Flashcards in L32_RNA Viruses 1 Deck (26):
What virus causes the common cold?
What is a picorna virus?
A small RNA virus
Name a few diseases caused by RNA viruses
Colds, Polio, HEP C, Dengue, HIV, MERS, Ebola, Rabies, Flu, Croup
Name some consequences of the high mutation rate of viruses
Resistance to antivirals, Barriers to vaccines, Reassortment of genome segments, Pandemics
What are the 3 common features of RNA viruses?
1 RNA is the genetic material AND the template for protein synthesis
2 The dual purpose of replication is to copy the genome and make mRNA
3 Diverse strategies have evolved to accomplish these dual goals.
What is the difference between negative and positive mRNA?
Positive RNA is the sense strand and is what can be translated directly to protein. Negative RNA is its the antisense strand and is the template for mRNA.
Where does RDRP do its work in most RNA viruses in the cell? What is an exception to this generalization?
Replication often occurs on cell membranes (endosomes, lysosomes, ER vesicles), some RNA viruses do this in the nucleus like the flu.
Does RDRP proofread?
NO, creates a lot of mutations and many different genomes
What is are 2vmechanism by which rapid evolution can occur in RNA viruses during genome replication?
Recombination. RDRP will start replicating one strand of RNA then all of a sudden switch the template without breaking the synthesized strand to create a hybrid. This happens quite frequently. 20% of poliovirus genomes are recombinant after 1 growth cycle. Also Reassortment of Genome Segments in segmented RNA viruses
What helps keep quasispecies contained (relatively)
Selection pressure of the host which is not significantly changing.
What type of virus and family of viruses is the poliovirus in?
picornaviridae. in the enterovirus (infects the gut) family
Where does poliovirus infect the body first? where can it spread?
It varies from case to case. always starts in the gut. It then mutates to change its tissue tropism and can infect muscles and neurons
Describe the genome of poliovirus
+ ssRNA linear genome.
Is there a vaccine for polio? if so, how does it work?
vaccination with live or killed virus induces protective antibodies that help prevent the virus from attaching to the gut.
What is the main reason we can not get rid of polio virus?
Because it can survive in the environment, so if everyone is not immune it will continue to spread.
What is the mode of transmission of poliovirus? What species can it infect?
Fecal-oral. Persists in water supply, only infects humans!
What percentage of people who contract poliovirus in the gut experience symptoms?
95% asymptomatic acute GI infection
5% mild disseminated disease
1% Paralytic infection of motor neurons
What is the receptor that recognizes poliovirus?
How does poliovirus enter the cell?
Polio virus changes shape after binding to the receptor, capsid proteins become hydrophobic, capsid proteins form a pore through the membrane, RNA genome enters cell at plasma membrane or endosome membrane
Which RNA viruses must package RDRP in their Virion?
Negative ssRNA and dsRNA genomes.
What is an issue with + RNA genomes? How is this somewhat subverted?
Collisions occur between RDRP and ribosomes. Not a big problem, translation happens first when RDRP is scarce, and - RNA synthesis occurs later when RDRP is abundant.
How is polio diagnosed?
Motor neuron involvement with serology and culture
How do we treat poliovirus?
Control symptoms and breathing support if needed (iron lungs were used back in the day)
How can we prevent polio?
Vaccination and sanitation
Where is there endemic polio?
Pakistan, Nigeria, Sudan