Impaired neonatal natural killer-cell activity to herpes simplex virus: decreased inhibition of viral replication and altered response to lymphokines.

Human adult natural killer (NK) cells were recently demonstrated to inhibit herpes simplex virus (HSV) replication in vitro. In this study we compared the ability of newborn and adult NK cells to inhibit HSV replication. Cord blood mononuclear cells (MNCs) from healthy, term newborns and MNCs from adults were analyzed for their percentage of Leu-11+ cells and compared in vitro for their NK-cell activity against HSV-infected fibroblasts and the tumor cell line K562. Cord blood MNCs, compared with adult MNCs, had significantly lower percentages of Leu-11+ cells (5 vs 11%; P less than 0.01), less anti-K562 NK activity (6 vs 54 lytic units/10(7) cells; P less than 0.001), and less anti-HSV NK activity (5 vs 52% HSV plaque inhibition; P less than 0.02). Comparing individual neonates and adults with equal percentages of Leu-11+ cells, neonatal MNCs still had less NK activity against either target. When Leu-11+ MNCs were isolated using the fluorescence-activated cell sorter, neonatal Leu-11+ MNCs still inhibited HSV replication less than adult Leu-11+ MNCs (P less than 0.01). MNCs from some neonates had significant anti-K562 NK activity but poor anti-HSV NK activity, suggesting either nonidentical NK-cell subpopulations or specific suppression. Whereas neonatal NK activity against K562 was always augmented by prior exposure to either interferon (IFN) or interleukin-2 (IL-2), the neonatal NK activity against HSV-infected cells was only augmented for half of the neonates tested. Endogenous production of alpha-IFN and gamma-IFN by MNCs exposed to HSV-infected fibroblasts was the same for cells from neonates or from HSV-seronegative adults.(ABSTRACT TRUNCATED AT 250 WORDS)