Expression and processing of mature human frataxin after gene therapy in mice

Friedreich's ataxia is a degenerative and progressive multisystem disorder caused by mutations in the highly conserved frataxin (FXN) gene that results in FXN protein deficiency and mitochondrial dysfunction. While gene therapy approaches are promising, consistent induction of therapeutic FXN protein expression that is sub-toxic has proven challenging, and numerous therapeutic approaches are being tested in animal models. FXN (hFXN in humans, mFXN in mice) is proteolytically modified in mitochondria to produce mature FXN. However, unlike endogenous hFXN, endogenous mFXN is further processed into N-terminally truncated, extra-mitochondrial mFXN forms of unknown function. This study assessed mature exogenous hFXN expression levels in the heart and liver of C57Bl/6 mice 7-10 months after intravenous administration of a recombinant adeno-associated virus encoding hFXN (AAVrh.10hFXN) and examined the potential for hFXN truncation in mice. AAVrh.10hFXN induced dose-dependent expression of hFXN in the heart and liver. Interestingly, hFXN was processed into truncated forms, but found at lower levels than mature hFXN. However, the truncations were at different positions than mFXN. AAVrh.10hFXN induced mature hFXN expression in mouse heart and liver at levels that approximated endogenous mFXN levels. These results suggest that AAVrh.10hFXN can likely induce expression of therapeutic levels of mature hFXN in mice.

Expression and processing of mature human frataxin after gene therapy in mice

Friedreich's ataxia is a degenerative and progressive multisystem disorder caused by mutations in the highly conserved frataxin (FXN) gene that results in FXN protein deficiency and mitochondrial dysfunction. While gene therapy approaches are promising, consistent induction of therapeutic FXN protein expression that is sub-toxic has proven challenging, and numerous therapeutic approaches are being tested in animal models. FXN (hFXN in humans, mFXN in mice) is proteolytically modified in mitochondria to produce mature FXN. However, unlike endogenous hFXN, endogenous mFXN is further processed into N-terminally truncated, extra-mitochondrial mFXN forms of unknown function. This study assessed mature exogenous hFXN expression levels in the heart and liver of C57Bl/6 mice 7-10 months after intravenous administration of a recombinant adeno-associated virus encoding hFXN (AAVrh.10hFXN) and examined the potential for hFXN truncation in mice. AAVrh.10hFXN induced dose-dependent expression of hFXN in the heart and liver. Interestingly, hFXN was processed into truncated forms, but found at lower levels than mature hFXN. However, the truncations were at different positions than mFXN. AAVrh.10hFXN induced mature hFXN expression in mouse heart and liver at levels that approximated endogenous mFXN levels. These results demonstrate that AAVrh.10hFXN may induce expression of therapeutic levels of mature hFXN in mice.

Positron Emission Tomography Quantitative Assessment of Off-Target Whole-Body Biodistribution of I-124-Labeled Adeno-Associated Virus Capsids Administered to Cerebral Spinal Fluid

Based on studies in experimental animals demonstrating that administration of adeno-associated virus (AAV) vectors to the cerebrospinal fluid (CSF) is an effective route to transfer genes to the nervous system, there are increasing number of clinical trials using the CSF route to treat nervous system disorders. With the knowledge that the CSF turns over four to five times daily, and evidence in experimental animals that at least some of CSF administered AAV vectors are distributed to systemic organs, we asked: with AAV administration to the CSF, what fraction of the total dose remains in the nervous system and what fraction goes off target and is delivered systemically? To quantify the biodistribution of AAV capsids immediately after administration, we covalently labeled AAV capsids with iodine 124 (I-124), a cyclotron generated positron emitter, enabling quantitative positron emission tomography scanning of capsid distribution for up to 96 h after AAV vector administration. We assessed the biodistribution to nonhuman primates of I-124-labeled capsids from different AAV clades, including 9 (clade F), rh.10 (E), PHP.eB (F), hu68 (F), and rh91(A). The analysis demonstrated that 60-90% of AAV vectors administered to the CSF through either the intracisternal or intrathecal (lumbar) routes distributed systemically to major organs. These observations have potentially significant clinical implications regarding accuracy of AAV vector dosing to the nervous system, evoking systemic immunity at levels similar to that with systemic administration, and potential toxicity of genes designed to treat nervous system disorders being expressed in non-nervous system organs. Based on these data, individuals in clinical trials using AAV vectors administered to the CSF should be monitored for systemic as well as nervous system adverse events and CNS dosing considerations should account for a significant AAV systemic distribution.

Assessment of Safety and Biodistribution of AAVrh.10hCLN2 Following Intracisternal Administration in Nonhuman Primates for the Treatment of CLN2 Batten Disease

CLN2 disease is a fatal, childhood autosomal recessive disorder caused by mutations in ceroid lipofuscinosis type 2 (CLN2) gene, encoding tripeptidyl peptidase 1 (TPP-1). Loss of TPP-1 activity leads to accumulation of storage material in lysosomes and resultant neuronal cell death with neurodegeneration. Genotype/phenotype comparisons suggest that the phenotype should be ameliorated with increase of TPP-1 levels to 5-10% of normal with wide central nervous system (CNS) distribution. Our previous clinical study showed that intraparenchymal (IPC) administration of AAVrh.10hCLN2, an adeno-associated vector serotype rh.10 encoding human CLN2, slowed, but did not stop disease progression, suggesting that this may be insufficient to distribute the therapy throughout the CNS (Sondhi 2020). In this study, we assessed whether the less invasive intracisternal delivery route would be safe and provide a wider distribution of TPP-1. A study was conducted in nonhuman primates (NHPs) with intracisternal delivery to cerebrospinal fluid (CSF) of AAVrh.10hCLN2 (5 × 1013 genome copies) or phosphate buffered saline (PBS). No abnormal behavior was noted. CNS magnetic resonance imaging and clinical chemistry data were all unremarkable. Histopathology of major organs had no abnormal finding attributable to the intervention or the vector, except that in one out of two animals treated with AAVrh.10hCLN2, dorsal root ganglia showed mild-to-moderate mononuclear cell infiltrates and neuronal degeneration. In contrast to our previous NHP study (Sondhi 2012) with IPC administration where TPP-1 activity was >2 × above controls in 30% of treated brains, in the two intracisternal treated NHPs, the TPP-1 activity was >2 × above controls in 50% and 41% of treated brains, and 52% and 84% of brain had >1,000 vector genomes/μg DNA, compared to 0% in the two PBS NHP. CSF TPP1 levels in treated animals were 43-62% of normal human levels. Collectively, these data indicate that AAVrh.10hCLN2 delivered by intracisternal route is safe and widely distributes TPP-1 in brain and CSF at levels that are potentially therapeutic. Clinical Trial Registration: NCT02893826, NCT04669535, NCT04273269, NCT03580083, NCT04408625, NCT04127578, and NCT04792944.

