Abstract
Gp350, a late Epstein‐Barr‐virus (EBV) glycoprotein expressed on both the envelope of viral particles and EBV‐producing cells, is also the candidate for the development of an anti‐EBV subunit vaccine. This glycoprotein is thought to play an important role in anti‐EBV immunity. However, studies on the role of this viral antigen in cellular cytotoxicity and other immune functions have been hampered by the lack of a suitable model expressing gp350. We describe here a study in which we successfully transfected a gp350‐negative cell line resistant to natural‐killer(NK)‐cell activity (i.e., Raji) with a recombinant plasmid (pZIP‐MA) containing the EBV‐gp350 and the neomycin resistance gene. Three clones with a stable and strong expression of gp350 on their surface membrane, as demonstrated using a gp350‐specific (i.e., 2L10) monoclonal antibody (MAb) were isolated, characterized and used as targets in an antibody‐dependent cellular cytotoxicity (ADCC) assay. However, gp350 expression on 2 of the 3 isolated clones was not recognized by an anti‐gp350 MAb (72AI) which is specific to a unique gp350 epitope with a dual function (i.e., involved in both EBV binding to its target cell receptors and in Inducing virus‐neutralizing antibody). We have also found that gp350 expression on our 3 selected clones does not affect EBV‐receptor (CR2) density. Our model of gp350‐expressing, NK‐cell‐activity‐resistant targets revealed very useful In determining that gp350 serves as a target antigen for EBV‐specific ADCC. These gp350‐expressing cell clones appear to represent a valuable tool for diagnostic purposes (i.e., for detecting and titrating gp350 antibodies in patients with EBV‐associated diseases). Our approach should also prove useful for studying the expression of other cell‐surface‐associated viral and tumor antigens and their role in specific cellular immunity and immunosurveillance.