Effects of levamisole, an immunomodulator, upon murine encephalomyocarditis virus myocarditis.

To test the therapeutic efficacy of levamisole, 5-week-old DBA/2 mice were inoculated intraperitoneally with 10 plaque-forming units of encephalo-myocarditis virus. Levamisole (2.5 mg/kg/per day) was administered intraperitoneally daily, starting simultaneously with the virus inoculation, in experiment I for 14 days, and daily on days 14 to 28 in experiment II in mice that survived to 14 days after virus inoculation. In experiment I, survival was higher, the severity of myocarditis was less, and myocardial virus titers were lower in treated than in untreated animals. In experiment II, levamisole was not effective. No significant changes in serum neutralizing antibody titers occurred in either experiment. Furthermore, levamisole prevented associated lymphoid organ atrophy induced by the virus infection. An additional in vitro study revealed the absence of anti-viral activity of the drug. Thus, levamisole may have favorable effects upon encephalomyocarditis virus myocarditis by preventing the virus-induced lymphoid organ atrophy and reducing myocardial virus replication in the acute stage.