Anticipatory banking of samples enables diagnosis of adenylosuccinase deficiency following molecular autopsy in an infant with vacuolating leukoencephalopathy.

Adenylosuccinase deficiency is a rare inborn error of metabolism. We present a newborn who died at 52 days of age with clinical features suggestive of severe epileptic encephalopathy and leukodystrophy of unknown cause. Post-mortem examination showed an unusual vacuolar appearance of the brain. A molecular autopsy performed via singleton clinical exome analysis revealed a known pathogenic and a variant of uncertain significance in ADSL that encodes adenylosuccinase. Tests on previously stored plasma samples showed elevated succinyladenosine and succinylaminoimidazole carboxamide riboside levels. Adenylosuccinase activity in stored fibroblasts was only ~5% of control confirming the diagnosis of adenylosuccinase deficiency in the child. The parents opted for a chorionic villus biopsy in a subsequent pregnancy and had a child unaffected by adenylosuccinase deficiency. This report adds vacuolating leukodystrophy as a novel feature of adenylosuccinase deficiency and shows the power of biochemical investigations directed by genomic studies to achieve accurate diagnosis. Importantly, this case demonstrates the importance of anticipatory banking of biological samples for reverse biochemical phenotyping in individuals with undiagnosed disorders who may not survive.

IL-12 and IL-4 activate a CD39-dependent intrinsic peripheral tolerance mechanism in CD8(+) T cells.

Immune responses to protein antigens involve CD4(+) and CD8(+) T cells, which follow distinct programs of differentiation. Naïve CD8 T cells rapidly develop cytotoxic T-cell (CTL) activity after T-cell receptor stimulation, and we have previously shown that this is accompanied by suppressive activity in the presence of specific cytokines, i.e. IL-12 and IL-4. Cytokine-induced CD8(+) regulatory T (Treg) cells are one of several Treg-cell phenotypes and are Foxp3(-) IL-10(+) with contact-dependent suppressive capacity. Here, we show they also express high level CD39, an ecto-nucleotidase that degrades extracellular ATP, and this contributes to their suppressive activity. CD39 expression was found to be upregulated on CD8(+) T cells during peripheral tolerance induction in vivo, accompanied by release of IL-12 and IL-10. CD39 was also upregulated during respiratory tolerance induction to inhaled allergen and on tumor-infiltrating CD8(+) T cells. Production of IL-10 and expression of CD39 by CD8(+) T cells was independently regulated, being respectively blocked by extracellular ATP and enhanced by an A2A adenosine receptor agonist. Our results suggest that any CTL can develop suppressive activity when exposed to specific cytokines in the absence of alarmins. Thus negative feedback controls CTL expansion under regulation from both nucleotide and cytokine environment within tissues.

Spectrum of mutations in a cohort of UK patients with ADA deficient SCID: Segregation of genotypes with specific ethnicities.

Severe combined immunodeficiency (SCID) arises from a number of different genetic defects, one of the most common being mutations in the gene encoding adenosine deaminase (ADA). In the UK, ADA deficient SCID compromises approximately 20% of all known cases of SCID. We carried out a retrospective analysis of the ADA gene in 46 known ADA deficient SCID patients on whom DNA had been stored. Here, we report a high frequency of two previously reported mutations and provide a link between the mutations and patient ethnicity within our patient cohort. We also report on 9 novel mutations that have been previously unreported.

Preclinical demonstration of lentiviral vector-mediated correction of immunological and metabolic abnormalities in models of adenosine deaminase deficiency.

Gene transfer into autologous hematopoietic stem cells by γ-retroviral vectors (gRV) is an effective treatment for adenosine deaminase (ADA)-deficient severe combined immunodeficiency (SCID). However, current gRV have significant potential for insertional mutagenesis as reported in clinical trials for other primary immunodeficiencies. To improve the efficacy and safety of ADA-SCID gene therapy (GT), we generated a self-inactivating lentiviral vector (LV) with a codon-optimized human cADA gene under the control of the short form elongation factor-1α promoter (LV EFS ADA). In ADA(-/-) mice, LV EFS ADA displayed high-efficiency gene transfer and sufficient ADA expression to rescue ADA(-/-) mice from their lethal phenotype with good thymic and peripheral T- and B-cell reconstitution. Human ADA-deficient CD34(+) cells transduced with 1-5 × 10(7) TU/ml had 1-3 vector copies/cell and expressed 1-2x of normal endogenous levels of ADA, as assayed in vitro and by transplantation into immune-deficient mice. Importantly, in vitro immortalization assays demonstrated that LV EFS ADA had significantly less transformation potential compared to gRV vectors, and vector integration-site analysis by nrLAM-PCR of transduced human cells grown in immune-deficient mice showed no evidence of clonal skewing. These data demonstrated that the LV EFS ADA vector can effectively transfer the human ADA cDNA and promote immune and metabolic recovery, while reducing the potential for vector-mediated insertional mutagenesis.

