Fig. 3.

Ehrlichia-specific IgG antibody responses develop in mice immunized with the P28 outer membrane proteins. Ehrlichia muris-specific IgG antibody titers in all vaccinated groups before and after challenge were measured by IFA using slides prepared from E. muris cultured in DH82 cells. Higher titers of E. muris-specific IgG antibodies were observed in mice vaccinated with P28-9, P28-12, P28-14, P28-19, and the P28 mixture on day 28 after the last booster immunization before challenge than in the controls. The titers of E. muris-specific IgG antibodies measured after challenge were higher than the titers of antibodies in vaccinated mice before challenge, indicating that infection boosted the antibody response. Each symbol shows the value for an individual mouse. The short horizontal lines represent the means for the groups of mice before challenge (short broken lines) and after challenge (short black lines).