An analysis of factors influencing the isolation rate of herpes simplex virus

Attempts were made to improve the rate of isolation of herpes simplex virus (HSV) from clinical specimens by minimizing loss of virus infectivity during transportation and employing the most sensitive cells for isolation. Basical analyses using standard strains of type 1 and type 2 HSV indicated that virus titer decrease was marked even at low temperatures in environments free of proteinous stabilizer such as normal serum or tissue extract, negating the generally held concept that HSV is stable in distilled water. YLE (Earle-lactalbumin HYDROLYSATE-YEAST EXTRACT) medium containing 20% inactivated calf serum was determined to be a transport medium of choice, because degradation of suspended virus during storage and freeze-thawing was negligible and loss of virus during Millipore filtration was minimal. Special coating of the membrane could also be obviated by the use of this solution. In a cell susceptibility test using clinical specimens, secondary rabbit kidney (SRK) cells were the most sensitive, showing a quick development of cytopathic effect. Vero and RK-13 cells were the second best, whereas monkey kidney, HeLa and L cells were far less sensitive. A total of 136 specimens from suspected cases, sent by dermatologists, were tested using SRK cells, and 99 strains of type 1 and 15 strains of type 2 HSV were isolated. Excluding one case from which vaccinia virus was isolated, the isolation rate of HSV was 84.4%.