LcrV and V10 plague vaccines confer protection against pneumonic plague in guinea pigs. Hartley guinea pigs (cohorts of eight animals) were immunized by i.m. injection with 50 μg of rV10, rLcrV, or rF1 adsorbed to 25% Alhydrogel. Immunization occurred on days 0 and 21. A: Antibody responses to the three subunit vaccines were determined by ELISA. B: Mock-immunized (PBS) and rLcrV-, rF1-, and rV10-vaccinated guinea pigs (cohorts of eight animals) were challenged 42 days after the first vaccine administration via intranasal (i.n.) instillation of 250 MLD of Y. pestis CO92 (250,000 CFU). Animals were monitored for disease progression and survival for 14 days. Specific antibody responses were compared in guinea pigs immunized with rLcrV (C) and rV10 (D) using immune reactivity to overlapping 15- to 17-mer peptides spanning the full LcrV antigen via ELISA measurements. The box indicates amino acid residues that were deleted during the construction of rV10.