Coronaviruses

Question 1

Classify coronaviruses

Answer 1

Coronaviridae:

1) large enveloped viruses
2) + strand RNA with 5’ methyl-cap, 3’ poly-A tail
3) non-segmented genome
4) crown-like morphology under EM

**largest RNA viral genome known

Question 2

What are some major coronavirus structural proteins?

Answer 2

1) S (spike protein)
2) HE (haemagglutinin-esterase)
3) E (envelope)
4) M (membrane)
5) N (nucleocapsid)
6) RdRp (RNA-dependent RNA polymerase)
7) PLpro and 3CLpro (Papain-Like protease and 3C-L protease)

Question 3

What does spike protein do?

Answer 3

Mediates binding/fusion of CoV to host cell membrane

Question 4

Function of haemagglutinin-esterase?

Answer 4

Viral entry and exit

Question 5

Function of envelope protein?

Answer 5

Integral protein in viral membrane involved in morphogenesis, assembly and budding, and ion channel activity

Question 6

Function of membrane protein?

Answer 6

Its a TMP important in viral budding

Question 7

Function of nuclecapsid?

Answer 7

Binds to viral genomic RNA and to M protein for virion assembly and encapsidation

Question 8

Function of RdRp?

Answer 8

makes viral RNA; lacks proof-reading activity

Question 9

Function of PLpro and 3CLpro?

Answer 9

Cleaves viral polyprotein into mature viral proteins

*prime target for antiviral drug development

Question 10

Describe the 6 steps of CoV replication strategy:

Answer 10

1) virus enters and uncoats
2) +RNA genome is translated by host, then more so by RdRp
3) -RNA strands made
4) -RNA strands serve as template for making more +RNA progeny genomes and for making more mRNA to make proteins
5) mRNAs translated to make non-replication machinery polyproteins
6) RdRp’s lack of proofreading = huge variety of CoV genomes with different antigenicities and environmental advantages

Question 11

What are 4 diseases CoV cause?

Answer 11

1) Common cold (winter and early spring)
2) Croup (laryngealbronchitis in kids
3) Pneumonia (infants, elderly, IC patients)
4) SARS

**also known for exacerbating asthma and chronic bronchitis

Question 12

Common symptoms of CoV are:

Answer 12

1) cold symptoms
2) enteric infections in infants
3) rare neuro symptoms

*4) SARS –> high fever, dry cough, SOB, hypoxia, GI symptoms, lymphopenia, respiratory failure

Question 13

How is CoV transmitted?

Answer 13

Since its enveloped, it’s mainly by airborne water droplets

**SARS = mutated strain from bats (antigenic SHIFT) in China and Taiwan