Assessment of Residual Full-Length SV40 Large T Antigen in Clinical-Grade Adeno-Associated Virus Vectors Produced in 293T Cells

Efficient production of adeno-associated virus (AAV) vectors is a significant challenge. Human embryonic kidney HEK293T cells are widely used in good manufacturing practice facilities, producing higher yield of AAV vectors for clinical applications than HEK293 through the addition of a constitutive expression of SV40 large T antigen (SV40T), which stimulates Rep expression. However, the theoretical potential for tumorigenic consequences of a clinical AAV product containing residual DNA encoding SV40T, which may inhibit p53 growth suppressive functions is a safety concern. Although the risk is theoretical, to assure a low risk/high confidence of safety for clinical drug development, we have established a sensitive assay for assessment of functional full-length transcription competent SV40T DNA in HEK293T cell-produced AAV vectors. Using HEK293T generated 8, 9, and rh.10 serotype AAV vectors, the presence of SV40T in purified vector was assessed in vitro using quantitative polymerase chain reaction (qPCR) targeting a 129 bp amplicon combined with nested PCR targeting full-length SV40T DNA. Although low levels of the smaller amplicon were present in each AAV serotype, the full-length SV40T was undetectable. No transcription competent full-length SV40T DNA was observed by reverse transcription-quantitative polymerase chain reaction using an in vivo amplification of signal in mouse liver administered (2-10 × 1010 gc) 129 bp amplicon-positive AAV vectors. As a control for gene transfer, high levels of expressed transgene mRNAs were observed from each serotype AAV vector, yet, SV40T mRNA was undetectable. In vivo assessment of these three liver-tropic AAV serotypes, each with amplicon-positive qPCR SV40T DNA, demonstrated high transgene mRNA expression but no SV40T mRNA, that is, detection of small segments of SV40T DNA in 293T cell produced AAV inappropriately leads to the conclusion of residuals with the potential to express SV40T. This sensitive assay can be used to assess the level, if any, of SV40T antigen contaminating AAV vectors generated by HEK293T cells. ClinicalTrials.gov identifier: NCT03634007; NCT05302271; NCT01414985; NCT01161576.

Identification of Safe and Effective Intravenous Dose of AAVrh.10hFXN to Treat the Cardiac Manifestations of Friedreich's Ataxia

Friedreich's ataxia (FA) is a life-threatening autosomal recessive disorder characterized by neurological and cardiac dysfunction. Arrhythmias and heart failure are the main cause of premature death. From prior studies in murine models of FA, adeno-associated virus encoding the normal human frataxin gene (AAVrh.10hFXN) effectively treated the cardiac manifestations of the disease. However, the therapeutic dose window is limited by high level of human frataxin (hFXN) gene expression associated with toxicity. As a therapeutic goal, since FA heterozygotes have no clinical manifestations of FA, we estimated the level of frataxin (FXN) necessary to convert the heart of a homozygote to that of a heterozygote. In noncardiac cells, FA heterozygotes have 30-80% of normal FXN levels (17.7-47.2 ng/mg, average 32.5 ng/mg) and FA homozygotes 2-30% normal levels (1.2-17.7 ng/mg, average 9.4 ng/mg). Therefore, an AAV vector would need to augment endogenous in an FA homozygote by >8.3 ng/mg. To determine the required dose of AAVrh.10hFXN, we administered 1.8 × 1011, 5.7 × 1011, or 1.8 × 1012 gc/kg of AAVrh.10hFXN intravenously (IV) to muscle creatine kinase (mck)-Cre conditional knockout Fxn mice, a cardiac and skeletal FXN knockout model. The minimally effective dose was 5.7 × 1011 gc/kg, resulting in cardiac hFXN levels of 6.1 ± 4.2 ng/mg and a mild (p < 0.01 compared with phosphate-buffered saline controls) improvement in mortality. A dose of 1.8 × 1012 gc/kg resulted in cardiac hFXN levels of 33.7 ± 6.4 ng/mg, a significant improvement in ejection fraction and fractional shortening (p < 0.05, both comparisons) and a 21.5% improvement in mortality (p < 0.001). To determine if the significantly effective dose of 1.8 × 1012 gc/kg could achieve human FA heterozygote levels in a large animal, this dose was administered IV to nonhuman primates. After 12 weeks, the vector-expressed FXN in the heart was 17.8 ± 4.9 ng/mg, comparable to the target human levels. These data identify both minimally and significantly effective therapeutic doses that are clinically relevant for the treatment of the cardiac manifestations of FA.

Safety of Intravenous Administration of an AAV8 Vector Coding for an Oxidation-Resistant Human α1-Antitrypsin for the Treatment of α1-Antitrypsin Deficiency

α1-antitrypsin (AAT) deficiency is a common autosomal recessive hereditary disorder, with a high risk for the development of early-onset panacinar emphysema. AAT, produced primarily in the liver, functions to protect the lung from neutrophil protease; with AAT deficiency, unimpeded neutrophil proteases destroy the lung parenchyma. AAT is susceptible to oxidative damage resulting in an inability to inhibit its target proteases, neutrophil elastase, and cathepsin G. The major sites of oxidative modification on the AAT molecule are methionine residues 351 and 358. We have previously demonstrated that an engineered variant of AAT that resists oxidation by modifying both protein surface methionines (M351V and M358L) provides antiprotease protection, despite oxidative stress. In mice, intravenous delivery of the modified AAT(AVL) variant by AAV serotype 8, AAV8hAAT(AVL), primarily to the liver resulted in long-term expression of an AAT that resists oxidative inactivation. In this study, we evaluated the safety of intravenous administration of AAV8hAAT(AVL) in a dose-escalating, blinded, placebo-controlled toxicology study in wild-type mice. The study assessed organ histology and clinical pathology findings of mice, intravenously administered AAV8hAAT(AVL) at three doses (5.0 × 1011, 5.0 × 1012, and 5.0 × 1013 genome copies [gc]/kg), compared to control mice injected intravenously with phosphate-buffered saline. As previously demonstrated, administration of AAV8hAAT(AVL) resulted in dose-dependent expression of high, potentially therapeutic, levels of serum human AAT protein that persist for at least 6 months. Antibodies against the AAV8 capsid were elicited as expected, but there was no antibody detected against the AAT(AVL) protein generated by the AAV8hAAT(AVL) vector. There was no morbidity or mortality observed in the study. The data demonstrate that intravenous administration of AAV8hAAT(AVL) is safe with no significant adverse effect attributed to AAV8hAAT(AVL) vector at any dose. This study demonstrates that AAV8hAAT(AVL) has a safety profile consistent with the requirements for proceeding to a clinical study.

Quantitative Whole-Body Imaging of I-124-Labeled Adeno-Associated Viral Vector Biodistribution in Nonhuman Primates

A method is presented for quantitative analysis of the biodistribution of adeno-associated virus (AAV) gene transfer vectors following in vivo administration. We used iodine-124 (I-124) radiolabeling of the AAV capsid and positron emission tomography combined with compartmental modeling to quantify whole-body and organ-specific biodistribution of AAV capsids from 1 to 72 h following administration. Using intravenous (IV) and intracisternal (IC) routes of administration of AAVrh.10 and AAV9 vectors to nonhuman primates in the absence or presence of anticapsid immunity, we have identified novel insights into initial capsid biodistribution and organ-specific capsid half-life. Neither I-124-labeled AAVrh.10 nor AAV9 administered intravenously was detected at significant levels in the brain relative to the administered vector dose. Approximately 50% of the intravenously administered labeled capsids were dispersed throughout the body, independent of the liver, heart, and spleen. When administered by the IC route, the labeled capsid had a half-life of ∼10 h in the cerebral spinal fluid (CSF), suggesting that by this route, the CSF serves as a source with slow diffusion into the brain. For both IV and IC administration, there was significant influence of pre-existing anticapsid immunity on I-124-capsid biodistribution. The methodology facilitates quantitative in vivo viral vector dosimetry, which can serve as a technique for evaluation of both on- and off-target organ biodistribution, and potentially accelerate gene therapy development through rapid prototyping of novel vector designs.

