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exam1 virus pathogenesis Flashcards

1
Q

T/F parvovirus likes to replicate in actively dividing cells

A

True

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2
Q

Define LD50

A

Lethal dose 50 : the dose of the virus required to cause death in 50% of animals

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3
Q

Define ID50

A

infectious dose 50 : the dose of virus that will infect 50% of an experimental group of hosts/animals

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4
Q

What is the ID50 : LD50 ratio?

A

ratio of dose of a particular strain of virus that causes infection in 50% of individuals to the dose that kills 50% of individuals

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5
Q

Which of the following is true?

a. the higher the ID50 and LD 50, the more virulent the organism
b. the lower the ID50 and LD50, the more virulent the organism

A

b. the lower the ID50 and LD50, the more virulent the organism

MORE virulent =
low ID50 & LD50

LESS virulent =
high ID50 & LD50

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6
Q

Name 3 other ways to assess degree of virulence.

A
  1. degree of severity of illness (clinical signs)
  2. incubation period
  3. Degree of severity, location, and distribution of gross, histologic, and ultrastructural lesion in affected animals
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7
Q 
Which of the following is false. 
Virulence can be measured as :
a. incubation period 
b. the proportion of infections that are fatal or by the survival time until death. 
c. none of the above
A

c. none of the above

the proportion of infections that are fatal or by the survival time until death = severity of illness

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8
Q

All of the following are possible outcomes of virus-host interactions except :

a. severe disease
b. moderate disease
c. mild disease
d. subclinical infection
e. exposure without infection
f. death of animal
g. virus and host sun bathe at the beach together

A

I hope you know the answer….

its G

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9
Q

What are the steps in viral infection?

A
  1. entry of viruses & primary replication
  2. spread, tropism & infection of target organs
  3. virus-cell interactions, secondary replication
  4. tissue & organ injury
  5. Shedding

this journey will always face obstacles from the host!

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10
Q

Which of the following is NOT a route of entry of virus into the host?

a. conjunctiva
b. arthropod
c. capillary
d. anus
e. they are all routes of entry

A

e….yes even anus

as well as : 
respiratory
alimentary tract
urogenital tract
skin
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11
Q

Name a few defenses of the skin?

A

Dense outer layer of Keratin (mechanical barrier)
Low pH
presence of fatty acids
bacterial flora
dryness
component of innate and adaptive immunity (migratory dendritic cells - langerhan cells)

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12
Q

What are some examples of arthropods that transmit viruses?

A

culicoides (bluetongue in sheep)
ticks (louping-ill in sheep)
mosquitos (EEEV in horses)

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13
Q

give an example of a virus transmitted by the bite of an infected animal?

A

Rabies

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14
Q

give an example of a virus transmitted by contaminated needles?

A

EIA(equine infectious anemia)

HCV(hepatitis C)

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15
Q

Which of the following are defenses of mucous membranes in the conjuntiva?

a. virucidal proteins
b. dryness
c. IgA
d. both a and c

A

d. both a and c

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16
Q

Name a few defenses of the GI Tract

A 
mm of oral cavity/esophagus
acidity of stomach
alkaline intestine
layer of mucus on gut
lipolytic activity of bile
proteolytic activity of pancreatic enzymes
defensins
IgA
scavenging macrophages
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17
Q

Name 3 defenses of the Respiratory tract

A 
Mucociliary blanket
alveolar macrophages
NALT (nasal assocaited lymphoid tissue)
BALT (bronchus-associated lymph tissue)
temperature gradient

large viruses trapped in mucus are coughed out

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18
Q

Which Virus spreads via local spread on epithelial surface?

a. parvovirus
b. papillomavirus
c. rabies virus
d. retrovirus

A

b. papillomavirus

mechanism of local spreading on the epithelial surface :
replicate in epithelial cells at the site of entry –> local spread by infecting contiguous cells –> produce localized infections –> shedding OR +/- proceed to adjacent subepithelial tissues or beyond

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19
Q

After transversing the epithelium, viruses may reach the subepithelial layers, which may be facilitated by?

a. pinocytosis
b. inflammatory response to virus infection and/or destruction of epithelium
c. by transport pathways like transcytosis
d. both b and c

A

d. both b and c

b. inflammatory response to virus infection and/or destruction of epithelium
c. by transport pathways like transcytosis

viruses should not overcome local host defenses

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20
Q

Define disseminated infection

A

infection spreads beyond the primary site of infection

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21
Q

Define systemic infection

A

if a number of organs or tissues are infected

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22
Q

T/F unilateral shedding of viruses from the infected epithelium is critical to subepithelial spread.

