FIG. 8.
Immunofluorescence and TEM analysis of PLs infected in vitro or in vivo with FV3. (A) Representative images of cytocentrifuged PLs obtained from frogs after elicitation with heat-killed bacteria and either mock infected (a) or infected in vitro at an MOI of 3 for 2 days (b). Cells were fixed for 30 s in cold (−20°C) acetone, blocked with serum, and incubated with anti-FV3 BG11 MAb undiluted supernatant, followed by an FITC-conjugated goat anti-mouse Ab preadsorbed on Xenopus cells. Preparations were visualized with a Leica DMIRB inverted fluorescence microscope using a phase-contrast field (left side of frames a and b) or fluorescence (right side of frames a and b). A TEM view of macrophage-like cells infected in vitro is shown in frame c, and the viral capsid in the cytoplasm is shown at higher magnification in frame d. Arrow, viral particle; Nu, nucleus, Pv, phagocytic vesicle. (B) Representative images of cytocentrifuged PLs obtained from sham-infected (e) or infected (5 × 106 PFU of FV3) frogs at 2 days (f) or 3 days (g and h) and processed as described for panel A. Arrows depict positively stained infected cells.