Figure 6. The soluble monomeric F1 mutant protein elicits robust antibody titers and provides complete protection in a mouse model of pneumonic plague.
The immunogenicity and protective efficacy of F1mut-V and other plague immunogens were evaluated in a mouse model. (A) Balb/c mice, twelve per group, were vaccinated with various plague antigens adjuvanted with alhydrogel. (B) Immunization scheme. (C) Antigen-specific antibody (IgG) titers were determined by ELISA, using purified V (I), F1mut2 (II), or YscF35/67 (III) as the coating antigen. No significant cross-reactivity was observed between the antibodies produced against one plague antigen versus a different plague antigen that was coated on the ELISA plate. Error bars represent S.D. “***” denotes p<0.001 (ANOVA). (D) Survival of immunized mice against intranasal challenge with 90 LD50 of Y. pestis CO92. The survived mice were re-challenged with 9,800 LD50 at day-48 post-first challenge. See Materials and Methods for additional details. The animal mortality data was analyzed by Kaplan Meier's survival estimates and a p value of ≤0.05 was considered significant.