Fusion of RVG or gh625 to iduronate-2-sulfatase for the treatment of mucopolysaccharidosis type II

Mucopolysaccharidosis type II (MPSII) is a lysosomal storage disease caused by a mutation in the IDS gene, resulting in deficiency of the enzyme iduronate-2-sulfatase (IDS) causing heparan sulfate (HS) and dermatan sulfate (DS) accumulation in all cells. This leads to skeletal and cardiorespiratory disease with severe neurodegeneration in two thirds of sufferers. Enzyme replacement therapy is ineffective at treating neurological disease, as intravenously-delivered IDS is unable to cross the blood-brain barrier (BBB). Haematopoietic stem cell transplant is also unsuccessful, presumably due to insufficient IDS enzyme production from transplanted cells engrafting in the brain. We used two different peptide sequences (RVG and gh625), both previously published as BBB-crossing peptides, fused to IDS and delivered via haematopoietic stem cell gene therapy (HSCGT). HSCGT with LV.IDS.RVG and LV.IDS.gh625 was compared to LV.IDS.ApoEII and LV.IDS in MPSII mice at 6-months post-transplant. Levels of IDS enzyme activity in the brain and peripheral tissues were lower in LV.IDS.RVG and LV.IDS.gh625 treated mice than in LV.IDS.ApoEII and LV.IDS treated mice, despite comparable vector copy numbers. Microgliosis, astrocytosis and lysosomal swelling were partially normalised in MPSII mice treated with LV.IDS.RVG and LV.IDS.gh625. Skeletal thickening was normalised by both treatments to wild-type levels. Although reductions in skeletal abnormalities and neuropathology are encouraging, given the low levels of enzyme activity compared to control tissue from LV.IDS and LV.IDS.ApoEII transplanted mice, the RVG and gh625 peptides are unlikely to be ideal candidates for HSCGT in MPSII, and are inferior to the ApoEII peptide that we have previously demonstrated to be more effective at correcting MPSII disease than IDS alone

An improved AAV vector for neurological correction of the mouse model of Mucopolysaccharidosis IIIA

Patients with the lysosomal storage disease mucopolysaccharidosis IIIA (MPSIIIA) lack the lysosomal enzyme N-sulfoglucosamine sulfohydrolase (SGSH), one of the many enzymes involved in degradation of heparan sulphate. Build-up of undegraded heparan sulphate results in severe progressive neurodegeneration for which there is currently no treatment. Experimental gene therapies based on gene addition are currently being explored. Following pre-clinical evaluation in MPSIIIA mice, an AAVrh10 vector designed to deliver SGSH and sulfatase modifying factor 1 (SAF301) was trialled in four MPSIIIA patients showing good tolerance and absence of adverse events with some improvements in neurocognitive measures. Here we aimed to further improve SAF301 by removing sulfatase modifying factor 1 (SUMF1) and assess if expression of this gene is needed to increase the SGSH enzyme activity (SAF301b). Secondly, we exchanged the murine phosphoglycerate kinase (PGK) promotor with a chicken beta actin/CMV composite (CAG) promotor (SAF302) to see if we could further boost SGSH expression levels. The three different vectors were administered to MPSIIIA mice via intracranial injection and SGSH expression levels were compared 4 -weeks post-treatment. Removal of SUMF1 resulted in marginal reductions in enzyme activity. However, promotor exchange significantly increased the amount of SGSH expressed in the brain leading to superior therapeutic correction with SAF302. Biodistribution of SAF302 was further assessed using GFP (SAF302GFP), indicating that vector spread was limited to the area around the injection tract. Further modification of the injection strategy to a single depth with higher injection volume increased vector distribution leading to more widespread GFP distribution and sustained expression, suggesting this approach should be adopted in future trials

Morphological adaptation of a planktonic diatom to growth in Antarctic sea ice.

Chaetoceros dichaeta Ehrenberg is one of the most important planktonic diatom species in the Southern Ocean, making a significant contribution to the total biomass in the region. Our observations on both field and culture material have revealed the existence of a specialized form of C. dichaeta adapted to living in sea ice. This sea ice form differs from the planktonic form by the shape and orientation of the setae and the aperture length between sibling cells. Thus, the diameter of the chain is equivalent to the apical axes of the cells and is accompanied by a two order of magnitude decrease in minimal space requirement. Here, we report for the first time on the extraordinary overwintering strategy of a planktonic diatom in sea ice facilitated by its rapid morphological adaptation to changing environmental conditions. This morphological plasticity enables it to thrive in the confined space of the sea ice brine matrix and retain its numerical dominance in recurrent growing seasons and has likely evolved to optimally exploit the dynamic ecosystem of the seasonally ice-covered seas of the Southern Ocean