CD4 and HIV-1 infection: To address these issues we employed ELISA assays for three specific sub-types of IFN-I (IFNα, IFNβ and IFNω) and a bioassay that detects all sub-types of IFN-I (the iLiteTM luciferase reporter bioassay, PBL Laboratories) to determine IFN-I activity in peripheral blood plasma from uninfected subjects (n = 28) and subjects with untreated, asymptomatic, chronic HIV-1 infection (n = 61, median CD4 count 405/μl whole blood, median plasma HIV-1 RNA 30,316 copies/ml).