The findings described in the previous section provided us with a model system in which to examine the distribution of several structural and non-structural proteins in infected mammalian and tick cells (Fig. 2) . The analysis is complicated by the fact that the basic cellular morphology differs substantially between the mammalian and tick cell lines. Nevertheless, in acute infections in Vero and ISE6 cells, as well as in the persistently infected ISE6 cells, M, E, and NS3 proteins were localized to the perinuclear region, although some staining was seen throughout the cytoplasm (Fig. 2B) . NS1 exhibited a more punctate cytoplasmic staining pattern and NS5 showed a diffuse cytoplasmic staining pattern with occasional evidence of nuclear staining. Similar patterns were seen for all the viral proteins in both cells lines.