Towards metabolic sink therapy for mut methylmalonic acidaemia: Correctionof methylmalonyl-CoA mutase deficiency in T lymphocytes from a mut methylmalonic acidaemia child by retroviral-mediated gene transfer

The pathology associated with mut methylmalonic acidaemia (MMA) is caused b y systemic accumulation of methylmalonate. Therefore, removal of methylmalo nate from the circulation of affected individuals by an engineered metaboli c system is proposed as a potential treatment. The haematopoietic cell is a potential site for such a metabolic system because of its direct contact w ith the accumulated metabolite and the demonstrated safety and ease in util izing this cell. In this study, we assessed the feasibility of developing a haematopoietic cell-based methylmalonate sink by analysing propionate/meth ylmalonate metabolism in a variety of haematopoietic cells. The results sho w that propionate metabolism and methylmalonyl-CoA mutase (MCM) activity ar e intact in primary T cells, EBV-B cells, and CD34(+) haematopoietic stem c ell-derived granulocytes, whereas they are defective in those from a mut MM A child. Moreover, normal T and EBV-B cells clear methylmalonate from the m edium at a significant rate. Transduction of MCM-deficient T cells with a r ecombinant retrovirus encoding the human MCM cDNA results in correction of propionate metabolism. These results establish the basis for developing hae matopoietic cell-based metabolic sink therapy for mut MMA by T lymphocyte/h aematopoietic stem cell-directed gene transfer.