Interferon-independent Increases in Class I Major Histocompatibility Complex Antigen Expression Follow Flavivirus Infection

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Abstract
Summary Infection of tertiary-passaged mouse embryo fibroblasts by four flaviviruses, West Nile (WNV), Kunjin, Murray Valley encephalitis and Japanese B encephalitis, resulted in a six- to 10-fold increase in the expression of individual H-2K and H-2D class I major histocompatibility complex (MHC) antigens 16 to 48 h after infection. The mechanism(s) by which flaviviruses increased antigen expression has not been fully elucidated, but appears to be mediated partly independently of interferon-β (IFN-β) secretion, as anti-IFN-αβ antibodies partially inhibited the WNV-induced increase but totally prevented increases caused by the addition of (i) pure IFN-β, (ii) IFN-β-containing supernatants from WNV-infected mouse embryo fibroblasts (MEF), or (iii) polyinosinic-polycytidylic acid. Actinomycin D treatment of MEF, which inhibited mRNA synthesis by >90% as determined by [3H]uridine uptake, totally inhibited the increased MHC expression caused by WNV infection. Thus, the increase in class I MHC antigen expression following infection is dependent upon cellular RNA synthesis.