AGAINST YERSINIA PESTIS IN MICE

Abstract. A single, subcutaneous, 30-mg dose of either a combination of the Yersinia pestis proteins F11V or a F1-V fusion protein adsorbed to the adjuvant aluminum hydroxide, protected Hsd:ND4 mice for one year against pneumonic plague. The recombinant F11V vaccine provided significant protection as early as day 14 postimmuni-zation. The current Plague Vaccine USP in a single 0.2-ml dose did not provide significant protection in this mouse model. Antibody titers to F1 and V peaked at approximately 5–12 weeks postimmunization and were still detectable one year later. These F1 and V subunit vaccines may offer effective long-term immunity with a reduced dosage schedule when compared with the presently licensed, formalin-killed, whole-cell vaccine. Plague caused by the gram-negative bacterium Yersinia pestis still represents a serious public health threat in various regions of the world, as evidenced by the announcement of a plague outbreak in India in 1994,1, 2 which severely dis-rupted the commerce and the public health systems.3 Even though live and killed vaccines were available for human use to prevent plague, the reactogenicity, long immunization schedule, requirement for frequent boosts, general low ris