Rapid, seamless generation of recombinant poxviruses using host-range and visual selection

Vaccinia virus (VACV) was instrumental in eradicating variola virus (VARV), the causative agent of smallpox, from nature. Since this first use as a vaccine, VACV has been developed as a vector for therapeutic vaccines and as an oncolytic virus. These applications take advantage of VACVs easily manipulated genetics and broad host range as an outstanding platform to generate recombinant therapeutics. Several methods have been developed to generate recombinant VACV, including marker selection methods and transient dominant selection. Here, we present a refinement of a host-range selection method coupled with visual identification. Our method takes advantage of selective pressure generated by the host antiviral protein kinase R (PKR) coupled with a fluorescent fusion gene expressing mCherry-tagged E3L, one of two VACV PKR antagonists. This method permits rapid, seamless generation of rVACV in a variety of cell types.