Testing the Capacity to Over-Stabilize Viruses by Engineering Mutations into the Capsid of Bacteriophage ɸX174

An effective virus must successfully attach to a receptor on a host cell and inject its genetic material into the cell so that new viruses can be produced. Its ability to infect the host cell is highly dependent on both the binding capability of its capsid proteins as well their ability to modify their conformation to facilitate injection. Mutations in the genes encoding the capsid proteins can stabilize (or destabilize) two aspects of the virus – the folding of the capsid protein itself, thus its flexibility, and the attachment to the host receptor. Single stabilizing mutations in the protein capsid have been shown to increase the fitness of the virus. However, it is possible there is a limit to the extent that protein stability benefits a virus.  Capsid proteins that are too stable could have reduced flexibility and binding capacity, thereby reducing viral fitness. The bacteriophage ɸX174 has been successfully used as a model to predict the evolutionary patterns and behaviors of viruses through experimental manipulation of its genome. The Wichman-Miller Lab has successfully engineered single mutations predicted to be stabilizing into the major spike protein G of the phage’s capsid. The aim of this project is to combine these stabilizing mutations to create double, triple, etc., mutants, and assess their stability and capability to successfully infect a bacterial host. If overstabilization of a virus’s capsid proteins can predictably attenuate the virus, the technique may provide a new avenue for engineered vaccine development.

Bacteriophage ΦX174

In addition to its lack of pathogenicity and ability to form large populations, this bacteriophage has a small genome that can be easily manipulated, making it an efficient virus model.