Plague is still an endemic disease in different regions of the world. Increasing 
reports of incidence, the discovery of antibiotic resistance strains, and 
concern about a potential use of the causative bacteria Yersinia pestis as an 
agent of biological warfare have highlighted the need for a safe, efficacious, 
and rapidly producible vaccine. The use of F1 and V antigens and the derived 
protein fusion F1-V has shown great potential as a protective vaccine in animal 
studies. Plants have been extensively studied for the production of 
pharmaceutical proteins as an inexpensive and scalable alternative to common 
expression systems. In the current study the recombinant plague antigens F1, V, 
and fusion protein F1-V were produced by transient expression in Nicotiana 
benthamiana by using a deconstructed tobacco mosaic virus-based system that 
allowed very rapid and extremely high levels of expression. All of the 
plant-derived purified antigens, administered s.c. to guinea pigs, generated 
systemic immune responses and provided protection against an aerosol challenge 
of virulent Y. pestis.