[Electron microscopy studies on the proliferation of foot-and-mouth disease virus in cell cultures. III. Morphogenesis in cytoplasm].

The previous parts have been concerned with the participation of the cell nucleus in the formation of the RNA of FMD virus. However, the actual morphogenesis of the virus takes place in cytoplasm. In BHK cells, changes attributable to virus infection were visible by the second hour, with the formation of threads and large polysome complexes near the nucleus. Viral particles soon appeared between these structures. There were no pronounced foci of viroplasma, and it seemed that they were not necessary. Simultaneously new membranes formed in the cell. Clumps of viral particles were next visible in the cxtoplasma. The clumps became enveloped and were transported in this way to the periphery of the cell. Elsewhere there was uptake of particles in autophagic vacuoles, an expression of cellular defensive processes. In ultra-thin sections the virions measured 21-25 nm. Within vacuoles the inner part of the virus, the nucleoid, showed greater contrast than the periphery, the capsid. At first there were only slight changes in mitochondria. Liberation of virus by cell rupture occurred only after severe damage to the cell, particularly the lysosome membranes.