FIG 1.

Infectivity and ER-related properties of SHIV Envs. All virus preparations were normalized by reverse transcriptase (RT) activity and used to test infectivity and sensitivity to inhibition. (A) Infectivity of KY, KA, and KY62 Env-pseudotyped reporter viruses was tested in CD4⁺ CCR5⁺ Cf2Th cells. The Cf2Th CD4⁺ CCR5⁺ cells were lysed 48 h after infection and assayed for luciferase activity. All values are expressed as percent infection at a given virus level compared to the value observed for the maximum input of the KY virus. (B) The infectivity of full-length SHIVs was tested in PBMC pooled from three rhesus macaques. Cell supernatants were collected at the times indicated and assayed for RT activity. (C to F) Cold inactivation (C and E), sCD4 inhibition (D and E), and neutralization sensitivity (F) experiments were performed by using reporter viruses pseudotyped with the KB9, KY, KA, or KY62 Envs. (C) Single-round reporter viruses were incubated on ice for 0 to 24 h before infection. (D and F) Viruses were preincubated at 37°C with 0 to 20 μg/ml of sCD4 (D) or with 10 μg/ml of 2G12, b12, 39F, 17b, 4E10, or VRC01 or 5 μg/ml of PGT128 (F) 1 h before infection. All infections were performed in triplicate with Cf2Th CD4⁺ CCR5⁺ target cells, using RT-normalized levels of input virus. Cells were lysed after 48 h and evaluated for luciferase activity. Error bars represent standard errors of the means from two separate experiments. (E) sCD4 reactivity and cold sensitivity of the indicated SHIV Envs are shown. sCD4 reactivity was calculated as described in Materials and Methods and normalized to the ER_sCD4 of viruses pseudotyped with KY Env, which was set at a value of 1. Cold sensitivity was calculated as the reciprocal of the time (IT₅₀) on ice required to inactivate 50% of the viral infectivity.