Lecture 33. Virology I: Genetic Diversity Flashcards
What are viruses ?
Infectious, obligate intracellular parasites
What are viruses surrounded by ?
Protein coat and or lipid membrane
What do viruses within a host cell use to synthesis progeny virus particles ?
Cellular machinery
Where do viruses infect and replicate ?
Within cells
Are viruses cells ?
No
Where are all viral genomes packaged ?
Inside particles that mediate their transmission from host to host
What does the viral genome contain ?
Information necessary to initiate and complete an infectious cycle within a susceptible, permissive cell
Where are all successful virus able to establish themselves in ?
A host population
Why do viruses establish themselves in host populations ?
So viral survival is ensured
Why are viruses a perfect model for the concept of “survival of the fittest” ?
- Viruses that are too successful and kill their hosts eliminate themselves
- Viruses that are too passive and their replication is impeded by their hosts’ defences may be eliminated
What are viruses made of ?
- Capsid
- Proteins
- Genome
- May contain an envelope
What is a capsid ?
A protein shell
What are capsids made from ?
Identical proteins
What proteins may be present in viruses ?
- Enzymes
- Ion channels
- Immune modulators
What is contained in the genome of a virus ?
RNA or DNA
What is the viruses envelope ?
A lipid membrane
What is the function of the envelope ?
Block entry for enzymes
What are some structure of the viron ?
- Helical
- Polyhedral
- Icosahedral
- Spherical
- Complex
Who developed the seven genome types ?
David Baltimore
What is the genome type in group I ?
Double stranded DNA
What is the genome type in group II ?
Single stranded DNA
What is the genome type in group III ?
Double stranded RNA
What is the genome type in group IV ?
Single stranded positive sense RNA
What is the genome type in group V ?
Single stranded negative sense RNA
What is the genome type in group VI ?
Single stranded positive sense RNA reverse transcriptase
What is the genome type in group VII ?
Double stranded DNA reverse transcriptase
What can positive strand RNA do ?
Be translated into a protein immediately
What can a negative strand of RNA do ?
Cannot be translated therefore must be transcribed into positive sense mRNA before translation
What information is encoded within the virus genome ?
Gene products for:
- Virus genome replication
- Assembly and packaging of the genome
- Regulation of the virus replication cycle
- Modulation of host defences
- Spread to other cells and hosts
What information is not contained within the virus genome ?
- The genes necessary for complete protein synthesis
2. No gene encoding proteins for energy production or membrane synthesis
What must viral genomes be processed into so it can be read by host ribosomes ?
mRNA
What does an acute infection of poliovirus cause ?
Poliomyelitis
What group is poliovirus in ?
Group 4
What shape is poliovirus ?
Icosohedral
How many capsid proteins does poliovirus have ?
4
What are the capsid proteins contained in poliovirus ?
- VP1
- VP2
- VP3
- VP4
When is the pH of poliovirus stable ?
When its acidic
How many copies of proteins in a capsid of poliovirus ?
60
Who does poliovirus infect ?
People
How is poliovirus transmitted ?
Aerosol or ingestion (faecal-oral route)
What are the primary infection sites of poliovirus ?
Lymphoid tissue of pharynx and gut
What is the secondary infection site of poliovirus ?
Central nervous system
What causes paralysis and muscle weakness in poliovirus ?
Lytic infection of neurons
Who does the influenza virus affect ?
Birds, people, pigs, horses
What group is influenza in ?
Group V
What is in the structure of influenza ?
- Glycoproteins
- Matrix protein (M1)
- Matric ion channel (M2)
- Lipid bilayer
- Nucleocapsid protein
- Nuclear export protein
- RNA polymerase proteins
What are the two glycoproteins in influenza structure ?
- Neuroaminidase (NA)
2. Haemagglutinin (HA)
What are the 3 RNA polymerase proteins ?
- PB1
- PB2
- PA
How is influenza transmitted ?
Respiratory droplets
What is the primary infection site of influenza ?
Upper respiratory tract
When are you infectious with influenza ?
One or two days before symptoms
What is HIV ?
The causative agent of acquired immune deficiency syndrome (AIDS)
What type of infection is HIV ?
Persistent
How did HIV enter humans ?
Likely from chimpanzees
What does HIV do ?
Gradually destroys immune cells
What group is HIV in ?
Group VI
What is in the structure of HIV ?
- Envelope proteins (gp120)
- Capsule proteins (p24)
- Reverse transcriptase
- Lipid bilayer
How can HIV be transmitted ?
- Blood
- Sex
- Mother to child - before and during birth, breast milk
What is the primary infection of varicella zoster virus ?
Chickenpox
What type of infection is varicella zoster virus ?
Persistent
How is varicella zoster virus transmitted ?
Aerosols and direct contact with rash
When is varicella zoster virus infectious and how long does it remain infectious?
1-2 days before rash appears and lasts till all lesions have crusted over
Where does varicella zoster virus persist ?
Nerve ganglia
What is the reactivation of varicella zoster virus called ?
Shingles
What is the structure of varicella zoster virus ?
- Envelope proteins
- Tegument
- Nucleocapsid
What group is varicella zoster virus in ?
Group I
What is natural reservoir for severe acute respiratory syndrome ?
Bats
What are the three zoonotic coronaviruses ?
- 2002-2003 SARS-CoV
- 2012+ MERS-CoV
- 2019+ SARS-CoV-2
What group is coronavirus in ?
Group IV
What is in the structure of coronavirus ?
- Spike glycoprotein
- Nucleoprotein
- Membrane protein
- Envelope small membrane protein
How is SARS-CoV-2 transmitted ?
Respiratory droplet, aerosols, contaminated surfaces
When is SARS-CoV-2 infectious ?
2 days before symptoms
Where is the primary infection site of SARS-CoV-2 ?
Upper respiratory tract
