New viral vectors for Morquio syndrome type A gene therapy

Morquio syndrome type A disease is produced by the deficiency of the lysosomal enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS). In an approaching of treating this disease through gene therapy, we have reported the use of adenoassociated virus (AAV) vectors as tools to mediate the gene delivery both in-vitro and in-vivo, and to improve vector affinity to bone. In addition, it was observed that SUMF1 co-expression, by using separated GALNS and SUMF1 vectors, significantly increased intra- and extracellular enzyme activity. As a continuation, in this study we evaluated a new set of AAV vectors carrying both GALNS and SUMF1 cDNA into the same vector by using internal ribosome entry site (IRES), eitherviral (EMCV) or human (NRF). Furthermore, lentiviral vectors carrying GALNS or SUMF1 cDNA were also evaluated. All vectors were assessed by using HEK293 cells and Morquio A human skin fibroblasts. The higher enzyme activity levels with AAV vectors were obtained with SUMF1-IRES-GALNS vectors carrying either EMCV or NRF IRES, in comparison with the levels observed with AAV-GALNS:AAV-SUMF1 co-transduction. GALNS transduction in HEK293 cells mediated by the lentiviral vector allowed an up to 100- and 40-fold increment in comparison to the levels observed with the AAV-GALNS and AAV-GALNS:AAV-SUMF1 co-transduction, respectively. In cultured fibroblasts from Morquio syndrome type A patients, lentiviral vectors allowed higher enzyme activity levels than those observed with AAV vectors with or without the use of IRES sequences. These results show the potential use of lentivirus vectors for gene therapy for Morquio syndrome type A, although further studies about the issue of insertional mutagenesis should be performed.