Abstract

Haemophilia B, a deficiency in clotting factor IX (FIX), occurs in about 1 in 25.000 males. Of these patients, approximately 40% are characterized as having severe haemophilia (FIX below 1% of normal). Although the use of plasma-derived or rFIX has extended the lifespan of these patients, they remain afflicted by a variety of sequelae of the disease. Interestingly, a relatively small increase in the levels of FIX results in a dramatic increase in the quality of life, requiring rFIX substitution only prior to dental and surgical procedures. This latter trait of the disease suggests that gene therapy only needs to achieve modest expression and makes this disease a prime candidate for proof-of-concept of gene therapy. Current protocols for gene therapy entail the risk of malignant transformation. In addition the viral vectors may cause substantial pathology. Hence, the field requires the development of inherently safe gene therapy. Recently, developed protocols have been developed to transduce peripheral blood cells with high efficiency using RNA as a vector. These protocols in which the inherently safe RNA-based gene therapy approach will be validated and implemented for haemophilia B will provide in turn providing important proof-of concept for this type of therapy for more prevalent diseases but requires optimization of this strategy, probably by enhancing RNA stability using artificial nucleotides and modified UTRs, enhanced production of protein by codon usage optimization and the use of multi-cistronic constructs, and enhanced secretion of the protein employing target cell-tailored secretion signals.

Keywords: clotting factor IX, DNA Transfection, GFP expression, RNA stability, X-linked recessive disorder