Demonstration of Exogenous Genital Reinfection with Herpes Simplex Virus Type 2 by Restriction Endonuclease Fingerprinting of Viral DNA

Analyses of 17 coded isolates of herpes simplex virus type 2 (HSV-2) from genital and perigenital lesions of eight patients showed that recrudescent lesions could be the consequence of exogenous infection. The experimental design was based on earlier observations that no two epidemiologically unrelated isolates of herpes simplex virus type I or HSV-2 were identical as determined by the fingerprinting of viral DNAs with restriction endonucleases—enzymes that cleave DNA at specific sites. After 32P-Iabeled DNAs were extracted from infected cells, cleaved with restriction endonucleases (KpnI, HsuI, EcoRI, or BglII), and subjected to electrophoresis in agarose gels, analyses of DNA fragment patterns established that each member of seven pairs of isolates was identical to the other member but different from the isolates in other pairs. After the code was broken, it was found that of the remaining three isolates, two were successive isolates from one patient and one was a third, nonidentical isolate from a different patient. Thus, one patient yielded three isolates, of which the first two were identical and the third was different. A second patient yielded one isolate that contained one strain of HSV-2 and a second isolate that contained the original strain of HSV-2 and another, genetically distinct strain of virus. Thus, infection with HSV-2 in the same or nearby site can occur in the face of a prior infection with a genetically different strain of the same serotype.