Methylene blue uptake assay to determine cell viability.

293T cells were transfected with pNL4-3 and INI1 or SID-INI1 or shRNA constructs as described above, and after transfection, the cells were washed and then treated with 0.5% methylene blue (formulated in a 1:1 ratio of ethanol-water [vol/vol]) and incubated at room temperature for 1 h. After treatment, the cells were washed and dried. To each well, 1 ml of 1% SDS was added to solubilize cell membranes. The plates were incubated with agitation on a rotator at room temperature for 1 h. The resulting cell lysate was collected, and the methylene blue was measured by reading the optical density at 630 nm (OD₆₃₀) of the sample from each well.