Two new capture options for improved purification of large mRNA
P. Gagnon, B. Goričar, Š. Peršič, U. Černigoj, A. Štrancar
Cell & Gene Therapy Insights 2020; 6(7), 1035–1046
One of the barriers to development of industrial purification platforms for large mRNA has been an inadequate selection of high-performing capture-purification tools. Hybridization-affinity uses a polythymidine (Oligo dT) ligand to base-pair with the polyadenine tail of mRNA. It can be used for capture but it cannot discriminate dsRNA (double-stranded) from ssRNA (single-stranded) and it supports only brief cleaning with 100 mM sodium hydroxide. Traditional anion exchangers elute only mRNA smaller than about 500 bases unless the columns are heated to 50–70°C. Hydrophobic interaction chromatography (HIC) and reverse phase chromatography (RPC) separate ssRNA from dsRNA and short transcripts, but their sensitivity to fouling by proteins and aggregates makes them better suited for polishing than for capture. Better capture options are needed to meet the needs of large clinical trials, scale-up, and manufacture of vaccines. Beyond that, a new spectrum of gene therapy treatments await. This article introduces two new capture options that both eliminate dsRNA, DNA, and proteins in a wash step, then provide high-resolution polishing of ssRNA in an elution gradient at ambient temperature. One represents a new class of anion exchangers. The other exploits hydrogen bonding. Both support prolonged exposure to 1 M sodium hydroxide. Easy transition to either HIC or RPC provides high-resolution orthogonal polishing.