Herpesvirus Vector-Mediated Gene Delivery to Human Monocytes

Abstract

In vitro delivery of interferon-α (IFN-α) to cultured human monocytes by means of a replication-incompetent herpesvirus vector inhibits human immunodeficiency virus (HIV) replication. To explore the possibility of IFN-α 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-α 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 vdl207/IFN-α and added to monolayer cultures of HIV-infected monocytes, IFN-α 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.

Overview summary

Replication-incompetent herpes simplex virus (HSV) vectors have been shown to infect primary human monocytes efficiently and express foreign genes. In this report, we have investigated some of the technical aspects of HSV vector-mediated gene delivery into human monocytes. We show that primary monocytes, cultured in suspension for as little as one day, can be efficiently infected with replication-incompetent HSV vectors. Monocytes infected with one such vector that expressed an interferon-α (IFN-α) gene produced levels of IFN that were inhibitory to human immunodeficiency virus (HIV) replication. When these vector-infected monocytes were added to cultured monocytes previously infected with HIV, HIV replication and spread were significantly reduced. In addition, vector recovery experiments showed that the vector could be recovered for at least 7 days after initial infection, even though foreign gene expression was transient.