Epstein-Barr Virus-Lymphoid Cell Interactions III. Effect of Concanavalin A and Saccharides on Epstein-Barr Virus Penetration

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Abstract
To study some aspects of Epstein-Barr virus (EBV) penetration into human lymphoblastoid target cells, the effect of concanavalin A (ConA) and various saccharides on virus infectivity and cell susceptibility to EBV infection was examined. ConA treatment of the target cells, EBV, or EBV-cell complexes inhibited virus antigen expression. Several control experiments with .alpha.-D-methyl-mannoside elution of ConA, removal of nonfused EBV particles from the cell surface by trypsin treatment and addition of ConA at different times postinfection were performed to define the site of ConA action on EBV infection. ConA appeared to have a dual action: it inhibited EBV binding to virus receptors and it blocked the penetration of receptor-bound virus into target cells at a trypsin-sensitive stage, thus indicating that ConA prevented the fusion of viral envelope with the target cell membrane. A high sucrose concentration (0.25 M), known to inhibit cell membrane movements, also blocked EBV penetration at a trypsin-sensitive stage thus suggesting the implication of cell membrane movements and underlying activities (or both) in viral envelope fusion. Lower concentrations of various monosaccharides (0.12 M) did not influence EBV infection. Under conditions of ConA treatment that did not influence EBV infectivity and target cells susceptibility, ConA was able to mediate virus binding to EBV receptor-negative cell lines, but no virus antigens were expressed in these cells. The mere attachment of EBV to lymphoid cells apparently is not sufficient to lead to infection. The existence of a specific cellular mechanism that allows the penetration of EBV into the target (B) lymphocyte is postulated.