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Title: Improved lentiviral vectors for haematopoietic stem cell gene therapy of Mucopolysaccaridosis type IIIA
Author: Sergijenko, Ana
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2012
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Mucopolysaccharidosis type IIIA (MPS IIIA) is caused by mutations in the N-sulphoglucosamine sulphohydrolase (SGSH) gene, leading to cellular accumulation of heparan sulphate and progressive neurodegeneration in patients. One of the proposed treatment methods is haematopoietic stem cell (HSC) gene therapy, which should result in an excess of SGSH produced in the peripheral organs and brain. The pre-clinical feasibility of this approach was demonstrated by our group in a mouse model of MPS IIIA. However, the overall efficiency of this method was limited and a number of approaches to solving these issues were addressed in this project in order to bring this therapy closer to clinical application. Our first aim was to optimise transduction of HSCs using cytokines, bovine serum albumin (BSA), and chemicals, such as MG132, genistein and valproic acid. Addition of BSA with cytokines improved cell viability, addition of MG132/ BSA/ cytokines improved transduction, but also caused cellular toxicity, while addition of genistein was inefficient. Addition of valproic acid with cytokines resulted in increased number of colony forming units. Next, we generated clinically applicable third generation pCCL lentiviral vector backbones with the eGFP reporter gene driven by one of ubiquitous hPGK or myeloid specific hCD11b and hCD18 internal human promoters, and optimised production of lentiviral vectors to increase titre and reduce production cost. These lentiviral vectors were used to transduce lineage depleted HSCs and transplanted into WT mice. Full chimerism and over 80% transduction were achieved with an average of 5 vector copy numbers/ cell. The hCD11b promoter resulted in the highest eGFP expression in monocytes and B cells in blood, but was weaker than the hPGK in T cells. The hCD18 promoter was more monocyte-specific but weak. Significant numbers of GFP-positive microglial cells were present in the brain from all groups, with an average of 25% transduced CD11b-positive cells in perfused mice. We subsequently codon-optimised (CO) the SGSH gene significantly improving enzyme activity, and transduced lineage depleted WT cells with one of hCD18.SGSH-CO, hCD11b.SGSH-CO, or hPGK.SGSH-CO lentiviral vectors, or MPS IIIA cells with either hCD11b.SGSH-CO or hPGK.SGSH-CO lentiviral vectors. These transduced cells were transplanted into MPS IIIA mice and outcomes were measured 6 months later. Only treatment with the hCD11b.SGSH-CO-LV transduced WT or MPS IIIA HSCs corrected abnormal behaviour of MPS IIIA mice. However, all treatments resulted in complete GAG storage clearance in the periphery and brain, and significantly elevated enzyme activity in the brain, liver and spleen to 7-11%, 60-75%, and 170-250% of WT enzyme activity respectively. A fine threshold of over 8.6% brain enzyme activity appeared to be required for behavioural correction in MPS IIIA mice. Further assessment of treated mice for the amount of secondary storage, HS sulphation patterning, neuroinflammation and longevity are still required for complete therapeutic assessment. However, it appears that neurological correction of the MPS IIIA mouse using MPS IIIA cells is feasible using a clinically-relevant pCCL vector with the hCD11b promoter and the codon-optimised SGSH gene.
Supervisor: Wilkinson, Fiona; Bigger, Brian; Wynn, Robert Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Mucopolysaccharidosis ; haematopoietic stem cell ; gene therapy ; transplantation