A bacteriolytic agent that detects and kills Bacillus anthracis

The dormant and durable spore form of Bacillus anthracis is an ideal biological weapon of mass destruction. Once inhaled, spores are transported by alveolar macrophages to lymph nodes surrounding the lungs, where they germinate; subsequent vegetative expansion causes an overwhelming flood of bacteria and toxins into the blood, killing up to 99% of untreated victims. Natural and genetically engineered antibiotic-resistant bacilli amplify the threat of spores being used as weapons, and heighten the need for improved treatments and spore-detection methods after an intentional release. We exploited the inherent binding specificity and lytic action of bacteriophage enzymes called lysins for the rapid detection and killing of B. anthracis. Here we show that the PlyG lysin, isolated from the gamma phage of B. anthracis, specifically kills B. anthracis isolates and other members of the B. anthracis 'cluster' of bacilli in vitro and in vivo. Both vegetative cells and germinating spores are susceptible. The lytic specificity of PlyG was also exploited as part of a rapid method for the identification of B. anthracis. We conclude that PlyG is a tool for the treatment and detection of B. anthracis.

Pegylated arginine deiminase treatment of patients with unresectable hepatocellular carcinoma: results from phase I/II studies

PURPOSE

Recently, we reported that a large number of human hepatocellular cancer (HCC) cell lines were auxotrophic for arginine. Here we report the results obtained with the amino acid-degrading enzyme arginine deiminase (ADI) conjugated to polyethylene glycol (ADI-SS PEG 20,000 mw) as a means of lowering plasma arginine to treat HCC. The study was a cohort dose-escalation phase I/II study.

PATIENTS AND METHODS

Pharmacodynamic studies indicated an ADI-SS PEG 20,000 mw dose level of 160 U/m(2) was sufficient to lower plasma arginine from a resting level of approximately 130 micromol/L to below the level of detection (< 2 micromol/L) for more than 7 days, a dose later defined as the optimal biologic dose. All patients were to receive three cycles at the optimum biologic dose.

RESULTS

This therapy was well tolerated, even in patients who had no detectable plasma arginine for 3 continuous months of therapy. Of the 19 patients enrolled, two had a complete response, seven had a partial response, seven had stable disease, and three had progressive disease. The median survival for the 19 patients enrolled on this study was 410 days, with four patients still alive at present (> 680 days).

CONCLUSION

Elimination of all detectable plasma arginine in patients with HCC was well tolerated and seemed to be effective in the treatment of some patients with HCC. Further testing of ADI-SS PEG 20,000 mw in a larger population of individuals with HCC as well as other human tumors auxotrophic for arginine is warranted.

Arginine deprivation as a targeted therapy for cancer

Certain cancers may be auxotrophic for a particular amino acid, and amino acid deprivation is one method to treat these tumors. Arginine deprivation is a novel approach to target tumors which lack argininosuccinate synthetase (ASS) expression. ASS is a key enzyme which converts citrulline to arginine. Tumors which usually do not express ASS include melanoma, hepatocellular carcinoma, some mesotheliomas and some renal cell cancers. Arginine can be degraded by several enzymes including arginine deiminase (ADI). Although ADI is a microbial enzyme from mycoplasma, it has high affinity to arginine and catalyzes arginine to citrulline and ammonia. Citrulline can be recycled back to arginine in normal cells which express ASS, whereas ASS(-) tumor cells cannot. A pegylated form of ADI (ADI-PEG20) has been formulated and has shown in vitro and in vivo activity against melanoma and hepatocellular carcinoma. ADI-PEG20 induces apoptosis in melanoma cell lines. However, arginine deprivation can also induce ASS expression in certain melanoma cell lines which can lead to in vitro drug resistance. Phase I and II clinical trials with ADI-PEG20 have been conducted in patients with melanoma and hepatocellular carcinoma, and antitumor activity has been demonstrated in both cancers. This article reviews our laboratory and clinical experience as well as that from others with ADI-PEG20 as an antineoplastic agent. Future direction in utilizing this agent is also discussed.

