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Virology > Virus Pathogenesis > Flashcards

Virus Pathogenesis Flashcards

1
Q

virulence

A

measure of the degree of pathogenicity

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2
Q

T/F the higher the ID50 and LD50, the more virulent the organism.

A

F: less virulent

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3
Q

possible outcomes of virus-host interactions

A
  • exposure without infection
  • subclinical infection
  • mild disease
  • moderate disease
  • severe disease
  • death!!!!
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4
Q

pathogenesis of viral infection

A
  • entry of viruses and primary replication
  • spread, tropism, infection of target organs
  • virus-cell interactions, secondary replication
  • tissue and organ injury
  • shedding
  • death
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5
Q

skin defenses

A
  • dense outer layer of keratin
  • low pH
  • presence of fatty acids
  • bacterial flora
  • dryness
  • innate and adaptive immunity (migratory DC = Langerhans cells)
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6
Q

What route does blue tongue virus use to enter a host?

A

bite of arthropods (culicoides)

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7
Q

3 mucous membranes that can serve as routes of entry?

A
  1. conjunctiva
  2. oropharynx
  3. genitourinary tract
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8
Q

mucous membrane defenses

A

IgA

virucidal proteins

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9
Q

GI tract defenses

A
  • mucous membrane of oral cavity and esophagus
  • acidity of stomach
  • alkalinity of intestine
  • layer of mucus covering gut
  • lipolytic activity of bile
  • proteolytic activity of pancreatic enzymes
  • defensins
  • IgA
  • scavenging macrophages
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10
Q

Respiratory defenses

A
  • mucociliary blanket (moves stuff along)
  • alveolar macrophages
  • NALT
  • BALT
  • temp gradient
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11
Q

What facilitates viruses reaching the subepithelial layers?

A
  1. inflammatory response to virus and/or destruction of epithelium
  2. transport pathways like transcytosis
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12
Q

disseminated infection

A

infection spreads beyond the primary site of infection

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13
Q

systemic infection

A

if a number of organs or tissues are infected

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14
Q

What kind of release facilitates virus dispersal?

A

apical release

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15
Q

What kind of release facilitates systemic spread?

A

basolateral release

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16
Q

lymphatic spread

A

targeted migration and replication of virus within phagocytic leukocytes, specifically DC and macrophages, lymphocytes

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17
Q

viremia

A

presence of virus in the blood; may be free in blood or in a cell (lymphocyte)

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18
Q

primary viremia

A

initial entry of virus into blood after infection

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19
Q

secondary viremia

A

virus has replicated in major organs and once more entered circulation

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20
Q

passive viremia

A

direct inoculation of virus in blood

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21
Q

Examples of passive viremia?

A

bite of arthropods or contaminated syringe

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22
Q

active viremia

A

viremia following initial virus replication in host; release of virions from initial site of replication, such as lymphatics or epithelium of intestine to bloodstream

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23
Q

When would passive viremia occur?

A

day 0

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24
Q

When would primary viremia occur?

A

day 1-3

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25
Q

When would secondary viremia occur?

A

day 3-14

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26
Q

Do macrophages always kill viruses?

A

NO; virions may be phagocytosed and may replicate in macs and came emigrate through walls of small blood vessels as trojan horse

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27
Q

Trojan horse

A

viruses enter monocyte in lumen of blood vessel and cross blood tissue barrier then leave monocyte in the tissue

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28
Q

3 ways to clear virus from bloodstream

A
  1. mononuclear phagocytes in spleen, liver, bone marrow
  2. antibody clearance
  3. complement-mediated clearance
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29
Q

neurotropic virus

A

viruses that infect neural cells by neural or hematogenous spread

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30
Q

neuroinvasive virus

A

viruses that enter CNS after infection of a peripheral site

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31
Q

neurovirulent virus

A

viruses that cause disease of nervous tissue, manifested by neuro symptoms and often death

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32
Q

Is neuroinvasiveness and neurovirulence high or low for herpes simplex virus?

A

neuroinvasiveness: low
neurovirulence: high

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33
Q

Is neuroinvasiveness and neurovirulence high or low for Mumps virus?

A

neuroinvasiveness: high?
neurovirulence: low

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34
Q

Is neuroinvasiveness and neurovirulence high or low for rabies virus?

A

high for both!

100% lethality unless antiviral therapy administered shortly after infection

35
Q

neural spread of viruses

A
  • within axons
  • in perineural lymphatics
  • in endoneural space
  • via infected Schwann cells
36
Q

retrograde spread

A

travel opposite direction of nerve impulse flow; invades axon terminals then spreads to dendrite or cell body, then crosses synapse to reach next axon terminal

37
Q

anterograde spread

A

travel in direction of nerve impulse flow; virus invades dendrites or cell bodies and spreads to axon terminals, then crosses synaptic contacts to invade next dendrite

38
Q

centripetal movement

A

towards CNS

39
Q

centrifugal movement

A

from CNS within peripheral nerves to other locations in the body

40
Q

T/F neural spread of viruses can occur through olfactory routes

A

T: anterograde up olfactory nerve to CNS (olfactory bulb)

41
Q

methods to spread viruses through BBB

A
  1. increasing permeability of endothelial cells through secretion of TNF
  2. breakdown of endothelial cell junctions through MMP
  3. trojan horse (trafficked by monocytes)
42
Q

Is the incubation period long or short for systemic acute infections ?