A

FALSE

Directional shedding of viruses from the infected epithelium is critical to subepithelial spread.

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23
Q

apical release facilitates :
A. systemic spread
B. Virus dispersal

A

B. Virus dispersal

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24
Q

Basolateral release facilitates:
A. systemic spread
B. Virus dispersal

A

A. systemic spread

by providing access to underlying tissues.

viruses released from basolateral have increased chances of infection.

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25
Q

In subepithelial tissues, viruses can get access to :

a. lymphatics
b. phagocytes
c. tissue fluids
d. all of the above

A

d. all of the above

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26
Q

In Subepithelial invasion and lymphatic spread, trargeted migration and replication of viruses NOT within :

a. leukocytes
b. dendritics and macrophages
c. lymphocytes
d. neutrophils

A

d. neutrophils

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27
Q

T/F some viruses may pass straight through lymph nodes to enter blood stream.

A

True

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28
Q

T/F some viruses are processed and epitopes presented to dendritic cells

A

FALSE

some viruses are processed and epitopes presented to helper T-cells : immune response

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29
Q

What is Viremia ?

A

The presence of a virus in the blood.

virus may be free or in cells.

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30
Q

What is primary viremia?

A

initial entry of virus into the blood after infection

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31
Q

What is Secondary Viremia?

A

virus has replicated in major organs and once more entered the circulation

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32
Q

What is passive viremia?

A

direct inoculation of virus in blood. bite of arthropods or contaminated syringe

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33
Q

What is active viremia?

A

viremia following initial virus replication in host. release of virions from the initial site of replication, such a lymphatics or epithelium of intestine, to the blood stream

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34
Q

What happens to viruses in the bloodstream?

A
  1. free in plasma for short duration (parvovirus)

2. cell-associated viruses tend to cause prolonged viremia.

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35
Q

Cell associated viruses that cause prolonged viremia tend to multiply in what cell types?

A

Monocytes and lymphocytes

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36
Q

Which of the following is not a virus interaction with macrophages?

a. virions may be phagocytosed and destroyed
b. prolonged viremia
c. Tissue invasion
d. all of the above

A

d. all of the above

  • virions may be phagocytosed and destroyed
  • virions may be phagocytosed by macrophages and then replicate in them –> activated macrophages –> inflammatory and vasoactive mediators
  • tissue invasion via carriage of virus inside monocyte/macrophage that emigrate through the walls of small blood vessels (trojan horse)
  • virions may be phagocytosed and transferred passively to adjacent cells, where replication begins
  • macrophages may fail to phagocyose host cells containing virions–> prolonged viremia
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37
Q

Outline the virus path into tissue/organs via the bloodstream.

A
  1. fenestrate
  2. trafficking lymphocyte or monocytes
  3. transcytosis
  4. replication in endothelial cells
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38
Q

What is he referring to with the trojan horse?

A

trafficking of monocytes transport viruses

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39
Q

Which of the following is NOT a method of clearance of virus from the bloodstream?

a. antibody clearance
b. mononuclear phagocytes in the spleen, liver, bone marrow.
c. exocytosis
d. complement-mediated clearance

A

c. exocytosis

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40
Q

Define neurotropic virus

A

virus that can infect neural cells. infection may occur by neural or hematogenous spread

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41
Q

Define neuroinvasive virus

A

Viruses that enter the CNS after infection of a peripheral site

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42
Q

Define Neurovirulent virus

A

Viruses that cause disease of the nervous tissue, manifested by neurological symptoms and often death

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43
Q

Which of the following refers to neuroinvasive virus?

a. Viruses that cause disease of the nervous tissue, manifested by neurological symptoms and often death
b. Viruses that enter the CNS after infection of a peripheral site
c. virus that can infect neural cells. infection may occur by neural or hematogenous spread

A

b. Viruses that enter the CNS after infection of a peripheral site

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44
Q

Herpes simplex virus exhibits :

a. low neuroinvasiveness of CNS, but high neurovirulence
b. high neuroinvasiveness of CNS, but low neurovirulence

A

a. low neuroinvasiveness of CNS, but high neurovirulence

it always enters the peripheral nervous system, but rarely enters the CNS. when is does, the consequences are almost always severe, but not fatal

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45
Q

Mumps virus exhibits

a. no neuroinvasiveness, but high neurovirulence
b. neuroinvasiveness, but low neurovirulence

A

b. neuroinvasiveness, but low neurovirulence

most infections lead to invasion of CNS, but neurological disease is mild.

