HIV-1 Is Internalized in B Cells

<div><p>(A–D) Transmission electron microscopy of HIV-1–loaded, activated B cells and DC. Activated B cells were left untreated (panel A) or loaded with AT-2–inactivated HIV-1 X4 (MN) for 1 h at 4 °C (panel B) or at 37 °C for 2 h (panel C). Immature DC (panel D) that were loaded with the same preparation of HIV-1 and incubated at 37 °C for 2 h were used as controls. Arrows indicate viral particles that have been internalized in cytoplasmic vesicles.</p><p>(E) HIV-1 p24 levels in post-trypsin treatment supernatants (sup) and cell pellets of activated B cells (lys) that had been incubated with AT-2–inactivated HIV-1 X4 (MN) or HIV-1 R5 (Ba-L) for 2 h at 37 °C, and then incubated with 0.25% trypsin solution for 10 min at 37 °C. Controls included activated B cells without virus, which were negative for p24 (unpublished data).</p><p>(F) Activated B cells were incubated with HIV-1 R5 (Ba-L) on wet ice, then washed and shifted at 37 °C for the times indicated. Cells were then treated with trypsin or mock treated and added to T cells. Supernatants were collected every 4 d and tested for p24. Data are from single experiments representative of three independent experiments.</p>