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Flashcards in Viruses Deck (92):
1

papovavirus

circular dsDNA

2

parvovirus

ss linear DNA

3

circovirus

circular ssDNA, smallest autonomously propagated virus

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capsomeres

protein subunits that assembled together to form a capsid

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icosahedral symmetry

high level of structural integrity, 20 equilateral triangles

6

4 examples with icosahedral symmetry

adenovirus, poliovirus, hep a, hep e

7

the virus lifecycle

attachment, penetration, un-coating, replication, assembly, release FOLLOW A WELL ORDERED SERIES OF TEMPORAL EVENTS

8

three types of viral penetration: fewest to most layers

fusion, translocation, endocytosis (this is an energy dependent step)

9

when is the beginning of the "eclipse" phase?

uncoating

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viruses

have a strict dependence on host cell structural and metabolic components

11

range of virus sizes

20-30 nm (picorna) ---> 300 nm (pox)

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virion

the complete extracellular structure that transmits the infection

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double stranded RNA

is highly unusual

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nucleocapsid

the protein covered genome

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envelope

resembles cellular membranes. consists of lipid bilayer, proteins, and glycoproteins

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antisense strand mRNA

require virion associated polymerase activity

17

how many virus families infect humans?

21 (they are not alive and therefore do not fall on the tree of life)

18

the single most important classification of animal viruses

genomic nucleic acid

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hep a-e

are all in different virus families

20

current virus classification strategy

genome composition, genome structure and organization, and morphology (nucleocapsid architecture)

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species for the vaccine for smallpox

vaccinia virus

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helical symmetry

a type of morphology (identical protein subunits, protomers, self assemble into a helical array surrounding the nucleic acid (rigid highly elongated rods or flexible filaments

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initiation of infection

attachment, penetration, un-coating

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replicase

complex of viral proteins and/or host proteins required for viral nucleic acid replication (includes viral polymerase and co factors)

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RNA dependent DNA polymerase

enzyme needed for retroviral replication

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examples of positive sense RNA viruses

picornaviruses: (poliovirus, hep C, hep A)

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negative sense RNA

orthomyxovirus: influenza

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double stranded RNA

rotavirus (required capsid because is targeted by the immune system)

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retorvirus

HIV, SIV , HTLV

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negative sense RNA

paramyxoviruses (mumps, measles, parainfluenza virus, RSV)

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integrase

is a viral enzyme

32

flaviviruses

HCV (+) ss, enveloped

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orthomyxoviruses

influenza, enveloped, - ss

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coronaviruses

SARS, enveloped, + ss

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tissue tropism

the cell or tissue type that supports replication of a given virus

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sequence of virus spread

implantation @ portal of entry, local replication and local spread, dissemination from the portal of entry, multiplication in target organs, shedding of virus

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reason for clinical disease

is multiplication in the target organ

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most commons sites of viral implantation

respiratory, GI, skin penetrating, and genital routes

39

viruses spread

extra and intracellularly

40

dissemination can occur through

viremia, neural dissemination, cell trafficking, and direct cell-cell spread

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incubation period

the time between exposure to the virus and onset of disease

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determinants of viral pathogenesis

access of the virus to the tissue, virus susceptibility, cell permissiveness

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pathogenesis

results from disruption of normal cellular processes

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influenza/polio virus

host shutoff phenomenon

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hep c virus

persistent infection, liver disfunction

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HIV/T

cell syncytium

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factors contributing to viral diversity

mutation, recombination/reassortment, replication rate/number of progeny, selective pressure

48

DNA viruses have

proofreading polymerases and have one mutant per 100(0) genome copies

49

RNA viruses

do not have a proofreading function and produce one mutation per genome cope (leads to the generation of 'escape variants' and is problematic for development of antiviral therapies and vaccines)

50

quasispecies

dynamic distribution of related genomes

51

RNA viruses exist

near the "error threshold"