New therapeutic options for lysosomal storage disorders: enzyme replacement, small molecules and gene therapy

During the last few years, much progress has been made in the treatment of lysosomal storage disorders. In the past, no specific therapy was available for the affected patients, and management consisted solely of supportive care and treatment of complications. Since enzyme replacement therapy has been successfully introduced for patients with Gaucher disease, this principle of treatment has been taken into consideration for other lysosomal storage disorders as well. Clinical trials could demonstrate the clinical benefit of this therapeutic principle in Fabry disease, mucopolysaccharidoses type I, II and VI and in Pompe disease. However, the usefulness of enzyme replacement therapy is limited due to the fact that a given enzyme preparation does not have beneficial effects on all aspects of a disorder in the same degree. Additionally, clinical studies have shown that many symptoms of a lysosomal storage disorder even after long-term treatment are no more reversible. A further novel therapeutic option for lysosomal storage disorders consists of the application of small molecules that either inhibit a key enzyme which is responsible for substrate synthesis (substrate deprivation) or act as a chaperone to increase the residual activity of the lysosomal enzyme (enzyme enhancing therapy). Various gene therapeutic techniques (in vivo and ex vivo technique) have been developed in order to administer the gene that is defective in a patient to the bloodstream or directly to the brain in order to overcome the blood-brain barrier. This review will give an insight into these newly developed therapeutic strategies and will discuss their advantages and limitations.

A randomised phase II study of pegylated arginine deiminase (ADI-PEG 20) in Asian advanced hepatocellular carcinoma patients

BACKGROUND

Human hepatocellular carcinoma (HCC) cells are largely deficient of argininosuccinate synthetase and thus auxotrophic for arginine. This study aims to investigate the efficacy and pharmacodynamics of pegylated arginine deiminase (ADI-PEG 20), a systemic arginine deprivation agent, in Asian HCC patients.

METHODS

Patients with advanced HCC who were not candidates for local therapy were eligible and randomly assigned to receive weekly intramuscular injections of ADI-PEG 20 at doses of 160 or 320 IU m(-2). The primary end point was disease-control rate (DCR).

RESULTS

Of the 71 accruals, 43.6% had failed previous systemic treatment. There were no objective responders. The DCR and the median overall survival (OS) of the intent-to-treat population were 31.0% (95% confidence interval (CI): 20.5-43.1) and 7.3 (95% CI: 4.7-9.9) months respectively. Both efficacy parameters were comparable between the two study arms. The median OS of patients with undetectable circulating arginine for more than or equal to and <4 weeks was 10.0 (95% CI: 2.1-17.9) and 5.8 (95% CI: 1.4-10.1) months respectively (P=0.251, log-rank test). The major treatment-related adverse events were grades 1-2 local and/or allergic reactions.

CONCLUSIONS

ADI-PEG 20 is safe and efficacious in stabilising the progression of heavily pretreated advanced HCC in an Asian population, and deserves further exploration.

Phase I/II study of pegylated arginine deiminase (ADI-PEG 20) in patients with advanced melanoma

Background Arginine deiminase (ADI) is an enzyme that degrades arginine, an amino acid that is important for growth and development of normal and neoplastic cells. Melanoma cells are auxotrophic for arginine, because they lack argininosuccinatesynthetase (ASS), a key enzyme required for the synthesis of arginine. Patients and methods Patients with advanced melanoma were treated with 40, 80 or 160 IU/m(2) ADI-PEG 20 i.m. weekly. Primary endpoints were toxicity and tumor response, secondary endpoints included metabolic response by (18)FDG-PET, pharmacodynamic (PD) effects upon circulating arginine levels, and argininosuccinate synthetase tumor expression by immunohistochemistry. Results 31 previously treated patients were enrolled. The main toxicities were grade 1 and 2 adverse events including injection site pain, rash, and fatigue. No objective responses were seen. Nine patients achieved stable disease (SD), with 2 of these durable for >6 months. Four of the 9 patients with SD had uveal melanoma. PD analysis showed complete plasma arginine depletion in 30/31 patients by day 8. Mean plasma levels of ADI-PEG 20 correlated inversely with ADI-PEG 20 antibody levels. Immunohistochemical ASS expression analysis in tumor tissue was negative in 24 patients, whereas 5 patients had <5 % cells positive. Conclusions ADI-PEG 20 is well tolerated in advanced melanoma patients and leads to consistent, but transient, arginine depletion. Although no RECIST responses were observed, the encouraging rate of SD in uveal melanoma patients indicates that it may be worthwhile to evaluate ADI-PEG 20 in this melanoma subgroup.

