Abstract : The objective of this project is to develop strategies which will allow the use of recombinant mutant pokeweed antiviral protein (PAP) as a potential countermeasure against biological warfare attempts employing pathogenic viruses. In order to increase the therapeutic index of the naturally occurring PAP, recombinant PAP mutants with superior antiviral activity and low toxicity will be constructed. The recombinant PAP mutants will be designed using the state-of-the-art technologies including X-ray crystallography, computer modeling, rational protein design and protein engineering.