FIG. 1.

Transgenic T. gondii parasites expressing OVA. Transfection vectors were engineered to express OVA in the parasite cytoplasm (Panel A.; ptubCAT-OVA/sagCAT), or secreted into the parasitophorous vacuole (Panel B.; ptubP30-OVA/sagCAT). For antigen expression in the cytoplasm, OVA-coding sequences were fused downstream of the first 19 amino acids of CAT (to enhance expression levels). For secreted antigen expression, OVA was fused downstream of the signal sequence derived from the parasite's major glycosyl-phosphatidylinositol-anchored surface antigen, P30. Phase-contrast and immunofluorescence images show HFFs infected with either CAT-OVA- or P30-OVA-transgenic parasites. CAT-OVA-transgenic cells show expression in the parasite cytoplasm (nucleus outlined in shadow) but not secreted into the PV. P30-OVA-transgenic cells secrete OVA into the PV (via dense granules, visible as small vesicles with the parasites). Bar, 10 μm.