MORE RAPID ISOLATION OF HERPES SIMPLEX VIRUS STRAINS, RESISTANT TO ACYCLOVIR WITH DIFFERENT tk GENE MUTATIONS IN A CONTINUOUS LINE OF HUMAN RHABDOMYOSARCOMA CELLS THAN IN LARYNGEAL CARCINOMA OR BOVINE KIDNEY CELLS

Virus isolation in cell cultures has long served as the “gold standard” for virus detection, and it is the method to which all others have been compared. Herpes Simplex virus (HSV) normally undergoes productive infection in culture, causing cell destruction and plaque formation. Virus isolation is used by clinical virology laboratories as the most sensitive and accurate method of detecting herpes viruses from clinical specimens. HSV replicates well in a number of different cell types of human, monkey, rabbit, guinea pig, and mouse origin. The performance of a culture system for isolation of resistant to acyclovir (ACV) HSV type 1 (HSV 1) and type 2 (HSV 2) mutants, of human rhabdomyosarcoma (RD), laryngeal carcinoma (HEp-2), and Madin-Darbey bovine kidney cells (MDBK), was evaluated. A total of 4 clinical strains were inoculated into RD, HEp-2, and MDBK cell culture tubes. The cultures were incubated aerobically with 5% CO₂ at 37^oC and observed daily for characteristic cytophathic effect (CPE) for 7 days. A comparison was made based on sensitivity, clarity of CPE, and ease of cell line manipulation. The data presented in this comparison indicate that the RD cell line was very sensitive to tk gene mutations HSV strains and is more rapid than HEp-2 and MDBK cells in displaying HSV-associated CPE. The RD cell line was easy to grow in cell culture. Being a continuous cell line, the cell grew rapidly and produced less acid during growth than did the diploid cell line, making pH problems minimal. CPE in the RD cell line was very similar to that seen in the HEp-2 cell line. The CPE consisted of distinct, clusters of rounded cells with associated multinucleated giant cells. The more uniform nature of the RD cell line, however, made the CPE much easier to detect in comparison to the HEp-2 cell line. Based on these observations, RD performed better in our laboratory than did HEp-2 and MDBK cells for detection of clinical strains of HSV, resistant to acyclovir with different tk mutations. This cell line appeared to be more sensitive to HSV than HEp-2 and MDBK cells.