Human astroviruses (HAstV) are a frequent cause of
gastroenteritis in young children and immunocompromised patients. To understand the early steps of HAstV
infection in the highly permissive Caco-2 cell line, the binding and entry processes of the virus were characterized. The half-time of virus binding to the cell surface was about 10 min, while virus decapsidation took around 130 min. Drugs affecting
clathrin-mediated endocytosis, endosome acidification, and actin filament polymerization, as well as those that reduce the presence of
cholesterol in the cell membrane, decreased the infectivity of the virus. The
infection was also reduced by silencing the expression of the
clathrin heavy chain (CHC) by RNA interference or by overexpression of dominant-negative mutants of
dynamin 2 and Eps15. Furthermore, the entry of HAstV apparently depends on the maturation of endosomes, since the
infection was reduced by silencing the expression of Rab7, a
small GTPase involved in the early- to late-endosome maturation. Altogether, our results suggest that HAstV enters Caco-2 cells using a
clathrin-dependent pathway and reaches late endosomes to enter cells. Here, we have characterized the mechanism used by human astroviruses, important agents of
gastroenteritis in children, to gain entry into their host cells. Using a combination of biochemical and genetic tools, we found that these viruses enter Caco-2 cells using a
clathrin-dependent endocytic pathway, where they most likely need to travel to late endosomes to reach the cytoplasm and begin their replication cycle.