Differential sensitivity of herpes simplex virus types 1 and 2 to human interferon: antiviral effects of interferon plus 9-beta-D-arabinofuranosyladenine.

With use of a standard assay for antiviral compounds, in which the compound to be tested is added after absorption of virus, the minimal inhibitory concentration (MIC) of human interferon for several strain of herpes simplex virus type 2 (HSV-2) is five to 10 times greater than it is for two strains of herpes simplex virus type 1 (HSV-1). This differential susceptibility of HSV types to interferon is found whether tests are done with a liquid overlay and microtiter plates or with agarose overlays and appears to be a distinguishing biological marker. When the MIC of interferon is tested by microtiter or agarose methods and interferon is allowed to incubate for 24 hr before virus is added, values for HSV-1 and HSV-2 are similar and much smaller in magnitude. These results support earlier data indicating that adenine arabinoside and interferon are synergistic against herpes simplex virus type 1 in vitro and indicate that these agents are additive but not synergistic against herpes simplex virus type 2.