Classification & Replication of Viruses (2)

Question 1

Viruses can replicate only in _____ cells of animals, plants, and bacteria

Answer 1

living cells

Question 2

Viruses are [intermediate/obligate] parasites that are metabolically inert when they are outside of their hosts

Answer 2

obligate

Question 3

What do viruses rely on?

Answer 3

on the metabolic processes of their hosts to reproduce themselves
the viral diseases we see are due to host’s response to it

Question 4

What is a prion?

Answer 4

a misfolded protein
not a virus, or any other recognized infectious agent

Question 5

What do all prions affect?

Answer 5

the structure of the brain or other neural tissue
progressive
have no known effective treatment
always fatal

Question 6

What are prions resistant to?

Answer 6

resistant to denaturation by chemical and physical agent

Question 7

What is a proteopathy?

Answer 7

disease of structurally abnormal proteins
a prion is an example of this

Question 8

What is the structure of a virus?

Answer 8

capsid
envelope
nucleic acid core (DNA or RNA)

Question 9

Viral proteins are “_______” to their receptor proteins

Answer 9

lock and key - initiating infection

Question 10

Both the ____ and ______ of a virus are antigenic, meaning that it causes an immune response triggered from antigens on the virus

Answer 10

capsid
envelope

Question 11

What is the capsid made of?

Answer 11

glycoproteins - capsomeres

Question 12

T/F: All viruses have an outer envelope

Answer 12

FALSE

Question 13

What is the function of a capsid?

Answer 13

protect the fragile nucleic acid genome from:
physical damage
chemical damage
enzymatic damage
protein subunits

Question 14

What are some properties of viruses?

Answer 14

heat sensitive
pH sensitivity
lipid solvents
chemicals
radiation and UV light
humidity

Question 15

T/F: Enveloped viruses are generally less sensitive to lipid solvents and heat

Answer 15

FALSE - more sensitive

Question 16

What are the 4 types of virus capsids?

Answer 16

isometric (icosahedral)
helical
complex
filamentous

Question 17

What’s an example of an icosahedral capsid?

Answer 17

herpes virus

Question 18

What is the structure of icosahedral capsid?

Answer 18

constructed of 20 equilateral triangular faces

Question 19

What is the structure of a helical capsid?

Answer 19

tubular construction with the subunits arranged around the nucleic acid in a coil

Question 20

What are examples of helical capsids?

Answer 20

rabies
flu
coronaviruses

Question 21

What are the 2 symmetrical types of capsids?

Answer 21

icosahedral
helical

Question 22

What are the 2 unsymmetrical capsid structures?

Answer 22

complex
filamentous

Question 23

What are examples of complex viruses?

Answer 23

small pox
phage

Question 24

What are filamentous viral capsid structures?

Answer 24

pleomorphic (able to assume different forms)

Question 25

What's an example of a filamentous capsid viral disease?

Answer 25

ebolavirus

Question 26

What is the family of viruses?

Answer 26

(-viridae)

Question 27

What is the genera of viruses?

Answer 27

(-virus)

Question 28

What is viral taxonomy based on?

Answer 28

morphology of vision, capsid, and envelope genome (RNA, DNA, SS, DS, etc) serological relationships (serotypes) replication strategy

Question 29

Coronaviridae is a [double/single]-stranded, [enveloped/unenveloped], [helical/icosohedral] [RNA/DNA] virus

Answer 29

single enveloped helical RNA

Question 30

Capsomeres are assembled from ______ and these can now be crystalized and studied for ________

Answer 30

proteins receptor binding (spike proteins)

Question 31

________ are specific to host cell receptors

Answer 31

Capsid proteins

Question 32

Capsid structural proteins are important for what?

Answer 32

viral stability and attachment

Question 33

What are non-structural proteins (functional)?

Answer 33

enzymes involved in viral replication

Question 34

_______ are generally formed against the structural proteins

Answer 34

Antibodies

Question 35

How do antibodies being found against non-structural proteins help?

