Differentiation of Herpes Simplex Virus Types 1 and 2 by Plaque Appearances on Semicontinuous Rabbit Lens Epithelial Cells in the Clinical Laboratory

Abstract

Herpes simplex virus type 1 (HSV1) and type 2 (HSV2) were differentiated on the basis of different plaque appearance on semicontinuous rabbit lens epithelial (RLE) cells. Plaques produced by HSV1 strains were small; the mean diameter was 1.29 ± 0.37 mm 3 days after inoculation. HSV2 strains produced large and small plaques, with the ratio of large to small about 20:1. The mean diameters of the large and the small plaques of HSV2 were 3.34 ± 0.56 mm and 0.97 ± 0.31 mm respectively 3 days after inoculation. The clones from the large plaques consistently produced large and small plaques and the small-plaque clones produced only small plaques. Round cells plus heterokaryotes were characteristic of the CPE of HSV1. Large plaques of HSV2 were produced by a large membranous syncytium that was liable to lyse. Small round cells were characteristic of the CPE of the small-plaque clones of HSV2. Glycoprotein C-negative (gC-) strains produced intermediate-sized plaques and a few pin point ones that consisted of membranous syncytia and round cells, respectively. Except for the HF strain (a reference strain of HSV1 producing a membranous syncytium on RLE cells), the result of the differentiation of HSV1 (179 strains) and HSV2 (40 strains) with the RLE plaque assay system was consistent with that of Syva's monoclonal antibody assay system and the restriction endonuclease digestion method.