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Sem 3: Viro > Host-Pathogen Interactions > Flashcards

Host-Pathogen Interactions Flashcards

1
Q

________ is the ability of a virus to cause disease in a host

A

Pathogenicity

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2
Q

_________ refers to the mechanism of development of a disease

A

Pathogenesis

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3
Q

What is virulence?

A

Quantitative measure of the degree of pathogenicity of a virus

**not an absolute property of a virus, depends on many variables

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4
Q

What is LD50?

A

Dose of a virus that causes death in 50% of animals

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5
Q

What is ID50?

A

Infectious dose 50

dose of a virus that will infect 50% of an experimental group

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6
Q

LD50 of 15 vs LD50 of 45, which is more virulent?

A

LD50 of 15

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7
Q

What mechanisms of defense does the skin have against viruses?

A
  1. Dense keratin layer
  2. Low pH
  3. Dryness
  4. Fatty acids
  5. Bacterial flora
  6. Components of innate and adaptive immunity
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8
Q

How can viruses enter through skin?

A
  1. Bite of arthropod
  2. Bite of animal
  3. Contaminated objects/ needles
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9
Q

What are routes of entry for a virus?

A
  1. Skin
  2. Mucus membranes
  3. GI tract
  4. Respiratory tract
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10
Q

What mechanisms of defense does the GI tract have against viruses? (9)

A
  1. MM of oral cavity
  2. Acidity of stomach
  3. Alkalinity of SI
  4. Layer of mucus
  5. Activity of bile
  6. Pancreatic enzymes
  7. Macrophages
  8. IgA
  9. Defensins
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11
Q

What mechanisms of defense does the resp tract have against viruses?

A
  1. Mucociliary blanket
  2. Alveolar macrophages
  3. NALT
  4. BALT
  5. Temp gradient
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12
Q

What is a disseminated infection?

A

One that spreads beyond primary site of infection

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13
Q

What is a systemic infection?

A

If a # of organs are infected

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14
Q

_________ of viruses from the infected epithelium is critical to subepithelial spread

A

Directional shedding

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15
Q

_______ release provides access to underlying tissues and facilitates systemic spread

A

Basolateral

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16
Q

________ release facilitates virus dispersal

A

Apical

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17
Q

What is viremia?

A

Presence of virus in blood

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18
Q

True or False: A virus may be free in blood or in a cell

A

TRUE

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19
Q

What is primary viremia?

A

Initial entry of a virus into the blood after infection

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20
Q

What is secondary viremia?

A

Virus that replicated in major organs and once more entered circulation

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21
Q

What is passive viremia?

A

Direct inoculation of virus in host, no initial replication elsewhere in host

Ex: contaminated syringe or bite of arthropod

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22
Q

What is active viremia?

A

Viremia following initial virus replication in host.

Release of virions from initial site of replication

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23
Q

True or False: Tick bites can transmit some viruses directly into the blood. This is called active viremia

A

FALSE - passive viremia

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24
Q

What is a neurotropic virus?

A

Virus that infects neural cells

Infection can occur by neural or hematogenous spread

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25
Q

What is a neuroinvasive virus?

A

Viruses that enters the CNS after infection of a peripheral site

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26
Q

What is neurovirulent virus?

A

Viruses that cause disease of nervous disease manifested by neuro symptoms and sometimes death

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27
Q

What does it mean for a virus to have low neuroinvasiveness but high neurovirulence?

A

Virus always enters peripheral nervous system and rarely enters CNS

when it does enter CNS, consequences are severe/fatal

28
Q

What does it mean for a virus to have high neuroinvasiveness but low neurovirulence?

A

Infection invades the CNS but neuro disease is mild

29
Q

What does it mean for a virus to have high neuroinvasiveness and high neurovirulence?

A

Virus infects peripheral nervous system and spreads to CNS with 100% lethality unless given antivirals shortly after infection

30
Q

What is retrograde spread?

A

Virus travels in opposite direction of nerve impulse

31
Q

What is anterograde spread?

A

Virus that travels in the same direction of a nerve impulse

32
Q

How can viruses spread to the CNS?

A
  1. Olfactory routes
  2. Through the BBB
33
Q

Secretory IgA is important in ___________ infections

A

Localized acute

34
Q

________ infections have a long incubation period

A

Systemic acute

35
Q

________ infections can cause pathology at distant sites

A

Systemic acute

36
Q

_________ infections have no viremia

A

Localized acute

37
Q

__________ is characterized by intensive shedding over a short period of time

A

Acute infection

38
Q

What is a persistent infection?

