD activity increased 2.2-fold after hydrodynamic injection of therapeutic plasmid. Mice injected with the luciferase control plasmid showed a high excretion of porphyrin precursors after phenobarbital administration whereas just a small increase was observed in AIP mice injected with the PBGD plasmid. Furthermore, motor disturbance was almost completely abolished in AIP mice treated with the therapeutic plasmid. CONCLUSIONS PBGD deficiency in erythroid tissue is not associated with phenotypic manifestations of acute porphyria. In contrast, PBGD over-expression in hepatocytes, albeit in a low proportion, reduced precursor accumulation, which is the hallmark of acute porphyric attacks. Liver-directed gene therapy might offer an alternative to liver transplantation applicable in patients with severe and recurrent manifestations.

Molecular heterogeneity of familial porphyria cutanea tarda in Spain: characterization of 10 novel mutations in the UROD gene

Background  Porphyria cutanea tarda (PCT) results from decreased hepatic uroporphyrinogen decarboxylase (UROD) activity. In the majority of patients, the disease is sporadic (S‐PCT or type I) and the enzyme deficiency is limited to the liver. Familial PCT (F‐PCT or type II) is observed in 20–30% of patients in whom mutations on one allele of the UROD gene reduce UROD activity by approximately 50% in all tissues. Another variant of PCT (type III) is characterized by family history of the disease although it is biochemically indistinguishable from S‐PCT.

PET imaging of thymidine kinase gene expression in the liver of non-human primates following systemic delivery of an adenoviral vector

Non-invasive in vivo imaging of transgene expression is currently providing very important means to optimize gene therapy regimes. Results in non-human primates are considered the most predictive models for the outcome in patients. In this study, we have documented that tumour and primary cell lines from human and non-human primates are comparably gene-transduced in vitro by serotype 5 adenovirus expressing HSV1-thymidine kinase. Transgene expression can be quantified in human and monkey cultured cells by positron emission tomography (PET) imaging when transduced cells are incubated with a fluoride-18 labelled penciclovir analogue. In our hands, PET images of cell cultures estimate the number of transduced cells rather than intensity of transgene expression once a threshold of TK per cell is reached. Interestingly, in vivo systemic administration of a clinical grade recombinant adenovirus expressing TK into macaques gives rise to an intense retention of the radiotracer in the liver parenchyma, providing an experimental system to visualize transgene expression that ought to be similar in human and macaques. Such imaging methodology might contribute to improve strategies based on adenoviral vectors.