Slowing late infantile Batten disease by direct brain parenchymal administration of a rh.10 adeno-associated virus expressing CLN2

Late infantile Batten disease (CLN2 disease) is an autosomal recessive, neurodegenerative lysosomal storage disease caused by mutations in the CLN2 gene encoding tripeptidyl peptidase 1 (TPP1). We tested intraparenchymal delivery of AAVrh.10hCLN2, a nonhuman serotype rh.10 adeno-associated virus vector encoding human CLN2, in a nonrandomized trial consisting of two arms assessed over 18 months: AAVrh.10hCLN2-treated cohort of 8 children with mild to moderate disease and an untreated, Weill Cornell natural history cohort consisting of 12 children. The treated cohort was also compared to an untreated European natural history cohort of CLN2 disease. The vector was administered through six burr holes directly to 12 sites in the brain without immunosuppression. In an additional safety assessment under a separate protocol, five children with severe CLN2 disease were treated with AAVrh.10hCLN2. The therapy was associated with a variety of expected adverse events, none causing long-term disability. Induction of systemic anti-AAVrh.10 immunity was mild. After therapy, the treated cohort had a 1.3- to 2.6-fold increase in cerebral spinal fluid TPP1. There was a slower loss of gray matter volume in four of seven children by MRI and a 42.4 and 47.5% reduction in the rate of decline of motor and language function, compared to Weill Cornell natural history cohort (P < 0.04) and European natural history cohort (P < 0.0001), respectively. Intraparenchymal brain administration of AAVrh.10hCLN2 slowed the progression of disease in children with CLN2 disease. However, improvements in vector design and delivery strategies will be necessary to halt disease progression using gene therapy.

Safety of Direct Intraparenchymal AAVrh.10-Mediated Central Nervous System Gene Therapy for Metachromatic Leukodystrophy

Metachromatic leukodystrophy, a fatal pediatric neurodegenerative lysosomal storage disease caused by mutations in the arylsulfatase A (ARSA) gene, is characterized by intracellular accumulation of sulfatides in the lysosomes of cells of the central nervous system (CNS). In previous studies, we have demonstrated efficacy of AAVrh.10hARSA, an adeno-associated virus (AAV) serotype rh.10 vector coding for the human ARSA gene to the CNS of a mouse model of the disease, and that catheter-based intraparenchymal administration of AAVrh.10hARSA to the CNS of nonhuman primates (NHPs) white matter results in widespread expression of ARSA. As a formal dose-escalating safety/toxicology study, we assessed the safety of intraparenchymal delivery of AAVrh.10hARSA vector to 12 sites in the white matter of the CNS of NHPs at 2.85 × 10¹⁰ (total low dose, 2.4 × 10⁹ genome copies [gc]/site) and 1.5 × 10¹² (total high dose, 1.3 × 10¹¹ gc/site) gc, compared to AAVrh.10Null (1.5 × 10¹² gc total, 1.3 × 10¹¹ gc/site) as a vector control, and phosphate buffered saline for a sham surgical control. No significant adverse effects were observed in animals treated with low dose AAVrh.10hARSA. However, animals treated with the high dose AAVrh.10ARSA and the high dose Null vector had highly localized CNS abnormalities on magnetic resonance imaging scans at the sites of catheter infusions, and histopathology demonstrated that these sites were associated with infiltrates of T cells, B cells, microglial cells, and/or macrophages. Although these findings had no clinical consequences, these safety data contribute to understanding the dose limits for CNS white matter direct intraparenchymal administration of AAVrh.10 vectors for treatment of CNS disorders.

Cocaine vaccine dAd5GNE protects against moderate daily and high-dose "binge" cocaine use

The cocaine vaccine dAd5GNE is comprised of a disrupted serotype 5 adenovirus gene therapy vector covalently conjugated to the cocaine analog GNE. The vaccine evokes a high titer of circulating anti-cocaine antibodies that prevent cocaine from reaching its cognate receptors in the central nervous system. Prior studies have demonstrated the efficacy of dAd5GNE in models of occasional, moderate cocaine use. However, previous studies have not sufficiently evaluated the efficacy of dAd5GNE in models of the repetitive and high-dose "binge" use patterns common in human addicts. In the present study, we evaluated the capacity of dAd5GNE vaccination to protect against "binge" cocaine use and circumstances where vaccinated addicts attempt to override the vaccine. We modeled repetitive daily cocaine use in vaccinated Balb/c mice and African green monkeys, and evaluated high-dose "binge" scenarios in Balb/c mice. In each model of daily use the dAd5GNE vaccine prevented cocaine from reaching the central nervous system. In the high-dose "binge" model, vaccination decreased cocaine-induced hyperactivity and reduced the number of cocaine-induced seizures. Based on this data and our prior data in rodents and nonhuman primates, we have initiated a clinical trial evaluating the dAd5GNE anti-cocaine vaccine as a potential therapy for cocaine addicts who wish to stop cocaine use. If dAd5GNE vaccination is safe and produces high anti-cocaine antibody titers in the clinic, we hypothesize that the vaccine will restrict the access of cocaine to the central nervous system and inhibit cocaine-induced "highs" even in the context of moderate daily and high-dose "binge" use that might otherwise cause a drug-induced overdose.

Anti-Phospho-Tau Gene Therapy for Chronic Traumatic Encephalopathy

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disorder caused by repetitive trauma to the central nervous system (CNS) suffered by soldiers, contact sport athletes, and civilians following accident-related trauma. CTE is a CNS tauopathy, with trauma-induced inflammation leading to accumulation of hyperphosphorylated forms of the microtubule-binding protein Tau (pTau), resulting in neurofibrillary tangles and progressive loss of neurons. At present, there are no therapies to treat CTE. We hypothesized that direct CNS administration of an adeno-associated virus (AAV) vector coding for an anti-pTau antibody would generate sufficient levels of anti-pTau in the CNS to suppress pTau accumulation thus interrupting the pathogenic process. Using a serotype AAVrh.10 gene transfer vector coding for a monoclonal antibody directed against pTau, we demonstrate the feasibility of this strategy in a murine CTE model in which pTau accumulation was elicited by repeated traumatic brain injury (TBI) using a closed cortical impact procedure over 5 days. Direct delivery of AAVrh.10 expression vectors coding for either of the two different anti-pTau antibodies to the hippocampus of these TBI mice significantly reduced pTau levels across the CNS. Using doses that can be safely scaled to humans, the data demonstrate that CNS administration of AAVrh.10anti-pTau is effective, providing a new strategy to interrupt the CTE consequences of TBI.

