Allogeneic hematopoietic stem cell transplantation in leukocyte adhesion deficiency type I and III.

Type I and III leukocyte adhesion deficiencies (LADs) are primary immunodeficiency disorders resulting in early death due to infections and additional bleeding tendency in LAD-III. The curative treatment of LAD-I and LAD-III is allogeneic hematopoietic stem cell transplantation (allo-HSCT). In this retrospective multicenter study, data were collected using the European Society for Blood and Marrow Transplantation registry; we analyzed data from 84 LAD patients from 33 centers, all receiving an allo-HSCT from 2007 to 2017. The 3-year overall survival estimate (95% confidence interval [CI]) was 83% (74-92) for the entire cohort: 84% (75-94) and 75% (50-100) for LAD-I and LAD-III, respectively. We observed cumulative incidences (95% CI) of graft failure (GF) at 3 years of 17% (9%-26%) and grade II to IV acute graft-versus-host disease (aGVHD) at 100 days of 24% (15%-34%). The estimate (95% CI) at 3 years for GF- and GVHD-II to IV-free survival as event-free survival (EFS) was 56% (46-69) for the entire cohort; 58% (46-72) and 56% (23-88) for LAD-I and LAD-III, respectively. Grade II to IV acute GVHD was a relevant risk factor for death (hazard ratio 3.6; 95% CI 1.4-9.1; P = .006). Patients' age at transplant ≥13 months, transplantation from a nonsibling donor, and any serological cytomegalovirus mismatch in donor-recipient pairs were significantly associated with severe acute GVHD and inferior EFS. The choice of busulfan- or treosulfan-based conditioning, type of GVHD prophylaxis, and serotherapy did not impact overall survival, EFS, or aGVHD. An intrinsic inflammatory component of LAD may contribute to inflammatory complications during allo-HSCT, thus providing the rationale for considering anti-inflammatory therapy pretreatment.

Effect of weight and maturation on busulfan clearance in infants and small children undergoing hematopoietic cell transplantation.

Little information is currently available regarding the pharmacokinetics (PK) of busulfan in infants and small children to help guide decisions for safe and efficacious drug therapy. The objective of this study was to develop an algorithm for individualized dosing of i.v. busulfan in infants and children weighing ≤12 kg, that would achieve targeted exposure with the first dose of busulfan. Population PK modeling was conducted using intensive time-concentration data collected through the routine therapeutic drug monitoring of busulfan in 149 patients from 8 centers. Busulfan PK was well described by a 1-compartment base model with linear elimination. The important clinical covariates affecting busulfan PK were actual body weight and age. Based on our model, the predicted clearance of busulfan increases approximately 1.7-fold between 6 weeks to 2 years of life. For infants age <5 months, the model-predicted doses (mg/kg) required to achieve a therapeutic concentration at steady state of 600-900 ng/mL (area under the curve range, 900-1350 µM·min) were much lower compared with standard busulfan doses of 1.1 mg/kg. These results could help guide clinicians and inform better dosing decisions for busulfan in young infants and small children undergoing hematopoietic cell transplantation.

Busulfan conditioning enhances engraftment of hematopoietic donor-derived cells in the brain compared with irradiation.

Hematopoietic stem cell gene therapy for neurological disorders relies on transmigration of donor-derived monocytes to the brain, where they can engraft as microglia and deliver therapeutic proteins. Many mouse studies use whole-body irradiation to investigate brain transmigration pathways, but chemotherapy is generally used clinically. The current evidence for transmigration to the brain after chemotherapy is conflicting. We compared hematopoietic donor cell brain engraftment after bone marrow (BM) transplants in busulfan- or irradiation-conditioned mice. Significantly more donor-derived microglial cells engrafted posttransplant in busulfan-conditioned brain compared with the irradiated, in both the short and long term. Although total Iba-1(+) microglial content was increased in irradiated brain in the short term, it was similar between groups over long-term engraftment. MCP-1, a key regulator of monocyte transmigration, showed long-term elevation in busulfan-conditioned brain, whereas irradiated brains showed long-term elevation of the proinflammatory chemokine interleukin 1α (IL-1α), with increased in situ proliferation of resident microglia, and significant increases in the relative number of amoeboid activated microglia in the brain. This has implications for the choice of conditioning regimen to promote hematopoietic cell brain engraftment and the relevance of irradiation in mouse models of transplantation.