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46
Q

Rabies virus exhibits

a. high neuroinvasiveness, but low neurovirulence
b. High neuroinvasiveness, and high neurovirulence

A

b. High neuroinvasiveness, and high neurovirulence

it readily infects the PNS and spread to the CNS with 100% lethality unless antiviral therapy is administed shortly after infection

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47
Q

Which of the following is correct regarding neural spread of viruses via transport of virus :

a. withing axons
b. in perineural lymphatics
c. in the endoneural space
d. via infected schwann cells
e. all of the above

A

e. all of the above

48
Q

Define Retrograde spread

A

travel opposite direction of nerve impulse flow.

49
Q

Define Anterograde spread

A

travel in the direction of nerve impulse flow.

50
Q

T/F In retrograde spread, the virus invades axon terminals and then spread to dendrite or cell body, then cross synapse to reach next axon terminal

51
Q

T/F In anterograde spread, the virus first invades axon terminals, and then cross synaptic contact to invade dendrite of next neuron.

A

FALSE
In anterograde spread, the virus invades dendrites or cells bodies and then spreads to axon terminals, and then cross synaptic contact to invade dendrite of next neuron.

52
Q

Centripetal movement of virus is?

a. towards CNS/brain
b. away from CNS/brain

A

a. towards CNS/brain

53
Q

Centrifugal movement is?

a. away from the brain
b. from CNS, within peripheral nerves, to other location in body
c. circles around the CNS

A

b. from CNS, within peripheral nerves, to other location in body

54
Q

Which viruses spread to CNS through olfactory route?

a. HSV
b. HSV, VSV
c. HSV, VSV, BDV
d. HSV, VSV, BDV, infA

A

d. HSV, VSV, BDV, infA

as well as HeV, CHIKV, LACV

moves anterograde

55
Q

Which viruses get into the CNS via the blood brain barrier?

a. HIV
b. SIV
c. HTLV-1
d. EV71
e. all of the above

A

e. all of the above

56
Q

Which cytokine causes increase permeability of the endothelial cells?

a. IL-2
b. IL-6
c. TNF

A

c. TNF

which anables viruses to get into the CNA

57
Q

explain the method of virus spread to CNS via the BBB

A
  1. TNF - increase permability of endothelail cells
  2. breakdown endothelial cell junctions through Matrix Metalloproteinase
  3. trojan horse (trafficked by monocytes)
58
Q

T/F In localized acute infections viremia can occur.

A

FALSE

In SYTEMIC acute infections viremia can occur.

59
Q

T/F in systemic acute infections secretory IgA is very important

60
Q

_____of infectious virions is crucial to the maintenance of infection in population.

61
Q

acute infection usually involves :

a. intensive shedding over a short period of time
b. minimal shedding over a short period of time

A

a. intensive shedding over a short period of time

62
Q

persistent infections can be shed at

a. higher titers for months to years.
b. lower titers for months to years

A

b. lower titers for months to years

63
Q

Define Tropism

A

The affinity of a virus for a particular host

64
Q

An enteric virus :

a. replicates in the gut, but in the skin
b. replicates in the gut, but in the urogenital tract
c. replicates in the gut, but in the lungs

A

c. replicates in the gut, but in the lungs

65
Q

A respiratory virus replicates:

a. in the lungs, but not in gut
b. in the lungs, but not in nerves
c. in the lungs, but not in skin

A

b. in the lungs, but not in nerves

66
Q

Define pantropic Virus

A

can replicate in more than one host organ/tissue

67
Q

Name some determinants of viral tropism

A
  • receptors on host cell
  • viral attachment proteins
  • viral enhancers
  • cellular protease req.
  • temperature of replication
  • acid liabilty and protease digestion
  • transcriptional control
  • anatomic barriers
  • host organ response to infection
68
Q

What is the rash of lyme disease referred to as?

69
Q

is papilloma systemic or localized?

70
Q

define disseminated

A

infection that spreads throughout

71
Q

3 common viruses of the skin are?

