12KO, 30KO, and HBZKO infectivity in primary human DCs. (A) The level of entry of HTLV ACH (WT), 30KO, 12KO, and HBZKO virions was determined by intracellular staining for the p19 Gag protein (white histogram) by fluorescence-activated cell sorting at 16 hours after virus exposure. The black histogram represents the staining of cells with the isotype control antibody. (B) Level of infection of DCs at 14 days after virus exposure, determined by the concentration of viral particles in the culture supernatant by the p19 Gag enzyme-linked immunoabsorbent assay. The results are presented as the percentage of HTLV-1 WT expression of the viral mutants. (C) Infection of DCs by 30KO in the presence (right) and absence (middle) of coexpression of the p30 c-DNA relative to WT HTLV (left), determined by the level of intracellular Tax at 1 week after infection. The black histogram refers to the antibody isotype control and the white histogram to the staining with the anti-Tax antibody.