Lentiviral Gene Therapy for Mucopolysaccharidosis II with Tagged Iduronate 2-Sulfatase Prevents Life-Threatening Pathology in Peripheral Tissues But Fails to Correct Cartilage

Deficiency of iduronate 2-sulfatase (IDS) causes Mucopolysaccharidosis type II (MPS II), a lysosomal storage disorder characterized by systemic accumulation of glycosaminoglycans (GAGs), leading to a devastating cognitive decline and life-threatening respiratory and cardiac complications. We previously found that hematopoietic stem and progenitor cell-mediated lentiviral gene therapy (HSPC-LVGT) employing tagged IDS with insulin-like growth factor 2 (IGF2) or ApoE2, but not receptor-associated protein minimal peptide (RAP12x2), efficiently prevented brain pathology in a murine model of MPS II. In this study, we report on the effects of HSPC-LVGT on peripheral pathology and we analyzed IDS biodistribution. We found that HSPC-LVGT with all vectors completely corrected GAG accumulation and lysosomal pathology in liver, spleen, kidney, tracheal mucosa, and heart valves. Full correction of tunica media of the great heart vessels was achieved only with IDS.IGF2co gene therapy, while the other vectors provided near complete (IDS.ApoE2co) or no (IDSco and IDS.RAP12x2co) correction. In contrast, tracheal, epiphyseal, and articular cartilage remained largely uncorrected by all vectors tested. These efficacies were closely matched by IDS protein levels following HSPC-LVGT. Our results demonstrate the capability of HSPC-LVGT to correct pathology in tissues of high clinical relevance, including those of the heart and respiratory system, while challenges remain for the correction of cartilage pathology.

Disturbances in mitochondrial bioenergetics and control quality and unbalanced redox homeostasis in the liver of a mouse model of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is a lysosomal storage disease caused by mutations in the gene encoding the enzyme iduronate 2-sulfatase (IDS) and biochemically characterized by the accumulation of glycosaminoglycans (GAGs) in different tissues. It is a multisystemic disorder that presents liver abnormalities, the pathophysiology of which is not yet established. In the present study, we evaluated bioenergetics, redox homeostasis, and mitochondrial dynamics in the liver of 6-month-old MPS II mice (IDS-). Our findings show a decrease in the activity of α-ketoglutarate dehydrogenase and an increase in the activities of succinate dehydrogenase and malate dehydrogenase. The activity of mitochondrial complex I was also increased whereas the other complex activities were not affected. In contrast, mitochondrial respiration, membrane potential, ATP production, and calcium retention capacity were not altered. Furthermore, malondialdehyde levels and 2',7'-dichlorofluorescein oxidation were increased in the liver of MPS II mice, indicating lipid peroxidation and increased ROS levels, respectively. Sulfhydryl and reduced glutathione levels, as well as glutathione S-transferase, glutathione peroxidase (GPx), superoxide dismutase, and catalase activities were also increased. Finally, the levels of proteins involved in mitochondrial mass and dynamics were decreased in knockout mice liver. Taken together, these data suggest that alterations in energy metabolism, redox homeostasis, and mitochondrial dynamics can be involved in the pathophysiology of liver abnormalities observed in MPS II.

Analysis of caregiver perspectives on patients with mucopolysaccharidosis II treated with pabinafusp alfa: results of qualitative interviews in Japan

BACKGROUND

Mucopolysaccharidosis type II (MPS II), or Hunter syndrome, is a rare X-linked metabolic disorder predominantly affecting males. Pabinafusp alfa, an iduronate-2-sulfatase enzyme designed to cross the blood-brain barrier, was approved in Japan in 2021 as the first enzyme replacement therapy targeting both the neuropathic and somatic signs and symptoms of MPS II. This study reports caregivers' experiences of MPS II patients receiving pabinafusp alfa through qualitative interviews.

METHODS

Semi-structured, qualitative interviews were conducted with caregivers at seven clinical sites in Japan using a semi-structured moderation guide (Voice of the Caregiver guide). Thematic analysis was applied to the interview transcripts to identify symptoms and health-related quality of life impacts at baseline, changes during treatment, and overall treatment experience.

RESULTS

Seven caregivers from 16 trial sites participated, representing seven children aged 8-18 years who had received pabinafusp alfa for 3.3-3.5 years at the time of the interviews. Data suggest a general trend toward improvement in multiple aspects, although not all caregivers observed discernible changes. Reported cognitive improvements included language skills, concentration, self-control, eye contact, mental clarity, concept understanding, following instructions, and expressing personal needs. Further changes were reported that included musculoskeletal improvements and such somatic changes as motor function, mobility, organ involvement, joint mobility, sleep patterns, and fatigue. Four caregivers reported improvements in family quality of life, five expressed treatment satisfaction, and all seven indicated a strong willingness to continue treatment of their children with pabinafusp alfa.

CONCLUSION

Caregivers' perspectives in this study demonstrate treatment satisfaction and improvement in various aspects of quality of life following therapy with pabinafusp alfa. These findings enhance understanding of pabinafusp alfa's potential benefits in treating MPS II and contribute to defining MPS II-specific outcome measures for future clinical trials.

Clinical characteristics and somatic burden of patients with mucopolysaccharidosis II with or without neurological involvement: An analysis from the Hunter Outcome Survey

Approximately two-thirds of patients with mucopolysaccharidosis II (MPS II; Hunter syndrome) have neuronopathic disease, with central nervous system involvement; one-third have non-neuronopathic disease. This analysis of data from the Hunter Outcome Survey (HOS) compared the clinical manifestations and surgical and nonsurgical procedure history in patients with neuronopathic or non-neuronopathic MPS II. Prospective patients were identified in July 2018 in HOS for inclusion in this analysis as those with stable cognitive impairment status as assessed at 10 years of age and at a minimum of one follow-up visit at 11 to <20 years of age. Patients were stratified according to cognitive impairment status at 10 years into neuronopathic and non-neuronopathic groups, and clinical manifestations and surgical and nonsurgical procedure history were compared between the two groups. In total, 193 patients had cognitive impairment status assessments available (at 10 years and 11 to <20 years of age), 151 of whom had stable cognitive impairment status and were included; 100/151 (66.2%) were in the neuronopathic group and 51/151 (33.8%) in the non-neuronopathic group. The proportion of patients demonstrating manifestations by system organ class and the number of surgical and nonsurgical procedures per patient were broadly comparable in the neuronopathic and non-neuronopathic groups both before and after patients' 10th birthdays. The most common manifestations before patients' 10th birthdays, including facial features, joint stiffness and limited function, and hepatomegaly were reported in >80% of patients in both groups. For the neuronopathic and non-neuronopathic groups, the median [10th percentile, 90th percentile] number of different types of surgical and nonsurgical procedures per patient (3 [1, 6] and 3 [1, 7], respectively) and of all procedures per patient (4 [1, 10] and 5 [2, 11], respectively) before patients' 10th birthdays were similar, although the type of procedure may have differed. Thus, in the first two decades of life, patients with non-neuronopathic disease were found to have similar somatic manifestations to those of the neuronopathic group and undergo procedures for complications as often as those with neuronopathic disease.

Frequency of iduronate-2-sulfatase gene variants detected in newborn screening for mucopolysaccharidosis type II in Japan

Mucopolysaccharidosis II (MPS II) is an X-linked, recessive, inborn metabolic disorder caused by defects in iduronate-2-sulfatase (IDS). The age at onset, disease severity, and rate of progression vary significantly among patients. This disease is classified into severe or mild forms depending on neurological symptom involvement. The severe form is associated with progressive cognitive decline while the mild form is predominantly associated with somatic features. Newborn screening (NBS) for MPS II has been performed since December 2016, mainly in Kyushu, Japan, where 197,700 newborns were screened using a fluorescence enzyme activity assay of dried blood spots. We diagnosed one newborn with MPS II with lower IDS activity, elevated urinary glycosaminoglycans, and a novel variant of the IDS gene. In the future, NBS for MPS II is expected to be performed in many regions of Japan and will contribute to the detection of more patients with MPS II, which is crucial to the early treatment of the disorder.

