Morphogenesis of Sindbis virus in three subclones of Aedes albopictus (mosquito) cells.

The morphogenesis of Sindbis virus in three Aedes albopictus subcloned cell lines was examined. Each line was distinguishable with respect to morphology, cytopathic response to infection, and progeny yield. C7-10 cells, which produced the highest titers of virus and exhibited the most severe cytopathic response, were characterized ultrastructurally by the presence of budding particles at the cell surface and at the membranes of internal vesicles. C6/36 cells, which displayed a moderate cytotoxic response, manifested similar features in response to Sindbis virus infection. Both cell types also produced a structure composed of an electron-dense matrix in which nucleocapsids were embedded. Internally matured virions were released by exocytosis from these cells. In addition to a lack of cytopathic effect, u4.4 cells also failed to exhibit obvious morphogenetic changes upon infection. Virus particles were occasionally seen within vesicles, but budding at the cell surface was not detected. The mechanism of release of internally matured virions was not apparent. These studies provide further evidence that these three subcloned mosquito cell lines represent different tissues in the larval or adult insect.