Virology Exam 1

Front 1

where do viroids replicate? Virusoids?

Back 1

- viroids: nucleus
- virusoids: cytoplasm

Front 2

list the building blocks of a non-enveloped virus starting from the smallest part to the largest

Back 2

1. protein subunit
2. structure unit
3. assembly unit
4. capsomer
5. capsid
6. nucleocapsid

Front 3

what are four constituents of the viral envelope?

Back 3

1. peplomer
2. spike proteins
3. matrix proteins
4. lipids

Front 4

where does the enveloped virus acquire its lipid bilayer?

Back 4

form the host cell

Front 5

what is the function of spike proteins and peplomers?

Back 5

to attach to a specific host cell receptor and bring the virus into the cell

Front 6

what gives a spike protein or peplomer its host specificity?

Back 6

carbohydrate side chain

Front 7

which type of viruses are most sensitive to disinfectants and the environment?

Back 7

enveloped viruses

Front 8

which types of viruses tend to be seasonal?

Back 8

enveloped viruses

Front 9

explain the basic pathogenesis of how an enveloped virus, after replication spreads the infection to other cells

Back 9

after replication, it buds out of the host cell, causing chronic, persistent infections, and disease

Front 10

why is an enveloped virus more sensitive to detergent than a non-enveloped virus?

Back 10

because the lipid bilayer is destroyed by detergent and the virus cannot survive without the envelope

Front 11

why are infections with non-enveloped viruses typically self-limiting, as opposed to enveloped viruses, which are chronic?

Back 11

because they lyse the host cell to reproduce

Front 12

what are the two types of viral symmetry?

Back 12

helical and icosahedral (cubical)

Front 13

list the possible types of nucleic acid that a virus could contain in its nucleocapsid

Back 13

- DNA: ss, ds, monopartite, multipartite
- RNA: ss, ds, monopartite, multipartite
- retroviruses are diploid; all others are haploid
- viruses never have both DNA and RNA

Front 14

list four families of DNA, non-enveloped viruses

Back 14

1. Hepadnaviridae
2. Parvoviridae
3. Papoviridae
4. Adenoviridae

Front 15

list three families of DNA, enveloped viruses

Back 15

1. Herpesviridae
2. Iridoviridae
3. Poxviridae

Front 16

list four families of RNA, non-enveloped viruses

Back 16

1. Picornaviridae
2. Caliciviridae
3. Reoviridae
4. Birnaviridae

Front 17

list nine families of RNA, enveloped viruses

Back 17

1. Togaviridae
2. Coronaviridae
3. Paramyxoviridae
4. Rhabdoviridae
5. Orthomyxoviridae
6. Arenaviridae
7. Bunyaviridae
8. Retroviridae
9. Flaviviridae

Front 18

what is the function of non-structural proteins?

Back 18

- enzymes
- replication
- regulatory proteins

Front 19

what is the function of integrase?

Back 19

integrates the proviral DNA of retroviruses into the host genome

Front 20

what are the suffixes and the correct font style of virus Order, Family, Genus, Species, strain?

Back 20

- Order: -virales, italics
- Family: -viridae, italics
- Genus: -virus, italics
- species/strain: any name, non-italicized

Front 21

ability to become infected

Back 21

susceptibility

Front 22

ability to replicate and produce progeny viruses (as allowed by the cell)

Back 22

permissivity

Front 23

location of first infected cells, and frequently not the site of disease signs

Back 23

portal of entry

Front 24

infection resulting in infectious progeny

Back 24

productive infection

Front 25

infection, where replication is initiated, but not completed, has limited gene expression, and produces no infectious progeny

Back 25

abortive infection

Front 26

infection where permissivity is transient or proportional to the cell population; few virions released

Back 26

restrictive infection

Front 27

infection where viral genomes are integrated into the cellular genomes, but not expressed; therefore, no infectious progeny

Back 27

latent infection

Front 28

infection characterized by activation of latency, new infectious progeny, disease flair-up, or a new immune response

Back 28

recrudescence

Front 29

what is a common reason why a viral infection may be abortive?