Characterization of heart disease in mucopolysaccharidosis type II mice

Mucopolysaccharidosis type II (MPSII) is a progressive lysosomal storage disease caused by mutations in the IDS gene, that leads to iduronate 2-sulfatase (IDS) enzyme deficiency. The enzyme catalyzes the first step of degradation of two glycosaminoglycans (GAGs), heparan sulfate (HS) and dermatan sulfate (DS). The consequences of MPSII are progressively harmful and can lead to death by cardiac failure. The aim of this study was to characterize the cardiovascular disease in MPSII mice. Thus, we evaluated the cardiovascular function of MPSII male mice at 6, 8, and 10 months of age, through functional, histological, and biochemical analyzes. Echocardiographic analyses showed a progressive loss in cardiac function, observed through parameters such as reduction in ejection fraction (46% in control versus 28% in MPS II at 10 months, P < .01) and fractional area change (31% versus 23%, P < .05). Similar results were found in parameters of vascular competence, obtained by echo Doppler. Both aortic dilatation and an increase in pulmonary resistance were observed at all time points in MPSII mice. The histological analyses showed an increase in the thickness of the heart valves (2-fold thicker than control values at 10 months). Biochemical analyzes confirmed GAG storage in these tissues, with a massive elevation of DS in the myocardium. Furthermore, an important increase in the activity of proteases such as cathepsin S and B (up to 5-fold control values) was found and could be related to the progressive loss of cardiac function observed in MPSII mice. In this work, we demonstrated that loss of cardiac function in MPSII mice started at 6 months of age, although its global cardiac capacity was still preserved at this time. Disease progressed at later time points leading to heart failure. The MPSII mice at later times reproduce many of the cardiovascular events found in patients with Hunter's disease.

Newborn screening for mucopolysaccharidosis type II: Lessons learned

We describe our experience with population-based newborn screening for mucopolysaccharidosis type II (MPS II) in 586,323 infants by measurement of iduronate-2-sulfatase activity in dried blood spots between December 12, 2017 and April 30, 2022. A total of 76 infants were referred for diagnostic testing, 0.01% of the screened population. Of these, eight cases of MPS II were diagnosed for an incidence of 1 in 73,290. At least four of the eight cases detected had an attenuated phenotype. In addition, cascade testing revealed a diagnosis in four extended family members. Fifty-three cases of pseudodeficiency were also identified, for an incidence of 1 in 11,062. Our data suggest that MPS II may be more common than previously recognized with a higher prevalence of attenuated cases.

Alterations of Plasmatic Biomarkers of Neurodegeneration in Mucopolysaccharidosis Type II Patients Under Enzyme Replacement Therapy

Mucopolysaccharidosis type II (MPS II) is a disorder caused by a deficient activity of iduronate-2-sulfatase, a lysosomal enzyme responsible for degrading glycosaminoglycans (GAGs). The abnormal storage of GAGs within lysosomes disrupts cellular homeostasis and leads to a severe symptomatology. Patients present neuropsychiatric impairment characterized by mental retardation and impaired cognition. The aim of this study was to quantify four neurodegeneration biomarkers in plasma: brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF-AA), neural cell adhesion molecule (NCAM) and cathepsin-D, as well as to identify possible correlations with urinary GAGs in seven patients undergoing treatment with ERT (Elaprase® 0.5 mg/kg of body weight). Patients with both severe and attenuated forms of MPS II showed signs of neurodegeneration in neuroimaging exams. Patients have a decrease in BDNF and PDGF-AA concentrations, and an increase in NCAM level compared to controls. No alterations in cathepsin-D concentration were seen. GAGs levels were higher in patients than in controls, but no significant correlations between GAGs and biomarkers were observed. These results evidence that patients have neurodegeneration and that monitoring these biomarkers might be useful for assessing this process. To this date, this is the first work to analyze these plasmatic markers of neurodegeneration in patients.

Generation and characterization of an immunodeficient mouse model of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (Hunter syndrome, MPS II) is an inherited X-linked recessive disease caused by deficiency of iduronate-2-sulfatase (IDS), resulting in the accumulation of the glycosaminoglycans (GAG) heparan and dermatan sulfates. Mouse models of MPS II have been used in several reports to study disease pathology and to conduct preclinical studies for current and next generation therapies. Here, we report the generation and characterization of an immunodeficient mouse model of MPS II, where CRISPR/Cas9 was employed to knock out a portion of the murine IDS gene on the NOD/SCID/Il2rγ (NSG) immunodeficient background. IDS-/- NSG mice lacked detectable IDS activity in plasma and all analyzed tissues and exhibited elevated levels of GAGs in those same tissues and in the urine. Histopathology revealed vacuolized cells in both the periphery and CNS of NSG-MPS II mice. This model recapitulates skeletal disease manifestations, such as increased zygomatic arch diameter and decreased femur length. Neurocognitive deficits in spatial memory and learning were also observed in the NSG-MPS II model. We anticipate that this new immunodeficient model will be appropriate for preclinical studies involving xenotransplantation of human cell products intended for the treatment of MPS II.

Evidence and recommendation for mucopolysaccharidosis type II newborn screening in the United States

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is an X-linked condition caused by pathogenic variants in the iduronate-2-sulfatase gene. The resulting reduced activity of the enzyme iduronate-2-sulfatase leads to accumulation of glycosaminoglycans that can progressively affect multiple organ systems and impair neurologic development. In 2006, the US Food and Drug Administration approved idursulfase for intravenous enzyme replacement therapy for MPS II. After the data suggesting that early treatment is beneficial became available, 2 states, Illinois and Missouri, implemented MPS II newborn screening. Following a recommendation of the Advisory Committee on Heritable Disorders in Newborns and Children in February 2022, in August 2022, the US Secretary of Health and Human Services added MPS II to the Recommended Uniform Screening Panel, a list of conditions recommended for newborn screening. MPS II was added to the Recommended Uniform Screening Panel after a systematic evidence review reported the accuracy of screening, the benefit of presymptomatic treatment compared with usual case detection, and the feasibility of implementing MPS II newborn screening. This manuscript summarizes the findings of the evidence review that informed the Advisory Committee's decision.

Evaluation of oxidative stress and mitochondrial function in a type II mucopolysaccharidosis cellular model: in vitro effects of genistein and coenzyme Q10

Mucopolysaccharidosis type II (MPS II or Hunter Syndrome) is a lysosomal disease caused by deficient degradation of glycosaminoglycans (GAGs) heparan sulfate and dermatan sulfate due to the deficiency of the enzyme iduronate-2-sulfatase. The main treatment for MPS II is the administration of the recombinant form of the enzyme, in a process known as enzyme replacement therapy (ERT). Oxidative damage can contribute to the pathophysiology of MPS II and treatment with ERT can reduce the effects of oxidative stress. For a better understanding of pathophysiology of MPS II, we evaluated biomarkers of mitochondrial dysfunction, DNA (Deoxyribonucleic acid) damage, antioxidant defenses, reactive species production and lysosomal size in IDS-deficient HEK 293 cells and investigate the in vitro effect of genistein and coenzyme Q10 (CoQ) on these biomarkers. An increase in the production of reactive species was demonstrated, as well as an increase in the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). Also, an increase in lysosomal volume and oxidative damage to DNA were verified. There was no evidence of a change in mitochondrial function in this cell model. In the HEK 293 (human embryonic kidney 293) knockout (KO) HP10 cell model we found that genistein at concentrations of 25 and 50 μm decreased in vitro the production of reactive species and the activity of the SOD enzyme, showing an antioxidant protective effect. Still, in these cells we verified that the coenzyme Q10 in the concentrations of 5 and 10 μm decreased in vitro the activity of the SOD enzyme and in the concentration of 10 μm decreased in vitro the DNA damage, also demonstrating antioxidant protection. In conclusion, MPS II knockout cells demonstrated oxidative stress and DNA damage and genistein, as well as coenzyme Q10, have been shown to have an important protective effect in vitro against these oxidative damages.

Non-invasive intravenous administration of AAV9 transducing iduronate sulfatase leads to global metabolic correction and prevention of neurologic deficits in a mouse model of Hunter syndrome

Hunter syndrome is a rare x-linked recessive genetic disorder that affects lysosomal metabolism due to deficiency of iduronate-2-sulfatase (IDS), with subsequent accumulation of glycosaminoglycans heparan and dermatan sulfates (GAG). Enzyme replacement therapy is the only FDA-approved remedy and is an expensive life-time treatment that alleviates some symptoms of the disease without neurocognitive benefit. We previously reported successful treatment in a mouse model of mucopolysaccharidosis type II (MPS II) using adeno-associated viral vector serotype 9 encoding human IDS (AAV9.hIDS) via intracerebroventricular injection. As a less invasive and more straightforward procedure, here we report intravenously administered AAV9.hIDS in a mouse model of MPS II. In animals administered 1.5 × 10¹² vg of AAV9.hIDS at 2 months of age, we observed supraphysiological levels of IDS enzyme activity in the circulation (up to 9100-fold higher than wild-type), in the tested peripheral organs (up to 560-fold higher than wild-type), but only 4% to 50% of wild type levels in the CNS. GAG levels were normalized on both sides of the blood-brain-barrier (BBB) in most of tissues tested. Despite low levels of the IDS observed in the CNS, this treatment prevented neurocognitive decline as shown by testing in the Barnes maze and by fear conditioning. This study demonstrates that a single dose of IV-administered AAV9.hIDS may be an effective and non-invasive procedure to treat MPS II that benefits both sides of the BBB, with implications for potential use of IV-administered AAV9 for other neuronopathic lysosomal diseases.

