RNA Virus 1 Flashcards Preview

Micro/Immuno Part 2 > RNA Virus 1 > Flashcards

Flashcards in RNA Virus 1 Deck (28):
1

Picorna

-colds and polio

2

flavi

hep C and dengue

3

retro

HIV

4

corona

MERS-middle east resp syndrome

5

filo

ebola

6

rhabdo

rabies

7

orthomyxo

flu

8

paramyxo

croup
measles

9

relevance of RNA viruses

-huge medical problem-flu, colds, diarrhea, hep C, AIDS
-high mutation rates:
-resistance to antivirals
-barriers to vaccines
-reassortment of genome segments
-pandemics
"scariest new bugs"-Quammen

10

common features of RNA viruses

-RNA is genetic material and template for protein synthesis
-the dual purpose of replication is to copy the genome and make mRNA
-diverse strategies have evolved to accomplish these dual goals

11

double stranded RNA

-uses RDRP to make + sense mRNA for proteins

12

ss RNA +

-can be used for protein synthesis
-must use RDRP to make - strand to make copies for more protein synthesis, and RDRP changes - back to + before reading it

13

ssRNA -

-can be replicated or transcribed to + by RDRP

14

+strand

-sense strand, coding= mRNA

15

- strand

-antisense strand
-template for mRNA

16

how to make RNA from RNA?

-RDRP
-allows viruses to cope their RNA genomes and to synthesize mRNA from RNA templates

17

RDRP

-cells do not have the enzymes to transcribe RNA from RNA
-therefore all rNA viruses encode and RNA pol to copy their RNA genome and make mRNA
-RDRP is highly efficient-poliovirus makes 50K copies in 8 hours!

18

where does RDRP do its job?

-cytoplasm-except flu- anchored to something
-RNA, RDRP, nucleoproteins, and accessory proteins don't float freely in cytoplasm
-replication often occurs on cell membranes (endo, lyso, ER vesicles)
-this concentrates all the components and increases efficiency

19

fidelity of RDRP is low

-doesn't proofread, works as an octomer
-error rates of 1 in 10^3-4
-all RNA virus stocks are mixtures of wild type and mutant forms

20

rapid evolution by recombination

-exchanging larger sections produces new genomes
-hybrid viruses may have new features (antigens, virulence)
-high freq event-up to 20% of poliovirus genomes are recombinant after 1 growth cycle

21

reassortment of genome segments

-segmented RNA viruses-Reo, Retro, Bunya, Arena, Orthomyxo
-segments can mix if cell is infected with multiple strains
-new variant can be highly virulent-fluuuuu

22

consequences of RNA virus genetic diversity

-mutants arise frequently
-new variants may cause new diseases
-drugs and vaccines lose effectiveness
-viruses are not pure populations-quasispecies

23

polio!

-+ssRNA linear mRNA molecule
-infects GI epithelial cells, may spread to muscles and neurons
-vaccination with live or killed virus induces protective antibodies
-WHO Global eradication program underway
-annual cases-296 as of oct 2, 2013

24

polio disease

-fecal oral
-persists in water
-humans only host
-95% asymptomatic acute GI infection
-5% mile disseminated disease
-1% paralytic infection of motor neurons

25

polio cycle

-enters cell via endocytosis or just docks- CD155
-ejects genome because capsid is pulled open by interaction with receptors (become hydrophobic)
-mRNA immediately translated to protein-then cleaved by self proteases
-RDRP replicates genome into - strand and copies it many times
-RDRP also transcribes - strand back to + strand so it can be translated
-when there is enough mRNA, RDRP just makes RNA genome to be packaged-when there are enough capsids around

26

issues with + RNA

-collisions occur b/n RDRP and ribosomes, not big problem
-translation first when RDRP is scarce
- - RNA synthesis occurs later when RDRP is abundant-then must be changed back into plus to be packaged

27

association of RDRP with virions

-all RNA viruses encode RDRP (retro-RT)
-dsRNA and - RNA must package RDRP into virion- can't be translated first
-+RNA may or may not package
-if RDRP not present, must translate first

28

polio clinical features

-motor neuron involvement
-serology and culture
-control symptoms, breathing support
-vaccine, sanitation, peace