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Veterinary Infectious Diseases > Introduction to Virology > Flashcards

Introduction to Virology Flashcards

1
Q

do viruses have a metabolic system of their own?

A

no

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2
Q

what cells do viruses infect?

A

prokaryotic cells or eukaryotic cells

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3
Q

what type of genome do viruses have?

A

DNA or RNA (unique in this)

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4
Q

what is the basic structure of a virus?

A

nucleic acid genome
protein coat
+/- envelope

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5
Q

what are the three basic types of capsid symmetry?

A

helical
icosahedral
complex

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6
Q

what virus families have complex symmetry?

A

bacteriophages
poxviruses

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7
Q

what is the structure of the rabies virus?

A

helical enveloped

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8
Q

what viruses have an icosahedral naked structure?

A

picornaviruses
polymaviruses

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9
Q

what viruses have an icosahedral enveloped structure?

A

herpesviruses

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10
Q

what does it mean for a virus to have an icosahedral structure?

A

isometric or cubic

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11
Q

what comprises the viral envelope?

A

lipid bilayer with protein

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12
Q

what may happen if many virions are released simultaneously?

A

integrity of host cell membrane may be compromised enough to lead to cell death

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13
Q

what are the two basic types of virus-encoded proteins?

A

structural and non-structural

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14
Q

what do structural proteins typically do?

A

capsid and genome packaging

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15
Q

what do nonstructural proteins primarily do?

A

enzymes: genome transcription, replication, and protein processing

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16
Q

if ssRNA serves as a message for translation (the same sense as mRNA), it is referred to as ____________________

A

positive-sense

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17
Q

if the viral RNA is antisense (or complementary) to that of mRNA- and thus cannot be translated directly- it is said to be ____________________

A

negative-sense

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18
Q

what are the steps to a virus attacking a host cell?

A

attachment
penetration
uncoating
multiplication
translation
assembly
release

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19
Q

what is important about viral genetics?

A

RNA polymerases typically lack error correction ability
viral antigens are important targets for immune response

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20
Q

where do DNA viruses usually replicate?

A

within the nucleus

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21
Q

where does the replication of most RNA viruses usually take place?

A

cytoplasm of cells
independent of nuclear machinery

22
Q

how does the RNA of some animal viruses differ from others?

A

some have mRNA function and can be directly translated
others have antisense: must first be transcribed into RNAs by a viral-encoded RNA-dependent RNA polymerase

23
Q

what are the general characteristics of viruses?

A

smaller than cells
some infect prokaryotic cells, some eukaryotic cells
simple and static structure; no metabolic system of their own
some destroy cells, others persist in latent or persistent state, other cause cellular malignant transformation

24
Q

how do viruses exit the cell?

A

enveloped viruses exit via budding
naked virions exit by lysing or exocytosis from the host cell

25
Q

what viruses only exit via the apical surface?

A

influenza virus
rabies virus
paramyxovirus

26
Q

how do viruses impact cell homeostasis?

A

metabolic derangements
cell lysis or fusion
neoplastic transformation
viral antigens
virus assembly
viral inclusions
reduced host cell DNA, RNA, protein synthesis

27
Q

what can cell infection result in?

A

normal
cell death
cytopathology
malignant transformation

28
Q

what can happen in cytopathology with cell infection?

A

syncytia
disruption of the cytoskeleton
inclusion bodies

29
Q

what is pathogenesis?

A

the origination and development of a disease
acute, chronic, latent, or persistent
susceptibility to infection is a result of a series of factors

30
Q

what is the pathogenesis of viral infection?

A

portal of entry
localized vs disseminated infection and tropism
number of cells infected
environmental/host factors
direct and indirect effects
virus-induced immunosuppression
virus-induced immunopathology
evasion of the immune system

31
Q

what are the host defenses?

A

physical/chemical barriers
non-specific immune defenses
antibody mediated immunity
cell mediated immunity

32
Q

what makes viruses a unique class of microorganism?

A

30-300nm
DNA or RNA genome
obligate intracellular
no cell-free culture

33
Q

the nucleic acid plus the capsid shell is often called

A

nucleocapsid

34
Q

what is the viral envelope derived from?

A

host cell membranes

35
Q

no known human or animal viruses have the ________________ structure

A

naked helical

36
Q

what does the envelope origin depend upon?

A

virus and cellular compartment where replication takes place

37
Q

what do envelope glycoproteins do?

A

mediate interactions between the virions and cells

38
Q

what is the genome of poxviruses?

A

dsDNA whose ends are covalently attached to each other

39
Q

what viral families have DNA but replicate in the cytoplasm?

A

poxviruses
iridoviruses

40
Q

what is a viral family that has RNA but replicates in the nucleus?

A

orthomyxoviruses

41
Q

what DNA viruses are associated with oncogenesis?

A

Marek’s disease virus
bovine, equine, and canine oral papillomaviruses

42
Q

what RNA viruses are associated with oncogenesis?

A

retroviridae: avian leukosis virus and feline leukemia virus

43
Q

the protein coat is formed of structural units called _________________

A

capsomeres

44
Q

what viruses are partially double-stranded DNA?

A

hepadnaviruses

45
Q

what can a viral genome encode?

A

a few to greater than 70-100 gene products

46
Q

what are some examples of evasion of the immune system?

A

infection of immunologically privileged sites
antigenic variability of virions
inhibition of INF-beta
decrease in MHC class I expression
inhibition in peptide processing and expression of immune system homologous structures

47
Q

what is an example of immunologic response mediating disease pathogenesis?

A

Borna disease in horses

48
Q

what does the host response include?

A

interferons
cytotoxic T lymphocytes
antibody producing B-lymphocytes
variety of effector molecules
complement

49
Q

what are some viral propagation methods?

A

host animals
embryonated eggs
cell/tissue culture
explant culture
primary cell cultures
continuous cell cultures

50
Q

what are some ways to do indirect enumeration of viruses?

A

hemaglutination
plaque forming assay
limiting dilution method

51
Q

what are some virus diagnostics?

A

virus isolation
Elisa
FA
virus neutralization, HI
PCR, restriction, hybridization, sequencing
RIA
protection tests
collection and submission of specimens

Veterinary Infectious Diseases (29 decks)

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