export_intro to virology

Question 1

Virus

Answer 1

Acellular infectious agent
Obligate parasites

Simplest is nucleic acid surrounded by protein coat (capsid)

Question 2

Virion

Answer 2

Complete virus component

In addition to genome and capsid, there is a matrix, envelope, and viral attachment proteins

Question 3

Viral genome

Answer 3

Segmented or contiguous

Either RNA or DNA

Question 4

Orientation of RNA molecules

Answer 4

Only in single-stranded

Negative or positive sense

Question 5

+sense ssRNA

Answer 5

In the correct orientation to be transcribed by ribosome -> protein synthesis

Question 6

-sense ssRNA

Answer 6

In the opposite orientation, can’t be used to produce protein
Must use -sense to generate a template (+sense) to produce protein

Question 7

ssDNA virus families

Answer 7

Parvoviridae

Question 8

dsDNA virus families

Answer 8

Herpesviridae
Hepadnaviridae

Adenoviridae

Papovaviridae

Poxiviridae

Question 9

dsRNA virus family

Answer 9

Reoviridae

Question 10

-ssRNA virus families

Answer 10

Orthomyxoviridae
Paramyxoviridae

Rhabdoviridae

Bunyaviridae

Arenaviridae

Filoviridae

Question 11

RNA virus properties

Answer 11

RNA is labile and transient
Replication in the cytoplasm

-sense RNA must carry polymerases

Prone to mutation

Question 12

What must all RNA viruses do?

Answer 12

Encode an RNA-dependent RNA polymerase

Question 13

Capsid shapes

Answer 13

Helical (tobacco mosaic)
Icosahedral (polio)

Complex (smallpox)

Question 14

Naked capsid viruses

Answer 14

Capsid is outermost layer
Environmentally stable
Released from cell by lysis

Question 15

Clinical consequences of naked capsid viruses

Answer 15

Spread easily
Dry out and retain infectivity

Survive adverse conditions of gut

Resistant to detergents

Question 16

Envelope viruses

Answer 16

Environmentally labile (can be disrupted)
Modify cell membrane during replication

Released by budding and cell lysis

Question 17

Clinical consequences of envelope viruses

Answer 17

Must stay wet
Cannot survive GI tract

Spreads in large droplets, secretions, etc.

Does not need to kill cell to spread

Question 18

Virus life cycle stages

Answer 18

Attachment
Entry

mRNA production

Protein and genome synthesis

Virion assembly

Egress

Question 19

Attachment/entry of viruses

Answer 19

Penetration/fusion
Receptor binding and fusion with membrane

Capsule enters the cell

Herpesviruses, paramyxoviruses, HIV

Question 20

Vesicular entry of virus

Answer 20

Envelope viruses can fuse with membrane and form a vesicle that is endocytosed, fusion of envelope and vesicle -> release of virus
Capsule viruses get into vesicle then lyse out into cell

Question 21

ssDNA viruses gene transcription

Answer 21

Form dsDNA virus and use RNA polymerase for replication

Question 22

Retrovirus gene transcription

Answer 22

+ssRNA virus

Uses viral reverse transcriptase to form dsDNA -> mRNA

Question 23

+ssRNA virus gene transcription

Answer 23

Form nRNA, no enzyme needed

Question 24

-ssRNA gene transcription

Answer 24

Use viral RdRp (enzyme) to form mRNA

Question 25

dsRNA virus gene transcription

Answer 25

Use viral RdRp (enzyme) to form mRNA

Question 26

Solutions for cellular DNA replication machinery not always available (DNA viruses)

Answer 26

Make cellular DNA replication machinery available | Encode viral proteins to synthesize genome

Question 27

Solutions for cellular DNA replication machinery not always available (RNA viruses)

Answer 27

+ss - cellular ribosomes can recognize, mRNA formed | -ss - encode a RdRp to form +ss strand, then see above

Question 28

Pathway for viral assembly and egression

Answer 28

Viral proteins form capsid subunits Subunits combine to form complete capsid Viral genome/virion selectively packaged into capsids Virus exits cell

Question 29

Virus budding example

Answer 29

HIV

Question 30

Egress via lysis

Answer 30

Cell is killed and virions are released

Question 31

Viral genetics

Answer 31

Virus genes need to change to alter their antigenicity Point mutations Recombination (HSV1 and HSV2 exchange DNA -> hybrids) Reassortment (segmented viruses, such as influenza)

Question 32

Cytopathic effect

Answer 32

When virus infection results in cellular damage

Question 33

Plaque assay

Answer 33

Put monolayer on plate and Add with sample of cells suspected to be infected with virus Observe plaques (cytopathic effect) Infectious virions

Question 34

Assess for viral Abs

Answer 34

ELISA | Western blot

Question 35

Assess for viral genome

Answer 35

PCR | RT-PCR

Question 36

Assess for viral Ags

Answer 36

ELISA

Question 37

EM viral diagnostics

Answer 37

Detects virion particles Helpful with emerging viruses Expensive and challenging

Question 38

Serology (Western blot) viral diagnostics

Answer 38

Detects anti-viral Abs Sensitive and quick Must wait for an immune response, and need to differentiate from previous infection