Development of Phage Lysins as Novel Therapeutics: A Historical Perspective

Bacteriophage lysins and related bacteriolytic enzymes are now considered among the top antibiotic alternatives for solving the mounting resistance problem. Over the past 17 years, lysins have been widely developed against Gram-positive and recently Gram-negative pathogens, and successfully tested in a variety of animal models to demonstrate their efficacy. A lysin (CF-301) directed to methicillin resistant Staphylococcus aureus (MRSA) has effectively completed phase 1 human clinical trials, showing safety in this novel therapeutic class. To validate efficacy, CF-301 is currently the first lysin to enter phase 2 human trials to treat hospitalized patients with MRSA bacteremia or endocarditis. If successful, it could be the defining moment leading to the acceptance of lysins as an alternative to small molecule antibiotics. This article is a detailed account of events leading to the first therapeutic use and ultimate development of phage-encoded lysins as novel anti-infectives.

Anti-inflammatory effects of Lactobacillus brevis (CD2) on periodontal disease

OBJECTIVES

To analyze the anti-inflammatory effects of Lactobacillus brevis extracts on periodontitis patients and to investigate the involved mechanisms in vitro on activated macrophages.

METHODS

Eight healthy subjects and 21 patients with chronic periodontitis were enrolled to analyze the effect of L. brevis-containing lozenges on periodontitis-associated symptoms and signs. Before and after the treatment, the patients received a complete periodontal examination. Saliva samples, collected before and after treatment, were analyzed for metalloproteinase and nitric oxide synthase (NOS) activity, immunoglobulin-A (IgA), prostaglandin E(2) (PGE(2)) and gamma-interferon (IFN-gamma) levels. Arginine deiminase (AD) and NOS activities were determined through a radiometric assay. Metalloproteinases were assayed by zymogram and Western blotting, whereas IgA, PGE(2) and IFN-gamma were assayed by enzyme-linked imunosorbent assay tests.

RESULTS

The treatment led to the total disappearance or amelioration of all analyzed clinical parameters in all patients. This was paralleled to a significant decrease of nitrite/nitrate, PGE(2), matrix metalloproteinase, and IFN-gamma levels in saliva samples.

CONCLUSION

Our results suggest that the anti-inflammatory effects of L. brevis could be attributed to the presence of AD which prevented nitric oxide generation. Our findings give further insights into the knowledge of the molecular basis of periodontitis and have a potential clinical significance, giving the experimental ground for a new innovative, simple and efficacious therapeutical approach of periodontal disease.

Cystic fibrosis: nutritional consequences and management

Life expectancy for patients with Cystic Fibrosis (CF) has steadily improved during the last three decades, and death in childhood is now uncommon. Nutrition is a critical component of the management of CF, and nutritional status is directly associated with both pulmonary status and survival. Expert dietetic care is necessary, and attention must be given to ensuring an adequate energy intake in the face of demands which may be increased by inadequately controlled malabsorption, chronic broncho-pulmonary colonisation by bacteria and fungi, exacerbations of acute lung infection, impaired lung function, and the need for rehabilitation, repair and growth. Pancreatic enzyme replacement therapy (PERT) is needed by up to 90% of CF patients in Northern Europe, where the 'severe' mutation deltaF508 predominates, but a smaller proportion in Mediterranean countries and elsewhere, because pancreatic insufficiency is one of few features of CF which correlate with genotype. Complications of CF including liver disease and CF-related diabetes pose further challenges. In addition, deficiency of specific nutrients including fat soluble vitamins (particularly A, E and K) essential fatty acids and occasionally minerals occur for a variety of reasons. Osteopenia is common and poorly understood. Liver disease increases the likelihood of vitamin D deficiency. Glucose intolerance and diabetes affect at least 25% of CF adults, and the diabetes differs from both types 1 and 2 diabetes mellitus, but it inversely correlates with prognosis. Management consists of anticipating problems and addressing them vigorously as soon as they appear. Supplements of vitamins are routinely given. Energy supplements can be oral, enteral or, rarely, parenteral. All supplements, including PERT, are adjusted to individual needs.

