Neuroendocrine hormones suppress macrophage-mediated lysis of herpes simplex virus-infected cells

Herpes simplex viruses (HSV) remain latent in sensory and peripheral ganglia and can be reactivated to cause recurrent HSV infections. Recent evidence has suggested that stress can induce an immunosuppressive state and increase the frequency and severity of recurrent herpes infections. Because macrophages play a central role in the host defense against HSV, the effects of stress-related neuroendocrine hormones on macrophage-HSV interactions were examined. Norepinephrine and epinephrine blocked the capacity of recombinant interferon-gamma (IFN-gamma) to activate murine macrophages to a cytotoxic state capable of selectively killing HSV-infected cells. In contrast, ACTH, dopamine, serotonin, and beta-endorphin had no effect. The suppression of IFN-gamma-induced, macrophage-mediated lysis of HSV-infected cells occurred concomitantly with a marked increase in macrophage intracellular cyclic AMP levels. Moreover, exogenous administration of dibutyryl cyclic AMP blocked induction of macrophage-mediated cytotoxicity, suggesting that the neurohormones were modulating macrophage function via an adrenergic receptor-mediated system. These findings demonstrate that selective stress-related neurohormones modify the cytolytic activity of macrophages against virus-infected cells and suggest a possible neuroendocrine-immunologic basis for the recurrence of HSV infection.