A

Foot and mouth disease
Lumpy skin disease
papillomavirus

72
Q

Ulcer involves which layers of the skin?

A

extends past the epidermis into the dermis layer.

73
Q

T/F Tumors often extend deep into the dermis.

74
Q

Define Papule

A

Solid elevations without fluid with sharp borders

75
Q

Which viruses commonly replicate in the GI tract?

a. rotavirus
b. norovirus
c. parvovirus
d. all of the above

A

d. all of the above

76
Q

Which of the following is NOT an injury associated with viral infection of the respiratory tract?

a. inflammation
b. exudation
c. increased ciliary activity
d. 2nd bacterial infection

A

c. increased ciliary activity

No - would have loss of ciliary activity

77
Q

Explain the concept of viral - bacterial synergism.

A

often seen in respiratory tract infections.
virus infects and damages the epithelium, allowing the bacteria to replicate. The virus can immuno suppress and clear the way for the bacteria to infect.

78
Q

Which of the following do NOT lead to encephalitis?

a. togaviruses
b. herpesviruses
c. flaviviruses
d. retoviruses

A

d. retoviruses

79
Q

Give an example on a disease that causes progressive myelination.

A

Canine distemper. can see seizures

80
Q

Neuronal vacuolation is common in which disease?

A

Prion disease

81
Q

What is a complication of viral infection in blood vessels?

A

Disseminated intravascular coagulation

82
Q

What is DIC?

A

Disseminated intravascular coagulation

widespread activation of clotting cascade that results in formation of blood clots in the small blood vessels throughout body

83
Q

define teratogenesis

A

abnormal development or arrests in development of the embryo or fetus

84
Q

BVDV Bovine Viral Diarrhea Virus caused what in non-pregnant animal?

a. mild infection
b. chronic infection
c. reduced WBC
d. both a and c

A

d. both a and c

mild infection, scours, milk drop, reduced WBC

85
Q

In what months of gestation will BVDV cause persistent infection in calves?

a. month 1
b. month 2-4
c. month 5-9

A

b. month 2-4

these will be immunotolerant calves

at month 1 there will be embryo death

86
Q

In what months of gestation will BVDV cause abortion, deformities, in calves?

a. month 1
b. month 2-4
c. middle 5-9 months
d. late 5-9 months

A

c. middle 5-9 months

87
Q

In what months of gestation will BVDV cause normal calves?

a. month 1
b. month 2-4
c. middle 5-9 months
d. late 5-9 months

A

d. late 5-9 months

88
Q

Explain how the calf becomes infected with BVDV.

A 
WHen the mother becomes infected between 2-4 months gestation, the virus passes to the fetus. the fetus does not have a developed immune system yet, so it cannot ID the virus as foreign and it becomes part of the calf. These calves have slow growth rate, secondary bact infection and often suffer from pneumonia.
sometimes this virus
can mutate into a
more lethal form, the
mucosal disease which
can be fatal to cow.
89
Q

Define Virus-induced immunopathology

A

Tissue injury mediate by host immune response (hypersensitivity rxns) to virus infection. it is the price paid by the host to clear a viral infection.

90
Q

T/F Immunopatholgy is often the cause of damage with viruses that are relatively cytolytic and persistent.

A

FALSE
Immunopatholgy is often the cause of damage with viruses that are relatively NON-cytolytic and persistent.

ex: infected cells are not immediately destroyed and immune response become chronic

91
Q

Which of the following are TRUE?

a. if immune response clears the infection by destroying a small number of virus infected cells, the host survives with minimal symptoms and no permanent damage.
a. if immune response clears the infection by destroying a large number of virus infected cells, the host survives with minimal symptoms and no permanent damage.

A

a. if immune response clears the infection by destroying a SMALL number of virus infected cells, the host survives with minimal symptoms and no permanent damage.

if a large number of cells are infected before immune induction, the same immune mediated destruction can cause severe or fatal pathological consequences.

92
Q

Please give one example of a disease that exhibits immunopathology.

A

autoimmune diseases

ex : moon blindness in horses

93
Q

Which of the following is the role of T cells in virus induced immunopathology?

a. directly destroy virus infected cells
b. release cytokines
c. both a and b
d. destroy host cells

A

c. both a and b

release cytokines such as TNF to damage cells

94
Q

T/F in virus-induced immunopathology there may be cytotoxic cell mediated lysis/killing of infected host cells.

