Biological Characteristics of Cloned Populations of Herpes Simplex Virus Types 1 and 2

Abstract

By using cloned types 1 and 2 herpes simplex virus, obtained by selecting large and small plaques produced by material from human lesions, studies were performed to compare properties between preparations of each type. Regarding the rate of inactivation by ultraviolet light, no differences were found between the two antigenic types and none between the preparations obtained from either type. In contrast, type 1 preparations were found to be more readily inactivated at 45 C than type 2. Plaque size of cloned preparations changed by passage in cell culture. A broader range of plaque sizes was obtained, and average plaque size was larger. After 20 passages, preparations obtained from different types gave rise to one of three kinds of cytopathic effect. The cytopathic effect produced by type 1 preparations remained as before 20 passages and consisted of round cells in a compact central mass. For type 2, two kinds of cytopathic effect were seen in cloned preparations. This consisted of aggregates of round cells (seen in preparations before 20 passages) or of large, loose aggregates of round cells of various sizes. Results from neutralization studies using virus before and after 20 passages in cell culture versus antisera prepared against live or ultraviolet-inactivated virus showed no differences between cloned preparations obtained from a given type.

Efficiency of Plating on Chick Embryo Cells and Kinetic Neutralization of Herpesvirus hominis Strains

“…Whether this antigenic difference is of sufficient magnitude and stability to warrant "type" distinctions is a matter of present controversy (6,9). Although antigenic character does not appear to vary with EOP in this or another study (8), or with other markers (12,13), there is great diversity in the degree of relatedness between strains within groups. Hampar et al (6) have suggested that H. hominis strains should be classified into one serological group as a species by the use of 7S antibodies and that late 19S antibodies should be used for determining subtypes within that species.…”

Permissiveness of rabbit monocytes and macrophages for herpes simplex virus type 1

“…Monolayers were infected at an MOI of 0.1, and supernatants were harvested after 2 to 3 days at 34°C, when almost total cytopathic effect was evident. Fluids were clarified by centrifugation, and the titers were determined on Vero cell monolayers (28).…”

“…Cells and fluids from triplicate wells were harvested at designated times postinfection and stored at -700C. Plaque titrations were done with the use of Vero cell monolayers (28).…”

“…After counting and viability determinations, cells from triplicate wells were seeded onto Vero cell monolayers in RPMI 1640 medium containing 0.9%o agarose. Plaques were counted at 3 days, after a second overlay of agarose containing neutral red (28). Electron microscopy.…”

“…At 15, 30, and 60 min, 1 ml of RPMI 1640 medium was added to the wells, and the supernatants were aspirated and pooled. After centrifugation to remove any cells that had detached, titers of fluids were determined in Vero cell monolayers to determine the amount of unadsorbed virus (28).…”