Human Receptor for Measles Virus (CD46) Enhances Nitric Oxide Production and Restricts Virus Replication in Mouse Macrophages by Modulating Production of Alpha/Beta Interferon

Complement regulatory protein CD46 is a human cell receptor for measles virus (MV). In this study, we investigated why mouse macrophages expressing human CD46 restricted MV replication and produced higher levels of nitric oxide (NO) in response to MV and gamma interferon (IFN-γ). Treatment of MV-infected CD46-expressing mouse macrophages with antibodies against IFN-α/β blocked NO production. Antibodies against IFN-α/β also inhibited the augmenting effect of MV on IFN-γ-induced NO production in CD46-expressing mouse macrophages. These antibodies did not affect NO production induced by IFN-γ alone. These data suggest that MV enhances NO production in CD46-expressing mouse macrophages through action of IFN-α/β. Mouse macrophages expressing a human CD46 mutant lacking the cytoplasmic domains were highly susceptible to MV. These cells produced much lower levels of NO and IFN-α/β upon infection by MV, suggesting the CD46 cytoplasmic domains enhanced IFN-α/β production. When mouse macrophages expressing tailless human CD46 were exposed to culture medium from MV-infected mouse macrophages expressing intact human CD46, viral protein synthesis and development of cytopathic effects were suppressed. Pretreating the added culture medium with antibodies against IFN-α/β abrogated these antiviral effects. Taken together, these findings suggest that expression of human CD46 in mouse macrophages enhances production of IFN-α/β in response to MV infection, and IFN-α/β synergizes with IFN-γ to enhance NO production and restrict viral protein synthesis and virus replication. This novel function of human CD46 in mouse macrophages requires the CD46 cytoplasmic domains.