Introduction To Viruses Flashcards
What is a virus?
They are a small non cellular organism. They are obligate intracellular pathogens which means they can only replicate inside the host cell. They are usually specific to their hosts.
What are the three types of structures of virus?
Icosahedral viruses have 20 faces of equilateral triangles.
Helical viruses bind round R/DNA in a helical fashion.
Complex viruses are shaped other than icosahedrons or helixes.
What is the structure of a virion?
Nucleic acid is enclosed in a protein capsid which is surrounded by a lipid envelope with spike projections which can be used for diagnosis and vaccine targets.
What are some modes of transmission and name some examples of diseases that utilise them?
Blood borne such as HIV, Hepatis B and C.
Sexual and vertical such as HIV and Hepatitis B.
Droplet such as Influenza l.
Airborne such as measles and chickenpox.
Close contact such as herpes.
Name four consequences of viral infections and what viruses fall into each category
Clearance of virus with either no, short or long term immunity such as no immunity Hepatitis C and long term immunity measles.
Chronic infection such as HIV.
Latent infection such as herpes.
Transformation which is a long term infection with altered cellular gene expression such as human papillomavirus.
What is viral latency?
Following primary infection some viruses lie dormant. The full viral genome is still in the host cell but expression is limited. Reactivation can occur and can or cannot cause apparent disease. More likely to happen in immunocompromised patients.
Herpes simplex virus.
Varicella zoster virus.
What are three mechanisms by which viruses can cause cancer.
They can drive cell proliferation by controlling cell cycle.
They can modulate apoptosis to prevent cell death.
Persistent viral infections can cause constant inflammatory processes which can cause cancer by reactive oxygen species.
Such as Hepatitis B and C which can cause hepatocellular carcinoma.
Human papillomavirus can cause cervical, anal and oropharyngeal cancers.
How can viruses be detected?
The whole organism can be detected. Part can be detected using antigen or nucleic acid.
An immune response to a pathogen so using antibodies can be used.
Microscopy or cell culture can be used.
What are some problems with antiviral therapy?
They are virustatic.
Toxic side effects.
Limited viral proteins that are potential targets due to virus using host cell enzymes to replicate.
What can antivirals be used for?
Prophylaxis to prevent infection.
Pre-emptive therapy when replication is detected but there are no symptoms.
Overt disease so for hidden.
Suppressive therapy to keep replication levels below that which would cause tissue damage in immunosuppressed patients.
How are viral infections prevented?
Immunisation Prophylactic treatment Infection prevention and control Blood or tissue screening Antenatal screening