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largest % chance of infection due to needle stick injury

hep b virus

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3 main types of genetic recombination

1. independent reassortment, 2. homologous recombination, 3. breakage/re-joining *REQUIRE A CELL INFECTED BY 2+ VIRUSES

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independent reassortment

segmented genomes -- causes antigenic SHIFT

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homologous recombination

can result in a chimeric genome resistant to both antiviral drugs

56

breakage/rejoining

requires nucleic acid break or fragmentation. occurs mainly with DNA viruses and large RNA viruses

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what does recombination do that point mutations cannot

juxtapose things that would have a low probability of meeting otherwise, juxtapose viral genomes with limited homology (intertypic recombination), transduce sequences from nonhomologous genomes (low frequency)

58

RNA viruses

represent major human pathogens and are ubiquitous, are diverse, and are adaptive

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circovirus

ss circular DNA, no envelope

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parvovirus

single stranded

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adenovirus

ds linear DNA, icosahedron, no envelope

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herpesvirus

ds linear DNA, icosahedron, yes envelope

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hepadnavirus

+ partial, - partial, icosahedral, enveloped

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DNA virus that does not replicate in the nucleus

poxvirus

65

DNA viruses that replicate in the nucleus use

RNA Pol II (multiple promoters, alternative splicing, code from both strands)

66

hallmark of DNA viruses is

that the expression of viral genes and viral DNA synthesis occur in a strictly defined, reproducible pattern

67

IE protiens

parental DNA, transactivators, transcription induced by host factors and carried in virions

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E protiens

parental DNA, DNA synthesis, (when host shutoff can occur), advantageous environment for viral replication

69

Late Proteins

progeny DNA, structural

70

Host DNA polymerase mediated

papilloma, parvo, only made during the s phase

71

viral polymerase mediated

adeno, herpes, pox

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parvovirus

B19

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transforming infection

type of infection in which cell proliferation is induced thereby leading to cancer

74

replication requires

a 3' primer (and goes 5'--->3')

75

bi-directional DNA synthesis

papoviruses, circular DNA

76

strand displacement

adenovirus

77

self priming

parvoviruses, ITR

78

rolling circle

herpes, RNA primers needed

79

Late phase includes

late gene expression, down regulation of early gene expression, induction of CPE

80

CMV infection

inclusion bodies

81

types of infection

latent (HSV, varicella), chronic (hep B, HIV, hepadna), acute (flu, hep A, adeno), slow (JCV)

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abortive infection

is not the same thing as an asymptomatic one. the infection fails to proceed, no virus is produced, but CPE may still result due to host immune response or activity of viral gene products

83

transforming infection

DNA alters the growth regulation of infected cells (papilloma, EBC) - usually oncogenesis is a mistake

84

parvovirus

DNA non enveloped, small, need helper virus (dependovirus +herpes, B19+dividing cells)

85

papovaviruses

DNA, non enveloped, icosahedral, ds circular 9papilloma, polyoma, narrow host cell range)

86

HPV

1. infection of basal epithelial layer, 2. amplification of episomal DNA, 3. maintenance replication in differentiating cels, 4. productive viral replication in differentiated cells

87

polyamoaviruses

DNA, BK, JC, MCV

88

adenovirus

non enveloped linear dsDNA (pink eye, hemorrhagic cystitis)

89

herpes

enveloped, large linear dsDNA, icosahedral, herpes is forever, tegument layer

90

acyclovir

ingested, injected, topical ointment, highly effective against HSV1 and 2, pro drug, TK phosphorylation in cell (triphosphate form generated in infected cells), guanine nucleotide terminated DNA synthesis (no 3' OH)

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hepadnavirus

occupational risk for health care workers, ~90 day incubation, cirrohis, mixed ssDNA/dsDNA

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pox virus

enveloped, dsDNA linear, REPLICATES IN CYTOPLASM, no need for nucleus, variola virus (small pox), vaccinia virus (cowpox-like vaccine)