The effect of anterograde persufflation on energy charge and hepatocyte function in donation after cardiac death livers unsuitable for transplant.

Donation after cardiac death (DCD) livers are considered to be marginal organs for solid organ and cell transplantation. Low energy charge (EC) and low purine quantity within the liver parenchyma has been associated with poor outcome after liver transplantation. The aim of this work was to assess the effect of anterograde persufflation (A-PSF) using an electrochemical concentrator on DCD liver energy status and hepatocyte function. Organs utilized for research were DCD livers considered not suitable for transplant. Each liver was formally split, and the control non-persufflated (non-PSF) section was stored in University of Wisconsin (UW) solution at 4°C. The A-PSF liver section was immersed in UW solution on ice, and A-PSF was performed via the portal vein with 40% oxygen. Tissue samples were taken 2 hours after A-PSF from the A-PSF and control non-PSF liver sections for snap freezing. Purine analysis was performed with photodiode array detection. Hepatocytes were isolated from A-PSF and control non-PSF liver sections using a standard organs utilized for research were DCD livers considered not suitable for transplant collagenase perfusion technique. Hepatocyte function was assessed using mitochondrial dehydrogenase activity {3-[4,5-dimethylthiazol-2-y1]-2,5-diphenyl tetrazolium bromide (MTT)} and the sulforhodamine B (SRB) assay for cell attachment. In DCD livers with <30% steatosis (n = 6), A-PSF increased EC from 0.197 ± 0.025 to 0.23 ± 0.035 (P = 0.04). In DCD livers with >30% steatosis (n = 4), A-PSF had no beneficial effect. After isolation (n=4, <30% steatosis), A-PSF was found to increase MTT from 0.92 ± 0.045 to 1.19 ± 0.55 (P < 0.001) and SRB from 2.53 ± 0.12 to 3.2 ± 0.95 (P < 0.001). In conclusion, A-PSF can improve the EC and function of isolated hepatocytes from DCD livers with <30% steatosis.

Tandem mass spectrometry, but not T-cell receptor excision circle analysis, identifies newborns with late-onset adenosine deaminase deficiency.

BACKGROUND: Adenosine deaminase (ADA)-severe combined immunodeficiency (SCID) is caused by genetic variants that disrupt the function of ADA. In its early-onset form, it is rapidly fatal to infants. Delayed or late-onset ADA-SCID is characterized by insidious progressive immunodeficiency that leads to permanent organ damage or death. Quantification of T-cell receptor excision circles (TRECs) or tandem mass spectrometry (tandem-MS) analysis of dried blood spots (DBSs) collected at birth can identify newborns with early-onset ADA-SCID and are used in screening programs. However, it is not clear whether these analyses can identify newborns who will have delayed or late-onset ADA-SCID before symptoms appear. OBJECTIVE: We performed a retrospective study to evaluate whether tandem-MS and quantitative TREC analyses of DBSs could identify newborns who had delayed-onset ADA-SCID later in life. METHODS: We tested stored DBSs collected at birth from 3 patients with delayed-onset ADA-SCID using tandem-MS (PCT EP2010/070517) to evaluate levels of adenosine and 2'-deoxyadenosine and real-time PCR to quantify TREC levels. We also analyzed DBSs from 3 newborns with early-onset ADA-SCID and 2 healthy newborn carriers of ADA deficiency. RESULTS: The DBSs taken at birth from the 3 patients with delayed-onset ADA-SCID had adenosine levels of 10, 25, and 19 µmol/L (normal value, <1.5 µmol/L) and 2'-deoxyadenosine levels of 0.7, 2.7, and 2.4 µmol/L (normal value, <0.07 µmol/L); the mean levels of adenosine and 2'-deoxyadenosine were respectively 12.0- and 27.6-fold higher than normal values. DBSs taken at birth from all 3 patients with delayed-onset ADA deficiency had normal TREC levels, but TRECs were undetectable in blood samples taken from the same patients at the time of diagnosis. CONCLUSION: Tandem-MS but not TREC quantification identifies newborns with delayed- or late-onset ADA deficiency.

