Epstein-Barr virus (EBV) infection of murine L cells expressing recombinant human EBV/C3d receptor

The normal host range of Epstein-Barr virus (EBV) is limited to primate B lymphocytes and certain epithelial cells that express the C3d/EBV receptor [complement receptor 2 (CR2, CD21)]. In the present study, expansion of the tissue tropism of EBV has been accomplished by stably transfecting the murine fibroblast L cell line with pMT.CR2. neo.1, a eukaryotic expression vector promoting the transcription of a complementary DNA insert encoding human CR2. High CR2-expressing transfected L cells were selected by fluorescence-activated cell sorting. The recombinant CR2 was shown to have the same molecular weight as wild-type CR2 from Raji cells and to mediate the binding by the transfectants of particles bearing the iC3b and C3d fragments of the third component of complement. All CR2-expressing L cells, but not nontransfected controls, also bound EBV, as assessed by indirect immunofluorescence. After a 60-hr culture, ≃ 0.5% of the CR2-expressing cells preincubated with EBV demonstrated immunofluorescent staining of EBV nuclear antigen with serum from a patient with nasopharyngeal carcinoma. No fluorescent staining of cells was seen with monoclonal antibodies to the early antigen complex or to gp350/220, indicating that the infection was predominantly latent. Infected cells cultured for up to 4 weeks remained EBV nuclear antigen-positive. The capacity of recombinant human CR2 to confer on murine L cells susceptibility to stable latent infection by EBV indicates that this receptor is a primary determinant of the tissue tropism of EBV and may facilitate studies of cell-specific factors that regulate the viral growth cycle.