Neuropathology in mouse models of mucopolysaccharidosis type I, IIIA and IIIB.

Mucopolysaccharide diseases (MPS) are caused by deficiency of glycosaminoglycan (GAG) degrading enzymes, leading to GAG accumulation. Neurodegenerative MPS diseases exhibit cognitive decline, behavioural problems and shortened lifespan. We have characterised neuropathological changes in mouse models of MPSI, IIIA and IIIB to provide a better understanding of these events.Wild-type (WT), MPSI, IIIA and IIIB mouse brains were analysed at 4 and 9 months of age. Quantitative immunohistochemistry showed significantly increased lysosomal compartment, GM2 ganglioside storage, neuroinflammation, decreased and mislocalised synaptic vesicle associated membrane protein, (VAMP2), and decreased post-synaptic protein, Homer-1, in layers II/III-VI of the primary motor, somatosensory and parietal cortex. Total heparan sulphate (HS), was significantly elevated, and abnormally N-, 6-O and 2-O sulphated compared to WT, potentially altering HS-dependent cellular functions. Neuroinflammation was confirmed by significantly increased MCP-1, MIP-1α, IL-1α, using cytometric bead arrays. An overall genotype effect was seen in all parameters tested except for synaptophysin staining, neuronal cell number and cortical thickness which were not significantly different from WT. MPSIIIA and IIIB showed significantly more pronounced pathology than MPSI in lysosomal storage, astrocytosis, microgliosis and the percentage of 2-O sulphation of HS. We also observed significant time progression of all genotypes from 4-9 months in lysosomal storage, astrocytosis, microgliosis and synaptic disorganisation but not GM2 gangliosidosis. Individual genotype*time differences were disparate, with significant progression from 4 to 9 months only seen for MPSIIIB with lysosomal storage, MPSI with astrocytocis and MPSIIIA with microgliosis as well as neuronal loss. Transmission electron microscopy of MPS brains revealed dystrophic axons, axonal storage, and extensive lipid and lysosomal storage. These data lend novel insight to MPS neuropathology, suggesting that MPSIIIA and IIIB have more pronounced neuropathology than MPSI, yet all are still progressive, at least in some aspects of neuropathology, from 4-9 months.

Genistein improves neuropathology and corrects behaviour in a mouse model of neurodegenerative metabolic disease.

BACKGROUND: Neurodegenerative metabolic disorders such as mucopolysaccharidosis IIIB (MPSIIIB or Sanfilippo disease) accumulate undegraded substrates in the brain and are often unresponsive to enzyme replacement treatments due to the impermeability of the blood brain barrier to enzyme. MPSIIIB is characterised by behavioural difficulties, cognitive and later motor decline, with death in the second decade of life. Most of these neurodegenerative lysosomal storage diseases lack effective treatments. We recently described significant reductions of accumulated heparan sulphate substrate in liver of a mouse model of MPSIIIB using the tyrosine kinase inhibitor genistein. METHODOLOGY/PRINCIPAL FINDINGS: We report here that high doses of genistein aglycone, given continuously over a 9 month period to MPSIIIB mice, significantly reduce lysosomal storage, heparan sulphate substrate and neuroinflammation in the cerebral cortex and hippocampus, resulting in correction of the behavioural defects observed. Improvements in synaptic vesicle protein expression and secondary storage in the cerebral cortex were also observed. CONCLUSIONS/SIGNIFICANCE: Genistein may prove useful as a substrate reduction agent to delay clinical onset of MPSIIIB and, due to its multimodal action, may provide a treatment adjunct for several other neurodegenerative metabolic diseases.

Abnormal telomere shortening in leucocytes of children with Shwachman-Diamond syndrome.

Haemopoietic dysfunction, ranging from single-lineage cytopenia to severe aplasia and/or myelodysplasia (MDS), is prominent in Shwachman-Diamond syndrome (SDS). To assess haemopoietic stem cell proliferation in SDS, we compared leucocyte telomere length in 12 patients with SDS to that of 41 controls, using an in-gel hybridization technique. SDS patients had an age-adjusted mean telomere length 1.4 kilobase pairs (kbp) shorter than controls (P < 0.0001). Patients with'non-severe' SDS (one- or two-lineage cytopenias; no MDS) had shortened telomeres (-1.4 kbp; P = 0.0004), as did those with 'severe' SDS. We conclude that stem cell hyperproliferation is a feature of SDS from its outset.