Pegylated arginine deiminase: a novel anticancer enzyme agent

Pegylated arginine deiminase (ADI-PEG20) is a novel anticancer enzyme that produces depletion of arginine, which is a nonessential amino acid in humans. Certain tumours, such as malignant melanoma and hepatocellular carcinoma, are auxotrophic for arginine. These tumours that are sensitive to arginine depletion do not express argininosuccinate synthetase, a key enzyme in the synthesis of arginine from citrulline. ADI-PEG20 inhibits human melanomas and hepatocellular carcinomas in vitro and in vivo. Phase I - II trials in patients with melanoma and hepatocellular carcinomas have shown the drug to have antitumour activity and tolerable side effects. Large Phase II trials and randomised, controlled Phase III trials are needed to determine its overall efficacy in the treatment of these malignancies and others.

In vivo anti-tumor activity of arginine deiminase purified from Mycoplasma arginini

Arginine deiminase (EC 3.5.3.6) was purified to homogeneity from the cell extract of Mycoplasma arginini by molecular-sieve, anion-exchange and arginine-affinity chromatographies. The purified enzyme was composed of 2 identical sub-units with a molecular weight of 45.000 and had a pI of 4.7. Its Vmax value and Km value for L-arginine were estimated to be 50 units/mg protein and 0.2 mM, respectively. It exerted maximal enzyme activity at pH 6.0-7.5 and at 50 degrees C. The arginine deiminase was stable at neutral pH. When injected i.v. into mice, the half-life of the arginine deiminase in blood was about 4 hr. In culture, the enzyme strongly inhibited the growth of 6 kinds of mouse tumor cell lines by depleting L-arginine in the culture media. When the in vivo growth-inhibitory activity of arginine deiminase was tested for the 6 tumor cell lines, i.p. administration of the purified enzyme effectively prolonged the survival time of the mice injected with all kinds of the tumor cell lines. Especially, the in vivo growth of a hepatoma cell line, MH134, was completely prevented by the daily administration at a dose of 0.2 mg/mouse for 14 days. These results raise the possibility of the use of the arginine deiminase derived from Mycoplasma arginini as a new anti-tumor drug.

Pain control after third molar surgery

The ideal agent for use after third molar surgery should alleviate pain, reduce swelling and trismus to a minimum, promote healing and have no unwanted effects. Of course, such an agent does not exist. For relief of pain, analgesics are the obvious choice. Where possible, an analgesic with additional anti-inflammatory properties should be used. There seems little to choose between aspirin, 1000 mg; diflunisal, 500 mg; ibuprofen, 400 mg and zomepirac sodium, 50 mg. In the subject allergic to aspirin and aspirin-like compounds, then paracetamol is the poor alternative. Surprisingly, the efficacy of most of the opioids in post-operative third molar pain is poor, and these drugs alone cannot be recommended for this purpose. Long-acting local anaesthetic solutions may be of value in some situations where extreme pain is likely to be a feature in the immediate post-operative period. However, there are no strict criteria for identifying such cases pre-operatively. Recent work on the use of corticosteroids would suggest that these drugs may be of value in reducing post-operative sequelae. Their future in dentistry in this rôle appears interesting and promising, and worthy of further study. Antihistamines and enzymes have been shown to be of little value, and the fact that these agents now receive little attention is evidence in its own right. The use of locally applied antimicrobials has been shown to be of little value in third molar surgery. In any case, their use is probably contraindicated because of the risk of sensitising the patient. The studies reviewed have not pointed to the effectiveness of the routine use of systemic antimicrobials in preventing or reducing postoperative sequelae after removal of impacted third molars in normal circumstances. Particular conditions, for example in patients susceptible to infection, may benefit by the use of prophylactic antimicrobials. However, each case must be judged on its individual merits, bearing in mind the attendant risks inherent in antimicrobial therapy. Finally, whatever agent is chosen for the control of the post-operative sequelae after third molar surgery, it must be borne in mind that, if the normal post-operative course occurs, then treatment is unlikely to extend beyond 48 h. Few doses of the particular agent will hence be used during this time period and thus the incidence of unwanted effects will be minimised.

Arginine deprivation, autophagy, apoptosis (AAA) for the treatment of melanoma

The majority of melanoma cells do not express argininosuccinate synthetase (ASS), and hence cannot synthesize arginine from citrulline. Their growth and proliferation depend on exogenous supply of arginine. Arginine degradation using arginine deiminase (ADI) leads to growth inhibition and eventually cell death while normal cell which express ASS can survive. This notion has been translated into clinical trial. Pegylated ADI (ADI-PEG20) has shown antitumor activity in melanoma. However, the sensitivity to ADI is different among ASS(-) melanoma cells. We have investigated and reviewed the signaling pathways which are affected by arginine deprivation and their consequences which lead to cell death. We have found that arginine deprivation inhibits mTOR signaling but leads to activation of MEK and ERK with no changes in BRAF. These changes most likely lead to autophagy, a possible mechanism to survive by recycling intracellular arginine. However apoptosis does occur which can be both caspase dependent or independent In order to increase the therapeutic efficacy of this form of treatment, one should consider adding other agent(s) which can drive the cells toward apoptosis or inhibit the autophagic process.

