FIG. 6.

Roles of HSPGs, NRP-1, and GLUT-1 in HTLV-3 Env-mediated entry. (A) CHO-K1 and CHO-K1-pgsA-745 cells were incubated overnight with MLV-based retroviral vectors pseudotyped with either HTLV-1 Env, HTLV-3 Env, or VSV-G and harvested 4 days later, and the titers were determined as described in Materials and Methods. Titers obtained on CHO-K1 were normalized to 100, and the relative titer was determined using the following formula: (titer on CHO-K1/titer on CHO-K1-pgsA-745) × 100. P values were as follows: HTLV-1 Env CHOK-1 versus CHO-K1-pgsA-745, <0.001; HTLV-3 Env CHOK-1 versus CHO-K1-pgsA-745, <0.001; VSV-G CHOK-1 versus CHO-K1-pgsA-745, >0.05. (B) 293 cells were incubated in either the presence or absence of 8 μg/ml of TU. Thirty minutes later, equal volumes of media containing either HTLV-1 Env, HTLV-2 Env, HTLV-3 Env, or VSV-G-pseudotyped vectors were added, so that the final concentration of TU was 4 μg/ml. Six hours later, the cells were washed, and the titers were determined 4 days later. P values were as follows: no treatment with HTLV-1 Env versus TU, <0.05; no treatment with HTLV-2 Env versus TU, <0.05; no treatment with HTLV-3 Env versus TU, <0.01; no treatment with VSV-G versus TU, >0.05. (C) C5/U87 and C8/U87 were incubated overnight with pseudotyped vectors, and the titers were determined as described above. Shown are means and SEM of four (A) or three (B and C) independent experiments. P values were as follows: HTLV-1 Env C5/U87 versus C8/U87, <0.001; HTLV-2 Env C5/U87 versus C8/U87, <0.05; HTLV-3 Env C5/U87 versus C8/U87, <0.01; VSV-G C5/U87 versus C8/U87, >0.05.