Advances in the Treatment of Neuronal Ceroid Lipofuscinosis

Neuronal ceroid lipofuscinoses (NCL) represent a class of neurodegenerative disorders involving defective lysosomal processing enzymes or receptors, leading to lysosomal storage disorders, typically characterized by observation of cognitive and visual impairments, epileptic seizures, ataxia, and deterioration of motor skills. Recent success of a biologic (Brineura®) for the treatment of neurologic manifestations of the central nervous system (CNS) has led to renewed interest in therapeutics for NCL, with the goal of ablating or reversing the impact of these devastating disorders. Despite complex challenges associated with CNS therapy, many treatment modalities have been evaluated, including enzyme replacement therapy, gene therapy, stem cell therapy, and small molecule pharmacotherapy. Because the clinical endpoints for the evaluation of candidate therapies are complex and often reliant on subjective clinical scales, the development of quantitative biomarkers for NCLs has become an apparent necessity for the validation of potential treatments. We will discuss the latest findings in the search for relevant biomarkers for assessing disease progression. For this review, we will focus primarily on recent pre-clinical and clinical developments for treatments to halt or cure these NCL diseases. Continued development of current therapies and discovery of newer modalities will be essential for successful therapeutics for NCL.

AREAS COVERED

The reader will be introduced to the NCL subtypes, natural histories, experimental animal models, and biomarkers for NCL progression; challenges and different therapeutic approaches, and the latest pre-clinical and clinical research for therapeutic development for the various NCLs. This review corresponds to the literatures covering the years from 1968 to mid-2019, but primarily addresses pre-clinical and clinical developments for the treatment of NCL disease in the last decade and as a follow-up to our 2013 review of the same topic in this journal.

EXPERT OPINION

Much progress has been made in the treatment of neurologic diseases, such as the NCLs, including better animal models and improved therapeutics with better survival outcomes. Encouraging results are being reported at symposiums and in the literature, with multiple therapeutics reaching the clinical trial stage for the NCLs. The potential for a cure could be at hand after many years of trial and error in the preclinical studies. The clinical development of enzyme replacement therapy (Brineura® for CLN2), immunosuppression (CellCept® for CLN3), and gene therapy vectors (for CLN1, CLN2, CLN3, and CLN6) are providing encouragement to families that have a child afflicted with NCL. We believe that successful therapies in the future may involve the combination of two or more therapeutic modalities to provide therapeutic benefit especially as the patients grow older.

Intrapleural Gene Therapy for Alpha-1 Antitrypsin Deficiency-Related Lung Disease

Alpha-1 antitrypsin deficiency (AATD) manifests primarily as early-onset emphysema caused by the destruction of the lung by neutrophil elastase due to low amounts of the serine protease inhibitor alpha-1 antitrypsin (AAT). The current therapy involves weekly intravenous infusions of AAT-derived from pooled human plasma that is efficacious, yet costly. Gene therapy applications designed to provide constant levels of the AAT protein are currently under development. The challenge is for gene therapy to provide sufficient amounts of AAT to normalize the inhibitor level and anti-neutrophil elastase capacity in the lung. One strategy involves administration of an adeno-associated virus (AAV) gene therapy vector to the pleural space providing both local and systemic production of AAT to reach consistent therapeutic levels. This review focuses on the strategy, advantages, challenges, and updates for intrapleural administration of gene therapy vectors for the treatment of AATD.

Paris I Dysfibrinogenemia: A Point Mutation in Intron 8 Results in Insertion of a 15 Amino Acid Sequence in the Fibrinogen γ-Chain

Paris I dysfibrinogenemia results in the production of a fibrinogen molecule containing a functionally abnormal γ-chain. We determined the basis of the molecular defect using polymerase chain reaction (PCR) to amplify the γ-chain region of the Paris I subject’s genomic DNA. Comparative sequence analysis of cloned PCR segments of normal and Paris I genomic DNA revealed only an A→G point mutation occurring at nucleotide position 6588 within intron 8 of the Paris I γ-chain gene. We examined six normal individuals and found only normal sequence in this region, indicating that this change is not likely to represent a normal polymorphism. This nucleotide change leads to a 45 bp fragment being inserted between exons 8 and 9 in the mature γparis I chain mRNA, and encodes a 15 amino acid insert after γ350 [M-C-G-E-A-L-P-M-L-K-D-P-C-Y]. Alternative splicing of this region from intron 8 into the mature Paris I γ-chain mRNA also results after translation into a substitution of S for G at position γ351. Biochemical studies of 14C-iodoacetamide incorporation into disulfide-reduced Paris I and normal fibrinogen corroborated the molecular biologic predictions that two additional cysteine residues exist within the γpariS I chain. We conclude that the insertion of this amino acid sequence leads to a conformationallyaltered, and dysfunctional γ-chain in Paris I fibrinogen.

In Vivo Potency Assay for Adeno-Associated Virus-Based Gene Therapy Vectors Using AAVrh.10 as an Example

The development of a drug product requires rigorous methods of characterization and quality control to assure drug potency. Gene therapy products, a relatively new strategy for drug design with very few licensed examples, represent a unique challenge for the measure of potency. Unlike traditional drugs, potency for a gene therapeutic is a tally of the measures of multiple steps, including infectivity, transcription, translation, protein modifications, proper localization of the protein product, and protein function. This is particularly challenging for products based on the adeno-associated virus (AAV) platform, which has poor in vitro infectivity, limiting the sensitivity and thus the usefulness of cell-based assays. A rigorous in vivo assay has been established that separately evaluates infection, transcription, and resulting protein levels with specifications for each based on real time polymerase chain reaction (DNA and RNA) and standard protein assays. For an acceptance criterion, an administered vector must have vector DNA, transgene mRNA, and transgene expressed protein each concurrently meet individual specifications or the production lot fails. Using the AAVrh.10 serotype as a model vector and three different transgenes as examples, the assay is based on intravenous administration of the vector to male mice. At 2 weeks, the harvested liver is homogenized and assessed for vector genome levels (to assess for vector delivery), mRNA (to assess vector infectivity and transcription), and protein in the liver or serum (to assess protein expression). For all AAV vectors, the assay is robust and reproducible: vector DNA (linearity 10²-10⁹ copies, coefficient of variation) intra-assay <0.8%, inter-assay <0.5%; mRNA intra-assay <3.3%, inter-assay <3.4%. The reproducibility of the assay for transgene expressed protein is product specific. This in vivo potency assay is a strategy for characterization and a quantitative lot release test, providing a path forward to meet regulatory drug requirements for any AAV gene therapy vectors.

