Mechanism of astrovirus entry into Graham 293 cells.

Astroviruses are intestinal pathogens associated with gastroenteritis in man and animals. The mechanism of internalization into host cells has not been reported previously. The cell entry pathway of serotype 1 human astrovirus into 293 cell line was studied biochemically and morphologically. Viral infection was monitored by indirect immunofluorescence. Infected cells were treated with the lysosomotropic agents ammonium chloride, methylamine, and dansylcadaverine or the ionophore monensin to raise the intraendosomal and intralysosomal pH. All drugs tested inhibited the early stages of infection whereas they did not interfere with the viral binding to the plasma membrane. The presence of astrovirus particles was detected by electron microscopy in coated pits and later in coated vesicles. The data indicate adsorptive endocytosis as the most probable mechanism by which astroviruses enter susceptible cells.