A

Infection shed at low titers for months to years

39
Q

What is tropism?

A

Specificity/ Affinity of a virus for a particular host tissue

40
Q

What is a pantropic virus?

A

Virus that can replicate in more than 1 host organ/tissue

41
Q

A family of viruses may prefer a particular organ for effective replication. The term used to describe this is _________-

A

Tropism

42
Q

__________ is a small distinct elevation with fluid

A

Vesicle

43
Q

_________ is a solid, palpable, elevated mass with distinct borders, extending deep into the dermis

A

Nodule / Tumor

44
Q

What are warts?

A

Benign skin growths that appear when a virus infects the TOP layer of skin

45
Q

_________ is an opening of the skin caused by sloughing of necrotic tissue, extending past the epidermis

A

Ulcer

46
Q

What is a papule?

A

Solid elevation WITHOUT fluid, sharp borders

47
Q

What is erythema?

A

Reddening of the skin

** consequence of viral infection

48
Q

How do viruses cause damage to the GI tract?

A

First enters GI tract via ingestion or hematogenous spread/systemic infection

  1. Destroys enterocytes due to viral replication
  2. GI disease, malabsorption, diarrhea
  3. Dehydration, acidosis, hemoconcentration
49
Q

What injuries are caused by viruses entering the resp tract?

A
  1. Loss of cilia
  2. Loss of mucus
  3. Inflammation
  4. Obstruction of airways
  5. ***secondary BacT infection (VIRAL-BACTERIAL SYNERGISM)
  6. Hypoxia
50
Q

What injuries are caused by viruses entering the CNS?

A
  1. Encephalitis or encephalomyelitis characterized by neuronal necrosis
  2. Neurophagia -Phagocytosis of neurons
  3. Perivascular cuffing - perivascular infiltrations of inflamm cells
  4. Progressive demyelination
  5. Neuronal vacuolation
51
Q

Which virus enters the CNS and causes progressive demyelination?

A

Canine distemper virus

52
Q

What injuries are caused by viruses damaging the endothelium?

A
  1. Petechial and ecchymotic hemorrhages
  2. DIC (blood clots in small vessels)
  3. Edema
  4. Infarction / ischemic necrosis
53
Q

__________ are larger areas of hemorrhage with ill defined margins

A

Ecchymoses hemorrhage

54
Q

What does petechiae hemorrhage look like?

A

small pinpoint lesions

55
Q

What is teratogenesis?

A

Abnormal development or arrests in development of the embryo or fetus

results in death or malformations during antenatal period

56
Q

What is virus induced immunopathology?

A

tissue injury mediated by host IR to virus infection

depends on balance between protective and destructive effects

57
Q

________ is the cause of damage with viruses that are non-cytolytic and persistent

A

Immunopathology

58
Q

What are results of immunopathology?

A
  1. Tissue damage from hypersensitivity rxn
  2. Autoimmune dz (Ex: moon blindness in horses)
  3. Inflammation-mediated tissue damage (ex: Fibrosis)
  4. Immunodeficiency
59
Q

What are mechanisms of virus induced immunopathology?

A
  1. The role of T cells
    - cytotoxic killing of host cells
    - cytokines from CD4+ and CD8+ cause inflamm. that becomes chronic against persistent infection
  2. TLRs - persistent activation causes production of pro inflamm cytokines
  3. Injury mediated by free radicals like nitric oxide and superoxide
  4. Toxicity from Ab response
  5. Vasculitis mediated by immune complex formation
60
Q

What is infectious bursal disease?

A

immunosuppression from viral induced immunopathology

  • virus caused atrophy of bursa of fabricius resulting in deficiency of B cells and immunosuppression
61
Q

What are characteristics of an inapparent infection?

A
  1. No CS or symptoms
  2. Few cells infected
  3. Stimulates host IR
  4. Possible source of virus spread
62
Q

What are characteristics of an acute infection?

A

= short term infection

  • obviously lasts a short time
  • rapid clearance from host IR
63
Q

What are characteristics of a latent infection?

A

= persistent infection

  • infection not detectable until reactivation occurs

-reactivated due to immunosuppression or by the action of a cytokine or hormone

64
Q

What are characteristics of a chronic infection?

A

= persistent infection

  • continuous shed of virus
    -usually limited to a specific infected tissue
65
Q

What are characteristics of a slow infection?

A

= persistent infection

  • prolonged incubation time, months-years

-slow, progressive, lethal dz

Ex: prions

Sem 3: Viro (17 decks)

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