The CypA-CA interaction hyper-stabilizes HIV-1 CA cores in a target cell-specific fashion. env-minus HIV-1, pseudotyped with VSV G, and bearing either WT or A92E mutant CA, was incubated with HeLa clone 3D (A) or MT4 cells (B) stably expressing hT5Cyp or hT5Cyp-H436Q, as indicated. Cells were treated with CsA or DMSO as control, for 16 hrs. As a control, to demonstrate, that signals in this assay required viral entry, virions lacking VSV G were used. The target cells were lysed and the cytoplasmic fraction (input) was pelleted through a 50% sucrose cushion to obtain the particulate fraction (pellet). The fractions were then analyzed by western blot with anti-p24 antibody. All experiments are representative of at least 2 repetitions.