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RUSVM Virology Spring17 > (Final) Host-Pathogen Interactions > Flashcards

(Final) Host-Pathogen Interactions Flashcards

1
Q

Do non-pathogenic viruses exist?

A

YES

Avirulent

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2
Q

What viral process causes damage to the host?

A

replication

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3
Q

What is the difference between pathogenicity and pathogenesis?

A

Pathogenicity: ability of a virus to cause disease

Pathogenesis: manner or mechanism of development of a disease

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4
Q

What is virulence?

A

measure of the degree of pathogenecity of an infecting virus

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5
Q

T/F: Virulence is an absolute property of viruses

A

FALSE

Depends on many different factors: viral, host, and environment

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6
Q

What viral factors affect the virulence of a pathogen?

A 
Genetic makeup
Portal of entry
Tropism to host organs
dose of infection
immuno evasion capabilities
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7
Q

What is the LD50?

A

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

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8
Q

What is the ID50?

A

Infectious dose 50: The dose of virus that will infect 50% of an experimental group of hosts/animals

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9
Q

T/F: If Virus A has an LD50 of 30 and Virus B has an LD50 of 100: Virus B is more virulent

A

False

Virus A is more virulent bc it takes less virus to kill 50% of the population

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10
Q

What protective barriers/factors must a virus surpass to enter a host through the skin?

A 
Outer layer of keratin
Low pH
Presence of fatty acids
Baterial flora
Dryness
Components of innate and adaptive immunity
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11
Q

How do viruses enter through the skin?

A

Bite of arthropods
Bite of an infected aniaml
Contaminated objections (like needles etc)

**a virus can never enter through healthy, non compromised skin. Must be a breach

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12
Q

What are some examples of MM viruses can enter the host?

A

Conjuctivia
Oropharynx
Genitourinary tract

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13
Q

What host defenses are present in the GI tract?

A 
MM of oral cavity and esophagus
Acidity of the stomach
Alkalinity of the intestine
Mucus covering the gut
Lipolytic activity of the bile
proteolytic activity of the pancreatic enzymes
Defensins, IgA, Macrophages
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14
Q

What hose defenses are present in the respiratory tract?

A

Mucociliary blanket
Alveolar marcrophages
Nasal and bronchus associated lymphoid tissue
Temperature gradient

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15
Q

What is the order of virus spread when entering through the epithelium?

A
  1. Spread of virus on the epithelial surface –> localized infection
  2. Spread to subepithelial– invasion and lymphatic spread
  3. To the blood stream and spread systemically
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16
Q

What is the difference between a disseminated infection and a systemic infection?

A

Disseminated infection: Infection that spreads beyond the primary site of infection

Systemic infection: When a number of tissues or organs are infected

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17
Q

Apical release of viral particles from the epithelium facilitates what?

A

virus dispersal

apical surface is in contact with vascular lumen

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18
Q

Basolateral release of viral particles from the epithelium facilitates what?

A

Systemic spread

Basolateral release provides access to underlying tissues

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19
Q

T/F:Viremia is the presence of virus in the blood

A

TRUE

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20
Q

What is the difference between PRIMARY and SECONDARY viremia?

A

Primary: initial entry of virus into the blood after infection

Secondary: Virus has replicated in major organs and re-enters of the blood circulation

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21
Q

How does one get PASSIVE viremia?

A

Direct inoculation of virus into the blood. Ex: Arthropod bites, contaminated syringe

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22
Q

T/F: Contracting west nile virus from a mosquito is an example of primary viremia

A

FALSE

This is PASSIVE viremia

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23
Q

What is active viremia?

A

Viremia following initial virus replication in epithelial cells –>lymphatics –> then passed into the blood stream

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24
Q

What cell can some viruses use to travel undetected through blood tissue barriers?

A

Monocytes

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25
Q

What are neurotropic viruses?

A

Viruses that can infect neural cells. Infection may occur by neural or hematogenous spread

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26
Q

What are neuroinvasive viruses?

A

Viruses that enter the CNS - AFTER infection of a peripheral site

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27
Q

What are neurovirulent viruses?

A

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

28
Q

T/F: Herpes simplex virus exhibits low neuroinvasiveness and high neurovirulence

A

TRUE

It rarely enters the CNS - but when it does the consequences are always severe if not fatal

29
Q

The rabies virus exhibits _________ neuroinvasiveness and ________ neurovirulence

A

HIGH and HIGH

30
Q

If a virus is said to have Retrograde spread, what direction is it spreading in relation to nerve impulse flow?

A

Opposite direction of nerve impulse flow

Invades axon terminals –> Dendrite or cell body –> crosses synapse to reach the next axon terminal

31
Q

T/F: If a virus is moving via anterograde spread it is traveling in the direction of nerve impulse flow

A

TRUE

Dendrites or cell bodies –> axon terminals –> crosses synaptic contacts to invade the next dendrite or cell body

32
Q

T/F: Neural spread of viruses to the CNS can occur through olfactory routes

A

TRUE

33
Q

What are three ways viruses can spread to the CNS through the BBB?

A
  1. increase permeability of the endothelial cells via secretion of TNF
  2. Breakdown of endothelial cell junctions through matrix metalloproteinase (MMP)
  3. Trafficking through monocytes
34
Q

What kind of viral shedding occurs in an acute infection, and for how long?

