The detection of Epstein-Barr virus receptors utilizing radiolabelled virus

Epstein-Barr virus (EBV) was labelled with 3H-thymidine and purified about 1000-fold from the culture medium by ultracentrifugation on 5 to 30% dextran gradients. The presence of the virus was monitored by radioactivity and Epstein-Barr virus-determined nuclear antigen (EBNA) induction in sensitive indicator cells (Ramos). Peaks for both activities occurred in the 17 to 18% dextran fractions. Unlabelled virus recovered in the peak fraction was labelled with 125I. Both thymidine and 125I-labelled purified virus bound quantitatively to receptor-positive Burkitt lymphoma-derived cell lines but not to EBV-receptor-negative T-lymphocyte-derived cell lines. Thymidine-labelled virus that was allowed to bind to Raji cells was present in the interior of briefly trypsinized cells after 3 h incubation at 37 degrees C. The results provide a convenient method for detecting the EBV receptor by radioactively labelled virus.