Glycosaminoglycan signatures in body fluids of mucopolysaccharidosis type II mouse model under long-term enzyme replacement therapy

Abstract

Mucopolysaccharidosis type II (MPS II) is a neurometabolic disorder, due to the deficit of the lysosomal hydrolase iduronate 2-sulfatase (IDS). This leads to a severe clinical condition caused by a multi-organ accumulation of the glycosaminoglycans (GAGs/GAG) heparan- and dermatan-sulfate, whose elevated levels can be detected in body fluids. Since 2006, enzyme replacement therapy (ERT) has been clinically applied, showing efficacy in some peripheral districts. In addition to clinical monitoring, GAG dosage has been commonly used to evaluate ERT efficacy. However, a strict long-term monitoring of GAG content and composition in body fluids has been rarely performed. Here, we report the characterization of plasma and urine GAGs in Ids knock-out (Ids-ko) compared to wild-type (WT) mice, and their changes along a 24-week follow-up, with and without ERT. The concentration of heparan-sulfate (HS), chondroitin-sulfate (CS), and dermatan-sulfate (DS), and of the non-sulfated hyaluronic acid (HA), together with their differentially sulfated species, was quantified by capillary electrophoresis with laser-induced fluorescence. In untreated Ids-ko mice, HS and CS + DS were noticeably increased at all time points, while during ERT follow-up, a substantial decrease was evidenced for HS and, to a minor extent, for CS + DS. Moreover, several structural parameters were altered in untreated ko mice and reduced after ERT, however without reaching physiological values. Among these, disaccharide B and HS 2s disaccharide showed to be the most interesting candidates as biomarkers for MPS II. GAG chemical signature here defined provides potential biomarkers useful for an early diagnosis of MPS II, a more accurate follow-up of ERT, and efficacy evaluations of newly proposed therapies.

Key messages

Plasmatic and urinary GAGs are useful markers for MPS II early diagnosis and prognosis.

CE-LIF allows GAG structural analysis and the quantification of 17 different disaccharides.

Most GAG species increase and many structural features are altered in MPS II mouse model.

GAG alterations tend to restore to wild-type levels following ERT administration.

CS+DS/HS ratio, % 2,4dis CS+DS, and % HS 2s are potential markers for MPS II pathology and ERT efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-022-02221-3.

iPS-derived neural stem cells for disease modeling and evaluation of therapeutics for mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a rare, lysosomal disorder caused by mutations in a gene encoding iduronate-2-sulfatase (IDS). IDS deficiency results in an accumulation of glycosaminoglycans (GAGs) and secondary accumulations of other lipids in lysosomes. Symptoms of MPS II include a variety of soft and hard tissue problems, developmental delay, and deterioration of multiple organs. Enzyme replacement therapy is an approved treatment for MPS II, but fails to improve neuronal symptoms. Cell-based neuronal models of MPS II disease are needed for compound screening and drug development for the treatment of the neuronal symptoms in MPS II. In this study, three induced pluripotent stem cell (iPSC) lines were generated from three MPS II patient-derived dermal fibroblast cell lines that were differentiated into neural stem cells and neurons. The disease phenotypes were measured using immunofluorescence staining and Nile red dye staining. In addition, the therapeutic effects of recombinant human IDS enzyme, delta-tocopherol (DT), and hydroxypropyl-beta-cyclodextrin (HPBCD) were determined in the MPS II disease cells. Finally, the neural stem cells from two of the MPS II iPSC lines exhibited typical disease features including a deficiency of IDS activity, abnormal glycosaminoglycan storage, and secondary lipid accumulation. Enzyme replacement therapy partially rescued the disease phenotypes in these cells. DT showed a significant effect in reducing the secondary accumulation of lipids in the MPS II neural stem cells. In contrast, HPBCD displayed limited or no effect in these cells. Our data indicate that these MPS II cells can be used as a cell-based disease model to study disease pathogenesis, evaluate drug efficacy, and screen compounds for drug development.

Identification and structure characterization of novel IDS variants causing mucopolysaccharidosis type II: A retrospective analysis of 30 Chinese children

BACKGROUND

Mucopolysaccharidosis type II (MPS II) or Hunter syndrome is a rare X-linked recessive genetic disease resulting from deficient activity of the iduronate-2-sulfatase(IDS) enzyme and the accumulation of glycosaminoglycans in almost all cells, tissues and organs, which makes viscera function impaired.This study retrospectively analyzed the clinical characteristics, leukocyte IDS activity and mutations in the IDS gene of 30 Chinese children with MPS II.

METHODS

Whole-exome sequencing (WES) was performed on samples of the 30 patients.

RESULTS

A total of 25 mutations were identified in the IDS genes including 16 previously reported and 9 novel mutations (6 frameshift: c.815-818dupAACG, c.1453dupA, c.1270-1271delGT, c.1484-1485insTA, c.854delA, c.12_13delCC;3missense: c.325 T > G, c.140 T > C, c.248 T > G).The computer simulations of the protein structure analysis of the novel missense mutations showed these amino acid replacements (W109G tryptophan replaced by the glycine, L47P leucine replaced by the proline, V83G valine replaced by glycine) near the active site of IDS protein sulfatase domain and would cause a severe impairment of protein structure and function.

CONCLUSIONS

Our study expands the spectrum of MPS II genotype, provides new insights into the molecular mechanisms of MPS II, and contributes to future studies of genotype-phenotypic associations to estimate prognosis and develop new treatment regimens.

A review of the clinical outcomes in idursulfase-treated and untreated Filipino patients with mucopolysaccharidosis type II: data from the local lysosomal storage disease registry

BACKGROUND

Mucopolysaccharidosis type II (MPS II; Hunter syndrome) is an X-linked multisystem disorder characterized by glycosaminoglycan (GAG) accumulation, caused by a deficiency of iduronate-2-sulfatase (I2S). Enzyme replacement therapy (ERT) with recombinant idursulfase (IDS), the standard of care, was started in the Philippines in 2017. This study reviewed the clinical outcomes in idursulfase-treated and untreated Filipino MPS II patients who were included in the local Lysosomal Storage Disease (LSD) registry of the Institute of Human Genetics-National Institutes of Health (IHG-NIH) from January 1999 to December 2019.

METHODS

A retrospective audit of records of MPS II patients listed in the registry was done. Qualified patients were divided into two cohorts: idursulfase-treated group (patients on enzyme replacement therapy, ERT, for ≥ 6 months) and untreated group. Baseline characteristics, including demographic data, biochemical results, neurocognitive classification, respiratory involvement, mortality, and adverse events, were recorded. Height, weight, cardiac pathology, liver and spleen sizes, six-minute walking test (6MWT), joint mobility, were determined at baseline and at year 1 and 2 of follow up.

RESULTS

Forty male patients were included in this review, with only 8 receiving ERT since 2017. The mean age at diagnosis was 6.99 years (SD 4.15; 0.75-20) and mean age at start of ERT was 14.03 years (SD 7.1; 4-21.5), more delayed than previous reports. Eighty percent have early progressive phenotype which was higher than reported average. The early growth pattern differed in our Filipino cohort, but was followed by the expected slowed growth in later years. Improvements in the following endpoints were observed in the treated cohort: height and weight, cardiac disease, liver and spleen sizes, and joint mobility. There were also positive effects on respiratory involvement and mortality rate. Adverse events were consistent with previous reports.

CONCLUSIONS

ERT is generally well tolerated and effective in reducing GAG storage and improving clinical endpoints among our Filipino MPS II patients. In untreated patients, typical disease progression was observed.

Therapy-type related long-term outcomes in mucopolysaccaridosis type II (Hunter syndrome) - Case series

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare, X-linked recessive multisystem lysosomal storage disease due to iduronate-2-sulfatase enzyme deficiency. We presented three unrelated Slovenian patients with the severe form of MPS II that received three different management approaches: natural course of the disease without received specific treatment, enzyme replacement therapy (ERT), and hematopoietic stem cell transplantation (HSCT). The decision on the management depended on disease severity, degree of cognitive impairment, and parent's informed decision. The current benefits of MPS II treatments are limited. The lifelong costly intravenous ERT brings significant benefits but the patients with severe phenotypes and neurological involvement progress to cognitive decline and disability regardless of ERT, as demonstrated in published reviews and our case series. The patient after HSCT was the only one of the three cases reported to show a slowly progressing cognitive development. The type of information from the case series is insufficient for generalized conclusions, but with advanced myeloablative conditioning, HSCT may be a preferred treatment option in early diagnosed MPS II patients with the severe form of the disease and low disease burden at the time of presentation.