AAVrh.10-Mediated APOE2 Central Nervous System Gene Therapy for APOE4-Associated Alzheimer's Disease

Alzheimer's disease (AD) is a progressive degenerative neurological disorder affecting nearly one in nine elderly people in the United States. Population studies have shown that an inheritance of the apolipoprotein E (APOE) variant APOE4 allele increases the risk of developing AD, whereas APOE2 homozygotes are protected from late-onset AD. It was hypothesized that expression of the "protective" APOE2 variant by genetic modification of the central nervous system (CNS) of APOE4 homozygotes could reverse or prevent progressive neurologic damage. To assess the CNS distribution and safety of APOE2 gene therapy for AD in a large-animal model, intraparenchymal, intracisternal, and intraventricular routes of delivery to the CNS of nonhuman primates of AAVrh.10hAPOE2-HA, an AAVrh.10 serotype coding for an HA-tagged human APOE2 cDNA sequence, were evaluated. To evaluate the route of delivery that achieves the widest extent of APOE2 expression in the CNS, the expression of APOE2 in the CNS was evaluated 2 months following vector administration for APOE2 DNA, mRNA, and protein. Finally, using conventional toxicology assays, the safety of the best route of delivery was assessed. The data demonstrated that while all three routes are capable of mediating ApoE2 expression in AD relevant regions, intracisternal delivery of AAVrh.10hAPOE2-HA safely mediated wide distribution of ApoE2 with the least invasive surgical intervention, thus providing the optimal strategy to deliver vector-mediated human APOE2 to the CNS.

Gene therapy for metachromatic leukodystrophy

Leukodystrophies (LDs) are rare, often devastating genetic disorders with neurologic symptoms. There are currently no disease-specific therapeutic approaches for these diseases. In this review we use metachromatic leukodystrophy as an example to outline in the brief the therapeutic approaches to MLD that have been tested in animal models and in clinical trials, such as enzyme-replacement therapy, bone marrow/umbilical cord blood transplants, ex vivo transplantation of genetically modified hematopoietic stem cells, and gene therapy. These studies suggest that to be successful the ideal therapy for MLD must provide persistent and high level expression of the deficient gene, arylsulfatase A in the CNS. Gene therapy using adeno-associated viruses is therefore the ideal choice for clinical development as it provides the best balance of potential for efficacy with reduced safety risk. Here we have summarized the published preclinical data from our group and from others that support the use of a gene therapy with AAVrh.10 serotype for clinical development as a treatment for MLD, and as an example of the potential of gene therapy for LDs especially for Krabbe disease, which is the focus of this special issue. © 2016 Wiley Periodicals, Inc.

Efficacy of an adenovirus-based anti-cocaine vaccine to reduce cocaine self-administration and reacqusition using a choice procedure in rhesus macaques

Immunopharmacotherapy offers an approach for treating cocaine abuse by specifically targeting the cocaine molecule and preventing its access to the CNS. dAd5GNE is a novel cocaine vaccine that attenuates the stimulant and the reinforcing effects of cocaine in rats. The goal of this study was to extend and validate dAd5GNE vaccine efficacy in non-human primates. Six experimentally naïve adult female rhesus monkeys (Macaca mulatta) were trained to self-administer 0.1mg/kg/injection intravenous (i.v.) cocaine or receive candy; then 4 monkeys were administered the vaccine and 2 monkeys were administered vehicle intramuscularly, with additional vaccine boosts throughout the study. The reinforcing effects of cocaine were measured during self-administration, extinction, and reacquisition (relapse) phases. Serum antibody titers in the vaccinated monkeys remained high throughout the study. There was no change in the preference for cocaine over candy over a 20-week period in 5 of the 6 monkeys; only one of the 4 (25%) vaccinated monkeys showed a decrease in cocaine choice. All 6 monkeys extinguished responding for cocaine during saline extinction testing; vaccinated monkeys tended to take longer to extinguish responding than control monkeys (17.5 vs. 7.0 sessions). Vaccination substantially retarded reacquisition of cocaine self-administration; control monkeys resumed cocaine self-administration within 6-41 sessions and 1 vaccinated monkey resumed cocaine self-administration in 19 sessions. The other 3 vaccinated monkeys required between 57 and 94 sessions to resume cocaine self-administration even in the context of employing several manipulations to encourage cocaine reacquisition. These data suggest that the dAdGNE vaccine may have therapeutic potential for humans who achieve cocaine abstinence as part of a relapse prevention strategy.

Fate of systemically administered cocaine in nonhuman primates treated with the dAd5GNE anticocaine vaccine

Cocaine use disorders are mediated by the cocaine blockade of the dopamine transporter in the central nervous system (CNS). On the basis of the concept that these effects could be obviated if cocaine were prevented from reaching its cognate receptors in the CNS, we have developed an anticocaine vaccine, dAd5GNE, based on a cocaine analog covalently linked to capsid proteins of an E1(-)E3(-) serotype 5 adenovirus. While the vaccine effectively blocks systemically administered cocaine from reaching the brain by mediating sequestration of the cocaine in the blood, the fact that cocaine also has significant peripheral effects raises concerns that vaccination-mediated redistribution could lead to adverse effects in the visceral organs. The distribution of systemically administered cocaine at a weight-adjusted typical human dose was evaluated along with cocaine metabolites in both dAd5GNE-vaccinated and control nonhuman primates. dAd5GNE sequestration of cocaine to the blood not only prevented cocaine access to the CNS, but also limited access of both the drug and its metabolites to other cocaine-sensitive organs. The levels of cocaine in the blood of vaccinated animals rapidly decreased, suggesting that while the antibody limits access of the drug and its active metabolites to the brain and sensitive organs of the periphery, it does not prolong drug levels in the blood compartment. Gross and histopathology of major organs found no vaccine-mediated untoward effects. These results build on our earlier measures of efficacy and demonstrate that the dAd5GNE vaccine-mediated redistribution of administered cocaine is not likely to impact the vaccine safety profile.

Comparative efficacy and safety of multiple routes of direct CNS administration of adeno-associated virus gene transfer vector serotype rh.10 expressing the human arylsulfatase A cDNA to nonhuman primates

Metachromatic leukodystrophy (MLD), a fatal disorder caused by deficiency of the lysosomal enzyme arylsulfatase A (ARSA), is associated with an accumulation of sulfatides, causing widespread demyelination in both central and peripheral nervous systems. On the basis of prior studies demonstrating that adeno-associated virus AAVrh.10 can mediate widespread distribution in the CNS of a secreted lysosomal transgene, and as a prelude to human trials, we comparatively assessed the optimal CNS delivery route of an AAVrh.10 vector encoding human ARSA in a large animal model for broadest distribution of ARSA enzyme. Five routes were tested (each total dose, 1.5 × 10(12) genome copies of AAVrh.10hARSA-FLAG): (1) delivery to white matter centrum ovale; (2) deep gray matter delivery (putamen, thalamus, and caudate) plus overlying white matter; (3) convection-enhanced delivery to same deep gray matter locations; (4) lateral cerebral ventricle; and (5) intraarterial delivery with hyperosmotic mannitol to the middle cerebral artery. After 13 weeks, the distribution of ARSA activity subsequent to each of the three direct intraparenchymal administration routes was significantly higher than in phosphate-buffered saline-administered controls, but administration by the intraventricular and intraarterial routes failed to demonstrate measurable levels above controls. Immunohistochemical staining in the cortex, white matter, deep gray matter of the striatum, thalamus, choroid plexus, and spinal cord dorsal root ganglions confirmed these results. Of the five routes studied, administration to the white matter generated the broadest distribution of ARSA, with 80% of the brain displaying more than a therapeutic (10%) increase in ARSA activity above PBS controls. No significant toxicity was observed with any delivery route as measured by safety parameters, although some inflammatory changes were seen by histopathology. We conclude that AAVrh.10-mediated delivery of ARSA via CNS administration into the white matter is likely to be safe and yields the widest distribution of ARSA, making it the most suitable route of vector delivery.