Kidney Failure Secondary to Hereditary Xanthinuria due to a Homozygous Deletion of the XDH Gene in the Absence of Overt Kidney Stone Disease.

Hereditary xanthinuria (HXAN) is a rare metabolic disorder that results from mutations in either the xanthine dehydrogenase (XDH) or the molybdenum cofactor sulfurase genes (MOCOS), respectively defining HXAN type I and type II. Hypouricemia, hypouricosuria, and abnormally high plasma and urine levels of xanthine, causing susceptibility to xanthine nephrolithiasis and deposition of xanthine crystals in tissues, are the metabolic hallmarks of HXAN. Several pathogenic variants in the XDH gene have so far been identified in patients with HXAN type I, but the clinical phenotype associated with the whole deletion of the human XDH gene is unknown. Herein, we report the case of a woman diagnosed with HXAN, whose molecular genetic testing revealed a homozygous microdeletion involving the XDH gene. Distinctive features of her medical history were the diagnosis of arterial hypertension and microalbuminuria at 22 years of age; a single pregnancy at the age of 25, complicated by proteinuria and transient kidney function deterioration in the third trimester; unexplained severe hypouricemia incidentally discovered during pregnancy; inability to breastfeed her newborn daughter due to primary agalactia; chronic kidney disease (CKD) stage 3 diagnosed at age 35; and progression to end-stage kidney disease over the next 12 years. Protocol noninvasive laboratory and imaging investigation was not informative as to the cause of CKD. This is the first description of the clinical phenotype associated with a natural knockout of the human XDH gene. Despite the lack of kidney histopathology data, the striking similarities with the phenotypes exhibited by comparable murine models validate the latter as useful sources of mechanistic insights for the pathogenesis of the human disease, supporting the hypothesis that the absence of xanthine dehydrogenase activity might represent a susceptibility factor for chronic tubulointerstitial nephritis, even in patients without kidney stones.

The ß-globin locus control region in combination with the EF1α short promoter allows enhanced lentiviral vector-mediated erythroid gene expression with conserved multilineage activity.

Some gene therapy strategies are compromised by the levels of gene expression required for therapeutic benefit, and also by the breadth of cell types that require correction. We designed a lentiviral vector system in which a transgene is under the transcriptional control of the short form of constitutively acting elongation factor 1α promoter (EFS) combined with essential elements of the locus control region of the ß-globin gene (ß-LCR). We show that the ß-LCR can upregulate EFS activity specifically in erythroid cells but does not alter EFS activity in myeloid or lymphoid cells. Experiments using the green fluorescent protein (GFP) reporter or the human adenosine deaminase (ADA) gene demonstrate 3-7 times upregulation in vitro but >20 times erythroid-specific upregulation in vivo, the effects of which were sustained for 1 year. The addition of the ß-LCR did not alter the mutagenic potential of the vector in in vitro mutagenesis (IM) assays although microarray analysis showed that the ß-LCR upregulates ~9% of neighboring genes. This vector design therefore combines the benefits of multilineage gene expression with high-level erythroid expression, and has considerable potential for correction of multisystem diseases including certain lysosomal storage diseases through a hematopoietic stem cell (HSC) gene therapy approach.

Treating gout - can hypouricemia produced by moderate doses of combined oral treatment give early treatment success? Preliminary observations.

Six male patients with gout were treated with combined oral medication (febuxostat, 120 mg/d, and benzbromarone, 50 or 100 mg/d), aiming at a more rapid success of uric acid lowering treatment (ULT) compared to guideline suggestions. By combined oral medication in moderate dosage, the sUA was reduced to <2 mg/dl in all cases. We conclude that, by the treatment schedule outlined, the majority of patients with gout can be cured within 1 - 2 years, with uricase treatment being necessary very rarely only.

A population study of Lesch-Nyhan disease in the UK.