Nonclinical safety evaluation of pabinafusp alfa, an anti-human transferrin receptor antibody and iduronate-2-sulfatase fusion protein, for the treatment of neuronopathic mucopolysaccharidosis type II

Pabinafusp alfa is a fusion protein comprising a humanized anti-human transferrin receptor (TfR) antibody and human iduronate-2-sulfatase. It was developed as a novel modality to target central nervous system-related symptoms observed in patients with mucopolysaccharidosis type II (MPS II, also known as Hunter syndrome). As the fusion protein contains an entire IgG1 molecule that binds TfR, there may be specific safety concerns, such as unexpected cellular toxicity due to its effector functions or its ability to inhibit iron metabolism, in addition to general safety concerns. Here, we present the comprehensive results of a nonclinical safety assessment of pabinafusp alfa. Pabinafusp alfa did not exhibit effector functions, as assessed by antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity studies in TfR-expressing hematopoietic cells. Repeat-dose toxicity studies in cynomolgus monkeys showed that pabinafusp alfa did not induce any significant toxicological changes at doses up to 30 mg/kg/week upon intravenous administration for up to 26 weeks. Interaction of transferrin with TfR was not inhibited by pabinafusp alfa, suggesting that the effect of pabinafusp alfa on the physiological iron transport system is minimal, which was confirmed by toxicity studies in cynomolgus monkeys. These findings suggest that pabinafusp alfa is expected to be safe for long-term use in individuals with MPS II.

A cDNA analysis disclosed the discordance of genotype-phenotype correlation in a patient with attenuated MPS II and a 76-base deletion in the gene for iduronate-2-sulfatase

We previously showed that the genotype-phenotype correlation in MPS II is well-conserved in Japan (Kosuga et al., 2016). Almost all of our patients with attenuated MPS II have missense variants, which is expected to result in residual activity of iduronate-2-sulfatase. In contrast, our patients with severe MPS II have so-called null-type disease-associated variants, such as nonsense variants, frame-shifts, gene insertions, gene deletions and rearrangement with pseudogene (IDS2), none of which are expected to result in residual activity. However, we recently encountered a patient with attenuated MPS II who had a presumable null-type disease-associated variant and 76-base deletion located in exon 1 that extended into intron 1. To investigate this discordance, we extracted RNA from the leukocytes of the patient and performed reverse transcription polymerase chain reaction. One of the bands of the cDNA analysis was found to include a nucleotide sequence whose transcript was expected to generate an almost full-length IDS mature peptide lacking only part of its signal peptide as well as only one amino acid at the end of the N-terminus. This suggests that an alternative splicing donor site is generated in exon 1 upstream of the deleted region. Based on these observations, we concluded that the phenotype-genotype discordance in this patient with MPS II was due to the decreased amount of IDS protein induced by the low level of the alternatively spliced mRNA, lacking part of the region coding for the signal peptide but including the region coding almost the full mature IDS protein. The first 25 amino acids at the N-terminus of IDS protein are a signal peptide. The alternative splice transcript has only 13 (1 M-13 L) of those 25 amino acids; 14G-25G are missing, suggesting that the exclusively hydrophobic 1 M-13 L of the signal peptide of IDS might have a crucial role in the signal peptide.

Evidence for inflammasome activation in the brain of mucopolysaccharidosis type II mice

Hunter syndrome or mucopolysaccharidosis type II (MPS II) is an X-linked recessive disease caused by the deficiency of iduronate 2-sulfatase (IDS), leading to storage of undegraded heparan and dermatan sulfate. Patients with the severe form present neurological abnormalities, but the mechanisms of such alterations are unknown. Here, we hypothesized that the undegraded substances found in this disease could be recognized as damage-associated molecular patterns (DAMPS), leading to activation of the inflammasome. Brains from 2 and 5 months normal and MPS II mice were studied. We observed an increase in cathepsin B activity in the brain tissue and leakage of this enzyme from the lysosome to the cytoplasm in a MPS II neuronal cell line, which is a known activator of the inflammasome. Furthermore, Caspase-1 activity and IL-1-beta levels were elevated at 5 months, confirming that this pathway is indeed altered. Our results suggest that undegraded GAG activate the inflammasome pathway in MPS II and future studies could focus on blocking such pathway to better understand the role of this process to the pathogenesis of MPS II.

Natural history of cognitive development in neuronopathic mucopolysaccharidosis type II (Hunter syndrome): Contribution of genotype to cognitive developmental course

The natural history of cognitive growth in the neuronopathic form of Mucopolysaccharidosis type II (MPS II) is not well defined especially their patterns of development and decline. The ability to predict the developmental course of the neurologically impaired patient is necessary to assess treatment outcomes aimed at the brain. Thirteen intravenous enzyme replacement therapy-treated Japanese patients with neuronopathic MPSII who had mutation analysis were followed on one standard measure of cognitive development over time. Six children in Group MS had missense mutations and 7 children in Group NT had null type mutations such as deletions, recombination with the pseudogene, and nonsense mutations. The patients as a whole demonstrated cognitive growth until about 36-42 months of age, followed by a plateau in development. The mean age equivalent score at age 3 was similar to that at age 6. While the decline was slow for the entire group, the patients in Group NT showed a more rapid decline than those in Group MS. Two patients with deletions showed decline to a very low level by age 5. The long plateau in cognitive development in patents with MPS II was substantiated and was consistent with other studies. This is the first demonstration that different mutation types within the neuronopathic MPS II patients are associated with different rates of decline. We also were able to identify the chronological age before which a trial would need to start in order to maintain cognitive growth and a ceiling beyond which a relatively normal outcome would not be likely.

Efficient engraftment of genetically modified cells is necessary to ameliorate central nervous system involvement of murine model of mucopolysaccharidosis type II by hematopoietic stem cell targeted gene therapy

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease (LSD) caused by a deficiency of the iduronate-2-sulfatase (IDS) that catabolizes glycosaminoglycans (GAGs). Abnormal accumulations of GAGs in somatic cells lead to various manifestations including central nervous system (CNS) disease. Enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are the currently available therapy for MPS II, but both therapies fail to improve CNS manifestations. We previously showed that hematopoietic stem cell targeted gene therapy (HSC-GT) with lethal irradiation improved CNS involvement in a murine model of MPS II which lacks the gene coding for IDS. However, the strong preconditioning, with lethal irradiation, would cause a high rate of morbidity and mortality. Therefore, we tested milder preconditioning procedures with either low dose irradiation or low dose irradiation plus an anti c-kit monoclonal antibody (ACK2) to assess CNS effects in mice with MPS II after HSC-GT. Mice from all the HSC-GT groups displayed super-physiological levels of IDS enzyme activity and robust reduction of abnormally accumulated GAGs to the wild type mice levels in peripheral organs. However, only the mice treated with lethal irradiation showed significant cognitive function improvement as well as IDS elevation and GAG reduction in the brain. These results suggest that an efficient engraftment of genetically modified cells for HSC-GT requires strong preconditioning to ameliorate CNS involvement in cases with MPS II.

The mutational spectrum of hunter syndrome reveals correlation between biochemical and clinical profiles in Tunisian patients

Background

Mucopolysaccharidosis type II (MPS II) or Hunter syndrome is an X-linked recessive lysosomal storage disorder resulting from deficient activity of iduronate 2-sulfatase (IDS) and the progressive lysosomal accumulation of sulfated glycosaminoglycans (GAGs).

Methods

A diagnosis of MPS II or Hunter syndrome was performed based on the following approach after a clinical and paraclinical suspicion. Two biochemical and molecular tests were carried out separately and according to the availability of the biological material.

Results

All patients in this cohort presented the most common MPS II clinical features. Electrophoresis of GAGs on a cellulose acetate plate in the presence of a high concentration of heparane sulfate showed an abnormal dermatan sulfate band in the patients compared with that in a control case. Furthermore, leukocyte IDS activity ranged from 0.00 to 0.75 nmol/h/mg of leukocyte protein in patients.

Five previously reported mutations were identified in this study patients: one splice site mutation, c.240 + 1G > A; two missense mutations, p.R88P and p.G94D; a large deletion of exon 1 to exon 7; and one nonsense mutation, p.Q396*. In addition, two novel alterations were identified in the MPS II patients: one frame shift mutation, p.D450Nfs*95 and one nonsense mutation, p.Q204*.

Additionally, five known IDS polymorphisms were identified in the patients: c.419–16 delT, c.641C > T (p.T214M), c.438 C > T (p.T146T), c.709-87G > A, and c.1006 + 38 T > C.

