VMC 211: General Veterinary Microbiology (1+1)

ATTACHMENT

• Attachment occurs via one or more of virus surface proteins to specific molecules of host cell. These cellular molecules are known as receptors.
  • The recognition of the receptor by the virion is highly specific. Some viruses have to to bind to a second type of cell surface molecule called coreceptor in order to infect a cell.
  • In some viruses binding to the receptor causes conformational changes in the virus protein that enables it to bind to the coreceptor.
  • Receptors and coreceptors are cell surface molecules usually glycoproteins. Eg: intrcellular adhesion molecule–I (ICAM-I),CD 155, CD 4, sialic acid containg glycoproteins, signaling lymphocyte activation molecule (SLAM)
• Virus attachment sites of naked viruses are on the capsid surface. For some viruses attachment occurs through specialized structure such as fibres and knobs of adeno virus and the spikes of rotavirus.
• For enveloped viruses the attachment sites are on the surface glycoproteins present on the envelope.
• Initially a virion is weakly bound to a cell at only one or few receptors. At this stage the attachment is reversible. Subsequently binding to many receptors occurs and the attachment becomes irreversible.