The study authors recruited patients with HIV who were depressed and those who were not depressed and studied the ex vivo effects of 3 medications -- a selective serotonin reuptake inhibitor (SSRI), a substance P antagonist, and a glucocorticoid antagonist -- on their NK cell activity. The authors noted that drugs were selected because each "affects underlying regulatory systems that have been extensively investigated in both stress and depression research as well as immune and viral research."

The scientists found that the SSRI citalopram and the substance P antagonist CP 96,345 -- but not the glucocorticoid receptor antagonist RU486 -- increased NK cell activity. According to corresponding author Dwight L. Evans, MD, Ruth Meltzer Professor and Chairman, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, "The present findings provide evidence that natural killer cell function in HIV infection may be enhanced by selective serotonin reuptake inhibition and also by substance P antagonism in both depressed and nondepressed individuals."

John H. Krystal, MD, Editor, Biological Psychiatry, who is affiliated with Yale University School of Medicine, New Haven, Connecticut, and the VA Connecticut Healthcare System, West Haven, Connecticut, comments: "There has been growing evidence that the compromise of immune function associated with depression influences the outcomes of infectious diseases and cancer. Antidepressant treatments are beginning to be studied for their potential positive effects on immune function."

Dr. Krystal added that the study "suggests that antidepressant treatment may have positive effects on natural killer cell activity in cells isolated from individuals infected with HIV with and without depression. This type of bridge between the brain and the rest of the body deserves further attention."

Dr. Evans agreed, noting that "these findings begin to pave the way towards initiating clinical studies addressing the potential role of serotonergic agents and substance P antagonists in improving natural killer cell innate immunity, possibly delaying HIV disease progression and extending survival with HIV infection."
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SOURCE: Biological Psychiatry

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