Introduction to Viruses Flashcards
Describe the possible shapes of a virus
Icosahedral : 20 faces
Helical: Protein binds around DNA/RNA in a helical fashion
Complex: Neither helical or icosahedral
What are obligate intracellular pathogens?
Viruses that only replicate inside a host cell
What can virus families be classified according to?
Virion shape / Symmetry
Presence or absence of envelope
Genome structure
Mode of replication
What is a virion
Extracellular form of virus
What encapsulates the nucleic acid of a virus?
A protein capsid
What surrounds the protein capsid?
A lipid envelope containing spike projections
What are the stages of virus replication?
Attachment
Uncoating
Replication of genomic nucleic acid
Protein synthesis
Virion assembly (insertion of virus proteins into a membrane)
Budding and release
What are the methods of viral transmission?
Blood bourne
Sexual
Vertical
Faecal - oral
Droplet
Airborne
Close contact
Vector-borne (indirect transmission of an infectious agent - occurs when a vector bites or touches a person)
Zoonotic ( a disease that normally exists in animals but can infect humans)
What might the coinfection of human and animal or bird strains in one organism lead to?
Recombination and generation of a new strain
What are the consequences of viral infection?
No, short or long lasting immunity
Chronic infection
Latent infection (lysogenic part of the cell cycle - lies dormant)
Transformation - long term infection with altered cellular gene expression
Describe the status of the viral genome during latency
Retained in host cell - expression is restricted (produces few antigen and no viral particles are produced)
What can reactivation cause?
May cause disease
When is reactivation most likely to occur?
In the immunocompromised - also where it is most severe
How can some viral infections lead to cancer?
Modulation of cell cycle control - driving cell proliferation
Modulation of apoptosis
Reactive oxygen species mediated damage
What are the three aspects of a virus that you can detect?
The whole organism
Part of an organism
the immune response to a pathogen
What is common in all antiviral agents?
They are virustatic none are virucidal
Inhibit the growth of the virus
Stops virus replicating
Why are there limited target proteins for antiviral drugs?
Virus utilises host cell enzymes in order to replicate
Give a reason why antiviral therapy is not used very commonly
Toxicity to the host cell is common
Give examples of when antiviral therapy may be used
Prophylaxis (prevents infection)
Pre-emptive therapy (evidence of infection- no symptoms)
Overt disease
Suppressive therapy - keeps viral replication below the rate that causes tissue damage
What are the possible methods of prevention of viral infections?
Immunisation (vaccination - active and passive)
Prophylactic treatment post exposure
Infection prevention and control measures
Antenatal screening
Viruses with what properties can be eradicated?
No animal reservoir
Clearly identifiable in diagnosis
No chronic state carrier
Efficient and practical intervention
Political and social support
