The effects of virus infection on the host cell
1-Cytocidal (death of infected cell)
- A cell can be directly killed by the virus,
- The virus kills the cell by
- Inhibition of synthesis of cellular DNA, RNA, and protein
- Lysing the cell during exit
- Viruses may replicate widely throughout the body without any disease symptoms if they do not cause significant cell damage or death
-e.g., adenovirus and poliovirus
2-Cell fusion
- Infection of cells with certain viruses causes the cells to fuse producing giant multinucleated cells (syncytia formation) -e.g. herpesviruses & paramyxoviruses
Title: Multinucleate giant cell of Tilapia lake virus infection in fish
3- Formation of intracytoplasmic or intranuclear inclusion bodies
- These are nuclear or cytoplasmic aggregates of partially folded expressed viral proteins at sites of replication
4-Transformation of cells
- Some viruses can transform normal cells into malignant cells
- The transformation is an irreversible genetic process caused by the integration of viral DNA into the host’s DNA
5-Non-Cytocidal changes in virus-infected cells
- Some viruses do not kill the cells in which they replicate
- They often cause persistent infection during which infected cells produce and release virions
- In such infections, overall cellular metabolism is little affected and no overt symptoms are seen
- In many instances, infected cells even continue to grow and divide
- This kind of interaction occurs in cells infected with RNA viruses, such as pestiviruses, arenaviruses, and retroviruses
“Not all viruses are bad for you”
- It’s true, most viruses have a pathogenic relationship with their hosts
- qBut they are not all bad
- Bacteriophages (or “phages”) found in the mucus membrane lining in the different tracts infect and destroy specific bacteria
- Viral infections at a young age are important to ensure the proper development of our immune systems
- In addition, the immune system is continuously stimulated by systemic viruses at low levels sufficient to develop resistance to other infections