Targeted cellular metabolism for cancer chemotherapy with recombinant arginine-degrading enzymes

It has been shown that a subset of human cancers, notably, melanoma and hepatocellular carcinoma (HCC) are auxotrophic for arginine (Arg), because they do not express argininosuccinate synthetase (ASS), the rate-limiting enzyme for the biosynthesis of arginine from citrulline. These ASS-negative cancer cells require Arg from extracellular sources for survival. When they are exposed to recombinant Arg-degrading enzymes, e.g. arginine deiminase (ADI) or arginase, they die because of Arg starvation; whereas normal cells which express ASS are able to survive. A pegylated ADI (ADI-PEG20) has been developed for clinical trials for advanced melanoma and HCC; and favorable results have been obtained. ADI-PEG20 treatment induces autophagy in auxotrophic cancer cells leading to cell death. Clinical studies in melanoma patients show that re-expression of ASS is associated with ADI-PEG20 resistance. ADI-PEG20 treatment down-regulates the expression of HIF-1α but up-regulates c-Myc in culture melanoma cells. Induction of ASS by ADI-PEG20 involves positive regulators c-Myc and Sp4 and negative regulator HIF1α. Since both HIF-1α and c-Myc play important roles in cancer cell energy metabolism, together these results suggest that targeted cancer cell metabolism through modulation of HIF-1α and c-Myc expression may improve the efficacy of ADI-PEG20 in treating Arg auxotrophic tumors.

Enzyme therapy for lysosomal storage disease: principles, practice, and prospects

Over the past three decades, enzyme therapy for lysosomal storage diseases has moved from an academic pursuit to direct delivery of effective clinical care for affected patients and families. This success is based on understanding the complexities of lysosomal biogenesis, lysosomal hydrolase sorting and hydrolytic requirements, and the target sites of pathology of these diseases. This article reviews these concepts and their application to the treatment of affected patients with Gaucher disease, Fabry disease, and mucopolysaccharidosis I. The principles, progress, and practice in these diseases provide prototypes for expansion of enzyme therapy to a growing set of these diseases.

Molecular basis and current strategies of therapeutic arginine depletion for cancer

Renewed interest in the use of therapeutic enzymes combined with an improved knowledge of cancer cell metabolism, has led to the translation of several arginine depletion strategies into early phase clinical trials. Arginine auxotrophic tumors are reliant on extracellular arginine, due to the downregulation of arginosuccinate synthetase or ornithine transcarbamylase-key enzymes for intracellular arginine recycling. Engineered arginine catabolic enzymes such as recombinant human arginase (rh-Arg1-PEG) and arginine deiminase (ADI-PEG) have demonstrated cytotoxicity against arginine auxotrophic tumors. In this review, we discuss the molecular events triggered by extracellular arginine depletion that contribute to tumor cell death.

Long-term therapy with NTBC and tyrosine-restricted diet in a murine model of hereditary tyrosinemia type I

In human patients with hereditary tyrosinemia type I (HT1) a combination therapy of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3 cyclohexane dione (NTBC) and dietary restriction of phenylalanine and tyrosine is currently widely used. We previously reported that the use of NTBC in a murine model of HT1 abolished acute liver failure but did not prevent the development of hepatocellular carcinoma (HCC) in the setting of nonrestricted protein intake. Here we present the results obtained with higher doses of NTBC plus dietary tyrosine restriction on long-term follow up (>2 years). Liver function tests and succinylacetone levels were completely corrected with this regimen and cancer-free survival was improved when compared to historical controls. However, while no HT1 animals had HCC at age 13 months, the incidence was 2/16 (13%) at age 18 months and 1/6 (17%) after 24 months. Thus, even the most stringent therapy could not prevent the emergence of HCC in the mouse model of HT1, even when initiated prenatally.