Back 29

because it is infecting a susceptible, but not permissive cell

Front 30

susceptibility

Back 30

ability to become infected

Front 31

permissivity

Back 31

ability to replicate and produce progeny viruses (as allowed by the cell)

Front 32

portal of entry

Back 32

location of first infected cells, and frequently not the site of disease signs

Front 33

productive infection

Back 33

infection resulting in infectious progeny

Front 34

abortive infection

Back 34

infection, where replication is initiated, but not completed, has limited gene expression, and produces no infectious progeny

Front 35

restrictive infection

Back 35

infection where permissivity is transient or proportional to the cell population; few virions released

Front 36

latent infection

Back 36

infection where viral genomes are integrated into the cellular genomes, but not expressed; therefore, no infectious progeny

Front 37

recrudescence

Back 37

infection characterized by activation of latency, new infectious progeny, disease flair-up, or a new immune response

Front 38

describe the 10-step virus replication cycle

Back 38

1. attachment
2. penetration
3. uncoating (nucleocapsid disintegrates)
4. transcription of early mRNA
5. translation of early proteins
6. replication of viral DNA
7. transcription of late RNA
8. translation of late proteins
9. assembly of virions
10. release

Front 39

what part of the virus binds to cellular receptors in order to gain entry to the cell?

Back 39

viral attachment proteins

Front 40

what are the three types of viral penetration, describe the mechanism, and what type of viruses use them.

Back 40

1. translocation: diffusion through the cell membrane; used by non-enveloped viruses
2. endocytosis: entire virus is enveloped into a phagosome and is activated when it becomes a phagolysosome; enveloped viruses use this
3. fusion: lipid envelope becomes part of the cell membrane and the naked nucleocapsid enters the cell; used by some enveloped viruses

Front 41

viral non-structural proteins that are involved with transcription, replication of viral nucleic acid, and cleavage of viral proteins

Back 41

virion-associated enzymes

Front 42

viral non-structural proteins that are involved with controlling the temporal sequence of viral genome expression (up-regulating and down-regulating cellular genes)

Back 42

regulatory proteins

Front 43

what type of cellular genes are up-regulated by viral regulatory proteins?

Back 43

Transactivators and oncogene products (such as growth factors, tumor suppressors)

Front 44

viral non-structural proteins that are involved with the modulation of infection by acting on other uninfected cells be (1) negating the effects of IFN, TNF, etc. and (2) reduce the inflammatory response and complement activation?

Back 44

virokines

Front 45

in what two basic ways do virokines modulate the infection by acting outside the host cell?

Back 45

1. negate the effects of IFN, TNF, etc.
2. reduce the inflammatory response, complement activation, etc.

Front 46

virion-associated enzymes

Back 46

viral non-structural proteins that are involved with transcription, replication of viral nucleic acid, and cleavage of viral proteins

Front 47

regulatory proteins

Back 47

viral non-structural proteins that are involved with controlling the temporal sequence of viral genome expression (up-regulating and down-regulating cellular genes)

Front 48

the process of producing virions after replication, transcription, and translation of viral components.

Back 48

assembly

Front 49

aligning of virions with the cell membrane before release

Back 49

maturation

Front 50

assembly

Back 50

the process of producing virions after replication, transcription, and translation of viral components.

Front 51

maturation

Back 51

aligning of virions with the cell membrane before release

Front 52

what is the basic process of maturation and release of an enveloped virus?

Back 52

- viral glycoproteins and matrix proteins are put into the host cell membrane
- the viral nucleocapsid aligns with the viral matrix proteins
- the virion buds from the cell and is released as a free infectious virion

Front 53

where do most RNA viruses replicate?

Back 53

the cytoplasm

Front 54

what is the process of (+)-strand RNA virus genome replication

Back 54

- parental (+) strand is used as mRNA for the synthesis of replication proteins
- the (-) strand is made from the (+) strand template
- the (+) strand is synthesized into many progeny strands from the (-) strand

Front 55

what is a major difference between the virion of a (+) strand and a (-) strand RNA virion?

Back 55

(-) strand RNA viruses must carry polymerase enzymes in the virion in order to synthesize (+) strand RNA after infection.

Front 56

what is the process of (-) strand RNA virus genome replication?

Back 56

- (+) strand RNA is produced from the parental (-) strand and the polymerase enzymes carried in the virion
- the resulting (+) strand RNA is used as mRNA to synthesize viral proteins
- the (+) strand is also used to synthesize progeny (-) sense progeny strands

Front 57

during the replication cycle, what type of nucleic acid do all viruses share?

Back 57

(+) strand RNA, somewhere in the cycle, which serves as mRNA for the translation of viral proteins

Front 58

Define the first six Baltimore System classifications of viruses

Back 58

I. dsDNA
II. ssDNA
III. dsRNA
IV. (+) sense RNA
V. (-) sense RNA
VI. (+) sense RNA that use reverse transcriptase to make DNA

Front 59

where do DNA viruses replicate? What is a notable exception?

