FIG. 5.

(A) Attachment. BMECs (Cell System Corp.) were exposed to 10 ng of p24 of pairs of viruses derived from brain (br) or from lymphoid tissues such as spleen (spln) or lymph nodes (LN) for 1 h at 37°C. Cells were then washed, detached, and lysed. Amounts of attached virus were determined by p24 ELISA of cell lysates. (B) Internalization. Viruses were added to BMECs for 4 h at 37°C. Cells were washed, trypsinized, washed again, and immediately lysed. Amounts of internalized HIV-1 were quantified by p24 ELISA of cell lysates. (C) Transcytosis. HIV-1 was added to the apical surface of BMECs for 16 h at 37°C, and amounts of transcytosed viruses were quantified by p24 ELISA in the lower chamber, corresponding to the basal surface. Results are representative of those from two independent experiments.