A

True.

with some non-cytopathic virus infection (HCV, HBV) destruction of infected cells by CD8+ effector T cells is main cause of damage to liver

95
Q

which of the following is true

a. CD4+ cells elaborate far more cytokines than CD8+ cells
b. CD8+ cells elaborate far more cytokines than CD4+ cells

A

a. CD4+ cells elaborate far more cytokines than CD8+ cells

and activate other non-specific effect cells like neutrophils

96
Q

Define cytokines

A

borad to loose category of small proteins that are important in cell signaling. they act as mediators and regulators of immune process and can cause inflammation

97
Q

Persistent activation of these receptors of innate host cells by viruses causes production of pro-inflammatory cytokines and interferons.

a. troll-like receptors
b. doll-like receptors
c. toll-like receptors
d. mott-like receptors

A

c. toll-like receptors

are expressed at host cell surface or within cells. they recognize invading viruses and their replicative intermediates.

98
Q

T/F normally free radicals inhibit viral replication

A

TRUE

BUT when produced in abundance, cause cell damage.

99
Q

Injury to cells can also be mediated by :

a. free radicals
b. Nitric Oxide
c. Superoxide
d. all of the above

A

d. all of the above….those are all free radicals

100
Q

T/F antigen response to viruses may also contribute to tissue damage

A

FALSE

ANTIBODY response to viruses may also contribute to tissue damage.

occurs when antibody binds infect cell, activates complement and causes inflammatory rxn.

101
Q

Spike proteins on Feline Infectious Peritonitis Virus (FIPV) bind to :

a. cytokines
b. antibodies
c. anitgens
d. neutrophils

A

b. antibodies

these anitbodies fail to neutralize the virus. instead there is antigen-antibody immunocomplex formation which activated the complement cascade and the result is vasculitis and edema

102
Q

T/F infection and damage to mononuclear phagocytes can protect an invading virus from phagocytic removal.

103
Q

Which of the following are immunodeficiency viruses?

a. HIV
b. HIV, SIV
c. HIV, SIV, BIV
d. HIV, SIV, BIV, FIV

A

d. HIV, SIV, BIV, FIV

these viruses infect and destroy different but specific cells of the immune system leading to immunosuppression

104
Q

Systemic infection by some viruses result in temporary suppression of both humoral and cell-mediated immune system, usually infect :

a. mononuclear phagocytes /lymphocytes
b. proteins
c. lymphocytes/neutrophils
d. mononuclear phagocytes/cytokines

A

a. mononuclear phagocytes /lymphocytes

105
Q

Explain Infectious Bursal disease in birds.

A

virus replication causes atrophy of the bursa and severe deficiency of B lymphocytes, resulting in immunosuppression. as a result infected birds become susceptible to other pathogens

106
Q

Name the types of viral infections

A
  1. inapparent infection
  2. Acute infection
  3. persistent/latent infection
    - Chronic infection
    - slow infection
107
Q

Which of the following are NOT characteristics of inapparent infections?

a. clinical signs evident
b. few cells infected
c. stimulate host immune response
d. possible source of virus spread.

A

a. clinical signs evident

clinical signs are not evident

108
Q

T/F in persistent infections the pathogen is cleared efficiently by the adaptive immune response.

A

FALSE

in persistent infections the pathogen is NOT cleared efficiently by the adaptive immune response.

109
Q

T/F Persistent infections always show clinical signs.

A

FALSE

Persistent infections DO NOT ALWAYS show clinical signs.

110
Q

What is latent infection?

A

infectious virus is not demostratable except when reactivation occurs.

111
Q

Reactivation in latent infections is often stimulated by:

a. action of a cytokine
b. action of a hormone
c. immunosuppression
d. all of the above

A

d. all of the above

112
Q

Viral Latency may be maintained by :

a. restricted expression of genes that prevent expression of proteins
b. virus genome maintained indefinitely in cell by integration of viral nucleic acid into host cell DNA.
c. all of the above
d. none of the above

A

c. all of the above

113
Q

What is an example of a virus that exhibits latent phase infection?

A
  • Infectious Bovine Rhinotracheitis

- cold sores

114
Q

T/F Chronic infections always begin as chronic

A

FALSE

Chronic infections DO NOT always begin as chronic

115
Q

Give an example of a chronic infection.

A

foot and Mouth disease in cattle

116
Q

give an example of a slow infection, where there is slow progressive lethal disease.

virology (8 decks)

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