Herpes simplex virus interferes with monocyte accessory cell function

HSV is a successful human pathogen that causes severe infections in immunocompromised adults and newborn humans. The possibility that HSV might evade host immune responses by interfering with accessory cell function was investigated in vitro using newborns' monocytes adhered to plastic. These cells lost their ability to present staphylococcal enterotoxin B to resting T cells in a stimulatory form after overnight culture with HSV. The interference with T cell proliferation required live virus and was abolished by heat- or UV inactivation. The T cell proliferative response was restored by the addition of IL-2. Furthermore, HSV-precultured monocytes had a reduced production of IL-1 alpha and TNF-beta after phorbol-ionomycin stimulation. Wild-type HSV and a HSV mutant lacking the primary virion host shutoff protein both interfered with IL-1 synthesis and presentation of staphylococcal enterotoxin B for T cell proliferation. These results suggest that HSV can interfere with the provision by human monocytes of costimulator factors that are essential for T cell stimulation. This effect of HSV may be due to secondary shutoff mechanisms that decrease host protein synthesis or secretion after HSV infection.