Herpesvirus vector-mediated gene delivery to human monocytes

In vitro delivery of interferon-alpha (IFN-alpha) to cultured human monocytes by means of a replication-incompetent herpesvirus vector inhibits human immunodeficiency virus (HIV) replication. To explore the possibility of IFN-alpha gene delivery by vector-infected human monocytes, monocytes were isolated and the culture conditions necessary for efficient vector infection and gene expression were examined. Monocytes were efficiently infected between 1 and 7 days after isolation. Expression of IFN-alpha was greater in cells infected 7 days after isolation compared to 1 day after isolation, but the levels of expression were equivalent regardless of whether cells were maintained in suspension or monolayer culture. When suspension-cultured monocytes were treated with vd120/IFN-alpha and added to monolayer cultures of HIV-infected monocytes, IFN-alpha was expressed and replication of HIV was inhibited. HIV replication was arrested even when HIV had spread through much of the monolayer. The persistence of the viral vector in infected cells was examined by a superinfection rescue assay using a second replication-incompetent herpes simplex virus, 5dl1.2. The initial replication-incompetent vector remained in a recoverable form for at least 7 days after delivery, even though foreign gene expression was transient.