Back 59

they replicate in the nucleus, except for Poxviridae

Front 60

what do viral early genes and late genes encode for?

Back 60

- early genes: non-structural proteins
- late genes: structural proteins

Front 61

how does size of the DNA virus relate to replication?

Back 61

the smaller DNA viruses are more dependent on the host cell, whereas larger DNA viruses have more control over the replication of their genomes

Front 62

what is required for DNA polymerase to begin the viral genome replication process in the nucleus?

Back 62

a primer

Front 63

name four families of dsDNA viruses

Back 63

1. Papoviridae
2. Adenoviridae
3. Herpesviridae
4. Poxviridae

Front 64

why can Poxviridae replicate in the cytoplasm, whereas other dsDNA viruses must use the cell nucleus?

Back 64

because Poxviridae carry all of the components necessary for viral transcription and translation in the virion

Front 65

name two families of ssDNA viruses

Back 65

1. Parvoviridae
2. Circoviridae

Front 66

what is a dependovirus? Give an example of one.

Back 66

a virus with such a small / incomplete genome, that it needs help from another virus to replicate. Example: Adeno-associated parvoviruses

Front 67

what is one family of partially-ds gapped DNA viruses?

Back 67

Hepadnaviridae

Front 68

what steps in viral replication are unique to the Hepadnaviridae (partially-ds gapped DNA viruses)?

Back 68

1. gap repair precedes mRNA synthesis
2. the mRNA encodes reverse transcriptase

Front 69

what two families of viruses use reverse transcriptase?

Back 69

1. Hepadnaviridae
2. Retroviridae

Front 70

what are three reasons that viral replication is error-prone?

Back 70

1. poor fidelity of DNA polymerase
2. rapid rate of replication
3. RNA viruses lack proof-reading mechanisms

Front 71

why do RNA viruses mutate faster than DNA viruses?

Back 71

because RNA is more susceptible to damage and RNA viruses lack the ability to proof-read during replication of their genomes

Front 72

the "original" virus (e.g. the lab-adapted "parent" strain)

Back 72

wild-type

Front 73

a virus newly obtained from a host

Back 73

field isolate

Front 74

different wild-types of the same virus

Back 74

strain

Front 75

strains that have mutated from the wild-type

Back 75

variant virus strains; variants

Front 76

wild-type

Back 76

the "original" virus (e.g. the lab-adapted "parent" strain)

Front 77

field isolate

Back 77

a virus newly obtained from a host

Front 78

strain

Back 78

different wild-types of the same virus

Front 79

variant virus strains; variants

Back 79

strains that have mutated from the wild-type

Front 80

what are the four "types" used to relate strains of viruses?

Back 80

1. serotype: related antigenically
2. genotype: related genetically
3. biotype
4. pathotype: e.g. one causes disease and one does not

Front 81

what are the two types of viral mutations and what is the difference between the two?

Back 81

1. spontaneous mutations: no mutagens involved
2. induced mutations: mutagens involved

Front 82

acquisition or lost ability of a virus to infect a new host; cross-species infection, causing new diseases in a new host

Back 82

host range mutations

Front 83

the main mechanism by which viruses become resistant to antiviral drugs

Back 83

drug resistance mutation

Front 84

change of a virus characterized by an increased ability to evade the specific immune system

Back 84

antibody escape mutations

Front 85

viruses that have mutated to a wild-type phenotype from a modified-live vaccine strain

Back 85

revertants

Front 86

host range mutations

Back 86

acquisition or lost ability of a virus to infect a new host; cross-species infection, causing new diseases in a new host

Front 87

antibody escape mutations

Back 87

change of a virus characterized by an increased ability to evade the specific immune system

Front 88

revertants

Back 88

viruses that have mutated to a wild-type phenotype from a modified-live vaccine strain

Front 89

mutations in essential genes, resulting in a dead virus

Back 89

lethal mutations

Front 90

selective removal of a portion of viral genome (gene or fragment) and the function it encodes

Back 90

deletion mutants

Front 91

viruses with a conditional lethal mutation that allows the virus to grow at elevated or reduced temperatures

Back 91

temperature-sensitive mutants

Front 92

lethal mutations

Back 92

mutations in essential genes, resulting in a dead virus

Front 93

deletion mutants

Back 93

selective removal of a portion of viral genome (gene or fragment) and the function it encodes

Front 94

temperature-sensitive mutants

Back 94

viruses with a conditional lethal mutation that allows the virus to grow at elevated or reduced temperatures

Front 95

during a mixed infection, the viral genome from one virus is enclosed in the capsid or envelope of another virus

Back 95

phenotypic mixing

Front 96

what is MOI?

