Gangliosides are essential endosomal receptors for quasi-enveloped and naked hepatitis A virus

The Picornaviridae are a diverse family of positive-strand RNA viruses that includes numerous human and veterinary pathogens1. Among these, hepatitis A virus (HAV), a common cause of acute hepatitis in humans, is unique in that it is hepatotropic and released from hepatocytes without lysis in small vesicles resembling exosomes(2,3). These quasi-enveloped virions (eHAV) are infectious and the only form of virus detected in blood during acute infection2. By contrast, non-enveloped, naked virions (nHAV) are shed in feces, stripped of membranes by bile salts during passage through bile ducts to the gut4. How these two distinct types of infectious hepatoviruses enter cells to initiate infection is enigmatic. Here we describe a genome-wide forward screen that identified glucosylceramide synthase (UGCG) and other components of the ganglioside synthetic pathway as crucial host factors required for cellular entry by hepatoviruses. We show that gangliosides, preferentially disialogangliosides, function as essential endolysosome receptors required for infection by both naked and quasi-enveloped virions. In the absence of gangliosides, both virion types are efficiently internalized through endocytosis, but capsids fail to uncoat and accumulate within LAMP1(+) endolysosomes. Gangliosides relieve this block, binding the capsid at low pH and facilitating a late step in entry involving uncoating and delivery of the RNA genome to the cytoplasm. These results reveal an atypical cellular entry pathway for hepatoviruses that is unique among picornaviruses.