The animation starts by brief explanation of the virus replication cycle. It is covered under three main headings 1) Initiation of infection 2) Replication and the expression of the virus genome 3) Release of the mature virions from the infected cells.
There are eight stages of virus replication these are 1) Attachment 2) Penetration 3) Uncoating 4) Gene expression 5) Genome Replication 6) Assembly 7) Maturation 8) Release
Penetration : Penetration occurs almost instantaneously after attachment and is a next step for gaining entry into the cytoplasm by crossing the plasma membrane. The penetration process differs for different viruses.
Penetration by the process of endocytosis is common to both enveloped and non-enveloped viruses. While some virus species can directly penetrate the plasma membrane and inject their genetic material into the cytoplasm, the majority of viruses enter cells via endocytosis. Direct penetration is observed only in non-enveloped viruses, membrane fusion is observed only in enveloped viruses. Some of the non-enveloped viruses like picornaviruses and phages are capable of directly injecting their genome into the host cell.
Thus, penetration allows the viruses to deliver their genome into the host cells to initiate replication. Uncoating follows penetration. Except for viruses that release their genome at the plasma membrane, penetration and uncoating are simultaneous.
The animation covers:
- Penetration process
- Endocytosis for influenza, hepatitis B, adenovirus
- Direct penetration of genome for circovirus, parovirus
- Membrane fusion for HIV, herpes simplex virus
- Clathrin mediated endocytosis
- Clathrin independent endcytosis
- Caveolae mediated endocytosis
- Lipid raft mediated endocytosis