Susceptibility of recent clinical isolates of herpes simplex virus to 5-ethyl-2'-deoxyuridine: preferential inhibition of herpes simplex virus type 2.

We examined the in vitro susceptibilities of three reference strains and 41 recent clinical isolates of herpes simplex virus types 1 and 2 to 5-ethyl-2'-deoxyuridine. This thymidine analog exerts a type 2-preferential but not a type 2-specific antiviral effect. Utilizing a microtiter assay with BHK-21 cells, we found that the mean (+/- standard deviation) 50% inhibitory dose for herpes simplex virus type 1 isolates was 0.58 +/- 0.30 micrograms/ml as compared with 0.33 +/- 0.20 microgram/ml for herpes simplex virus type 2 isolates. Isolates were typed according to their susceptibilities to (E)-5-(2-bromovinyl)-2'-deoxyuridine and by an indirect fluorescent-antibody technique in which monoclonal antibody combinations were used. A cytotoxicity assay in which the incorporation of [1',2'-3H]deoxyuridine was measured revealed a 50% inhibitory dose of 37.5 micrograms/ml, suggesting a favorable therapeutic index for this compound.