Herpes T virus variants. Isolation and characterization.

Abstract

Herpes T virus obtained from squirrel monkeys appears to be composed of a mixed population of large and small plaques. By clonal selection it was possible to obtain a large plaque and a small plaque strain. The latter which formed a minor component in the parent population differed from its companion large plaque type in all in-vitro markers studied: plaque size, CPE development, infectivity to host cell cultures both in degree and in titer, polykaryocyte development, rate of adsorption and thermostability characteristics. LPV measured 3 mm and SPV 1 mm as seen in rabbit kidney cell cultures 6 days post inoculation. This size difference was also seen in simian, mammalian and avian cell cultures. The CPE caused by LPV differed from SPV both in appearance and in the time of development. LPV had a greater capacity to form polykaryocytes in almost all cell cultures examined, while SPV was deficient in this regard and failed to form polykaryocytes in rabbit kidney, mouse embryo kidney, cat kidney and chick fibroblast cell cultures. LPV was more thermostable than SPV — at 56° C SPV lost 100% infectivity within 10 minutes, while LPV lost 63%. When the adsorption rates of the two clones were compared, LPV adsorbed at a faster rate with 60% being adsorbed within 15 minutes, in contrast to 31% with SPV. Plaque morphology, development of CPE, in-vitro virulence to cell cultures, formation of polykaryocytes, rate of adsorption and thermostability were useful markers for the characterization of Herpes T virus variants.