Conclusions

The high level of urine GAGs and the deficiency of iduronate 2-sulfatase activity was associated with the phenotype expression of Hunter syndrome. Molecular testing was useful for the patients’ phenotypic classification and the detection of carriers.

Case report of endoprosthesis -Y implantation in severe respiratory failure in the MPSII patient; comparison with literature data

Background

The tracheobronchomalacia is a life-threatening complication of mucopolysaccharidosis (MPS) without known effective, optimal treatment. The severe expiratory collapse of the trachea and bronchi is one of causes of the high rate of deaths in the course of airway impairment in MPSII patients.

Case presentation

Due to the adynamic tracheobronchomalacia despite of enzymatic treatment (ERT) in our MPSII patient, a life-saving tracheal bifurcated type-Y endoprosthesis (a self-expanding, metal stent for the prosthesis of tracheal and bronchial stenosis) was implanted. In the followed months, the breathing efficiency improved, but then gradual worsening, progression of bronchi occlusion at the stent border resulted in patient’s death.

Conclusion

The Y-stent implantation appears to be a short-term, life-saving solution without satisfactory long-term effects due to the progress of peripheral bronchomalacia and increased tissue proliferation and granulation, that arises during the illness’ course.

Mucopolysaccharidosis Type II: One Hundred Years of Research, Diagnosis, and Treatment

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) was first described by Dr. Charles Hunter in 1917. Since then, about one hundred years have passed and Hunter syndrome, although at first neglected for a few decades and afterwards mistaken for a long time for the similar disorder Hurler syndrome, has been clearly distinguished as a specific disease since 1978, when the distinct genetic causes of the two disorders were finally identified. MPS II is a rare genetic disorder, recently described as presenting an incidence rate ranging from 0.38 to 1.09 per 100,000 live male births, and it is the only X-linked-inherited mucopolysaccharidosis. The complex disease is due to a deficit of the lysosomal hydrolase iduronate 2-sulphatase, which is a crucial enzyme in the stepwise degradation of heparan and dermatan sulphate. This contributes to a heavy clinical phenotype involving most organ-systems, including the brain, in at least two-thirds of cases. In this review, we will summarize the history of the disease during this century through clinical and laboratory evaluations that allowed its definition, its correct diagnosis, a partial comprehension of its pathogenesis, and the proposition of therapeutic protocols. We will also highlight the main open issues related to the possible inclusion of MPS II in newborn screenings, the comprehension of brain pathogenesis, and treatment of the neurological compartment.

Mucopolysaccharidosis type II (Hunter syndrome): Clinical and biochemical aspects of the disease and approaches to its diagnosis and treatment

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare X-linked lysosomal storage disease caused by mutations of the gene encoding the lysosomal enzyme iduronate-2-sulfatase (IDS), the role of which is to hydrolytically remove O-linked sulfates from the two glycosaminoglycans (GAGs) heparan sulfate (HS) and dermatan sulfate (DS). HS and DS are linear, heterogeneous polysaccharides composed of repeating disaccharide subunits of l-iduronic acid (IdoA) or d-glucuronic acid, (1→4)-linked to d-glucosamine (for HS), or (1→3)-linked to 2-acetamido-2-deoxy-d-galactose (N-acetyl-d-galactosamine) (for DS). In healthy cells, IDS cleaves the sulfo group found at the C-2 position of terminal non-reducing end IdoA residues in HS and DS. The loss of IDS enzyme activity leads to progressive lysosomal storage of HS and DS in tissues and organs such as the brain, liver, spleen, heart, bone, joints and airways. Consequently, this leads to the phenotypic features characteristic of the disease. This review provides an overview of the disease profile and clinical manifestation, with a particular focus on the biochemical basis of the disease and chemical approaches to the development of new diagnostics, as well as discussing current treatment options and emerging new therapies.

Agreement between results of meta-analyses from case reports and clinical studies, regarding efficacy and safety of idursulfase therapy in patients with mucopolysaccharidosis type II (MPS-II). A new tool for evidence-based medicine in rare diseases

Background

A preliminary exploratory study shows solid agreement between the results of case reports and clinical study meta-analyses in mucopolysaccharidosis Type I (MPS-I) adult patients. The aim of the present study is to confirm previous results in another patient population, suffering from mucopolysaccharidosis Type II (MPS-II).

Methods

A systematic review and meta-analysis of case reports published by April 2018 was conducted for MPS-II patients treated with enzyme replacement therapy (ERT). The study is reported in accordance with PRISMA and MOOSE guidelines (PROSPERO database code CRD42018093408). The assessed population and outcomes were the same as previously analyzed in a meta-analysis of MPS-II clinical studies. The primary endpoint was the percent of clinical cases showing improvement in efficacy outcome, or no harm in safety outcome after ERT initiation. A restrictive procedure to aggregate case reports, by selecting standardized and well-defined outcomes, was proposed. Different sensitivity analyses were able to evaluate the robustness of results.

Results

Every outcome classified as “acceptable evidence group” in our case report meta-analysis had been graded as “moderate strength of evidence” in the aforementioned meta-analysis of clinical studies. Sensitivity, specificity, and positive-negative predictive values for results of both meta-analyses reached 100%, and were deemed equivalent.

Conclusions

Aggregating case reports quantitatively, rather than analyzing them qualitatively, may improve conclusions in rare diseases and personalized medicine. Additionally, we propose some methods to evaluate publication bias and heterogeneity of the included studies in a meta-analysis of case reports.

Assessing the impact on caregivers caring for patients with rare pediatric lysosomal storage diseases: development of the Caregiver Impact Questionnaire

Background

Capturing the impact of caring for patients with debilitating rare disease is important for understanding disease burden. We aimed to develop and validate an instrument to measure the impact on caregivers of caring for children with three lysosomal storage diseases (LSDs): metachromatic leukodystrophy (MLD), neuronopathic mucopolysaccharidosis type II (MPS II) and mucopolysaccharidosis type IIIA (MPS IIIA).

Methods

A draft instrument was developed based on targeted literature searches and revised through sequential qualitative interviews with caregivers of patients first with MLD (n = 16), then with MPS II (n = 22), and finally with MPS IIIA (n = 8). The instrument, which covered domains of physical, emotional, social and economic burden, was refined at each stage of development based on caregiver feedback. Saturation of major concepts was reached during concept elicitation (MLD and MPS II).

Results

It was confirmed that caring for a patient with an LSD impacts social functioning, emotional/psychological functioning, physical functioning, daily activities, and finances/work productivity. Results from cognitive debriefing of the draft questionnaires were considered during each round of interviews, resulting in a final set of items that caregivers found clear and easy to understand. The Caregiver Impact Questionnaire (CIQ) has 30 items in five domains: (1) social functioning (7 items); (2) impact on daily activities (5 items); (3) emotional/psychological functioning (10 items); (4) physical functioning (6 items); and (5) financial impact (2 items).

Conclusions

These findings demonstrate that the content of the CIQ is relevant for determining the impact of caring on caregivers of patients with MLD, MPS II and MPS IIIA.

Electronic supplementary material

The online version of this article (10.1186/s41687-019-0140-3) contains supplementary material, which is available to authorized users.

Recovery of Vision following Enzyme Replacement Therapy in a Patient with Mucopolysaccharidosis Type II, Hunter Syndrome

We analyzed the effects of enzyme replacement therapy (ERT) on the visual acuity and visual fields of a patient with mucopolysaccharidosis type II, Hunter syndrome, with degeneration of the retina and abnormalities of the optic nerve. After the ERT, there was an improvement of the visual acuity and visual fields and an improvement of the activities of daily living. Despite the late onset of Hunter syndrome in this patient, ERT was still able to improve the visual function. We conclude that ERT should be considered regardless of the age of the manifestations of the signs and symptoms of Hunter syndrome.

Evaluation of cerebrospinal fluid heparan sulfate as a biomarker of neuropathology in a murine model of mucopolysaccharidosis type II using high-sensitivity LC/MS/MS

Mucopolysaccharidosis type II (MPS II or Hunter syndrome) is a lysosomal storage disorder caused by a deficiency of iduronate-2-sulfatase (IDS), an enzyme that catabolizes glycosaminoglycans (GAGs) including heparan sulfate (HS) and dermatan sulfate (DS). GAG accumulation leads to severe neurological and somatic impairments. At present, the most common treatment for MPS II is intravenous enzyme replacement therapy; however, the inability of recombinant IDS to cross the blood-brain barrier (BBB) restricts therapeutic efficacy for neurological manifestations. We recently developed a BBB-penetrating IDS fusion protein, JR-141, and demonstrated its ability to reduce GAG accumulation in the brain of human transferrin receptor knock-in and Ids knock-out mice (TFRC-KI/Ids-KO), an animal model of MPS II, following intravenous administration. Given the impossibility of measuring GAG accumulation in the brains of human patients with MPS II, we hypothesized that GAG content in the cerebrospinal fluid (CSF) might serve as an indicator of brain GAG burden. To test this hypothesis, we optimized a high-sensitivity method for quantifying HS and DS in low-volume samples by combining acidic methanolysis and liquid chromatography-tandem mass spectrometry (LC/MS/MS). We employed this method to quantify HS and DS in samples from TFRC-KI/Ids-KO mice and revealed that HS but not DS accumulated in the central nerve system (CNS). Moreover, concentrations of HS in CSF correlated with those in brain. Finally, intravenous treatment with JR-141 reduced levels of HS in the CSF and brain in TFRC-KI/Ids-KO mice. These results suggest that CSF HS content may be a useful biomarker for evaluating the brain GAG accumulation and the therapeutic efficacy of drugs in patients with MPS II.

