Abstract
Movements of HVJ envelope antigens integrated into Ehrlich ascites tumor cell membranes were observed during cell fusion reaction by electron microscopy using ferritin-conjugated anti-HVJ envelope antibody. Many fusion sites of viral envelopes with cell membrane were seen randomly on fused cell surfaces. The viral envelope antigens derived from individual virions were seen not dispersed but patched on the cell surface. On culture of fused cells, endocytosis of the cell membrane occurred at areas containing viral antigens. Antigens thus disappeared from the cell surface, and they were transferred to newly formed cytoplasmic vesicles, which were observed just under the cell membrane. On further incubation, vesicles containing viral antigens gathered to the base of the cytoplasmic projection. No vesicles containing viral antigens were observed at other areas of the cytoplasm. At this incubation period, cytoplasmic projection developed on one side of the cell. The surface of this projection was clustered by many microvilli-like protrusions. Some viral antigens were exposed on the protrusions. One possible mode of viral antigen accumulation to a specific site (like cap) of the fused cell may be by integration of viral antigens into vesicles by endocytosis of the cell membrane and re-exposure to a scheduled area of the cell by exocytosis.
