Productive HHV-6 infection and IL-12 suppression. Productive HHV-6 infection is not required for IL-12 suppression. (A) PBMCs and Mϕs were infected with HHV-6A. At 6 days later, the cells were harvested and analyzed for viral DNA by means of a quantitative real-time PCR assay. β-actin DNA was measured in parallel to normalize for cell number. The data shown are from one representative donor and are expressed as HHV-6 genome equivalents per cell. (B) PBMCs were incubated with HHV-6A supernatant that was previously inactivated or not by UV-light treatment. Cells were immediately harvested for the initial time point (0) and then after 4 and 6 days. (C) Mϕs were incubated for 17 hours with HHV-6A and treated or not with UV light, after which the infectious supernatants were replaced with fresh media. At 24 hours later, the cells were stimulated with IFN-γ and LPS. Supernatants were harvested and tested for IL-12 p70 by ELISA. Mean results (± standard error [SE]) from 2 donors are presented.