Answer 35

can help in differentiating animals vaccinated with inactivated recombinant vaccines, from those naturally infected (DIVA principle)

Question 36

What are the capsid and envelope responsible for?

Answer 36

recognition of the host cell (receptor binding)

Question 37

The capsid and envelope initially take the form of binding a specific _______ to a _________

Answer 37

virus-attachment protein to a cellular receptor molecule

Question 38

What are the 7 classes of viral genomes?

Answer 38

dsDNA ssDNA dsRNA -ssRNA +ssRNA ss+RNA (retrovirus) gapped dsDNA = +mRNA

Question 39

What is a promiscuous virus?

Answer 39

capable of infecting several species (like rabies)

Question 40

What is a plastic virus?

Answer 40

exhibiting adaptability to change or variety in the environment (like influenza)

Question 41

SARS-CoV-2 (Coronavirus) is [plastic/promiscuous]

Answer 41

promiscuous - any mammal with ACE 2 receptor is susceptible

Question 42

What is a strain?

Answer 42

a well-characterized virus

Question 43

What is virulence?

Answer 43

different strains possessing different properties

Question 44

What is an isolate?

Answer 44

refers to the virus recovered from a specific host or location

Question 45

What is a serotype?

Answer 45

generally means that immunity is NOT conferred by previous exposure to a different type

Question 46

What are the 4 main groupings of viruses on the basis of epidemiological criteria?

Answer 46

enteric viruses respiratory viruses arboviruses oncogenic viruses

Question 47

What are arboviruses?

Answer 47

"arthropod-born viruses" replicate in their hematophagous arthropod hosts and are then transmitted by bite to vertebrate hosts

Question 48

T/F: Viruses must replicate in living

Answer 48

TRUE

Question 49

T/F: All cells will support replication of particular viruses

Answer 49

FALSE - not all do

Question 50

Both viruses and cells have _____ and an affinity (_______) between them that results in attachment

Answer 50

receptors complementarity

Question 51

In the 1930s, _____ was used to titrate influenza virus. Since the 1950s, ______ have been used

Answer 51

embryonated egg cell cultures

Question 52

What does syncytia mean?

Answer 52

giant cells

Question 53

What are cytopathic effects in cell culture?

Answer 53

1. cells pile up, losing the property of inhibition and thus form giant cells or syncytia 2. form inclusions in the cytoplasm or nucleus 3. die

Question 54

What does cytopathic cell mean?

Answer 54

kill cell becoming the host

Question 55

T/F: All cells are cytopathic (will kill the host)

Answer 55

FALSE example: Bovine Viral Diarrhea (BVD), virus is present and replicating but cells look normal

Question 56

What happens in a persistent, productive viral infection?

Answer 56

no cytopathic effect: little metabolic disturbance cells continue to divide may be loss of the special functions of some differentiated cells

Question 57

What happens in a transformation viral infection?

Answer 57

alteration in cell morphology cells can be passaged indefinitely

Question 58

What is a plaque assay? What do you do in this?

Answer 58

area with cells: blue (due to staining) area with white: where virus grew and killed cells count the plaques in the highest dilutions - "plaque-forming units" or "pfu/mL"

Question 59

What is a quantitative assays of viruses - tissue culture infective dose 50?

Answer 59

virus titration experiments which can be used to quantify virus titers by investigating the cytopathic effects of a virus on an inoculated host cell culture4 compared to the widely used plaque assays, TCID50 assays offer the advantage that even viruses that do not form plaques or infect cell monolayers can be quantified.

Question 60

What is quantitative assays of viruses - tissue vulture infective dose 50 used for?

Answer 60

characterize strain by measuring virulence used when quantity of virus at various steps is important producing vaccines

Question 61

T/F: Viruses can also be grouped based on epidemiological criteria, such as clinical presentation

Answer 61

TRUE

Question 62

_________ can measure the infectivity of viral particles through quantitative assays that observe cytopathic effects in cell cultures

Answer 62

Laboratories

Question 63

T/F: The steps of DNA and RNA replication for viruses is completely different

Answer 63

FALSE - however, the mechanism of replication differs significantly