AIM: The aims of this study were to identify all people with Lesch-Nyhan disease (LND) born in the UK between 1988 and 2008, and to obtain a clinical profile including age at diagnosis, genetic background, family history, neurological signs, and medications. METHOD: Potential participants were contacted through the British Paediatric Neurology Surveillance Unit. Questionnaires were sent to each child's paediatric neurologist or primary consultant. Two purine laboratories provided metabolic information. RESULTS: Twenty-three live males with LND in the 0- to 20-year age band and eight live males over the age of 20 years were identified. Thirty-one live people with LND were identified in the UK in 2008, giving a prevalence of 1 in 2 million people. Over the 20 years of study, there was a mean incidence rate of 0.18 per 100 000 live births, range 0 to 0.5. INTERPRETATION: To our knowledge, this study is the first to provide details of the prevalence and incidence of LND in the UK. The data highlight that clinical profiles, at the time of diagnosis, and management of the disease are variable. There is the need for ongoing monitoring of allopurinol dosage and metabolic screening.

Metabolite and thymocyte development defects in ADA-SCID mice receiving enzyme replacement therapy.

Deficiency of adenosine deaminase (ADA, EC3.5.4.4), a housekeeping enzyme intrinsic to the purine salvage pathway, leads to severe combined immunodeficiency (SCID) both in humans and mice. Lack of ADA results in the intracellular accumulation of toxic metabolites which have effects on T cell development and function. While untreated ADA-SCID is a fatal disorder, there are different therapeutic options available to restore ADA activity and reconstitute a functioning immune system, including enzyme replacement therapy (ERT). Administration of ERT in the form of pegylated bovine ADA (PEG-ADA) has proved a life-saving though non-curative treatment for ADA-SCID patients. However, in many patients treated with PEG-ADA, there is suboptimal immune recovery with low T and B cell numbers. Here, we show reduced thymus cellularity in ADA-SCID mice despite weekly PEG-ADA treatment. This was associated with lack of effective adenosine (Ado) detoxification in the thymus. We also show that thymocyte development in ADA-deficient thymi is arrested at the DN3-to-DN4 stage transition with thymocytes undergoing dATP-induced apoptosis rather than defective TCRß rearrangement or ß-selection. Our studies demonstrate at a detailed level that exogenous once-a-week enzyme replacement does not fully correct intra-thymic metabolic or immunological abnormalities associated with ADA deficiency.

Co-therapy with S-adenosylmethionine and nicotinamide riboside improves t-cell survival and function in Arts Syndrome (PRPS1 deficiency).

Arts syndrome or phosphoribosyl-pyrophosphate-synthetase-1 (PRPS1) deficiency is caused by loss-of-function mutations in the PRPS1 gene (Xq22.3). PRPS1 is an initial and essential step for the synthesis of the nucleotides of purines, pyrimidines, and nicotinamide. Classically, affected males present with sensorineural hearing loss, optic atrophy, muscular hypotonia, developmental impairment, and recurrent severe respiratory infections early in life. Treatment of a 3-year old boy with S-adenosylmethionine (SAM) replenished erythrocyte purine nucleotides of adenosine and guanosine, while SAM and nicotinamide riboside co-therapy further improved his clinical phenotype as well as T-cell survival and function.

Acute effect of milk on serum urate concentrations: a randomised controlled crossover trial.

OBJECTIVES: Recent observational studies have highlighted the beneficial role of dairy ingestion in gout prevention. The aims of this study were to determine the acute effects of milk ingestion on serum urate concentrations and examine the mechanisms of these effects. METHODS: This was a short-term randomised controlled crossover trial of milk in 16 healthy male volunteers. The following products were tested (each 80 g protein): soy control, early season skim milk, late season skim milk (containing high concentrations of orotic acid, a naturally occurring uricosuric agent) and ultrafiltrated MPC 85 skim milk. Each participant received a single dose of each product in random order. Serum and urine were obtained immediately before and then hourly over a 3 h period after ingestion of each study product. RESULTS: Ingestion of the soy control led to an increase in serum urate concentrations by approximately 10%. In contrast, ingestion of all milks led to a decrease in serum urate concentrations by approximately 10% (p<0.0001). All products (including soy) rapidly increased the fractional excretion of uric acid (FEUA). Late season milk led to a greater increase in FEUA than MPC 85 (p=0.02) and early season milk (p=0.052). There were no differences over time in serum oxypurines or purine-containing nucleosides. However, all products increased the fractional excretion of xanthine. CONCLUSIONS: Intact milk has an acute urate-lowering effect. These data provide further rationale for long-term intervention studies to determine whether such dietary interventions have an adjunctive role in the management of individuals with hyperuricaemia and gout.

Analysis of the HPRT1 gene in 35 Italian Lesch-Nyhan families: 45 patients and 77 potential female carriers.

