Ultrastructure of measles virus in cultures of hamster cerebellum.

Replication of Edmonston strain of measles virus in cultures of hamster central nervous system tissue was studied by electron microscopy of ultrathin sections. Infected cultures were fixed from 3 hr to 39 days postinoculation (PI). Measles nucleocapsid was first seen within the cytoplasm of giant cells, the latter appearing 5 to 6 days PI. Measles virus particles were most abundant at 10 days PI and appeared to bud off from areas of the cell membrane along which nucleocapsid was aligned. Intranuclear nucleocapsid was more abundant at later stages, and by 39 days PI entire nuclei were seen to be occupied. By this time, the cytoplasmic formations, which had been sequestered by membranes, appeared to lose their regular structure. Budding viral particles at 39 days PI were of a much simplified structure and did not involve the alignment of nucleocapsid about their periphery.