Efficacy of Idursulfase therapy in patients with Mucopolysaccharidosis type II who initiated enzyme replacement therapy in adult age. A systematic review of the literature

BACKGROUND

Enzyme replacement therapy (ERT) has been shown to decrease urine glycosaminoglycans (uGAGs) and liver and spleen volumes, and to improve clinical symptoms in mucopolysaccharidosis type II (MPS-II) patients.

METHODS

A systematic search of the literature, from inception to August 2017, was conducted to identify randomized trials or observational studies including ≥1 MPS-II patients with ERT initiated in adult age (≥16 years) and evaluating ERT efficacy. Evidence was rated according to GRADE criteria. Common efficacy outcomes of the clinical studies were analyzed. Case reports were separately evaluated.

RESULTS

One randomized clinical trial, 4 observational studies and 5 case reports were selected. ERT decreased uGAG levels and liver and spleen size with moderate evidence level and led to anti-ERT antibody and IRRS development in a significant proportion of patients with moderate evidence level. There were no conclusive results for beneficial effects on 6MWT, respiratory, cardiac and neurological function, joint mobility, sleep disorders of respiratory origin, and quality of life.

LIMITATIONS

Excluding one observational study, all others were not conducted specifically in the target population (ERT ≥16 years). Data were from subgroup analyses of selected studies. There was a great heterogeneity between study designs and clinical outcomes evaluated.

CONCLUSIONS

ERT improves uGAGs and liver/spleen volume with a moderate evidence level in MPS-II patients initiating therapy as adults, although the putative associated clinical benefit is unclear.

Chaperone effect of sulfated disaccharide from heparin on mutant iduronate-2-sulfatase in mucopolysaccharidosis type II

Small molecules called pharmacological chaperones have been shown to improve the stability, intracellular localization, and function of mutated enzymes in several lysosomal storage diseases, and proposed as promising therapeutic agents for them. However, a chaperone compound for mucopolysaccharidosis type II (MPS II), which is an X-linked lysosomal storage disorder characterized by a deficiency of iduronate-2-sulfatase (IDS) and the accumulation of glycosaminoglycans (GAGs), has still not been developed. Here we focused on the Δ-unsaturated 2-sulfouronic acid-N-sulfoglucosamine (D2S0), which is a sulfated disaccharide derived from heparin, as a candidate compound for a pharmacological chaperone for MPS II, and analyzed the chaperone effect of the saccharide on IDS by using recombinant protein and cells expressing mutated enzyme. When D2S0 was incubated with recombinant human IDS (rhIDS) in vitro, the disaccharide attenuated the thermal degeneration of the enzyme. This effect of D2S0 on the thermal degeneration of rhIDS was enhanced in a dose-dependent manner. D2S0 also increased the residual activity of mutant IDS in patient fibroblasts. Furthermore, D2S0 improved the enzyme activity of IDS mutants derived from six out of seven different mutations in HEK293T cells transiently expressing them. These results indicate that D2S0 is a potential pharmacological chaperone for MPS II.

Ten years of the Hunter Outcome Survey (HOS): insights, achievements, and lessons learned from a global patient registry

Mucopolysaccharidosis type II (MPS II; Hunter syndrome; OMIM 309900) is a rare lysosomal storage disease with progressive multisystem manifestations caused by deficient activity of the enzyme iduronate-2-sulfatase. Disease-specific treatment is available in the form of enzyme replacement therapy with intravenous idursulfase (Elaprase®, Shire). Since 2005, the Hunter Outcome Survey (HOS) has collected real-world, long-term data on the safety and effectiveness of this therapy, as well as the natural history of MPS II. Individuals with a confirmed diagnosis of MPS II who are untreated or who are receiving/have received treatment with idursulfase or bone marrow transplant can be enrolled in HOS. A broad range of disease- and treatment-related information is captured in the registry and, over the past decade, data from more than 1000 patients from 124 clinics in 29 countries have been collected. Evidence generated from HOS has helped to improve our understanding of disease progression in both treated and untreated patients and has extended findings from the formal clinical trials of idursulfase. As a long-term, global, observational registry, various challenges relating to data collection, entry, and analysis have been encountered. These have resulted in changes to the HOS database platform, and novel approaches to maximize the value of the information collected will also be needed in the future. The continued evolution of the registry should help to ensure that HOS provides further insights into the burden of the disease and patient care and management in the coming years.

Clinical, biochemical and molecular characteristics of Filipino patients with mucopolysaccharidosis type II - Hunter syndrome

BACKGROUND

Mucopolysaccharidosis type II, an X-linked recessive disorder is the most common lysosomal storage disease detected among Filipinos. This is a case series involving 23 male Filipino patients confirmed to have Hunter syndrome. The clinical and biochemical characteristics were obtained and mutation testing of the IDS gene was done on the probands and their female relatives.

RESULTS

The mean age of the patients was 11.28 (SD 4.10) years with an average symptom onset at 1.2 (SD 1.4) years. The mean age at biochemical diagnosis was 8 (SD 3.2) years. The early clinical characteristics were developmental delay, joint stiffness, coarse facies, recurrent respiratory tract infections, abdominal distention and hernia. Majority of the patients had joint contractures, severe intellectual disability, error of refraction, hearing loss and valvular regurgitation on subspecialists' evaluation. The mean GAG concentration was 506.5 mg (SD 191.3)/grams creatinine while the mean plasma iduronate-2-sulfatase activity was 0.86 (SD 0.79) nmol/mg plasma/4 h. Fourteen (14) mutations were found: 6 missense (42.9%), 4 nonsense (28.6%), 2 frameshift (14.3%), 1 exon skipping at the cDNA level (7.1%), and 1 gross insertion (7.1%). Six (6) novel mutations were observed (43%): p.C422F, p.P86Rfs*44, p.Q121*, p.L209Wfs*4, p.T409R, and c.1461_1462insN[710].

CONCLUSION

The age at diagnosis in this series was much delayed and majority of the patients presented with severe neurologic impairment. The results of the biochemical tests did not contribute to the phenotypic classification of patients. The effects of the mutations were consistent with the severe phenotype seen in the majority of the patients.

Clinical and Genetic Characteristics of Romanian Patients with Mucopolysaccharidosis Type II

BACKGROUND

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare X-linked disorder caused by deficiency of iduronate-2-sulfatase (I2S) enzyme, which leads to the accumulation of partially digested glycosaminoglycans (GAGs) in the lysosomes and induces multisystemic alteration (coarse facial features; skeletal dysplasia; hepatosplenomegaly; joint stiffness and contractures; heart, lung, vision, and hearing disability; profound neurological decline).The purpose of this study is to present the clinical and genetic characteristics of Romanian patients with Hunter syndrome and the genotype-phenotype correlation.

MATERIAL AND METHODS

15 unrelated patients, with MPS II ranging from mild (4 subjects) to severe phenotype (11 subjects) aged 2 to 20 years, were evaluated clinically, cognitive development, enzyme assay and molecular analysis.

RESULTS

The molecular analysis of the 15 unrelated Romanian MPS II patients has identified 15 different mutations (2 major genetic defects (13%) and 13 minor genetic defects (87%)): microdeletions and point mutations (missense, nonsense), seven of them described for the first time-deletion encompassing 3 to exon 7; c823G>T, pD275Y; c.1600A>C (pN534H); c.102_10delAG (p.D5Cfs*11); c.448_471del (p.P150_P157del); c.421delA (p.I141Yfs*72); and c.419-1G>C. The major genetic defects were correlated with a severe course of disease.

CONCLUSION

This is the first study on the clinical and molecular characterization of the MPS II Romanian patients. This study supports the evidence of the mutational heterogeneity of the I2S gene as well as the difficulty to correlate genotype and phenotype in the patients with MPS II.

