Minimum requirement of donor cells to reduce the glycolipid storage following bone marrow transplantation in a murine model of Fabry disease

Restoration of peripheral neuropathy in Fabry mice via intrathecal administration of an adeno-associated virus vector encoding mGLA cDNA

Anderson-Fabry disease (FD) is an X-linked lysosomal storage disorder caused by a pathological variant of the α-galactosidase A (GLA) gene that results in deficient GLA activity. GLA deficiency leads to the accumulation of globotriaosylceramide (Gb3) and lyso-Gb3 in many tissues. A certain number of FD patients have burning pain or acroparesthesia in the feet and hands since childhood. Enzyme replacement therapy (ERT) is available for FD patients. However, ERT does not dramatically improve these FD-related peripheral neuropathic pain. We generated an adeno-associated virus serotype PHP.eB (AAV-PHP.eB) vector encoding mouse GLA cDNA, which was administered to FD mice intrathecally (it) or intravenously (iv). In the it-administered AAV (it-AAV) FD mice, the GLA enzyme activity in the lumbar dorsal root ganglion (DRG) was significantly greater than that in the untreated (NT) FD mice, and the level of activity was similar to that in wild-type (WT) B6 mice. However, in iv-administered AAV (iv-AAV) FD mice, GLA activity in the DRG did not increase compared to that in NT FD mice. Gb3 storage in the DRG of it-AAV FD mice was reduced compared to that in the DRG of NT FD mice. However, compared with NT FD mice, iv-AAV FD mice did not exhibit a significant reduction in the expression of the Gb3 substrate. Compared with WT mice, FD mice were thermally hyposensitive at 52 °C according to the hot plate test. The it-AAV FD mice showed significant recovery from thermal hyposensitivity. However, the iv-AAV FD mice did not exhibit significant improvement in thermal hyposensitivity. These results suggest that the intrathecal delivery of AAV-PHP.eB-mGLA may be a valuable tool for the treatment of FD-related peripheral neuropathic pain.

Usefulness of antibody-drug conjugate as preconditioning for hematopoietic stem cell-targeted gene therapy in wild-type and Fabry disease mouse models

BACKGROUND

Fabry disease (FD) is characterized by deficient activity of α-galactosidase A (GLA). Consequently, globotriaosylceramide (Gb3) accumulates in various organs, causing cardiac, renal, and cerebrovascular damage. Gene therapies for FD have been investigated in humans. Strong conditioning is required for hematopoietic stem cell-targeted gene therapy (HSC-GT). However, strong conditioning leads to various side effects and should be avoided. In this study, we tested antibody-based conditioning for HSC-GT in wild-type and FD model mice.

METHODS

After preconditioning with an antibody-drug conjugate, HSC-GT using a lentiviral vector was performed in wild-type and Fabry model mice. In the wild-type experiment, the EGFP gene was introduced into HSCs and transplanted into preconditioned mice, and donor chimerism and EGFP expression were analyzed. In the FD mouse model, the GLA gene was introduced into HSCs and transplanted into preconditioned Fabry mice. GLA activity and Gb3 accumulation in the organs were analyzed.

RESULTS

In the wild-type mouse experiment, when anti-CD45 antibody-drug conjugate was used, the percentage of donor cells at 6 months was 64.5%, and 69.6% of engrafted donor peripheral blood expressed EGFP. When anti-CD117 antibody-drug conjugate and ATG were used, the percentage of donor cells at 6 months was 80.7%, and 73.4% of engrafted donor peripheral blood expressed EGFP. Although large variations in GLA activity among mice were observed in the FD mouse experiment for both preconditioning regimens, Gb3 was significantly reduced in many organs.

CONCLUSIONS

Antibody-based preconditioning may be an alternative preconditioning strategy for HSC-GT for treating FD.

Lipid-induced lysosomal damage after demyelination corrupts microglia protective function in lysosomal storage disorders

Neuropathic lysosomal storage disorders (LSDs) present with activated pro‐inflammatory microglia. However, anti‐inflammatory treatment failed to improve disease pathology. We characterise the mechanisms underlying microglia activation in Niemann–Pick disease type A (NPA). We establish that an NPA patient and the acid sphingomyelinase knockout (ASMko) mouse model show amoeboid microglia in neurodegeneration‐prone areas. In vivo microglia ablation worsens disease progression in ASMko mice. We demonstrate the coexistence of different microglia phenotypes in ASMko brains that produce cytokines or counteract neuronal death by clearing myelin debris. Overloading microglial lysosomes through myelin debris accumulation and sphingomyelin build‐up induces lysosomal damage and cathepsin B extracellular release by lysosomal exocytosis. Inhibition of cathepsin B prevents neuronal death and behavioural anomalies in ASMko mice. Similar microglia phenotypes occur in a Niemann–Pick disease type C mouse model and patient. Our results show a protective function for microglia in LSDs and how this is corrupted by lipid lysosomal overload. Data indicate cathepsin B as a key molecule mediating neurodegeneration, opening research pathways for therapeutic targeting of LSDs and other demyelinating diseases.

