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Fourteen strains of eastern equine encephalitis (EEE) virus were isolated from Aedes albopictus mosquitoes collected in Polk County, Florida. These are the first isolations of an arbovirus of proven public health and veterinary importance from naturally infected Ae. albopictus in the United States since established populations of this introduced mosquito were first discovered in 1985. The widespread distribution of Ae. albopictus in Florida and in other areas of the United States where EEE is endemic raises concern that this species may become an epizootic and epidemic vector of EEE virus.

SUMMARYVaricella-zoster virus (VZV) has been isolated and serially propagated in a continous cell line derived from a human malignant melanoma tumour. Human melanoma cells (HMC) have been further evaluated as a substrate for the production of cell-free virus and compare favourably with human embryo cells. Within 6o h after inoculation with VZV-infected cells, HMC monolayers incubated at 32 °C exhibited advanced syncytial cytopathic effect, and the overlying culture medium contained > io 2 p.f.u./ml. The cell pellet from a mechanically dispersed I5o cm 2 monolayer yielded lO 5 p.f.u, after sonic disruption, while the medium (' scraping medium') in which the cells had been harvested contained up to one log more infectious virus than was found in the cells from the same monolayer. When infected cells were subjected to Dounce homogenization, most of the infectivity was found in the nuclear fraction.The concentration and purification of cell-free virus were also investigated. Concentration was carried out by three methods: ultracentrifugation, dialysis against hydrophilic compounds and liquid polymer phase separation. The first two procedures caused considerable loss of biological activity, whereas precipitation with 8 % polyethylene glycol resulted in a 5o-fold increase in titre. Purification of cell-free virus with retention of infectivity was achieved by rate zonal centrifugation in linear potassium tartrate gradients. Infectious virus was also recovered after sedimentation in combination equilibrium-viscosity gradients of potassium tartrate and glycerol, but not after centrifugation to equilibrium in caesium chloride gradients.

An oncornavirus isolated from a squirrel monkey (Saimiri sciureus) lung culture has a density of 1.16 to 1.17 grams per milliliter, contains 70S RNA, and has an RNA-directed DNA polymerase that prefers Mg2+ over Mn2+ in an assay in which polyribocytidylate - oligodeoxyguanylate (12-18) is used as a synthetic template. Morphologically, the virus resembles Mason-Pfizer monkey virus but is antigenically distinct from this virus. The virus grows in cells of human, chimpanzee, rhesus monkey, canine, and mink origin, but not cells of squirrel monkey origin. On the basis of its properties, the newly isolated virus can be classified as a retravirus.