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Vilo > nidovirales > Flashcards

nidovirales Flashcards

1
Q

what genome do nidovirales have?

A

ss + strand RNA genome

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2
Q

what is the taxonomy of nidovirales?

A

Order: Nidovirales
–families: Coronoviridae, Roniviridae, Ateriviridae

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3
Q

describe the virus particles of coronoviridae members

A

-lipid envelope with proteins: S Protein (spike for receptor binding and membrane fusion), HE (hemagglutinin-Acetyl Esterase), E (small envelope protein for budding), M (membrane for contact toi nucleocapsid)
-nucleocapsid: Genome and N - Protein
-no ikosehadral internal structure of the virion

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4
Q

describe the SARS-CoV-2 infection cycle

A

1.viral entry via membrane fusion with viral entry via endocytosis
2.translation of ORF1a and ORF1b
3.Polyprotein processing
4.Formation of replication organelles
5.replication of gRNA and transcription of sg-mRNA
6.Translation of structural and accessory proteins
7.assembly of nucleocpasid
8.Formation of virion: virion maturation, spike cleavage
9.excocytosis

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5
Q

which receptors are used by coronaviruses?

A

-Mouse Hepatitis Virus: CEACAM1a
-SARS Cov: ACE2
-Hcov-229E: APN

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6
Q

what determines host tropoism in coronaviruses infections?

A

receptor

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7
Q

describe the structure of the S-Protein of SARS-CoV-2

A

-trimer (3 protomers)
-receptor-binding subunit
-membrane fusion subunit

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8
Q

what is highly variable between different coronaviruses? What is conserved?

A

variable: set of accessory proteins
conserved: ORF1a/1b

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9
Q

what does the genome of Coronaviruses look like?

A

-RNA genome (ss +)
-5’ UTR with cap
-9-14 ORFS
-3’UTR with poly A

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10
Q

What does the translation of ORF1a of coronoviruses look like?

A

translation of ORF1a stops at leaky stop codon –> read through at 25 % of the cases –> -1 frameshift

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11
Q

Explain the replication of Coronaviruses

A

1.translation of incoming genome
2.assembly of replicase
3.synthesis of complete - strand which is complementary to + strand
4.synthesis of many + strand genomes on- strand template

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12
Q

explain transcription of coronaviruses

A

special mechanism: discontinous transcription (leader primed):
-negative strand Synthesis Starts at 3’ end of genome
-stop at internal genomic sequence of - strand –> base pairing between TRS (transcription regulating sequence) of - strand and leader TRS of + genome strand RNA (=Transfer)
-restart of RNA synthesis and completion of - strand synthesis (5’ends of all negative strands identical = each RNa includes leader sequence)
-subgenomic negative strand RNA serves as template for synthesis of mRNA
-capping by viral enzymes

–>a nested set of 3’ co-terminal mRNAs with identical 5’ sequence is generated

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13
Q

explain the translation of coronaviruses

A

-from each mRNA only the 5’proximal ORF is translated –> functionally monocystronic
-ORF1ab region is processed by virus encoded proteases

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14
Q

What functions as RNA proofreading in coronaviruses? Which model? What is required?

A

3’->5’ exonuclease activity of NAsp14 –> backtracking model

The proofreading requires dimer

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15
Q

What is the function of nsp1 in mpuse hepatitis virus?

A

blocking the IFN response of the host

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16
Q

what is the function of nsp1 in SARS coronavirus?

A

-binds to 40S ribosomal subunit
-stops translation of cellular mRNA
-modifies 5’end of mRNA to render it translationally incompetent
-induces endonucleatic cleavage of mRNA near the 5’ end

17
Q

how is SARS coronavirus mRNA protected from nsp1 activity?

A

leader sequence in mRNA of virus

18
Q

What can SARS CoV-2 induce in cells? What is needed for that?

A

Membrane alterations –> pore spanning –> nsp3 and nsp4 are minimal constituents

19
Q

how is SARS cov-1transmitted? When is virus secretion high?

A

droplet and smear infections –> respiratory and fecal-oral route –> especially high virus secretion in acute phase (fever)

20
Q

what is the incubation time of SARS CoV-1?

A

4 to 6 (up to 10)

21
Q

what is the mortality of SARS CoV-1?

A

4-40 %, depending on age

22
Q

How does SARS CoV-1 fulfil Kochs Postulates?

A

-virus isolated from patients
-cultivation in cell cultures
-experimental infections of macaques causes SARS like symptoms
-re-ioslation from diseased animals –> animal model

23
Q

How was SARS-1 stopped?

A

disruption of chain of infection
-fever controls at borders
-telephone hotlines
-specialized fever clinics
-protection masks
-diagnosis in only 12 h
-quarantine
-effective surveillance

24
Q

Why were the methods to stop SARS-1 effective but is not for example in infleunza viruses or SARS-CoV-2 ?

A

Onset of symptoms before secretion of infectious virus

25
Q

Can bat coronovarisues infect humans?

A

A SARS like cluster of circulating bat coronaviruses shows potential for human emergence –> antibodies do not cross-neutralize

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