Electron microscope observations of African swine fever virus in tissue culture cells

African swine fever virus, Hinde isolate, grown in a stable pig kidney cell line and primary pig kidney cells, was examined for successive stages in the development of the virus particle. The mature particle has a hexagonal outer membrane structure (diameter 175-215 micron) surrounding an electron lucent region and a dense nucleoid (diameter 72-89 micron). The increase in particle production in the cell cytoplasm is consistent with both the rise in infectivity as measured in pig kidney cell cultures and the rise of hemadsorption titer as measured in leukocyte cultures.