Suppression of nicotine-induced pathophysiology by an adenovirus hexon-based antinicotine vaccine

Despite antismoking campaigns, cigarette smoking remains a pervasive addiction with significant societal impact, accounting for one of every five deaths. Smoking cessation therapies to help smokers quit are ineffective with a high recidivism rate. With the knowledge that nicotine is the principal addictive compound of cigarettes, we have developed an antismoking vaccine based on the highly immunogenic properties of the hexon protein purified from the serotype 5 adenovirus (Ad) capsid. We hypothesized that an effective antinicotine vaccine could be based on coupling the nicotine hapten AM1 to purified Ad hexon protein. To assess this, AM1 was conjugated to hexon purified from serotype 5 Ad to produce the HexonAM1 vaccine. C57Bl/6 mice were sensitized by 10 daily nicotine administrations (0.5 mg/kg, subcutaneous) to render the mice addicted to nicotine. Control groups were sensitized to phosphate-buffered saline (PBS). The mice were then immunized with HexonAM1 (4 μg, intramuscular) at 0, 3, and 6 weeks. By 6 weeks, the HexonAM1-vaccinated mice had serum antinicotine antibody titers of 1.1×10(6)±7.6×10(4). To demonstrate that these high antinicotine titers were sufficient to suppress the effects of nicotine, HexonAM1-vaccinated mice were evaluated for nicotine-induced hypoactive behavior with nicotine challenges (0.5 mg/kg wt) over 5 weeks. In all challenges, the HexonAM1-vaccinated mice behaved similar to PBS-challenged naive mice. These data demonstrate that a vaccine comprised of a nicotine analog coupled to Ad hexon can evoke a high level of antinicotine antibodies sufficient to inhibit nicotine-induced behavior. The HexonAM1 vaccine represents a platform paradigm for vaccines against small molecules.

Adenovirus capsid-based anti-cocaine vaccine prevents cocaine from binding to the nonhuman primate CNS dopamine transporter

Cocaine addiction is a major problem for which there is no approved pharmacotherapy. We have developed a vaccine to cocaine (dAd5GNE), based on the cocaine analog GNE linked to the capsid proteins of a serotype 5 adenovirus, designed to evoke anti-cocaine antibodies that sequester cocaine in the blood, preventing access to the CNS. To assess the efficacy of dAd5GNE in a large animal model, positron emission tomography (PET) and the radiotracer [(11)C]PE2I were used to measure cocaine occupancy of the dopamine transporter (DAT) in nonhuman primates. Repeat administration of dAd5GNE induced high anti-cocaine titers. Before vaccination, cocaine displaced PE2I from DAT in the caudate and putamen, resulting in 62±4% cocaine occupancy. In contrast, dAd5GNE-vaccinated animals showed reduced cocaine occupancy such that when anti-cocaine titers were >4 × 10(5), the cocaine occupancy was reduced to levels of <20%, significantly below the 47% threshold required to evoke the subjective 'high' reported in humans.

Disrupted adenovirus-based vaccines against small addictive molecules circumvent anti-adenovirus immunity

Adenovirus (Ad) vaccine vectors have been used for many applications due to the capacity of the Ad capsid proteins to evoke potent immune responses, but these vectors are often ineffective in the context of pre-existing anti-Ad immunity. Leveraging the knowledge that E1(-)E3(-) Ad gene transfer vectors are potent immunogens, we have developed a vaccine platform against small molecules by covalently coupling analogs of small molecules to the capsid proteins of disrupted Ad (dAd5). We hypothesized that the dAd5 platform would maintain immunopotency even in the context of anti-Ad neutralizing antibodies. To test this hypothesis, we coupled cocaine and nicotine analogs, GNE and AM1, to dAd5 capsid proteins to generate dAd5GNE and dAd5AM1, respectively. Mice were pre-immunized with Ad5Null, resulting in high titer anti-Ad5 neutralizing antibodies comparable to those observed in the human population. The dAd5GNE and dAd5AM1 vaccines elicited high anti-cocaine and anti-nicotine antibody titers, respectively, in both naive and Ad5-immune mice, and both functioned to prevent cocaine or nicotine from reaching the brain of anti-Ad immune mice. Thus, disrupted Ad5 evokes potent humoral immunity that is effective in the context of pre-existing neutralizing anti-Ad immunity, overcoming a major limitation for current Ad-based vaccines.

Anti-cocaine vaccine based on coupling a cocaine analog to a disrupted adenovirus

The challenge in developing an anti-cocaine vaccine is that cocaine is a small molecule, invisible to the immune system. Leveraging the knowledge that adenovirus (Ad) capsid proteins are highly immunogenic in humans, we hypothesized that linking a cocaine hapten to Ad capsid proteins would elicit high-affinity, high-titer antibodies against cocaine, sufficient to sequester systemically administered cocaine and prevent access to the brain, thus suppressing cocaine-induced behaviors. Based on these concepts, we developed dAd5GNE, a disrupted E1-E3- serotype 5 Ad with GNE, a stable cocaine analog, covalently linked to the Ad capsid proteins. In pre-clinical studies, dAd5GNE evoked persistent, high titer, high affinity IgG anti-cocaine antibodies, and was highly effective in blocking cocaine-induced hyperactivity and cocaine self-administration behavior in rats. Future studies will be designed to expand the efficacy studies, carry out relevant toxicology studies, and test dAd5GNE in human cocaine addicts.

AAV-directed persistent expression of a gene encoding anti-nicotine antibody for smoking cessation

Current strategies to help tobacco smokers quit have limited success as a result of the addictive properties of the nicotine in cigarette smoke. We hypothesized that a single administration of an adeno-associated virus (AAV) gene transfer vector expressing high levels of an anti-nicotine antibody would persistently prevent nicotine from reaching its receptors in the brain. To test this hypothesis, we constructed an AAVrh.10 vector that expressed a full-length, high-affinity, anti-nicotine antibody derived from the Fab fragment of the anti-nicotine monoclonal antibody NIC9D9 (AAVantiNic). In mice treated with this vector, blood concentrations of the anti-nicotine antibody were dose-dependent, and the antibody showed high specificity and affinity for nicotine. The antibody shielded the brain from systemically administered nicotine, reducing brain nicotine concentrations to 15% of those in naïve mice. The amount of nicotine sequestered in the serum of vector-treated mice was more than seven times greater than that in untreated mice, with 83% of serum nicotine bound to immunoglobulin G. Treatment with the AAVantiNic vector blocked nicotine-mediated alterations in arterial blood pressure, heart rate, and locomotor activity. In summary, a single administration of a gene transfer vector expressing a high-affinity anti-nicotine monoclonal antibody elicited persistent (18 weeks), high titers of an anti-nicotine antibody that obviated the physiologic effects of nicotine. If this degree of efficacy translates to humans, AAVantiNic could be an effective preventative therapy for nicotine addiction.

