Viruses As Causes Of Disease 24.11.23 Flashcards
Define a virus
An infectious, obligate intracellular parasite, comprising genetic material (DNA or RNA) surrounded by a protein coat and/or a membrane
What are the 5 different shapes of viruses?
Helical
Icosahedral
Complex
Non-enveloped
Enveloped
Slide 13
5 steps of virus replication
- Attachment to specific receptor
- Cell entry
- Host cell interaction + replication
- Assembly of virion
- Release of new virus particles
Explain attachment stage of virus replication.
Attachment to specific receptor
Explain cell entry stage of virus replication.
Unloading of virion within cell
Explain host cell interaction + replication stage of virus replication.
- migration of genome to cell nucleus
- transcription to mRNA using host materials
- translation of viral mRNA to produce:
Structural proteins
Viral genome
Non-structural proteins e.g. enzymes
Explain assembly of virion stage of virus replication.
Assembly of virion
Explain release of new virus particles stage of virus replication.
A) bursts out —> cell death e.g. rhinovirus
B) budding/exocytosis e.g. HIV/influenza
What are the 5 ways viruses cause disease?
A) direct destruction of host cells
B) Modification of host cell
C) ‘Over-reactivity’ of immune system
D) Damage through cell proliferation
E) Evasion of host defences
Give an example of a virus which causes direct destruction of host cells.
poliovirus —> host cell lysis and death after a viral replication period of 4 hours
Give an example of a virus which causes modification of host cell.
Rotavirus —> atrophies villi and flattens epithelial cells, decreases small intestine surface area, nutrients incl. sugar not absorbed, hyperosmotic state, profuse diarrhoea
Give an example of a virus which causes ‘over-reactivity’ of immune system.
Hepatitis B
Give an example of a virus which causes ‘damage through cell proliferation’.
Human papillomavirus —> cervical cancer
Give an example of a virus which causes ‘evasion of host defences’.
Herpesviridae
