Phototracking Vaccinia Virus Transport Reveals Dynamics of Cytoplasmic Dispersal and a Requirement for A36R and F12L for Exit from the Site of Wrapping.

The microtubule cytoskeleton is a primary organizer of viral infections for delivering virus particles to their sites of replication, establishing and maintaining subcellular compartments where distinct steps of viral morphogenesis take place, and ultimately dispersing viral progeny. One of the best characterized examples of virus motility is the anterograde transport of the wrapped virus form of vaccinia virus (VACV) from the trans-Golgi network (TGN) to the cell periphery by kinesin-1. Yet many aspects of this transport event are elusive due to the speed of motility and the challenges of imaging this stage at high resolution over extended time periods. We have established a novel imaging technology to track virus transport that uses photoconvertible fluorescent recombinant viruses to track subsets of virus particles from their site of origin and determine their destination. Here we image virus exit from the TGN and their rate of egress to the cell periphery. We demonstrate a role for kinesin-1 engagement in regulating virus exit from the TGN by removing A36 and F12 function, critical viral mediators of kinesin-1 recruitment to virus particles. Phototracking viral particles and components during infection is a powerful new imaging approach to elucidate mechanisms of virus replication.