Association between brain structural anomalies, electroencephalogram and history of seizures in Mucopolysaccharidosis type II (Hunter syndrome)

Mucopolysaccharidosis type II or Hunter syndrome (MPS II) is a genetic disease that can course with intellectual impairment and central nervous system (CNS) alterations. To date, no report has documented electroencephalogram (EEG) measures associated with CNS alterations, detected by imaging studies, and the history of seizures in patients with MPS II. Therefore, we decided to search this association. We included 9 patients with MPS II and performed imaging studies of the brain to detect the presence of cortico-subcortical atrophy, enlarged subarachnoid space and supratentorial ventricular size. Additionally, we performed EEG studies in sleep and awake conditions and a complete clinical description. Five out of the nine patients presented history of seizures and all except one patient (88.9%) presented some CNS structural alteration in the imaging studies, being the most frequent the cortico-subcortical atrophy (77.8%). The EEG results showed low amplitude in all patients and low voltage in sleep condition in eight patients with interhemispheric asymmetry in six patients during awake and sleep conditions. Although the five patients with history of seizures did not present a distinctive EEG anomaly, four of them presented some structural alteration in the imaging studies. In conclusion, most patients presented structural alterations in the CNS; likewise, all of them presented EEG anomalies mainly during sleep conditions. However, a clear association between EEG, CNS and the history of seizures was not established.

Non-myeloablative preconditioning with ACK2 (anti-c-kit antibody) is efficient in bone marrow transplantation for murine models of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease caused by the deficient activity of iduronate 2-sulfatase (IDS), which is involved in the lysosomal catabolism of the glycosaminoglycans (GAGs) dermatan and heparan sulfate. Such a deficiency leads to the accumulation of undegraded GAGs in some organs. Although enzyme replacement therapy is available as a treatment of MPS II, there are some limitations, such as the requirement of weekly administration for whole life. To avoid such limitations, hematopoietic cell transplantation (HSCT) is a possible alternative. In fact, some report suggested positive effects of HSCT for MPS II. However, HSCT has also some limitations. Strong conditioning regimens can cause severe side effects. For overcome this obstacle, we studied the efficacy of ACK2, an antibody that blocks KIT, followed by low-dose irradiation as a preconditioning regimen for HSCT using a murine model of MPS II. This protocol achieves 58.7±4.92% donor chimerism at 16weeks after transplantation in the peripheral blood of recipient mice. GAG levels were significantly reduced in liver, spleen, heart and intestine. These results indicated that ACK2-based preconditioning might be one of the choices for MPS II patients who receive HSCT.

Oxidative and nitrative stress and pro-inflammatory cytokines in Mucopolysaccharidosis type II patients: effect of long-term enzyme replacement therapy and relation with glycosaminoglycan accumulation

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease caused by a deficient activity of iduronate-2-sulfatase, leading to abnormal accumulation of glycosaminoglycans (GAG). The main treatment for MPS II is enzyme replacement therapy (ERT). Previous studies described potential benefits of six months of ERT against oxidative stress in patients. Thus, the aim of this study was to investigate oxidative, nitrative and inflammatory biomarkers in MPS II patients submitted to long term ERT. It were analyzed urine and blood samples from patients on ERT (mean time: 5.2years) and healthy controls. Patients presented increased levels of lipid peroxidation, assessed by urinary 15-F2t-isoprostane and plasmatic thiobarbituric acid-reactive substances. Concerning to protein damage, urinary di-tyrosine (di-Tyr) was increased in patients; however, sulfhydryl and carbonyl groups in plasma were not altered. It were also verified increased levels of urinary nitrate+nitrite and plasmatic nitric oxide (NO) in MPS II patients. Pro-inflammatory cytokines IL-1β and TNF-α were increased in treated patients. GAG levels were correlated to di-Tyr and nitrate+nitrite. Furthermore, IL-1β was positively correlated with TNF-α and NO. Contrastingly, we did not observed alterations in erythrocyte superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities, in reduced glutathione content and in the plasmatic antioxidant capacity. Although some parameters were still altered in MPS II patients, these results may suggest a protective role of long-term ERT against oxidative stress, especially upon oxidative damage to protein and enzymatic and non-enzymatic defenses. Moreover, the redox imbalance observed in treated patients seems to be GAG- and pro-inflammatory cytokine-related.

Severe tracheal and bronchial collapse in adults with type II mucopolysaccharidosis

Background

Mucopolysaccharidosis type II (MPSII) patients frequently suffer from dyspnoea caused by restrictive airway disease due to skeletal abnormalities as well as glycosaminoglycans (GAG) accumulation at different levels of the airway, including the trachea. In this study we describe the extent of the tracheal and bronchial narrowing, the changes in airway diameter during respiration and the effects of these obstructions on respiratory function in adult MPSII patients.

Methods

Five adult MPSII patients (mean age 40 years) were included. Pulmonary function tests and in- and expiratory chest CT scans were obtained. Cross-sectional areas of trachea and main bronchi were measured at end-inspiration and -expiration and percentage collapse was calculated.

Results

There was diffuse narrowing of the entire intra-thoracic trachea and main bronchi and severe expiratory collapse of the trachea in all patients. At 1 cm above the aortic arch the median % collapse of the trachea was 68 (range 60 to 77 %), at the level of the aortic arch 64 (range 21–93 %), for the main bronchi this was 58 (range 26–66 %) on the left and 44 (range 9–76 %) on the right side. The pulmonary function tests showed that this airway collapse results in obstructive airway disease in all patients, which was severe (forced expiratory volume <50 % of predicted) in four out of five patients.

Conclusion

In adult MPS II patients, central airways diameters are strikingly reduced and upon expiration there is extensive collapse of the trachea and main bronchi. This central airways obstruction explains the severe respiratory symptoms in MPSII patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0425-z) contains supplementary material, which is available to authorized users.

The natural history of growth in patients with Hunter syndrome: Data from the Hunter Outcome Survey (HOS)

Hunter syndrome (mucopolysaccharidosis type II) affects growth but the overall impact is poorly understood. This study investigated the natural history of growth and related parameters and their relationship with disease severity (as indicated by cognitive impairment). Natural history data from males followed prospectively in the Hunter Outcome Survey registry and not receiving growth hormone or enzyme replacement therapy, or before treatment start, were analysed (N=676; January 2014). Analysis of first-reported measurements showed short stature by 8years of age; median age-corrected standardized height score (z-score) in patients aged 8-12years was -3.1 (1st, 3rd quartile: -4.3, -1.7; n=68). Analysis of growth velocity using consecutive values found no pubertal growth spurt. Patients had large head circumference at all ages, and above average body weight and body mass index (BMI) during early childhood (median z-score in patients aged 2-4years, weight [n=271]: 1.7 [0.9, 2.4]; BMI [n=249]: 2.0 [1.1, 2.7]). Analysis of repeated measurements over time found greater BMI in those with cognitive impairment than those without, but no difference in height, weight or head circumference. Logistic regression modelling (data from all time points) found that increased BMI was associated with the presence of cognitive impairment (odds ratio [95% CI], 3.329 [2.313-4.791]), as were increased weight (2.365 [1.630-3.433]) and head circumference (1.749 [1.195-2.562]), but not reduced height. Unlike some other MPS disorders, there is no evidence at present for predicting disease severity in patients with Hunter syndrome based on changes in growth characteristics.

A method for measuring disease-specific iduronic acid from the non-reducing end of glycosaminoglycan in mucopolysaccharidosis type II mice

Mucopolysaccharidosis type II (MPS II) is an X-linked lysosomal storage disorder arising from deficiency of iduronate-2-sulfatase (IDS), which results in progressive accumulation of glycosaminoglycans (GAGs) in multiple tissues. Accumulated GAGs are generally measured as the amount of total GAGs. However, we recently demonstrated that GAG accumulation in the brain of MPS II model mice cannot be reliably detected by conventional dye-binding assay measuring total GAGs. Here we developed a novel quantitative method for measurement of disease-specific GAGs based on the analysis of 2-sulfoiduronic acid levels derived from the non-reducing terminal end of the polysaccharides by using recombinant human IDS (rhIDS) and recombinant human iduronidase (rhIDUA). This method was evaluated on GAGs obtained from the liver and brain of MPS II mice. The GAGs were purified from tissue homogenates and then digested with rhIDS and rhIDUA to generate a desulfated iduronic acid from their non-reducing terminal end. HPLC analysis revealed that the generated iduronic acid levels were markedly increased in the liver and cerebrum of the MPS II mice, whereas the uronic acid was not detected in wild-type mice. These results indicate that this assay clearly detects the disease-specific GAGs in tissues from MPS II mice.

