Filamentous structures associated with Epstein-Barr virus-infected cells

Characterization of the restricted component of Epstein-Barr virus early antigens as a cytoplasmic filamentous protein

Four monoclonal antibodies produced against the restricted component of the Epstein-Barr virus (EBV) early antigen (EA-R) precipitated a polypeptide with an approximate molecular weight of 85,000. Three of these antibodies prepared against the native 85,000-molecular-weight protein (85K protein) reacted by immunofluorescence with acetone-fixed smears but not methanol-fixed smears of EBV-producing cells activated with tumor-promoting agent and sodium butyrate. The fourth monoclonal antibody which was produced against the denatured 85K protein reacted with both acetone-fixed cells and methanol-fixed cells. Blocking of direct immunofluorescence by the different monoclonal antibodies established that these monoclonal antibodies were directed against three different epitopes expressed on the 85K protein. The cytoplasmic staining pattern produced by each antibody was granular during the first 24 to 28 h after induction, developed into filamentous structures about 36 h after induction, and then began to aggregate after 48 h. Similar structures were observed in human placental cells transfected by EBV DNA and stained with three of the monoclonal antibodies. These results suggest that the EA-R polypeptide is assembled into filaments during the EBV lytic cycle. The significance of this in regards to replication has yet to be determined. Biochemical characterization of this major EA-R component did not reveal any major differences in this protein isolated from different cell lines.

Ultrastructural studies on cell fusion induced by Epstein-Barr virus or N-butyrate and 12-O-tetradecanoylphorbol-13-acetate. Brief report

The morphological changes which occur in Raji cells during EBV induced fusion are described. Of particular interest is the formation of local contacts between cells, at these points the plasmalemmae of the two cells become disorganized and cytoplasmic bridges are formed.

Ultrastructural studies on human lymphoblastoid cells treated with n-butyrate and 12-O-tetradecanoylphorbol-13-acetate

The effects of n-butyrate and/or 12-O-tetradecanoylphorbol-13-acetate (TPA) on Raji and P3HR-1 cells were examined using electron microscopy. n-Butyrate treatment caused a decrease in the number and elongation of surface microvilli. In addition, well-developed rough endoplasmic reticulum and a marked decrease in condensed chromatin clumps were observed in the nucleus. The filamentous structures and nuclear membrane-like structures, which were not reported previously, appeared occasionally in the nucleus. On the other hand, in the cells treated with TPA no marked morphological changes were observed except the higher cytoplasmic:nuclear ratio. n-Butyrate-induced morphological changes were not inhibited when combined with TPA or retinoic acid. Electron microscopic studies showed remarkable differences in morphological change in these cells treated with n-butyrate and/or TPA.