TEMPERATURE-SENSITIVE STEPS IN THE TRANSPORT OF SEMLIKI-FOREST VIRUS ENVELOPE PROTEINS IN MOSQUITO C6 36 CELLS/

We have analysed the temperature dependence of the transport of Semlik i Forest virus (SFV) envelope proteins in mosquito cells, the natural host cells of alphaviruses. These cells are cultivated at a lower temp erature (28 degrees C) and have a different lipid composition as compa red to mammalian cells. When the incubation temperature was reduced at early times after infection, the onset of virus shedding was delayed and the maximal titers decreased correspondingly to the temperature. N o virus was shed at 12 degrees C. No evidence was observed for a block of virus release due to a shift of the sites of virus maturation. Whe n the incubation temperature was reduced at later times after infectio n a critical temperature of 12 degrees C was again observed. At this t emperature no transport of viral proteins took place, p62 remained unc leaved, the glycan processing of E(1) did not occur and the envelope p roteins accumulated in a pre-Golgi compartment. We suggest a mathemati cal formula which allows the extrapolation of transport data to the te mperature at which intracellular protein transport becomes blocked.