Monitoring of dipeptidyl peptidase-IV (DPP-IV) activity in patients with mucopolysaccharidoses types I and II on enzyme replacement therapy - Results of a pilot study

OBJECTIVES

Mucopolysaccharidoses (MPSs) are a group of rare, inherited metabolic disorders which result from the lack of one of the lysosomal enzymes responsible for the degradation of glycosaminoglycans. Early recognition of MPS is important as it enables prompt implementation of enzyme replacement therapy (ERT). Dipeptidyl peptidase-IV (DPP-IV) is a ubiquitous ectopeptidase which activity has been associated with the cell surface protein CD26. Our aims were to investigate plasma DPP-IV activity in untreated patients with MPS type II in comparison to control individuals and to evaluate changes of DPP-IV during ERT in MPS I or II patients.

DESIGN AND METHODS

One MPS I and five MPS II patients were treated with ERT for up to 19 months. DPP-IV activity was measured in plasma with a colorimetric method using Gly-Pro-p-nitroanilide as a substrate. The reference intervals were observed in 17 healthy donors and in 9 MPS II individuals before ERT implementation.

RESULTS

DPP-IV activity ranged from 557 to 1959 nmol/ml/h (median and interquartile range: 1453 [955– 1554], n = 17) in plasma of control samples. In 9 untreated MPS II individuals, DPP-IV activity was higher and ranged from 2565 to 5968 nmol/ml/h (median and interquartile range: 4458 [4031–5161]). In 6 MPS patients receiving ERT, DPP-IV activity ranged from 2984 to 8628 nmol/ml/h. No declining tendency was observed during the treatment.

CONCLUSIONS

DPP-IV activity is a good, newa nd valuable biomarker distinguishing between MPS and healthy individuals. However, it is not a useful marker of treatment efficacy and is unsuitable for monitoring.

Enzymatic replacement therapy for Hunter disease: Up to 9 years experience with 17 patients

Hunter disease is an X-linked lysosomal storage disorder characterized by progressive storage of glycosaminoglycans (GAGs) and multi-organ impairment. The central nervous system (CNS) is involved in at least 50% of cases. Since 2006, the enzymatic replacement therapy (ERT) is available but with no effect on the cognitive impairment, as the present formulation does not cross the blood-brain barrier. Here we report the outcome of 17 Hunter patients treated in a single center. Most of them (11) started ERT in 2006, 3 had started it earlier in 2004, enrolled in the phase III trial, and 3 after 2006, as soon as the diagnosis was made. The liver and spleen sizes and urinary GAGs significantly decreased and normalized throughout the treatment. Heart parameters improved, in particular the left ventricular mass index/m(2) decreased significantly. Amelioration of hearing was seen in many patients. Joint range of motion improved in all patients. However, no improvement on respiratory function, eye, skeletal and CNS disease was found. The developmental quotient of patients with a CNS involvement showed a fast decline. These patients were no more testable after 6 years of age and, albeit the benefits drawn from ERT, their quality of life worsened throughout the years. The whole group of patients showed a consistent residual disease burden mainly represented by persistent skeletal disease and frequent need of surgery. This study suggests that early diagnosis and treatment and other different therapies which are able to cross the blood-brain barrier, might in the future improve the MPS II outcome.

Cognitive, medical, and neuroimaging characteristics of attenuated mucopolysaccharidosis type II

The phenotype of attenuated mucopolysaccharidosis type II (MPS II), also called Hunter syndrome, has not been previously studied in systematic manner. In contrast to the "severe" phenotype, the "attenuated" phenotype does not present with behavioral or cognitive impairment; however, the presence of mild behavior and cognitive impairment that might impact long-term functional outcomes is unknown. Previously, significant MRI abnormalities have been found in MPS II. Recent evidence suggests white matter abnormalities in many MPS disorders.

METHODS

As the initial cross-sectional analysis of a longitudinal study, we studied the association of brain volumes and somatic disease burden with neuropsychological outcomes, including measures of intelligence, memory, and attention in 20 patients with attenuated MPS II with a mean age of 15.8. MRI volumes were compared to 55 normal controls.

RESULTS

While IQ and memory were average, measures of attention were one standard deviation below the average range. Corpus callosum volumes were significantly different from age-matched controls, differing by 22%. Normal age-related volume increases in white matter were not seen in MPS II patients as they were in controls. Somatic disease burden and white matter and corpus callosum volumes were significantly associated with attention deficits. Neither age at evaluation nor age at starting treatment predicted attention outcomes.

CONCLUSIONS

Despite average intelligence, attention is compromised in attenuated MPS II. Results confirm an important role of corpus callosum and cortical white matter abnormality in MPS II as well as the somatic disease burden in contributing to attention difficulties. Awareness by the patient and caregivers with appropriate management and symptomatic support will benefit the attenuated MPS II patient.

Identification of 17 novel mutations in 40 Argentinean unrelated families with mucopolysaccharidosis type II (Hunter syndrome)

Mucopolysaccharidosis type II (MPSII) is an X-linked lysosomal storage disorder caused by deficiency of the enzyme iduronate-2-sulfatase (IDS). The human IDS gene is located in chromosome Xq28. This is the first report of genotype and phenotype characterization of 49 Hunter patients from 40 families of Argentina. Thirty different alleles have been identified, and 57% were novel. The frequency of de novo mutations was 10%. Overall, the percentage of private mutations in our series was 75%.

Genetic analysis of 17 children with Hunter syndrome: identification and functional characterization of four novel mutations in the iduronate-2-sulfatase gene

Mucopolysaccharidosis type II (MPS II) is a rare X-linked disorder caused by alterations in the iduronate-2-sulfatase (IDS) gene. In this study, IDS activity in peripheral mononuclear blood monocytes (PMBCs) was measured with a fluorimetric enzyme assay. Urinary glycosaminoglycans (GAGs) were quantified using a colorimetric assay. All IDS exons and intronic flanks were bidirectionally sequenced. A total of 15 mutations (all exonic region) were found in 17 MPS II patients. In this cohort of MPS II patients, all alterations in the IDS gene were caused by point nucleotide substitutions or small deletions. Mutations p.Arg88His and p.Arg172* occurred twice. All mutations were inherited except for p.Gly489Alafs*7, a germline mutation. We found four new mutations (p.Ser142Phe, p.Arg233Gly, p.Glu430*, and p.Ile360Tyrfs*31). In Epstein-Barr virus (EBV)-immortalized PMBCs derived from the MPS II patients, no IDS protein was detected in case of the p.Ser142Phe and p.Ile360Tyrfs*31 mutants. For p.Arg233Gly and p.Glu430*, we observed a residual expression of IDS. The p.Arg233Gly and p.Glu430* mutants had a residuary enzymatic activity that was lowered by 14.3 and 76-fold, respectively, compared with healthy controls. This observation may help explain the mild disease phenotype in MPS II patients who had these two mutations whereas the p.Ser142Phe and p.Ile360Tyrfs*31 mutations caused the severe disease manifestation.

Mucopolysaccharidosis type II: identification of 30 novel mutations among Latin American patients

In this study, 103 unrelated South-American patients with mucopolysaccharidosis type II (MPS II) were investigated aiming at the identification of iduronate-2-sulfatase (IDS) disease causing mutations and the possibility of some insights on the genotype-phenotype correlation The strategy used for genotyping involved the identification of the previously reported inversion/disruption of the IDS gene by PCR and screening for other mutations by PCR/SSCP. The exons with altered mobility on SSCP were sequenced, as well as all the exons of patients with no SSCP alteration. By using this strategy, we were able to find the pathogenic mutation in all patients. Alterations such as inversion/disruption and partial/total deletions of the IDS gene were found in 20/103 (19%) patients. Small insertions/deletions/indels (<22 bp) and point mutations were identified in 83/103 (88%) patients, including 30 novel mutations; except for a higher frequency of small duplications in relation to small deletions, the frequencies of major and minor alterations found in our sample are in accordance with those described in the literature.

Mucopolysaccharidosis Type II and the G374sp Mutation

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a rare, X-linked disease caused by a deficiency of the lysosomal enzyme iduronate-2-sulfatase, which catalyses a step in the catabolism of glycosaminoglycans resulting in accumulation of heparan and dermatan sulfate in many organs and tissues. This accumulation favors the appearance of neurologic involvement, severe airway obstruction, skeletal deformities, and cardiomyopathy, especially mitral and aortic valve regurgitation. In severe cases, obstructive airway disease and cardiac failure due to valvular dysfunction are the most common causes of death within the second decade of life. However, in mild cases, intelligence remains normal, stature is almost normal and death usually occurs due to cardiac failure in the fourth decade of life. We report the presentation, diagnosis, management, and outcome of 2 siblings with MPS II and the G374sp mutation at the nucleotide c.1246 of the gene encoding for the iduronate-2-sulfatase.