TCR-binding of OKT3SU- or OKT3SUx-displaying lentiviral particles.

The Jurkat T-cell line was used as TCR CD3⁺ target cells. The background fluorescence was determined by incubating cells with viral particles devoid of envelope glycoproteins (white area). Binding assays were performed with vectors particles generated with wild-type amphotropic MLV glycoproteins (WT-A), OKT3SU, or OKT3SUx glycoproteins as indicated. Target cells were either pretreated (broken line) with soluble anti-CD3 antibodies, or not pretreated (black area), before incubation with the viral particles. Virion binding was detected by flow cytometry using anti-SU antibodies.