intro to virology
What is a virus? An obligate intracellular parasite comprising of genetic material often surrounded by a protein coat/capsid and sometimes a membrane (envelope)
What is the viral life cycle? The process of virus attachment, entry, replication, assembly, and release from the host cell.
What are the components present in all viruses? Viral genome (DNA or RNA) and Viral Capsid (a protein coat).
What is an envelope in some viruses? A lipid bilayer with glycoproteins, which can help the virus bind to cells.
What are the two essential components found in all viruses? Viral genome (DNA or RNA) and Viral Capsid (a protein coat).
Are enveloped viruses more or less resistant to environmental constraints compared to non-enveloped viruses? Less resistant.
What is the main role of the capsid? To protect the viral genomic material.
What are DNA and RNA fragile to? pH, heat, drying, UV.
What does the capsid ensure in terms of the viral genomic material? Delivery into the cell.
What can proteins on the capsid be recognised by? Host cell receptors.
What are the three forms of capsid? Helical, Icosahedral, Scaffolded Icosahedral
What is packaging in virology? Placement of viral genome inside a capsid or an envelope
What is the structure of the capsid? Closed 3-dimensional
Does the capsid have holes? No, it is stable
What is the capsid built of? Repeating protein structures
What is the outer protein coat of a virus called? Capsid
What are the protein subunits that make up the capsid called? Capsomers
What is an example of viral symmetry? Icosahedral symmetry
How do we study viral capsids? Using CryoEM (Transmission electron cryomicroscopy).
What is the composition of the viral envelope? Lipid bilayer.
What is the role of the viral envelope in virus attachment to cells? It is involved in virus attachment to cells.
How does the viral envelope interact with the host cell membrane? It can fuse with the host cell membrane.
How does the virus exit cells while using the cell machinery? Through the viral envelope.
What potential benefit can the viral envelope provide to the virus? It can avoid cell damage and potentially avoid the immune response.
What are non-enveloped viruses more resistant to? pH, heat, dryness, alcohol, soap
What do non-enveloped viruses usually cause more of? cellular damage
What happens when non-enveloped viruses exit cells? They disrupt the integrity of the membrane and can cause cell lysis
What is a capsid? A protein coat that encloses and protects the genetic material/genome.
What are capsomers? Clusters of proteins that compose the capsid.
What are peplomers? Proteins on the envelope of the virus (like Glycoprotein).
What is a complete virus particle called? A virion.
Why is knowing the structure of viruses important? It can help in creating treatments and developing vaccines.
Name some substances that can kill viruses. Soap, alcohol, bleach.
Who is responsible for the classification of viruses? ICTV (International Committee on Taxonomy of Viruses).
How are viruses grouped in terms of phenotypic characteristics? By morphology, nucleic acid type, replication, host, and disease caused.
What are the two main types of nucleic acid in viruses? DNA and RNA.
How many groups are there in the Baltimore classification system? 7.
What are the groups in the Baltimore classification system based on? Nucleic acid, sense, and method of replication.
How are viruses named? Viruses are named after the disease they cause, the organisms they infect, the place where they were first found, or after the scientist who first identified the virus.
Where does the name 'Poliovirus' come from? It comes from the poliomyelitis disease.
Where does the name 'Zika virus' come from? It comes from the Zika forest in Uganda where the virus was first isolated in 1947.
Where does the name 'Rous Sarcoma virus' come from? It is a combination of the disease it causes, the organism it infects, the place where it was first found, and the scientist who first identified the virus.
Where does the name 'Epstein-Barr virus' come from? It was named after M.A. Epstein and Yvonne Barr, the scientists who discovered the virus.
Why is the term 'Hepatitis' used for liver inflammation? The term traces back to the Ancient Greek noun 'hepar', meaning 'liver', because the disease inflames the liver's tissue.
What is a susceptible cell A susceptible cell has a functional receptor for a given virus - the cell may or may not be able to support viral replication
What is a resistant cell A resistant cell has no receptor - it may or may not be competent to support viral replication
What is a permissive cell A permissive cell has the capacity to replicate virus - it may or may not be susceptible
What is a susceptible and permissive cell A susceptible AND permissive cell is the only cell that can take up a virus particle and replicate it
Are viral particles meta stable Yes
What does meta stable mean ? Stable enough to protect the genome but unstable enough to come apart following infection due to weak non covalent bojds
What are the 5 stages of the infectious cycle 1. Attachment to cells
2. Enter & uncoating
3. mRNA
3. Translation using host ribosomes
4. Assembly
5. Egress (exit)
What two things make a virus a viral pathogen/ disease Have effects on the host due to infection and replication
Effect the host response/immune response
The capacity of a virus to cause disease/virulance can be quantified by 4 variables : - Virus titer
- Mean time to death
- Mean time to appearance of signs
- Measurement of fever, weight loss
What are symptoms of disease What only you can feel
What are signs of disease What others can detect
Other than humans what else can viruses effect - Plants/vegetation
- Livestock
- Wild or domesticated animals
What are 4 ways can viruses be beneficial Oncolytic viruses
Alternatives to antibiotics
Gene therapy
Biological control-an alternative to pesticides?
What is cytopathic effect (CPE) in cell culture? Cytopathic effect (CPE) in cell culture refers to the structural changes in cells caused by viral infection, which can be observed under a microscope.