Back 96

multiplicity of infection: basically the amount of viable progeny viruses generated from one parent virus

Front 97

occurring at a high MOI, the total yield of virions remains constant, but the number of infectious virions diminishes (due to defective mutations)

Back 97

interference

Front 98

viral genome becomes part of the cellular genome, and for example, activate Onc genes, causing tumor and cancer development in animals

Back 98

integration

Front 99

phenotypic mixing

Back 99

during a mixed infection, the viral genome from one virus is enclosed in the capsid or envelope of another virus

Front 100

interference

Back 100

occurring at a high MOI, the total yield of virions remains constant, but the number of infectious virions diminishes (due to defective mutations)

Front 101

integration

Back 101

viral genome becomes part of the cellular genome, and for example, activate Onc genes, causing tumor and cancer development in animals

Front 102

either the virus changed, allowing it to replicate without killing the cell or the cell changed, allowing it to replicate the virus without being lysed

Back 102

persistence

Front 103

intramolecular genetic exchanges between viruses, resulting in a new virus or variant

Back 103

recombination

Front 104

in viruses with segmented genomes, exchange of these gene segments to produce a new hybrid virus

Back 104

reassortment

Front 105

persistence

Back 105

either the virus changed, allowing it to replicate without killing the cell or the cell changed, allowing it to replicates the virus without being lysed

Front 106

recombination

Back 106

intramolecular genetic exchanges between viruses, resulting in a new virus or variant

Front 107

reassortment

Back 107

in viruses with segmented genomes, exchange of these gene segments to produce a new hybrid virus

Front 108

morphological changes of virally infected cells, such as rounding, lysis, detachment, syncytia, and inclusion bodies

Back 108

cytopathic effect

Front 109

cytopathic effect

Back 109

morphological changes of virally infected cells, such as rounding, lysis, detachment, syncytia, and inclusion bodies

Front 110

what are two causes of a cytopathic effect?

Back 110

1. direct pathological injury of infected cells
2. side-effect: altered metabolism due to virus replication

Front 111

what comprises the VAP (viral attachment protein) of a:
- non-enveloped virus
- enveloped virus

Back 111

- non-enveloped virus: part of the capsid or a protein extending from the capsid
- enveloped viruses: spike or peplomer glycoproteins in the envelope

Front 112

what host enzyme does a DNA virus use to transcribe its genome to mRNA in the nucleus?

Back 112

DNA-dependent RNA polymerase II

Front 113

which three families of RNA viruses replicate in the nucleus, as opposed to the cytoplasm?

Back 113

1. Orthomyxoviridae
2. Coronaviridae
3. Retroviridae

Front 114

which types of viruses have infectious naked genomes?

Back 114

- DNA viruses (except Poxviridae)
- (+) sense RNA viruses (except Retroviridae)

Front 115

what are four ways viruses inhibit cell metabolism in order to reproduce?

Back 115

1. inhibit cellular transcription mechanisms (so cell will make viral mRNA)
2. inhibition of RNA processing pathways (so cell uses maturation pathways on viral mRNA)
3. inhibition of cellular translation (so viral proteins are encoded)
4. inhibition of host cell DNA synthesis (competition for NA precursors & redirect host cell enzymes for viral DNA synthesis)

Front 116

what are four ways that viruses change cell structure?

Back 116

1. membrane fusion → syncytia
2. change permeability of the plasma membrane → cell lysis
3. disruption of cytoskeleton → rounding of the cells
4. incorporation of cytoskeletal components into infected cell structures → inclusion bodies

Front 117

multiple, continuous transmissions; disease presence in a defined population/region/time

Back 117

enzootic

Front 118

peaks in incidence exceeding the endemic (enzootic) baseline

Back 118

epizootic

Front 119

worldwide viral enzootics

Back 119

panzootic

Front 120

enzootic

Back 120

multiple, continuous transmissions; disease presence in a defined population/region/time

Front 121

epizootic

Back 121

peaks in incidence exceeding the endemic (enzootic) baseline

Front 122

panzootic

Back 122

worldwide viral epizootics

Front 123

number of new cases over number of subjects over a period of time

Back 123

incidence or attack rate

Front 124

continuous reporting of reportable diseases

Back 124

surveillance

Front 125

moment of infection to onset of clinical signs

Back 125

incubation period

Front 126

moment of infection to first day of virus shedding

Back 126

generation time

Front 127

from the first day to last day of virus shedding

Back 127

period of infectivity

Front 128

surveillance

Back 128

continuous reporting of reportable diseases

Front 129

incubation period

Back 129

moment of infection to onset of clinical signs

Front 130

generation time

Back 130

moment of infection to first day of virus shedding

Front 131

period of infectivity

Back 131

from the first day to last day of virus shedding

Front 132

what are six modes of transmission by viruses?