A

long

43
Q

What is the duration of immunity for localized acute infections?

A

variable, may be short

lifelong for systemic

44
Q

T/F secretory IgA is important for localized acute infections?

A

T : veryyyy

45
Q

T/F the shedding of infectious virions is crucial to the maintenance of infection in populations

A

T

46
Q

How are acute infections shed?

A

intensive shedding over a short time period

47
Q

How are persistent infections shed?

A

shed at lower titers for months to years

48
Q

tropism

A

specificity/affinity of a virus for a particular host tissue

49
Q

pantropic viruses

A

can replicate in more than one host organ/tissue

50
Q

rash

A

general term applied to any temporary eruption on the skin

51
Q

What disease causes a bulls eye rash?

A

Lyme disease

52
Q

vesicle on skin

A

small distinct elevation with fluid
localized = papilloma
disseminated = lumpy skin disease

53
Q

ulcer

A

opening in skin caused by sloughing of necrotic tissue, extending past epidermis

54
Q

nodule

A

palpable, solid, elevated mass with distinct borders

*extends deep into dermis = tumor

55
Q

warts

A

benign skin growths that appear when a virus infects the top layer of skin

56
Q

papule

A

solid elevations without fluid with sharp borders

57
Q

erythema

A

reddening of skin, consequence of systemic viral infections (endothelial injury in blood vessels throughout body, including those of subcutaneous tissues)

58
Q

GI tissue injury

A

destruction of enterocytes -> malabsorption, diarrhea, dehydration, acidosis, hemoconcentration

59
Q

viral-bacterial synergism

A

when the respiratory tract is infected with both virus and bacteria the % mortality is greater than each alone combined

60
Q

Which virus causes progressive demyelination?

A

canine distemper

61
Q

What disease can cause neuronal vacuolation?

A

Prion disease

62
Q

Petechiae hemorrhage

A

pin point /small spots

63
Q

ecchymoses hemorrhage

A

larger areas of hemorrhage, ill defined margins

64
Q

disseminated intravascular coagulation (DIC)

A

complication arising from viral infections of blood vessels; widespread activation of clotting cascade -> blood clots in small blood vessels throughout body

65
Q

What happens when clotting proteins in blood are used up in DIC?

A

severe bleeding can occur from various sites

66
Q

teratogenesis

A

abnormal development or arrests in development of embryo or fetus -> death or malformations during antenatal period

67
Q

What can cause congenital hydraencephaly in calves and how does it present?

A

BVDV -> recumbence, depression, dome shaped skull

68
Q

What happens to a non-pregnant animal with BVDV?

A

usually mild infection, scours, milk drop, reduced WBCs

69
Q

What happens when a pregnant cow has a transient infection of BVDV?

A

naturally immune

70
Q

What occurs when a cow with a 1 month pregnancy has BVDV?

A

embryo death

71
Q

What occurs when a cow with 2-4 month pregnancy has BVDV?

A

persistent infection (PI calves) -> immunotolerant

72
Q

What occurs when a cow with 5-9 month pregnancy has BVDV?

A

middle: abortion, deformities
late: normal calves

73
Q

What is the danger of an immunotolerant calf?

A

the virus can mutate to become cytopathic and cause a superinfection -> can infect other viremic animals and lead to fatal mucosal disease

74
Q

virus induced immunopathology

A

tissue injury mediated by host immune response to virus infection; cause of damage with viruses that are persistent -> chronic immune response

75
Q

What happens when NO and superoxide are produced in abundance?

A

cell damage! normally inhibit viral replication

76
Q

When do antibody mediated inflammatory reactions involve toxicity?

A
  • engagement of IgG with Fc receptors on inflammatory cells which causes inflammatory release
  • following deposition of viral antigen-antibody complexes in capillary beds, leading to activation of complement cascade
77
Q

What causes immune complex-mediated vasculitis and what is a common sign?

A

feline infectious peritonitis; distended abdomen

78
Q

What can happen when macrophages release IL10?

A

skew immune response from TH1 to TH2 -> diminishes cell-mediated immunity

79
Q

infectious bursal disease

A

virus replication causes atrophy of bursa and deficiency of B lymphocytes resulting in immunosuppression

80
Q

inapparent infections

A

clinical signs and symptoms are not evident; too few cells may be infected

81
Q

persistent infection

A

pathogen not cleared efficiently by adaptive immune response -> infectious virus demonstrable continuously whether or not there is ongoing disease

82
Q

latent infection

A

infectious virus not demonstrable except when reactivation occurs -> often stimulated by immunosuppression and/or action of cytokine or hormone (ex. cold sores)

83
Q

chronic infection

A

virus continuously shed from or is present in infected tissue; sometimes starts as acute infection (ex. foot and mouth disease in cattle)

84
Q

slow infection

A

prolonged incubation period, lasting months or years; quantities of infectious virus gradually increase during a very long preclinical phase; slow lethal progressive disease (ex. prions)

Virology (16 decks)

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