Viruses and Virology Flashcards
What did Dmitri Iwanowski find?
Tobacco plants can infect each other
What did the Chamberland filter show?
That viruses exist
What is a virus?
- Smallest infectious agent (20-300nm)
- Cannot replicate independently
- Cannot be seen by a microscope
What are general properties of a virus?
- Small
- Contain DNA or RNA
- Simple structure
How do viruses replicate?
Viral components are produced in the eclipse phase and are eventually assembled to make a final viral particle
What are the 3 structures in a virus?
- Nucleic acid
- Protein coat (capsid)
- Viral envelope
What 2 shapes can a virus be?
Rod or round
What symmetry do rod viruses have?
Helical symmetry
What symmetry do round viruses have?
Icosahedral symmetry
What are the properties of a icosahedron?
20 faces
30 edges
12 vertices
Are enveloped or non enveloped viruses more stable?
Non enveloped (naked)
What is a capsid?
- Protein shell
- Molecules arranged precisely
- Capsomeres are subunits of a capsid
What is icosahedral symmetry?
Identical protein subunits arranged together
What is the purpose of metastability?
It protects the viral genome and facilitates the delivery of it, achieved by symmetry of it’s subunits.
What 3 things is classification based on?
- diseases
- the host they infect
- virus particle morphology and nucleic acid
List the order of taxonomy for viruses
Order
Family
Subfamily
Genus
Species
What classification system is most commonly used?
Baltimore classification system
How many classes does the Baltimore classification system use?
7
What are the 2 unconventional viruses?
Viroids and Prions
Name some properties of viroids
- circular ssRNA
- rod or dumb bell shaped
- no proteins
Name some properties of pirions
- slowly replicate in host
- no nucleic acid
- abnormal forms of normal cellular proteins
What are the 3 goals of a virus?
1) get into the cell
2) make the virus
3) leave the cell
What is the difference between enveloped virus entry and non-enveloped virus entry?
- Enveloped entry fuses with membrane and then with endosomes at a low pH
- Non-enveloped has direct entry over the plasma membrane
What is the definition of viral tropism?
The specificity of a virus to a specific host cell
What are the 6 steps for viral replication?
1) Attachment
2) Entry
3) Uncoating
4) Viral NA + protein synthesis
5) Assembly
6) Release
What is replication of RNA viruses dependant on?
RNA dependant RNA polymerase
Name some in vivo culture systems
- animal
- plant
- bacteria
- chicken eggs
Name the in vitro culture system
cell culture
How are chicken eggs used as a culture system?
Many compartments can be used, the eggs are incubated at 37 degrees for 2-3 days. You observe the embryo for death/ changes.
What are CPEs?
Observable differences due to viral infection such as shrinking, syncytium, inclusion bodies and apoptosis
Define hemadsorption?
Infected cells bind to and absorb red blood cells
What are the two main ways of quantifying a virus?
- Measuring the number of viral particles (electron microscopy)
- Measuring the number of infectious viral particles (ELISA or IMF)
What are the 4 stages of the virus growth cycle?
1) Inoculation
2) Eclipse
3) Burst
4) Burst size
Name 3 portals of virus entry
- Conjunctiva
- Respiratory tract
- Gastrointestinal tract
- Skin
- Genital tract
- Congenital infection
How can your eye catch a virus?
Due to accidental introduction or from respiratory tract by droplets. Usually the herpes virus or adenovirus.
How do you get a virus in your respiratory tract?
Inhalation of middle sized droplets
What does the vagina do to avoid viruses?
Produce mucus and have a low pH
How does the gastrointestinal tract protect itself from viruses?
- acid
- low pH
- enzymes
- bile
How can your skin get a virus?
- Trauma/inoculation
- Medical procedures
- Insect/ animal bites
What is pathogenesis?
The ability/ capacity for a virus to cause disease
What is virulence?
The measure of pathogenesis of the infecting virus
How can viruses be quantified?
- Measure of lesions
- Measure fever/ weight loss
- Mean time to appearance of disease
- Mean time to death
- Virus titre
- Mortality/ hospitalisation rate
- Reduction in CD47 cell
What are the 3 phases of HIV?
1) acute phase
2) chronic phase
3) AIDs phase
What are some properties of HIV?
- Enveloped
- Lethal amount of calcium and influx of protein
- 2 surface glycoproteins
What factor can affect virulence?
Age
What do virus virulence genes affect?
- Toxins
- Viral replication
- Enables virus to spread to host
- Modulators of immune response
What are the 4 types of vaccine?
- nucleic acid vaccine
- subunit of an organism
- killed whole organism
- weakened form
What is a weakened vaccine?
Weakened form of the virus, may not be good for immunocompromised people but gives a strong and lasting response.
What is a inactivated vaccine?
Whole virus is dead so no replication, good for immunocompromised people but not a strong response
What is a subunit vaccine?
One more more subunits of the surface of the virus, good for immunocompromised people but not very strong response
What is a nucleic acid/ genetic vaccine?
Genes are given to host cells to be expressed for an immune response, quick and easy to develop and significant promise for development for future vaccines
What must an effective vaccination programme be?
Cheap and safe
What 3 factors does an effective vaccine need?
1) antigen stability
2) ease of diagnosis
3) no animal reservoirs
What can antivirals do?
Stop infection once it has started, there are over 1000 available on the US market
What do anti-HIV drugs do?
- control viral replication
- inhibit viral replication at different phases of replication