Back 132

1. horizontal
2. vertical
3. zoonotic
4. vector-borne
5. iatrogenic
6. nosocomial

Front 133

which type of viruses usually use direct contact in horizontal transmission? Indirect contact?

Back 133

- direct: enveloped
- indirect: non-enveloped

Front 134

virus integrated into the genome of the ovum, with transcription and replication in the offspring, which passes from generation-to-generation

Back 134

Germline transmission

Front 135

Germline transmission

Back 135

virus integrated into the genome of the ovum, with transcription and replication in the offspring, which passes from generation-to-generation

Front 136

what are four methods of viral vertical transmission?

Back 136

1. transplacentally
2. perinatally
3. colostrum/milk
4. germline transmission

Front 137

what are five families of arboviruses?

Back 137

1. Togaviridae
2. Flaviviridae
3. Bunyaviridae
4. Reoviridae
5. Rhabdoviridae

Front 138

what is the difference between a biological vector and a mechanical vector?

Back 138

viruses in biological vectors replicate and magnify in the vectors, and have efficient transmission; viruses in mechanical vectors do not replicate, and are therefore not efficient for transmission.

Front 139

viral diseases transmissible under NATURAL CONDITIONS from vertebrate animals to humans

Back 139

zoonotic transmission

Front 140

zoonotic transmission

Back 140

viral diseases transmissible under NATURAL CONDITIONS from vertebrate animals to humans

Front 141

true or false: most viral infections cause mild or asymptomatic diseases

Back 141

true

Front 142

what are five common routes of entry of viruses into the body?

Back 142

1. respiratory tract
2. GI tract
3. conjunctiva
4. genitourinary tract
5. skin (epidermis)

Front 143

what are three types of viruses that commonly infect the host through a compromise in the skin?

Back 143

1. Herpesvirus
2. Papillomavirus
3. Poxvirus

Front 144

why are non-enveloped viruses most suitable for GI tract infection? What is an example of an enveloped virus that infects the GI tract?

Back 144

- the viral envelope is susceptible to extreme pH and enzymatic conditions to of the GI tract
- Coronaviridae are enveloped viruses that have evolved to favor the GI tract

Front 145

what is the difference between primary viremia and secondary viremia?

Back 145

- primary: virus uses blood to transport from infection site to target replication sites
- secondary viremia: blood takes viruses replicated in organs to other sites, where it causes clinical manifestations

Front 146

what is the primary site of replication for viruses that spread via the lymphatic system?

Back 146

epithelial cells, vascular endothelium

Front 147

why does the immune system recognize that a cell is infected with a virus before progeny viruses are produced?

Back 147

because of viral protein presentation by the MHC-I antigen

Front 148

what are four ways in which the immune system destroys virus-infected cells and the basic mechanism?

Back 148

1. Cytotoxic T cells: perforin
2. Ig-complex mediated cytotoxicity: low level of Ig via the Classical pathway
3. Ig dependent cell-mediated cytotoxicity: mediated by Fc receptors on phagocytes
4. NK cells: activated by IFN or viral glycoproteins, they non-specifically kill virus-infected cells

Front 149

what is the epitope for neutralizing antibodies?

Back 149

viral attachment proteins

Front 150

what are the two basic ways in which neutralizing antibodies kill viruses?

Back 150

1. at attachment/entry stage, but this requires a large amount of antibodies
2. antibody-virus complexes destroyed by cellular enzymes: more effective

Front 151

which antibody provides mucosal immunity?

Back 151

IgA

Front 152

what are the most effective types of viral vaccines and why?

Back 152

MLV. Because the vaccines are still infective, but not pathogenic. This allows for better immune development

Front 153

what are the three basic roles of adjuvants?

Back 153

1. prolonged retention and slow release of vaccine
2. macrophage activation
3. chemotactic for lymphocytes, leading to lymphokine secretion

Front 154

what is a chimeric virus?

Back 154

a recombinant virus used in vaccines that has the antigens of one virus but the nucleic acid of a less pathogenic virus

Front 155

comment on modified-live versus killed vaccines:
- route of administration
- dose and cost
- number of doses
- use of adjuvant
- duration of immunity
- antibody class
- development of CMI
- heat stability
- risk of reversion

Back 155