There is increasing interest in the use of
topical microbicides to help prevent the spread of
sexually transmitted diseases (STD).
Undecylenic acid (UA), a monosaturated
fatty acid, is the active ingredient in a number of over-the-counter (OTC) antifungal spray powders, that also exhibits in vitro antibacterial and
antiviral activity, including herpes simplex virus (HSV) activity. We, therefore, evaluated UA as a topical
microbicide against genital HSV
infection using the murine and guinea pig models of
genital herpes. Mice were administered a 20%
solution of UA in
polyethylene glycol (PEG) vehicle, vehicle alone or
phosphate buffered saline (PBS) intravaginally immediately prior to vaginal challenge with HSV-2. Pre-treatment with UA decreased the number of mice that became infected (P < 0.001 vs. PBS or vehicle control), developed symptoms (P <0.001) or died (P <0.001). However, when treatment was extended to either 5 min prior to or after viral inoculation, protection was lost. Similar findings were found using the guinea pig model, where UA treatment completely prevented HSV-2 vaginal
infection when given immediately prior to HSV-2 inoculation (P<0.001 vs. PBS or vehicle control). Thus, UA, an approved OTC medication, provided significant protection against HSV disease and
infection only when applied immediately before viral inoculation, indicating that better formulations were needed to extend the duration of protection.