Evaluation of quantitative anti-F1 IgG and anti-V IgG ELISAs for use as an in vitro-based potency assay of plague vaccine in mice.

Quantitative anti-F1 and anti-V IgG enzyme-linked immunosorbent assays (ELISAs) were developed to measure the serological response of female Swiss Webster mice after vaccination with the recombinant fusion protein, rF1-V, which is being developed as a plague vaccine. Several fundamental parameters of the ELISA were evaluated: specificity, precision, accuracy, and stability. Experimental results suggested that a potency assay based upon the serological response of female Swiss Webster mice, as measured by quantitative anti-F1 IgG and anti-V IgG ELISAs, might be used to evaluate the rF1-V fusion protein vaccine.

Short- and long-term efficacy of single-dose subunit vaccines against Yersinia pestis in mice.

A single, subcutaneous, 30-microg dose of either a combination of the Yersinia pestis proteins F1+V or a F1-V fusion protein adsorbed to the adjuvant aluminum hydroxide, protected Hsd:ND4 mice for one year against pneumonic plague. The recombinant F1+V vaccine provided significant protection as early as day 14 postimmunization. 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.