EVENTS RELATED TO EPSTEIN-BARR-VIRUS BINDING AND SUPERINFECTION OF RAJI CELLS

Raji cells, a CR2-positive Burkitt lymphoma cell line, incubated in no rmal human serum, activate C3 and fix C3-derived fragments. The presen ce of these molecules on the cell surface does not affect subsequent E pstein-Barr virus (EBV) binding but it prevents superinfection. On the other hand, EBV superinfection is enhanced if Raji cells were incubat ed with heat-inactivated serum whose C3 fragments may bind only throug h receptor-binding sites. These results indicate that the region on ce ll surface offering the covalent site to C3 fragments would be essenti al for EBV superinfection. Incubation of Raji cells for 1 min with EBV results in the phosphorylation of CR2 and of a high-molecular-weight protein followed by their dephosphorylation, completed already after 2 0 min. This finding ascribes to EBV a prompt action through its recept or, different from that of other compounds causing a prolonged CR2 pho sphorylation. Our data suggest that at least two binding sites are req uired for EBV superinfection of Raji cells or that specific patterns o f CR2 phosphorylation may modulate Raji superinfection by EBV.