Recovery in aqueous two-phase systems of nanoparticulates applied as surrogate mimics for viral gene therapy vectors

The partition behaviour of nanoparticulate inclusion bodies (IBs) in various states of purity were evaluated as surrogate mimics for adenovirus and retrovirus products in method scouting experiments with aqueous two-phase systems (ATPSs). Such systems are proposed for effective, high capacity downstream processing (DSP) of viral gene therapy vectors. Studies with mimics provided simple descriptions of particle partition which may benefit the field of vector DSP, where experimental material is rarely available for research and development in quantities and concentrations representative of clinical manufacture. Polyethylene glycol (PEG)–salt and PEG–dextran ATPSs were screened in respect of the partition recovery of IBs from crude feedstocks. Select candidate systems were similarly evaluated with limited preparations of adenovirus and retrovirus with respect to fractional recoveries of infectivity and particle number. Maintenance of the former was good, whilst comparison of the latter with quantitation of unwashed and washed IBs indicated poor utilisation of the inherent high capacities of ATPSs in viral experiments. This is discussed in the context of the volumetric throughput and capacities reported in the literature for the recovery of infective viruses in ultracentrifugation and chromatographic processes.