Abstract
Cell fusion proceeded gradually in measles virus-infected cells incubated at 35 °C. Shift-up of incubation temperature to 39 °C induced rapidly increased cell fusion in spite of the cessation of de novo synthesis of the fusion (F) protein. Pulse-chase experiments showed that there was little difference in the acquisition of immunoreactivity by haemagglutinin (H) and F proteins between the two temperatures. H protein was detected on the cell surface 60 min after the chase at either temperature. However, appearance of F protein on the cell surface took less than 3 h at 39 °C whereas it took 5 h at 35 °C. These data indicate that temperature elevation induces more efficient expression of F protein on the cell surface accompanied by marked syncytium formation in measles virus-infected cells.