anti vira ange Flashcards
1
Q
What is a virus?
A
infectious obligate intracellular parasite.
2
Q
What do viruses rely on?
A
- host - relient on the machinery of the host cell to carry out of replicatoin
- Genome = DNA or RNA [both can be single or double]. Always have a nucleic based genome
- Genome into a cell —> replicated. Produce viral particles with protein capsid allowing them to move.
3
Q
How would we view a virus?
A
electron microgram
4
Q
What are typical viruses
A
- Rhabdovirus
- Bullet shape virus
- Rotavirus
5
Q
What are the typical morphology categories of a virus?
A
- Symmetrical (?)
- Non-enveloped - outcase pure protein (?)
- Enveloped - membrane is derived from lipid membrane
- Pleomorphic - distinguished shaped.
- Capsid surrounded by a tegument - a bunch of protein in coat encapsulated within an envelope.
6
Q
In what 2 ways do viruses carry and use their genetic information?
A
- Some viruses use genomes of RNA and never had DNA at all in their replicaiton cycle
- Genomes of RNA that they carry around as their coding potential which they convert back to DNA inside the capsid of the virus or inside the host cell using a virally encoded enzyme which is completely unique to viruses called reverse transcriptase.
7
Q
What is negative sense?
A
- Some viruses carry their RNA
- if they do that, they need to copy the RNA into complementary mRNA (so it can attach onto the ribosome) then they can make it into their genome —> protein
- mRNA translated by ribosome
8
Q
What is the positive sense?
A
- mRNA sense
- attaches into the ribosome
9
Q
What are the consequences of RNA viral genome type?
A
- RNA viruses uses own polymerase to replicate. Theses do not have proof reading capacity.
- Results in high incident of mutations accumulating = rapid evolution
- RNA is is inherently biochemically less stable than DNA. Limit to the size of RNA Genome. Largest = coronaviruses [30 kilobases long]
- Can use complex coding strategies to make more proteins. Overlapping reading frames which means single a single stretch of nucleic acid could encode different proteins if the ribosome translate in the different reading frames.
10
Q
What are the consequences of DNA viral genome type?
A
More stable and big = plenty room for acquiring extra genes - accessory genes
11
Q
What are segmented genomes?
A
- Segmented genomes. where 23 chromosomes where it is physically discrete pieces of nucleic acids are encoding different genes of the virus
- allow recombination (reassortment) where different genes of different species virus mix.
- if they co-infect the same cells, they can mix themselves and creates new combination …. antigenic variability [influenza]
12
Q
What is the generic viral replication cycle?
A
- virus begins outside with the nucleic genetic information inside the capsid.
- the capside can be pure protein or may have an envelope coat and lipid envelope.
- virus attaches to cell surface membrane glycoprotein/protein ie: virus receptor
- Attaches to the virus receptor and enters the cell
- Once inside, the capside falls away exposing the viral genome to the machinery of the cell
- Then the viral genome might be directly converted to mRNA, or mRNA (itself) turned into protein.
- It can use its own polymerase or the cellular polymerase to replicate itself and make all the different genome.
- New viral particles assemble.
- Cell they leave die = pathways would have recognise it is infected.
13
Q
What is the replication cycle of HIV - 1?
A
- HIV viron with spike protein Gp120 binds to the cell receptor CD4 (on Th cells)
- Virus is brought closer to the cell surface where it engage with the second co-receptor CCR5 and/or CXCR4 (depending macrophage or Tcell)
- virus membrane and host membrane fuse and release viral particle which then undergoes reverse transcription.
- Produces DNA
- The Viral enzyme integrase is integrated/spliced into the host own DNA. This causes the viral genome to look like the host DNA
- This is transcribed by host into RNA form template
- Assemble a new virus particles and budded out of the cell.
14
Q
What is the replication cycle of the Influenza viral replication cycle?
A
- influenza latches onto glycoproteins and glycolipids on the surface of the cell
- Causes the cell to take in particle: endocytosis
- Fuse its contents with the endosomal lipids
- Releases 8 genomic segments of the RNA
- Those RNA segments enter the nucleus where RNA dependent RNA polymerase copy —> mRNA and replicate into new genomes
- Leave nucleus, binds to ribosomes.
- Made into proteins and new genomes move to cell surface alongside proteins. Bud and leave the cell
15
Q
Endosome
A
intracellular sorting organelles in eukaryotic cells. These are acidic cells
16
Q
What is meant by the cytopathic effect?
A
- death of the cell due to the virus. Usually as a result of the virus lysing the cell
- this could be due to shut down of host protein synthesis or accumulation of proteins
- Cell triggered apoptosis and dies as a result
17
Q
What is a plaque
A
- when cell die form a “bacterial colony”
- each dot, each plaque, is the result of a single cell originally being infected by a singla virus particle
- as virus replicated, it killed the cells and left a hole which is stained as clear hole, admist the rest of the cells stined with stain
18
Q
What can we use the plaque assay to do?
A
- quantify how many virus particles infected in a particlular preparation of virus.
- each plaque is part of the number of cells being infected by a single virus particle
- you make a dilution and putting them on monolayers of cells. After 2/3 days you count number of plaque that are formed
19
Q
What happens if they don’t form plaque, what do they form?
A
- Syncitium assay
- fuse all the cells together around them
- Virus with surface protein that can fuse at neutrol pH often fuse cells together
20
Q
How do you detect viruses in the lab and clinic?
A
viral genome , antigen, particels
21
Q
SERIOLOGY
A
detection of immune response to the virus
22
Q
In a person, when can we pick up the virus?
A
- 2-3 weeks later
- when that person seroconverts. ie: make an immune response
- detected by taking blood, looking in serum for present of antibodies for that virus.
- SERIOLOGY = detection of immune response to the virus.
