Cytolytic human T-Cell clones expressing epstein-barr virus specificity and HLA restriction

Abstract In an earlier study, we established long-term bulk (uncloned) human, T-cell (BTC) cultures which displayed EBV-specific and HLA-restricted lytic activities. The present study demonstrates the feasibility of isolating and propagating clones of CTLs which express EBV specificity and HLA restriction. A total of 7 independent cloned cultures derived from 2 of the initially established BTC cultures were found to exert reproducible, preferential lytic activity towards EBV-infected autologous or HLA-A/B-matched allogenic B blasts. The conclusion that the cloned effectors were indeed exerting EBV-specific and HLA-restricted lysis was supported by the results of cold-target inhibition experiments. In addition, it was found that a monoclonal anti-HLA antibody (W3/62) could effectively block the observed lytic effect. Data have been presented suggesting that very early after exposure of B blasts to high multiplicity of EBV, the putative virus-specific component(s) involved in the CTL recognition event is derived directly from the envelope of input EBV, i.e. «from without» . Such susceptible EBV-infected blasts could be converted to the insusceptible state following brief exposure to papain, which presumably removes membrane-integrated EBV-envelope material from infected cell surfaces. Using this approach, the time required for cell-surface expression of newly synthesized EBV component(s), conferring susceptibility to virus-specific CTLs, was investigated. The results indicate that EBV-infected and papain-treated B blasts acquire optimal susceptibility to the lytic effect of effector T cells 3-4 days following infection. This conversion of infected blasts from the insusceptible to the susceptible state was blocked by the protein-synthesis inhibitor pactamycin only when added immediately and not at 6 h after papain treatment. On the other hand, papain-treated infected blasts incubated in presence of phosphonoacetic acid, a known inhibitor of EBV-DNA synthesis, were lysable by the effectors. Taken together, the results imply that EBV-specific envelope protein(s) inserted in targetcell surfaces either «from without» or de novo synthesized (from within) presumably represent the putative target(s) for virus-specific CTLs in the context of HLA-A/B antigen(s).