Sequential cellular changes produced by African horse-sickness virus in monkey kidney cells.

M~)flkey kidney stable ceIIs developed characterist:c changes when infected with ail known types of African horse-sickness virus. First, there was an increase in the size of ceII nuclei. Then, basophilic Feulgen-positive granules were seen in the v:cin;ty of nucleoli. The granules increased in number and were scattered throughout the nucleus. As infection progressed, the nucleolus became covered with basophilic Feulgen-positive substance, and nuclear chromatin began to accumulate at the periphery or the nucleus. Nuclei became sm aller, and the nuclear chromatin eventually merged to form several Feulgen-positive bodies which had a smooth surface at the last stage of infection. In ele:tron micrographs, partic!es of Afr!can hor~e·sickness virus were seen mainly in the nucleus. Clusters of virus particles were observed around the denatured nucleoli. Most particles were ovoid, with diameters between 45 and 75 miIIi micron. Occasionally, virus part~cles were seen in denatured cytoplasm that had numerous vacuoles surrounded by endoplasmic reticulum. Dense bodies of various sizes were observed in the cytoplasm.