Cdc42 is required for HIV-1 transfer across DC-CD4⁺ T cell infectious synapses. (A) Impact of silencing in DCs of cytoskeletal rearrangement proteins. (Left panel) Western blots for Cdc42 and Rac1 protein expression. (Middle panel). DC-CD4⁺ T cell infectious synapses counts. (Right panel). HIV-1 infection transfer to Jurkat CD4⁺ T cells. Data are mean ± SD of 5 independent experiments. (B) Confocal microscope images of DC-Jurkat CD4⁺ T cell infectious synapses. White thin arrows indicate viral particles on membrane extensions. *“Hairy” appearance of the DC surface. Thick white arrows indicate the presence of viral aggregates at the infectious synapse. **Loss of membrane extensions at the surface of the Cdc42-depleted DCs. Bar represents 5 μm. (C) Quantitation of the number of thin membrane extensions, dendrites, and lamellipodia in DCs after Cdc42 and Rac1 silencing. White arrows point to membrane extensions; and double-white asterisks, the DC-surface devoid of membrane extensions. The plot at right shows quantitation of membrane extensions, dendrites, and cell surface covered with lamellipodia (right panel). Data are mean ± SD of 4 independent experiments. (D) Impact of Cdc42 mutant nucleofection in DCs on HIV-1 transfer to resting autologous CD4⁺ T lymphocytes. Data are mean ± SD of 2 independent experiments. (E) Quantitation of the number of membrane extensions in DCs after Cdc42 mutant nucleofection. Data are mean ± SD of 3 independent experiments. *P < .05 (Student t test). Bonferroni test with an α-error value of 5% has been applied to all panels with multiple comparisons.