FIG. 4.

Intracellular localization of the HBsAg(S)16E7 fusion protein analyzed by confocal microscopy. A representative Vero cell expressing HBsAg(S)16EE7 stained with an anti-FLAG antibody (green). Cells were counterstained with propidium iodide (red). Each photograph represents a single confocal section within a series in the xy and xz planes. (A) Three consecutive sections in the xy plane through the basal (xy1), medial (xy2), and apical (xy3) levels. The HBsAg(S)16E7 protein accumulates in large perinuclear structures derived from the ER and Golgi. In addition, a punctuate pattern of smaller vesicles containing fusion protein is seen scattered throughout the cytoplasm. These vesicles appear to migrate to the periphery, where they are exocytosed. Arrowheads point to HBsAg(S)16E7 protein into vesicular structures in neighboring untransfected cells. These are particle aggregates likely coming from the cell in the center, which was the only one transfected in this field. (B) Three cross-sections of the cells in the plane xz (perpendicular to the plane of adherence) at the levels indicated in xy2, showing large stained structures that are in tight contact with the nucleus and small vesicles that migrate distally to the periphery of the cell. The arrowhead in xz3 points to HBsAg(S)16E7 fusion protein captured by an untransfected cell. Bar, 20 μm.