Table 2.

Examples of viruses with alternative entry mechanisms

Herpes viruses	Many herpes viruses can bind to multiple receptors via accessory viral proteins or proteins that can bind to multiple receptors [67], [68]. Depending on cell type and virus isolate, herpes simplex virus-1 can undergo fusion at the plasma membrane or in macropinosomes. The latter is either pH-independent or acid-activated [69]. Epstein–Barr virus has distinct envelope proteins that define binding to different receptors on B cells and epithelial cells, and distinct entry pathways.
Influenza A viruses	They use alternative endocytic mechanisms: clathrin-mediated endocytosis; micropinocytosis, and macropinocytosis [70], [71], [72]. In addition to sialic acid, the virus needs unidentified co-receptors [73]. The dependence on actin dynamics differs between polarized and non-polarized host cells [74].
African swine fever virus	This large DNA virus enters macrophages by macropinocytosis and clathrin-mediated endocytosis [75].
Uukuniemi virus	This bunyavirus enters endosomes in dendritic cells using DC-SIGN, a mannose-specific lectin [76]. Uptake is clathrin-mediated. In cell types lacking DC-SIGN, the receptors are not known, but the endocytic mechanism is micropinocytic [77].
Avian retro viruses	Different isoforms of the same receptor support penetration of avian sarcoma and leukosis viruses from distinct endosomes (early endosomes versus maturing endosomes) [78].
Rhinoviruses	Serotypes that use ICAM-1 as receptor enter via clathrin-mediated endocytosis and micropinocytosis. Among these, members of the A serotype are routed for acid-activated uncoating in recycling endosomes and members of the B serotype in maturing endosomes [79].