AAVrh.10-mediated expression of an anti-cocaine antibody mediates persistent passive immunization that suppresses cocaine-induced behavior

Cocaine addiction is a major problem affecting all societal and economic classes for which there is no effective therapy. We hypothesized an effective anti-cocaine vaccine could be developed by using an adeno-associated virus (AAV) gene transfer vector as the delivery vehicle to persistently express an anti-cocaine monoclonal antibody in vivo, which would sequester cocaine in the blood, preventing access to cognate receptors in the brain. To accomplish this, we constructed AAVrh.10antiCoc.Mab, an AAVrh.10 gene transfer vector expressing the heavy and light chains of the high affinity anti-cocaine monoclonal antibody GNC92H2. Intravenous administration of AAVrh.10antiCoc.Mab to mice mediated high, persistent serum levels of high-affinity, cocaine-specific antibodies that sequestered intravenously administered cocaine in the blood. With repeated intravenous cocaine challenge, naive mice exhibited hyperactivity, while the AAVrh.10antiCoc.Mab-vaccinated mice were completely resistant to the cocaine. These observations demonstrate a novel strategy for cocaine addiction by requiring only a single administration of an AAV vector mediating persistent, systemic anti-cocaine passive immunity.

In vivo gene transfer strategies to achieve partial correction of von Willebrand disease

von Willebrand disease (VWD), the most common hereditary coagulation disorder, results from mutations in the 52-exon gene for von Willebrand factor (VWF), which encodes an 8.4-kB cDNA. Studies with VWF cDNA plasmids have demonstrated that in vivo gene transfer to the liver will correct the coagulation dysfunction in VWF(-/-) mice, but the correction is transient. To develop gene therapy for VWF that would mediate long-term expression of the VWF cDNA in liver, we first evaluated segmental pre-mRNA trans-splicing (SPTS) with two adeno-associated virus (AAV) serotype 8 vectors, each delivering one-half of the VWF cDNA. However, although the two vectors functioned well to generate VWF multimers after infection of cells in vitro, the efficiency of SPTS was insufficient to correct the VWF(-/-) mouse in vivo. As an alternative, we assessed the ability of a lentiviral vector to transfer the intact murine VWF cDNA in vivo directly to the neonatal liver of VWF(-/-) mice, using generation of VWF multimers, bleeding time, and bleeding volume as efficacy parameters. The VWF lentivirus generated VWF multimers and partially or completely corrected the coagulation defect on a persistent basis in 33% of the treated VWF-deficient mice. On the basis of the concept that partial persistent correction with gene transfer could be beneficial in VWD patients, these observations suggest that lentiviral delivery of VWF cDNA should be explored as a candidate for gene therapy in patients with a severe form of VWD.

Novel cocaine vaccine linked to a disrupted adenovirus gene transfer vector blocks cocaine psychostimulant and reinforcing effects

Immunotherapy is a promising treatment for drug addiction. However, insufficient immune responses to vaccines in most subjects pose a challenge. In this study, we tested the efficacy of a new cocaine vaccine (dAd5GNE) in antagonizing cocaine addiction-related behaviors in rats. This vaccine used a disrupted serotype 5 adenovirus (Ad) gene transfer vector coupled to a third-generation cocaine hapten, termed GNE (6-(2R,3S)-3-(benzoyloxy)-8-methyl-8-azabicyclo [3.2.1] octane-2-carboxamido-hexanoic acid). Three groups of rats were immunized with dAd5GNE. One group was injected with (3)H-cocaine, and radioactivity in the blood and brain was determined. A second group was tested for cocaine-induced locomotor sensitization. A third group was examined for cocaine self-administration, extinction, and reinstatement of responding for cocaine. Antibody titers were determined at various time-points. In each experiment, we added a control group that was immunized with dAd5 without a hapten. The vaccination with dAd5GNE produced long-lasting high titers (>10(5)) of anti-cocaine antibodies in all of the rats. The vaccination inhibited cocaine-induced hyperlocomotor activity and sensitization. Vaccinated rats acquired cocaine self-administration, but they showed less motivation to self-administer cocaine under a progressive-ratio schedule than control rats. When cocaine was not available in a session, control rats exhibited 'extinction burst' responding, whereas vaccinated rats did not. Moreover, when primed with cocaine, vaccinated rats did not reinstate responding, suggesting a blockade of cocaine-seeking behavior. These data strongly suggest that our dAd5GNE vector-based vaccine may be effective in treating cocaine abuse and addiction.

Induction of megakaryocytes to synthesize and store a releasable pool of human factor VIII

von Willebrand factor (VWF) is a complex plasma glycoprotein that modulates platelet adhesion at the site of a vascular injury, and it also serves as a carrier protein for factor (F)VIII. As megakaryocytes are the only hematopoietic lineage to naturally synthesize and store VWF within alpha-granules, this study was performed to determine if expression of a FVIII transgene in megakaryocytes could lead to trafficking and storage of FVIII with VWF in platelet alpha-granules. Isolex selected CD34+ cells from human G-CSF mobilized peripheral blood cells (PBC) and murine bone marrow were transduced with a retrovirus encoding the B-domain deleted form of human FVIII (BDD-FVIII). Cells were then induced with cytokines to form a population of multiple lineages including megakaryocytes. Chromogenic analysis of culture supernatant from FVIII-transduced human cells demonstrated synthesis of functional FVIII. Treatment of cells with agonists of platelet activation (ADP, epinephrine, and thrombin receptor-activating peptide) resulted in the release of VWF antigen and active FVIII into the supernatant from transduced cells. Immunofluorescence analysis of cultured human and murine megakaryocytes revealed a punctate pattern of staining for FVIII that was consistent with staining for VWF. Electron microscopy of transduced megakaryocytes using immunogold-conjugated antibodies colocalized FVIII and VWF within the alpha-granules. FVIII retained its association with VWF in human platelets isolated from the peripheral blood of NOD/SCID mice at 2-6 weeks post-transplant of transduced human PBC. These results suggest feasibility for the development of a locally inducible secretory pool of FVIII in platelets of patients with hemophilia A.

The role of the D1 domain of the von Willebrand factor propeptide in multimerization of VWF

While studying patient plasma containing an unusual pattern of von Willebrand factor (VWF) multimers, we discovered a previously unreported phenomenon: heavy predominance of dimeric VWF. Genomic analysis revealed a new congenital mutation (Tyr87Ser) that altered the final stages of VWF biosynthesis. This mutation in the propeptide (VWFpp) resulted in synthesis of dimeric VWF with an almost complete loss of N-terminal multimerization. The multimer pattern in patient plasma appears to result from separate alleles' synthesizing wild-type or mutant (dimeric) VWF, with homodimers composing the predominant protomeric species. We have expressed VWF protein containing the Tyr87Ser mutation and analyzed the intracellular processing and resulting VWF biological functions. The expressed dimeric VWF displayed a loss of several specific functions: collagen binding, factor VIII binding, and ristocetin-induced platelet binding. However, granular storage of dimeric VWF was normal, demonstrating that the lack of multimerization does not preclude granular storage. Although the tertiary structure of the VWFpp remains unknown, the mutant amino acid is located in a region that is highly conserved across several species and may play a major role in the multimerization of VWF. Our data suggest that one function of the highly cysteine-rich VWFpp is to align the adjacent subunits of VWF into the correct configuration, serving as an intramolecular chaperone. The integrity of the VWFpp is essential to maintain the proper spacing and alignment of the multiple cysteines in the VWFpp and N-terminus of the mature VWF.

