FIGURE 4.

Immunization with tetra-antigen TMV vaccine results in minimal pathology in liver and spleen following a lethal challenge with F. tularensis LVS. C57BL/6 mice were immunized and challenged as shown in Figure 3A. Liver and spleens were collected from unvaccinated controls as well as vaccinated mice on days 7, 14, and 21 post-challenge. Hematoxylin and eosin-stained sections of liver (A) were evaluated for histopathological lesions at the indicated times post-challenge. The arrows and arrow heads indicate granulomas in livers of unvaccinated controls and mice immunized with tetra-antigen TMV vaccine. (B) Number of granulomas were quantitated in uninfected and unvaccinated controls on day 7 post-challenge by counting the number of granulomas in 10 random fields under 10× magnification by two independent investigators in a blinded fashion (n = 3 mice/group). The data were analyzed by unpaired t-test and the P-values were determined. (C) Hematoxylin and eosin stained sections of spleens were evaluated for histopathological lesions at the indicated times post-challenge. The experiments were conducted with 3–4 mice/group/time point and the representative images are shown. The sections were observed and images were taken on a Nikon Eclipse microscope using VIS-Elements AR Version 5.02 software (magnification 10×; bar = 200 μM). Ψ, all unvaccinated mice succumbed to infection by day 14 post-challenge and hence were not available for comparisons.