Anti-BlyS antibody reduces the immune reaction against enzyme and enhances the efficacy of enzyme replacement therapy in Fabry disease model mice

Formation of antibodies against a therapeutic enzyme is an important complication during enzyme replacement therapy (ERT) for lysosomal storage diseases. Fabry disease (FD) is caused by a deficiency of alpha-galactosidase (GLA), which results in the accumulation of globotriaosylceramide (GL-3). We have shown immune tolerance induction (ITI) during ERT in FD model mice by using an anti-B lymphocyte stimulator (anti-BlyS) antibody (belimumab). A single dose of the anti-BlyS antibody temporarily lowered the percentage of B cells and IgG antibody titer against recombinant human GLA. Administration of a low maintenance dose of the anti-BlyS antibody suppressed the B cell population and immunotolerance was induced in 20% of mice, but antibody formation could not be prevented. We then increased the maintenance dose of the anti-BlyS antibody and immunotolerance was induced in 50% of mice. Therapeutic enzyme distribution and clearance of GL-3 were also enhanced by a high maintenance dose of the anti-BlyS antibody.

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.

Glycosphingolipid storage in Fabry mice extends beyond globotriaosylceramide and is affected by ABCB1 depletion

Aim:

Fabry disease is caused by α-galactosidase A deficiency leading to accumulation of globotriaosylceramide (Gb₃) in tissues. Clinical manifestations do not appear to correlate with total Gb₃ levels. Studies examining tissue distribution of specific acyl chain species of Gb₃ and upstream glycosphingolipids are lacking.

Material & methods/Results:

Thorough characterization of the Fabry mouse sphingolipid profile by LC-MS revealed unique Gb₃ acyl chain storage profiles. Storage extended beyond Gb₃; all Fabry tissues also accumulated monohexosylceramides. Depletion of ABCB1 had a complex effect on glycosphingolipid storage.

Conclusion:

These data provide insights into how specific sphingolipid species correlate with one another and how these correlations change in the α-galactosidase A-deficient state, potentially leading to the identification of more specific biomarkers of Fabry disease.

Fabry disease is caused by a shortage of the enzyme α-galactosidase A leading to storage of a fat called globotriaosylceramide (Gb₃) in tissues. Disease severity does not appear to correlate directly with total Gb₃. Importantly, Gb₃ is comprised of many highly related but distinct species. We examined levels of Gb₃ species and precursor molecules in Fabry mice. Gb₃ species and storage are unique to each tissue. Furthermore, storage is not limited to Gb₃; precursor fats are also elevated. Detailed analyses of differences in storage between the normal and α-galactosidase A-deficient state may provide a better understanding of the causes of Fabry disease.

Effect of donor chimerism to reduce the level of glycosaminoglycans following bone marrow transplantation in a murine model of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder caused by deficient activity of the iduronate-2-sulfatase. This leads to accumulation of glycosaminoglycans (GAGs) in the lysosomes of various cells. Although it has been proposed that bone marrow transplantation (BMT) may have a beneficial effect for patients with MPS II, the requirement for donor-cell chimerism to reduce GAG levels is unknown. To address this issue, we transplanted various ratios of normal and MPS II bone marrow cells in a mouse model of MPS II and analyzed GAG accumulation in various tissues. Chimerism of whole leukocytes and each lineage of BMT recipients' peripheral blood was similar to infusion ratios. GAGs were significantly reduced in the liver, spleen, and heart of recipients. The level of GAG reduction in these tissues depends on the percentage of normal-cell chimerism. In contrast to these tissues, a reduction in GAGs was not observed in the kidney and brain, even if 100 % donor chimerism was achieved. These observations suggest that a high degree of chimerism is necessary to achieve the maximum effect of BMT, and donor lymphocyte infusion or enzyme replacement therapy might be considered options in cases of low-level chimerism in MPS II patients.

Enzyme augmentation therapy enhances the therapeutic efficacy of bone marrow transplantation in mucopolysaccharidosis type II mice

Before the availability of an enzyme replacement therapy (ERT) for mucopolysaccharidosis type II (MPS II), patients were treated by bone marrow transplantation (BMT). However, the effectiveness of BMT for MPS II was equivocal, particularly at addressing the CNS manifestations. To study this further, we subjected a murine model of MPS II to BMT and evaluated the effect at correcting the biochemical and pathological aberrations in the viscera and CNS. Our results indicated that BMT reduced the accumulation of glycosaminoglycans (GAGs) in a variety of visceral organs, but not in the CNS. With the availability of an approved ERT for MPS II, we investigated and compared the relative merits of the two strategies either as a mono or combination therapy. We showed that the combination of BMT and ERT was additive at reducing tissue levels of GAGs in the heart, kidney and lung. Moreover, ERT conferred greater efficacy if the immunological response against the infused recombinant enzyme was low. Finally, we showed that pathologic GAGs might potentially represent a sensitive biomarker to monitor the therapeutic efficacy of therapies for MPS II.