viral lifecyle

Question 1

What are the 8 steps in a viral lifecycle

Answer 1

1)binding to cell surface proteins
2)entry
3)uncoating
4)replication
5)transcription
6)translation
7)vision assembly
8)release

Question 2

What are the 7 steps of viral replication

Answer 2

1)adsorption (attachment)
2)entry
3)uncoating
4)genome replication and transcription
5)synthesis of virus components
6)assembly
7)release (and maturation)

Question 3

What do viruses use as receptors

Answer 3

Components of cell membrane

Question 4

What is adsorption(attachment) in viral replication

Answer 4

Random collision of virus to come into contact with receptor to attach to the cell for interaction between specific proteins on viral surface

Question 5

What might some viruses use during adsorption (attachment)

Answer 5

May use more than one host cell receptor to gain entry into cell e.g HIV

Question 6

What are neutralising antibodies

Answer 6

Specific for virion attachment proteins during adsorption to block interaction with receptors and prevent entry into cell

Question 7

What is the influenza virus receptor

Answer 7

Sialic acid

Question 8

What does the influenza virus recognise to enter a cell

Answer 8

Carbohydrate molecules present on glycoproteins

Question 9

What are two glycoproteins on the surface of the influenza virus

Answer 9

Haemagluttinin and neuraminidase

Question 10

What is a function of neuraminidase

Answer 10

Cuts the carbohydrate from the sialic acid to prevent the haemagluttinin from rebinding to sialic acid on surface of cell

Question 11

What does again influenza HA (hemaggultinin) preferably bind to

Answer 11

SA (sialic acid) - a (alpha) - 2,3-gal-terminated saccharides

Question 12

What does human influenza virus HA (hemagglutinin) prefer to bind to

Answer 12

SA (sialic acid) - a (alpha) - 2,6- Gal - terminated saccharides

Question 13

What occurs during the entry process (penetration) during viral replication

Answer 13

Endocytosis
Fusion of virus envelope with cell membrane

Question 14

What occurs during the uncoating process during viral replication

Answer 14

Release of viral genomes
Cell enzymes (lysosomes) strip off the virus protein coat
Virion no longer detected - “eclipse period”

Question 15

How does HIV attach and enter into cells

Answer 15

surface unit (glycoprotein 120) protein attaches to CD4 receptors on target cell

Question 16

What else does HIV require to attach and enter a cell other than CD4 receptors

Answer 16

Co-receptor required - chemokine receptors:
-7 transmembrane domains
-CXCR4 - T-cell
-CCR5 - macrophage

Question 17

What is the mechanism of how influenza virus enters a cell

Answer 17

Hydrogen ions pumped into endosome lowering pH in endosome
Causes conformational change in HA (hemagglutinin)
Allows fusion of viral envelope with endosomal membrane

Question 18

What is the process for SARS CoV in attachment and entry into a cell

Answer 18

S glycoprotein cleaved by TMPRSS2
Facilitates viral activation
Essential host factors for SARS-CoV-2 pathogenicity
TMPRSS2 is a potential target for antiviral drugs

Question 19

How do non-enveloped viruses (poliovirus) enter and uncoat in target cell

Answer 19

Virus taken up into endosome
Conformational changes to viral structure proteins
Result in formation of a pore in endosomal membrane
Viral RNA is released into cytoplasm

Question 20

Where does the process of assembly in viral replication occur

Answer 20

May take place in cell nucleus, cytoplasm or most enveloped viruses at plasma membrane

Question 21

What is the process of release in viral replication

Answer 21

Sudden rupture of cell (non-enveloped virus)
Gradual extrusion (budding) of enveloped virus through cell membrane
May occur together with assembly

Question 22

What is virus budding driven by

Answer 22

Virus protein interactions

Question 23

What does the influenza virus require to become active when infected host cell when replicated

Answer 23

All 7 segmented RNA genomes

Question 24

What is HIV maturation driven by

Answer 24

Virion protease

Question 25

What state does HIV need to be in to be infections

Answer 25

Only mature HIV is infectious

Question 26

What does DNA dependent DNA polymerase make

Answer 26

Makes DNA from DNA

Question 27

What does DNA dependant RNA polymerase make

Answer 27

Makes RNA from DNA

Question 28

What does RNA dependant RNA polymerase make

Answer 28

Makes RNA from RNA

Question 29

What does RNA dependant DNA polymerase make (reverse transcriptase)

Answer 29

Makes DNA from RNA

Question 30

What do all RNA viruses encode

Answer 30

An RNA dependant RNA polymerase

Question 31

What are characteristics of +ive strand RNA viruses

Answer 31

Genomic RNA acts as mRNA on cell entry
Translated to produce the polymerase

Question 32

What are characteristics of -ive strand RNA viruses

Answer 32

Need to carry polymerase in the virion
Required to convert -ive RNA to +ive mRNA after entry

Question 33

What type of transcription does HIV undergo

Answer 33

Transcripts (alternative splicing)

Question 34

How do anti-viral drugs work and what it uses

Answer 34

Attachment antagonists
Inhibit uncoating
Inhibit DNA/RNA synthesis
Block maturation

Question 35

How does the drug amantadine work with influenza drug targets

Answer 35

Block the ability to lower the pH within endosome and block aspects of uncoating process

Question 36

What are neuraminidase inhibitors and what do they do

Answer 36

Drug to treat influenza and block the virus being able to released from an infected cell