The von Willebrand factor propeptide (VWFpp) traffics an unrelated protein to storage

The von Willebrand factor (VWF) propeptide (VWFpp) is critical for the targeting of VWF multimers to storage granules. VWFpp alone efficiently navigates the storage pathway in AtT-20 and endothelial cells and chaperones mature VWF multimers to storage granules when the two proteins are expressed in cis or in trans. To further define the role of VWFpp in granular sorting, we examined its ability to sort an unrelated protein, C3alpha into the regulated secretory pathway. Chimeric constructs of VWFpp and the alpha-chain of C3 were developed. The C3alpha protein expressed alone did not sort to granules in AtT-20 cells. The trans expression of C3alpha and VWFpp resulted in granular storage of VWFpp but no corresponding storage of C3alpha. When C3alpha is expressed as a single chain molecule with VWFpp that was rendered uncleavable by furin, C3alpha is re-routed to storage and is colocalized with VWFpp. The uncleavable protein was expressed in bovine aortic endothelial cells where it sorted to Weibel-Palade bodies, colocalized with bovine VWF, and was released when agonist stimulated. We now demonstrate that VWFpp re-routes a constitutively secreted protein to the regulated storage pathway. Furthermore, our studies suggest that the VWFpp storage signal is contained within amino acids 201 to 741.

Genetic induction of a releasable pool of factor VIII in human endothelial cells

Although it is known that factor VIII (FVIII) plasma levels increase rapidly in response to a number of stimuli, the biological stimuli behind this release is less clear. Previously, we showed that FVIII can traffic together with von Willebrand factor (vWF) into storage granules in a pituitary tumor cell line, AtT-20; however, AtT-20 cells could not be used to address the release or functional activity of released FVIII. To investigate the regulated secretion of stored FVIII, endothelial cells with intact agonist-stimulated release pathways were used. Human umbilical vein endothelial cells (HUVECs) were transduced with retroviral FVIII construct [hFVIII(V)] to create a FVIII/vWF storage pool. Immunofluorescent staining of transduced cells demonstrated FVIII in Weibel-Palade bodies. In contrast, the transduction of hFVIII(V) into HT-1080 and HepG2 cells displayed FVIII only in the cytoplasm. We studied the regulated release of both FVIII and vWF from endothelial cells after agonist-induced stimulation and demonstrated a parallel release of FVIII and vWF proteins. This released FVIII was functionally active. Hence, endothelial cells transduced with hFVIII(V) store FVIII together with vWF in Weibel-Palade bodies, creating a releasable storage pool of both proteins. Because FVIII secretion can be physiologically regulated by agonists in culture, this may explain the pharmacological agonist-induced release of FVIII by drugs such as desmopressin in vivo and suggests vascular endothelium as a reasonable target of gene therapy of hemophilia A.

Intracellular trafficking of factor VIII to von Willebrand factor storage granules

In plasma, von Willebrand factor (vWf) associates with Factor VIII (FVIII); however, the site at which these proteins first interact has not been defined. Administration of 1-desamino-8-D-arginine vasopressin (DDAVP) causes a rapid, concomitant elevation in plasma levels of both vWf and FVIII, suggesting the existence of a DDAVP-releasable storage pool for both proteins. To determine whether vWf and FVIII can associate intracellularly and colocalize to storage vesicles, we transfected AtT-20 cells with vWf and FVIII expression plasmids. FVIII alone was not detectable within storage granules; however, transfection of vWf cDNA into the same cell caused FVIII to alter its intracellular trafficking and to undergo granular storage, colocalizing to the vWf-containing granules. In contrast, colocalization of FVIII was not observed when these cells were transfected with plasmids encoding defective FVIII-binding vWf mutants. Transfection of bovine endothelial cells with FVIII further demonstrated vesicular storage of FVIII with vWf in Weibel-Palade bodies. Since gene therapy of hemophilia A may ultimately target endothelium or hematopoietic stem cells, the interaction between vWf and FVIII within a secretory cell is important. Thus, vWf can alter the intracellular trafficking of FVIII from a constitutive to a regulated secretory pathway, thereby producing an intracellular storage pool of both proteins.

Paris I dysfibrinogenemia: a point mutation in intron 8 results in insertion of a 15 amino acid sequence in the fibrinogen gamma-chain

Paris I dysfibrinogenemia results in the production of a fibrinogen molecule containing a functionally abnormal gamma-chain. We determined the basis of the molecular defect using polymerase chain reaction (PCR) to amplify the gamma-chain region of the Paris I subject's genomic DNA. Comparative sequence analysis of cloned PCR segments of normal and Paris I genomic DNA revealed only an A-->G point mutation occurring at nucleotide position 6588 within intron 8 of the Paris I gamma-chain gene. We examined six normal individuals and found only normal sequence in this region, indicating that this change is not likely to represent a normal polymorphism. This nucleotide change leads to a 45 bp fragment being inserted between exons 8 and 9 in the mature gamma Paris I chain mRNA, and encodes a 15 amino acid insert after gamma 350 [M-C-G-E-A-L-P-M-L-K-D-P-C-Y]. Alternative splicing of this region from intron 8 into the mature Paris I gamma-chain mRNA also results after translation into a substitution of S for G at position gamma 351. Biochemical studies of 14C-iodoacetamide incorporation into disulfide-reduced Paris I and normal fibrinogen corroborated the molecular biologic predictions that two additional cysteine residues exist within the gamma Paris I chain. We conclude that the insertion of this amino acid sequence leads to a conformationally-altered, and dysfunctional gamma-chain in Paris I fibrinogen.

Strongyloides stercoralis in chronic renal failure: safe therapy with thiabendazole

The pharmacodynamics of thiabendazole (TBZ) and its metabolite, 5OH-thiabendazole (5OH-TBZ), were studied in an anephric patient with Strongyloides stercoralis pneumonitis. No toxic manifestations were noted in the patient, and serum TBZ and 5OH-TBZ levels were comparable to those in eunephric patients. We conclude that thiabendazole, in the usual recommended dose of 25 mg/kg twice daily, given to patients with compromised renal function is reasonable and safe.

A hemolytic plaque assay for the detection of direct and indirect antibody-forming cells to keyhole limpet hemocyanin

A procedure is described for the in vitro enumeration of individual lymphoid cells producing antibody against Keyhole Limpet Hemocyanin (KLH) by a modification of the hemolytic plaque technique. Optimal conditions for the coupling of KLH to sheep erythrocytes by chromic chloride are described. Plaque-forming cells are detected in a liquid monolayer slide chamber assay system. The kinetics of the in vivo primary and secondary PFC responses of both rabbit popliteal lymph node cells and mouse spleen cells are described. Both direct (IgM) and indirect (IgG) plaque-forming cells can be enumerated. The method can also be used to detect an in vitro anamnestic response in dispersed rabbit lymph node cell suspensions. The method is simple, extremely sensitive and the results correlate with those previously obtained in which newly synthesized antibody was detected in similar systems using the coprecipitation assay.