• Viruses attach to proteins known as cellular receptors or attachment factors on the surface of the host cell
  • All viruses react specifically with a receptor on a cell surface using a receptor-binding protein in a key–and–lock fashion, making it impossible to dislodge. This binding is referred to as virus attachment.
  • Thus why viruses are restricted to a certain host, tissues and cells due to binding specificity.
  • The virus receptors on cells are often glycoproteins or glycolipids
  • High-affinity interactions between viral proteins and cellular receptors drive conformational changes in the proteins’ structures that activate signalling cascades and destabilize the plasma membrane, leading to pore formation and internalization of the virus
  • It is worth noting that a receptor could be accompanied by an additional co-receptor that triggers a particular entry pathway or stabilizes the virus at the plasma membrane.
  • Common viral receptors include sialylated glycans, cell adhesion molecules such as immunoglobulin superfamily members and integrins, and phosphatidylserine receptors.

Viral tropism and cellular receptors

  • CD4 (cluster of differentiation 4) is a glycoprotein found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells
  • HIV use more than one receptor for attachment and entry