Identification of herpes simplex virus infection by immunoperoxidase and in situ hybridization methods.

Seven cases of visceral herpes simplex virus (HSV) infection were observed in five cases of hematopoietic disease and in one case each of a newborn baby and a pregnant woman. These seven cases were studied with an immunoperoxidase method and in situ hybridization. In HSV lesions of squamous epithelium, the immunoperoxidase method using rabbit anti-human HSV revealed positive staining, mainly in the nucleus but with some cytoplasmic staining. DNA in situ hybridization revealed stronger positive staining in the nucleus. In HSV hepatitis positive staining was seen in the nucleus and cytoplasm, both by immunoperoxidase and in situ hybridization methods. In the newborn baby, HSV lesions were observed in the brain only, with numerous positive astrocytes identified by the immunoperoxidase method and a few positive astrocyte nuclei by in situ hybridization. Cultured human fetal fibroblasts from the lung were infected with HSV. The immunoperoxidase method revealed diffuse positive staining in the nucleus and in the cytoplasm whereas in situ hybridization revealed fibrillar positive staining in the nucleus only. Thus, the immunoperoxidase method using rabbit anti-human HSV can detect the presence of HSV protein more sensitively than in situ hybridization, probably because of the greater quantity of HSV protein compared with HSV DNA in infected cells.