Old drug reduces herpes symptoms, spread in animal tests

Antidepressant tranylcypromine might also work as antiviral

An antidepressant drug suppresses the herpes simplex virus. Tranylcypromine, marketed since the 1960s as Parnate, inhibited initial herpes infection in animal tests, reduced flare-ups in previously infected animals and rendered them less infectious to others, researchers report in the Dec. 3 Science Translational Medicine.

Tranylcypromine blocks the activity of LSD1, a protein found in humans and other mammals. The herpesvirus uses LSD1 to activate some of its own genes to infect a host and later to awaken from its dormant state in the host’s sensory nerve cells. The activation unleashes the virus, causing symptoms.

In blocking such viral gene activation, tranylcypromine makes an epigenetic change in the virus — an alteration in its gene activity that doesn’t change the underlying DNA structure. Since tranylcypromine targets a host protein and not the virus itself, it might reduce the evolution of drug-resistant viral strains, say the researchers, who are from the National Institute of Allergy and Infectious Diseases in Bethesda, Md., and other institutions.

Tested in mice, rabbits and guinea pigs, tranylcypromine prevented some initial herpes infections and genital flare-ups. In some cases it worked better when combined with a herpes drug called acyclovir. In guinea pigs, tranylcypromine reduced the amount of virus transmittable to other animals.

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