A

Acute infection= intensive shedding over a short period of time

35
Q

T/F: Persistent infections can be shed at high titers for months to years

A

FALSE

shed at LOW titers for months to years

36
Q

What is viral tropism?

A

The specificity or affinity of a virus for a particular host tissue

37
Q

What is special about pantropic viruses?

A

Can replicate in more than one host organ or tissue

38
Q

What are some skin injuries of viral infections?

A

Rash, vesicles, ulcers, nodules, warts, papules, erythema

39
Q

Viral infection to the GI tract can occur in what two ways?

A

Ingestion and hematogenous spread/systemic infection

40
Q

What pathogenesis may occur due to viral infections in the GI tract?

A

Destruction of enterocytes due to viral replication - hypersecretion

GI dz, malabsorption, diarrhea

pronounced dehydration, acidosis, hemoconcentration

41
Q

What damage can occur to the villi of the GI tract due to virus replication?

A

Blunting, fusion of villi, atrophy

42
Q

What damage may occur in the Respiratory tract due to a viral infection?

A

Loss of ciliary activity, loss of integrity of the lining mucosal layer, destruction of epithelium, inflammation, exudation, influx of inflammatory cells, airway obstruction - respiratory distress, secondary bacterial infection

43
Q

When a virus infects the CNS, what injuries would you expect to occur?

A

Encephalitis or encephalomyelitis characterized by neuronal necrosis, phagocytosis of neurons (neurophagia), and perivascular infiltrations of inflammatory cells (perivascular cuffing)

44
Q

What neuronal injury does canine distemper cause?

A

Progressive dymyelination

45
Q

What is a neuronal injury caused by prion diseases that can be observed on histo?

A

Neuronal vacuolation

46
Q

Damage to the endothelium by a virus can be observed grossly by what lesions?

A

Petechia (pin point hemorrhages) and ecchymoses (larger areas of hemorrhage)

47
Q

T/F: Viruses of the hemopoietic system can lead to DIC

A

TRUE

clots form in small blood vessels all over the body - clotting factors get used up –> that is followed by systemic hemorrhage and multi organ failure

48
Q

What is teratogenesis?

A

Abnormal development or arrests in development of an embryo or fetus - due to a viral pathogen

*may result in death or malformations during the antenatal period

49
Q

A tissue injury mediated by host immune response to a virus infection is called what?

A

Virus induced immunopathology

*depends on the delicate balance between the protective and destructive effects of the host immune response to viruses

50
Q

What are some examples of immunopathology due to viral infections?

A
  1. tissue damage mediated by hypersensitivity reactions
  2. Autoimmune dz
  3. Inflammation-mediated tissue damage (fibrosis)
  4. Immunodeficiency disorders
51
Q

What cells play a crucial role in cell mediated lysis and killing of infected host cells?

A

Cytotoxic T cells (CD8+)

52
Q

The release of cytokines from what cells can contribute to inflammation associated with viral infections?

A

CD4+ and CD8+ T cells

53
Q

Persistent activation of what receptors of innate host cells caused by viruses, will increase the production of pro-inflammatory cytokines and interferons?

A

Toll-like receptors

54
Q

T/F: Injury can due to viral infections can be mediated by free radicals such as nitric oxide and superoxide

A

TRUE

55
Q

Can antibody responses to viruses contribute to tissue damage?

A

YES

Toxicity from antibody response

56
Q

Feline infectious peritonitis can cause what immune complex dz?

A

Immune complex-mediated vasculitis

57
Q

T/F: Viruses can cause immunosuppression

A

TRUE

virus induced immunopathology

**Infectious burasal dz - virus replication causes atrophy of the bursa which creates a deficiency of B lymphocytes = immunosuppression

58
Q

What is an inapparent infection?

A

When an animal is infected with a virus but shows no clinical signs

  • too few cells may be infected
  • stimulate host immune response
  • possible source of virus spread
59
Q

T/F: Acute infection or short infection has a rapid clearance from host immune response

A

TRUE

Short clinical course and rapid clearance from host immune response

60
Q

T/F: If an animal has a latent viral infection, they can/will test positive for the infecting virus

A

FALSE

Latent infections: infectious virus is not demonstrable except when reactivation occurs. Reactivation is usually stimulated by immunosuppression or cytokines or hormones

61
Q

T/F: Acute infection followed by latent infection - means that the virus is continuously shed from or is present in infected tissue

A

FALSE

Latent should be replaced with CHRONIC to make this correct

62
Q

What is a slow persistent infection?

A

Prolonged incubation period lasting months or years

*usually a slow progressive, lethal dz

63
Q

Which once of the following is NOT usually a feature of persistent viral infection?

  1. Virus may remain dormant in host cell
  2. Reactivation (clinical dz) occurs during stress
  3. Intermittent shedding of virus for long periods
  4. Rapid clearance from host immunity
A

4

Characteristic of acute viral infections

64
Q

A virus is continuously shed from or is present in infected tissue. What type(s) of infection is this?

A

Persistent/Chronic

65
Q

T/F: Latent viral infections can evade the immune system

A

TRUE

bc they are not active or producing proteins, so they are hidden

66
Q

Can a chronic infection occupy any part of the body?

A

No. There are specific organs where chronic viral infections will reside

67
Q

T/F: Slow persistent infections are characterized by a fast incubation period followed by slow onset of clinical dz.

A

FALSE

SLOWWWWWW incubation period

RUSVM Virology Spring17 (23 decks)

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