Immune response to enzyme replacement therapies in lysosomal storage diseases and the role of immune tolerance induction

The US Food and Drug Administration (FDA) and National Organization for Rare Disease (NORD) convened a public workshop titled "Immune Responses to Enzyme Replacement Therapies: Role of Immune Tolerance Induction" to discuss the impact of anti-drug antibodies (ADAs) on efficacy and safety of enzyme replacement therapies (ERTs) intended to treat patients with lysosomal storage diseases (LSDs). Participants in the workshop included FDA staff, clinicians, scientists, patients, industry, and advocacy group representatives. The risks and benefits of implementing prophylactic immune tolerance induction (ITI) to reduce the potential clinical impact of antibody development were considered. Complications due to immune responses to ERT are being recognized with increasing experience and lengths of exposure to ERTs to treat several LSDs. Strategies to mitigate immune responses and to optimize therapies are needed. Discussions during the workshop resulted in the identification of knowledge gaps and future areas of research, as well as the following proposals from the participants: (1) systematic collection of longitudinal data on immunogenicity to better understand the impact of ADAs on long-term clinical outcomes; (2) development of disease-specific biomarkers and outcome measures to assess the effect of ADAs and ITI on efficacy and safety; (3) development of consistent approaches to ADA assays to allow comparisons of immunogenicity data across different products and disease groups, and to expedite reporting of results; (4) establishment of a system to widely share data on antibody titers following treatment with ERTs; (5) identification of components of the protein that are immunogenic so that triggers and components of the immune responses can be targeted in ITI; and (6) consideration of early ITI in patients who are at risk of developing clinically relevant ADA that have been demonstrated to worsen treatment outcomes.

Arginine deprivation in cancer therapy

PURPOSE OF REVIEW

There has been an increased and renewed interest in metabolic therapy for cancer, particularly Arg deprivation. The purpose of this review is to highlight recent studies that focus on Arg-dependent malignancies with Arginine (Arg)-degrading enzymes, including arginase and Arg deiminase.

RECENT FINDINGS

New developments in this area include understanding of the role of most significantly downregulated gene regulating amino acid metabolism, argininosuccinate synthetase and its expression and therapeutic relevance in different tumors. Recent studies have also shed light on the mechanism of tumor cell death with Arg deprivation, with arginase and pegylated Arg deiminase. Particularly important is understanding the mechanism of resistance that cancers develop after such drug exposure. Finally, recent clinical trials have been performed or are ongoing to use Arg deprivation as treatment for advanced malignancies.

SUMMARY

Arg deprivation is a promising approach for the treatment of various malignancies.

Intracerebral injection of sulfamidase delays neuropathology in murine MPS-IIIA

Lysosomal storage disorders (LSD) are rare inherited metabolic diseases in which genetic alterations affect lysosomal proteins. Mucopolysaccharidosis type IIIA (MPS-IIIA) is an LSD characterized by reduced activity of sulfamidase (heparan-N-sulfatase, EC3.10.1.1), which degrades the sulfated glycosoaminoglycan heparan sulfate. The central nervous system (CNS) is the main site of pathology in MPS-IIIA, resulting in reduced neurological function and neurocognitive decline. Neuropathological changes include lysosomal vacuolation of heparan sulfate and lipids in neurons, glia, and perivascular cells and the formation of axonal spheroids and ectopic dendrites. At present there is no effective treatment for the CNS effects of LSD as enzyme administered intravenously cannot cross the blood-brain barrier. We have previously established and characterized a mouse model of MPS-IIIA, and in the present study, we injected recombinant human sulfamidase directly into the brain at 6, 12 or 18 weeks of age. Treatment reduced vacuolation and gliosis and delayed the onset of ubiquitin-positive neurodegenerative changes in widespread areas of MPS-IIIA brain, assessed at 24 weeks of age. However, ubiquitin-positive axonal spheroids already detectable by 6 weeks of age were unaffected by treatment at any age, suggesting their irreversibility and thus indicating the importance of early detection of MPS-IIIA and instigation of therapy.

