dsRNA viruses (rotavirus) Flashcards
(33 cards)
What is the Baltimore Classification?
The Baltimore Classification clusters viruses into families depending on their type of genome (genome footprint).
dsDNA, ssDNA, dsRNA, (+)ssRNA, (-)ssRNA, (+)ssRNA with a dsDNA intermediate and gapped DNA.
Which one the statements is False?
1) Restriction enzymes in E.coli prevent replication of the virus.
2) We have a full dsRNA in our genome.
3) Though there are many members of dsRNA viruses, only few are pathogenic to humans.
2!
Why are there only few dsRNA viruses that can infect humans?
We do not have any dsRNA in our genome, thus we have several fast-acting innate immune sensors that detect dsRNA (like Toll like receptor 3 and Protein Kinase 3).
Rotavirus is a ______ virus, with a ____________ capsid and a ____ ________ genome.
dsRNA, non-enveloped (naked), segmented linear
(T/F) Because the rotavirus is a naked virus, it helps mount an immune response against the virus.
True!
What are the pros and cons to a virus having segmented genomes (ex. rotavirus)?
Cons: difficult to package all the segments (missing segment: non-infectious)
Pros: If co-infection of two rotaviruses, ability to shuffle (the less performing virus will steal a segment and get better than the other virus)
Briefly answer the following questions about Rotavirus?
1) What is its family + genus?
2) What are the associated diseases? Where does it infect (tropism)?
3) What is the mode of transmission?
4) What does it interact with?
1) Family: Reoviridae. Genus: Rotavirus.
2) It causes GASTROENTERITIS. It infects the epithelium of the small intestine. At first, it infects the upper intestine and as disease progresses it affects distal parts.
3) Fecal-Oral
4) Integrins and Sialic acids
Rotavirus is made of spikes outside formed by proteins _____ and _____.
The outer capsid contains the protein _____, while the intermediate capsid contains ______ and the inner capsid contains __________.
VP8, VP5
VP7, VP6, VP2
Match the VP proteins with their functions:
1) VP1
2) VP2
3) VP3
4) VP4 (which matures into VP8 and VP5)
5) VP6
6) VP7
A) Non-functional but matures into functional VP8 and VP5
B) Encodes for RNA-dependent RNA polymerase. Forms the core of the replication unit
C) Neutralization of antigen
D) Structural and species-specific antigen
E) Stimulates viral RNA replication. Forms the core of the replication unit
F) Encodes for methyltransferase mRNA capping enzyme. Forms the core of the replication unit
1) VP1: Encodes for RNA-dependent RNA polymerase. Forms the core of the replication unit
2) VP2: Stimulates viral RNA replication. Forms the core of the replication unit
3) VP3: Encodes for methyltransferase mRNA capping enzyme. Forms the core of the replication unit.
4) VP4 (which matures into VP8 and VP5): Non-functional but matures into functional VP8 and VP5
5) VP6: Structural and species-specific antigen
6) VP7: Neutralization of antigen
VP8 and VP5 are part of the spikes of Rotavirus. Briefly describe their functions.
VP8: located at the DISTAL terminal of the spike, is responsible for the VIRUS-LIGAND interaction
VP5: facilitates the HOST CELL PENETRATION through the conformation rearrangement and membrane fusion.
How does NSP4, produced by segment 10 of Rotavirus, cause diarrhea/other symptoms (6 ways)?
1) Paracrine effects on neighboring cells
2) Impact Ca2+ signaling pathways (PLC)
3) Inhibition of sucrase/maltase (can no longer breakdown sugars - fatigue)
4) Villi flattening (retention is inhibited)
5) Activation of the enteric nervous system (pain)
6) Serotonin receptor 5-HT3
It causes a complete imbalance of electrolytes, causing diarrhea + dehydration.
How does rotavirus get cleared relatively easily?
1) Immune system recognizes dsRNA viruses very quickly
2) The lack of envelope prevents the virus to hide from the immune system
3) The damages in the small intestine epithelium contribute to mounting immune system
What does NSp & VP stand for?
NSp: non-structural protein (accessory proteins like proteases)
VP: viral protein (essential part of the virus, like the capsid proteins)
The mRNA of Rotavirus has ____________ but lacks a _______ _____.
It contains ______ RNA segments coding for ____ different proteins.
RbRP ___ and ___ are attached to segments.
5’methylated cap; polyA tail
11; 12
VP1 and VP3
Match the first three steps of the Rotavirus replication cycle:
1) Step 1
2) Step 2
3) Step 3
A) Lower calcium concentrations trigger UNCOATING (loss of VP7) of the triple-layered particle (TLP) and membrane PENETRATION by VP5. Loss of the OUTER CAPSID (due to the change in pH) and release of the double-layered particle (DLP) into the cytosol.
B) The rotavirus virion first ATTACHES to the target cell using VP8 which bind SIALIDATED (modified by sialic acid) form of INTEGRIN .
C) Non-clathrin, non-caveolin- mediated ENDOCYTOSIS delivers the virion to the EARLY ENDOSOME.
Step 1: The rotavirus virion first ATTACHES to the target cell using VP8 which bind SIALIDATED (modified by sialic acid) form of INTEGRIN .
Step 2: Non-clathrin, non-caveolin- mediated ENDOCYTOSIS delivers the virion to the EARLY ENDOSOME.
Step 3: Lower calcium concentrations trigger UNCOATING (loss of VP7) of the triple-layered particle (TLP) and membrane PENETRATION by VP5. Loss of the OUTER CAPSID (due to the change in pH) and release of the double-layered particle (DLP) into the cytosol.
Why is the formation of DLP critical?
1) Hides the dsRNA (removing all layers would cause immune system to attack it)
2) Enable the diffusion of the metabolites (aka nucleotides) to INITIATE TRANSCRIPTION.
(T/F) Once (+) sense RNA is synthesized in the DLP of rotavirus, translation begins within the DLP, as the VP1 contains polymerase activity and VP3 caps mRNA.
True!
(T/F) VP3 has guanylyltransferase, N-7-methylase and 2’-O-methylase activites.
True!
_________ and ________ are key for rotavirus.
Timing; Location
What can (+)RNAs serve as in rotaviruses?
1) As mRNAs for translation
2) As templates for synthesis of (-)RNA during genome replication
All (+) RNAs contain a conserved ________ sequence in 3’ that is recognized by _____ and ______ used to prime (-) strand synthesis once the (+) RNAs are attached to the ______ layer, of the inner capsid protein ______.
UGACC
VP1; VP3
Inner; VP2
(T/F) RNA transcription using RdRp for rotavirus is primer dependent.
False!
They do not need a 3’ OH primer, they need a UGACC sequence.
The first proteins to be synthesized are NSP1 and NSP3. What are the functions of these proteins?
NSP1: Blocks immune response - gives virus more time to replicate to infect more cells.
NSP3: Blocks host translation, allows virus to hijack the host cells.
Which one of the statements is false regarding rotavirus?
1) Rotavirus replicate their genome in the early stage of their lytic cycle.
2) Once RdRp synthesizes mRNA, the mRNA leaves the DLP.
1 is false.
Rotavirus replicate their genome in the LATE stage of their lytic cycle, when it is time to leave. There is no point in replication of the genome if it can not be packaged. Therefore, they synthesize everything first and then the genome.
