Interferon induction by human herpesvirus 6 in human mononuclear cells

Interferon (IFN) production after inoculation with human herpesvirus 6 (HHV-6) was studied in peripheral blood mononuclear cells from 10 HHV-6-seropositive healthy adults and five samples of cord blood mononuclear cells. When the cells were exposed to HHV-6 at a multiplicity of infection of 10(-2) 50% tissue culture infectious doses/cell, IFN activity was detected as early as 12 h after exposure to HHV-6, plateaued at days 2-5, and gradually decreased thereafter. IFN was also induced by ultraviolet-inactivated but not heat-inactivated HHV-6. The response of cord blood mononuclear cells was lower than that of the cells from healthy adults. The activity of all IFN samples was stable to acid and exclusively neutralized by anti-human IFN-alpha. The IFN-producing cell population was mainly non-T cells and monocytes. Furthermore, exogenous IFN suppressed HHV-6 replication. Production of IFN-alpha may be an important part of the host response to HHV-6.