Recombinant human sulphamidase: expression, amplification, purification and characterization

Mucopolysaccharidosis type IIIA (MPS IIIA, Sanfilippo A syndrome) is a lysosomal storage disease that causes a profound neurological deterioration. The disorder is caused by a deficiency of the lysosomal enzyme sulphamidase which is a requisite for the degradation of heparan sulphate. To facilitate the development of enzyme-replacement strategies for MPS IIIA patients, we have constructed a high-level expression system for recombinant human sulphamidase in Chinese hamster ovary (CHO) cells. An expression construct containing a methotrexate-resistant dihydrofolate reductase (DHFR) gene allowed amplification of expression levels from less than 1 mg of sulphamidase per litre of culture medium to approx. 15 mg/l. Unlike many cell lines made by gene amplification in DHFR-deficient CHO cells, and utilizing the normal DHFR gene, these cell lines appeared to be stable in the absence of selective pressure. Recombinant human sulphamidase was purified from unamplified and amplified cell lines. The native enzyme was found to be a dimer of 115 kDa. Denaturing and reducing SDS/PAGE revealed a subunit size of 62 kDa. Kinetic analysis demonstrated that the recombinant enzyme had broadly similar kinetic characteristics to sulphamidase purified from liver. Recombinant human sulphamidase was able to correct the storage phenotype of MPS IIIA fibroblasts after endocytosis via the mannose-6-phosphate receptor.

Immune response to enzyme replacement therapy in lysosomal storage disorder patients and animal models

The lysosomal storage disorders (LSD) are a group of severe multiple pathology disorders characterized by enzyme deficiencies which cause the lysosomal accumulation of undegraded or partially degraded macromolecules. Enzyme replacement therapy (ERT) has been developed as a therapy for LSD patients. However, immune responses to ERT have been reported in some individuals from LSD animal model and LSD human patient studies. Antibodies can have adverse effects during ERT, which include hypersensitivity/anaphylactic reactions, enzyme inactivation, altered targeting, and increased enzyme turnover. The monitoring of antibody production during replacement therapy is an important consideration for patient management, as high-titer antibodies can affect the safety and efficacy of the therapy.

Effect of cisternal sulfamidase delivery in MPS IIIA Huntaway dogs--a proof of principle study

Mucopolysaccharidosis type IIIA (MPS IIIA) results from lack of functional sulfamidase (SGSH), a lysosomal enzyme. Its substrate, heparan sulfate, and other secondarily-stored compounds subsequently accumulate primarily within the central nervous system (CNS), resulting in progressive mental deterioration and early death. Presently there is no treatment. As a potential therapeutic strategy, recombinant human sulfamidase (rhSGSH) was administered into the CSF (via the cerebellomedullary cistern) of three adult MPS IIIA dogs either twice with a 4 day interval, or weekly for up to 4 weeks. The dogs were euthanased 24 h post-injection along with one untreated unaffected and two MPS IIIA controls. We have examined the three dimensional pattern of distribution of enzyme in the CNS and its ability to reduce primary substrate storage. High concentrations of rhSGSH protein, with up to 39-fold normal enzyme activity levels were detected within widespread areas of the CNS. RhSGSH protein was also detectable by immunohistochemistry in neurons and glia in all three enzyme-treated dogs. In both weekly-treated dogs, relative levels of a heparan sulfate-derived disaccharide, measured using tandem mass spectrometry, were lower in many brain regions when compared to untreated MPS IIIA controls. A moderately severe meningitis was also present as well as antibodies to rhSGSH in CSF/plasma. These findings demonstrate proof of principle that MPS IIIA can be treated by intracisternal enzyme replacement warranting further experiments in animals tolerant to rhSGSH. This enzyme delivery method may represent a means of treating neuropathology in MPS IIIA and other lysosomal storage disorders affecting the CNS.

Enzyme Replacement Therapy: A Review and Its Role in Treating Lysosomal Storage Diseases

Lysosomal storage diseases (LSDs) are a heterogeneous group of genetic disorders caused by defects in lysosomal function that lead to multiorgan system damage. Due to wide clinical variability within even a single disorder, making a diagnosis can be difficult and identification may be delayed. Enzyme replacement therapy (ERT) was first approved as a treatment for the LSD Gaucher disease in 1991. ERT development for other LSDs followed, and ERT is currently approved for eight LSDs in the United States. ERT may help slow progression and improve clinical symptoms, but it cannot affect neurologic features due to its inability to cross the blood-brain barrier. Additional therapies for LSDs that have been investigated include stem cell transplants, gene therapy, small molecule approaches, and genome editing. Although newer approaches seem promising, there is no "cure" for any LSDs, and management remains focused on early diagnosis and treatment. [Pediatr Ann. 2018;47(5):e191-e197.].