BACKGROUND: Lesch-Nyhan (LND) disease is an inborn error of purine metabolism which results from deficiency of the activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT). In the classical form of the disease the activity of the enzyme is completely deficient and the patient has cognitive impairment, spasticity, dystonia and self-injurious behaviour, as well as elevated concentrations of uric acid in blood and urine that leads to consequences such as nephropathy, urinary tract calculi and tophaceous gout. There are disease variants without self-injurious behaviour. In these cases neurological manifestations may vary widely. The HPRT1 gene is located on the X chromosome in position Xq26-27.2, and mutations have been found in quite a large number of patients. OBJECTIVE: Documenting our experience with the diagnosis of LND in 45 Italian patients from 35 nonrelated families and 77 females at risk of being carriers of the condition. DESIGN: Internal review. SETTING: An institute devoted to the investigation and care of patients with rare diseases. RESULTS: In 94% of the LND families gDNA sequencing of the patients was informative while in 6% a cDNA study was required. For the carrier females gDNA sequencing was informative in 71% of the families, 23% required qPCR studies and 6% required segregation studies combined with enzymatic activity testing. Classical cDNA studies proved to be unreliable in carrier females as there is a significant risk of failure to detect the mutated allele. Four novel HPRT1 mutations were found: c.145C>T (p.Leu49Phe), c.112C>T (p.Pro38Ser), c.89_96dup8 (p.Glu33Argfs) and c.506dupC (p.Arg170Thrfs). CONCLUSION: In the diagnosis of LND it is very important to consider all the possible alterations of the HPRT1 gene when searching for mutations especially if no affected male is available. Biochemical assessment of the enzymatic activity of HPRT in an affected male is the ideal starting point for molecular analysis of the gene.

Refractory gout - does it exist?

Refractory gout (RG) has been increasingly recognized to be a major problem in clinical care. Patients diagnosed with RG have been assumed to be non-adherent, or under-dosed, to the greater part. In a minority, pathophysiological mechanisms have been discussed. During the last two decades, however, none of the studies differentiated non-adherence from impaired response to drug treatment. A definition of adherence has been proposed in the case of allopurinol treatment (oxipurinol in serum, >20 µmol/l), which would seem to confirm a dose of about 50 mg/d being taken by the patients. Guidelines for treating gout published by national or international rheumatology societies do provide very little, if any, information on how to evaluate patients with RG. Coinciding with the development of the xanthine oxidase inhibitor, febuxostat, a moderate increase in the number of publications on RG was observed, with a sharp rise following after its approval for clinical use. It was demonstrated recently that intensive training and supervision of patients with gout resulted in very low numbers of patients not reaching treatment targets. It should be remembered that allopurinol, is an ideal instrument for differentiating non-adherence from true impaired response. We conclude that, apart from very rare patients, needing confirmation of such a diagnosis by metabolic ward studies, RG does not exist, and with close to hundred percent, treatment failure is due to patient and physician behavior.

Quantification of Plasma and Urine Thymidine and 2'-Deoxyuridine by LC-MS/MS for the Pharmacodynamic Evaluation of Erythrocyte Encapsulated Thymidine Phosphorylase in Patients with Mitochondrial Neurogastrointestinal Encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare disorder caused by mutations in TYMP, leading to a deficiency in thymidine phosphorylase and a subsequent systemic accumulation of thymidine and 2'-deoxyuridine. Erythrocyte-encapsulated thymidine phosphorylase (EE-TP) is under clinical development as an enzyme replacement therapy for MNGIE. Bioanalytical methods were developed according to regulatory guidelines for the quantification of thymidine and 2'-deoxyuridine in plasma and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for supporting the pharmacodynamic evaluation of EE-TP. Samples were deproteinized with 5% perchloric acid (v/v) and the supernatants analyzed using a Hypercarb column (30 × 2.1 mm, 3 µm), with mobile phases of 0.1% formic acid in methanol and 0.1% formic acid in deionized water. Detection was conducted using an ion-spray interface running in positive mode. Isotopically labelled thymidine and 2'-deoxyuridine were used as internal standards. Calibration curves for both metabolites showed linearity (r > 0.99) in the concentration ranges of 10-10,000 ng/mL for plasma, and 1-50 µg/mL for urine, with method analytical performances within the acceptable criteria for quality control samples. The plasma method was successfully applied to the diagnosis of two patients with MNGIE and the quantification of plasma metabolites in three patients treated with EE-TP.