CD63 down regulation also affects HIV-1 replication in late events of life cycle. U1/HIV-1 cells (5 × 105 cells/well) were transfected with CD63-specific siRNA. Two days after transfection, cells were induced with 3 phorbol 12-myristate 13-acetate (PMA, 5 × 10-6 M). Three days later, HIV-1 p24 protein in cell lysates (A) and culture supernatants (B) were detected with DCs using p24 Capture ELISA kit (ImmunoDiagnostics, Woburn, MA).