Virus morphogenesis in the cell: methods and observations.

Viruses carry out many of their activities inside cells, where they synthesise proteins that are not incorporated into viral particles. Some of these proteins trigger signals to kidnap cell organelles and factors which will form a new macro-structure, the virus factory, that acts as a physical scaffold for viral replication and assembly. We are only beginning to envisage the extraordinary complexity of these interactions, whose characterisation is a clear experimental challenge for which we now have powerful tools. Conventional study of infection kinetics using virology, biochemistry and cell biology methods can be followed by genome-scale screening and global proteomics. These are important new technologies with which we can identify the cell factors used by viruses at different stages in their life cycle. Light microscopy, electron microscopy and electron tomography, together with labelling methods for molecular mapping in situ, show immature viral intermediates, mature virions and recruited cell elements in their natural environment. This chapter describes how these methods are being used to understand the cell biology of viral morphogenesis and suggests what they might achieve in the near future.