Asymmetrical flow field-flow fractionation in purification of an enveloped bacteriophage ϕ6

Basic and applied virus research requires specimens that are purified to high homogeneity. Thus, there is much interest in the efficient production and purification of viruses and their subassemblies. Advances in the production steps have shifted the bottle neck of the process to the purification. Nonetheless, the development of purification techniques for different viruses is challenging due to the complex biological nature of the infected cell cultures as well as the biophysical and -chemical differences in the virus particles. We used bacteriophage ϕ6 as a model virus in our attempts to provide a new purification method for enveloped viruses. We compared asymmetrical flow field-flow fractionation (AF4)-based virus purification method to the well-established ultracentrifugation-based purification of ϕ6. In addition, binding of ϕ6 virions to monolithic anion exchange columns was tested to evaluate their applicability in concentrating the AF4 purified specimens. Our results show that AF4 enables one-hour purification of infectious enveloped viruses with specific infectivity of ~1 × 10¹³ PFU/mg of protein and ~65-95% yields. Obtained purity was comparable with that obtained using ultracentrifugation, but the yields from AF4 purification were 2-3-fold higher. Importantly, high quality virus preparations could be obtained directly from crude cell lysates. Furthermore, when used in combination with in-line light scattering detectors, AF4 purification could be coupled to simultaneous quality control of obtained virus specimen.