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Virology > Host Pathogen Interactions > Flashcards

Host Pathogen Interactions Flashcards

1
Q

Describe pathogenicity VS pathogenesis VS pathogen.

A
  1. Pathogenicity
    -ability of virus to cause disease in host
  2. Pathogenesis
    -mech of development of disease
  3. Pathogen
    -virus that causes disease
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2
Q

Describe virulence VS avirulent.

A
  1. Virulence
    -quantitative/relative measure of degree of pathogenicity of infecting virus
    -not an absolute property of a virus (depends on variables)
  2. Avirulent
    -not virulent
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3
Q

Describe lethal dose VS infectious dose.

A
  1. Lethal dose (LD50)
    -dose of virus needed to cause death of 50% of animals
  2. Infectious dose (ID50)
    -dose of virus that will infect 50% of animals
    LOWER THE ID50 OR LD50 = MORE VIRULENT
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4
Q

Describe the routes of entry of viruses into host.

A
  1. Skin [outer layer of keratin, low pH, FA, bacterial flora, dryness, innate & adaptive immunity]
    -bite (arthropod/animals), contaminated objects (needle)
  2. Mucous membrane
  3. GIT [mucous membrane, acidity/alkalinity, lipolytic/proteolytic, defensins, IgA, scavenging macrophages]
  4. Respiratory tract [mucociliary, alveolar macrophages, NALT, BALT, temp]
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5
Q

Describe the subepithelial invasaion & lymphatic spread.

A
  1. Disseminated infection
    -inf that spreads beyond primary site of inf
  2. Systemic infection
    -# of organs/tissues infected
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6
Q

Describe directional shedding of viruses from infected epithelium.

A

critical to subepithelial spread
1. Apical release
-virus dispersal
2. Basolateral release
-access to underlying tissue = systemic spread

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7
Q

Describe primary viremia VS secondary viremia.

A
  1. Primary
    -initial entry of virus into blood after inf
  2. Secondary
    -virus replicated in major organs & enter circ
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8
Q

Describe active viremia VS passive viremia.

A
  1. Active
    -release of virions from initial site of replication -> blood stream
  2. Passive
    -direct inoculation of virus in host (contaminated obj or arthropod bite) -> no initial replication elsewhere in host before
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9
Q

Describe how viruses spread via nerves in the host.

A
  1. Neurotropic virus
    -virus infect neural cells
    -inf occur via neural or hematogenous spread
  2. Neuroinvasive virus
    -virus enter CNS after inf of peripheral site
  3. Neurovirulent virus
    -virus cause disease of nervous tissue
    -neurological symptoms & death
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10
Q

Describe examples of virus spread via nerves in host.

A
  1. Virus w low neuroinvasiveness of CNS but high neurovirulence
    -enters PNS but rarely CNS
    -severe consequences severe/fatal when it does
  2. Virus w neuroinvasiveness but low neurovirulence
    -inf lead to invasion of CNS but neuro disease is mild
  3. Virus w high neuroinvasiveness & high neurovirulence
    -infects PNS & spreads to CNS w 100% lethality unless antiviral therapy is given after infection
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11
Q

Describe retrograde VS anterograde spread.

A
  1. Retrograde
    -travel in opp direction of nerve impulse flow
    -invades axon terminals & spread to dendrite or cell body & cross synapse to reach next axon terminal
  2. Anterograde
    -travel in direction of nerve impulse flow
    -virus invade dendrite or cell body & spread to axon terminals & cross synaptic contact to invade dendrite of next neuron
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12
Q

Describe other ways viruses can spread thru the CNS.

A

-olfactory
-BBB

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13
Q

Describe localized & systemic acute viral infections.

A
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14
Q

Describe acute VS persistent infections in virus shedding.

A
  1. Acute
    -intensive shedding over short time period
  2. Persistent
    -shed at lower titers for months to yrs
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15
Q

Describe tropism VS pantropic viruses.

A
  1. Tropism
    -specificity/affinity of virus for a particular host tissue
  2. Pantropic virus
    -replicate in more than one host organ/tissue
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16
Q

Describe virus injury to organs/tissues in the skin.

A
  1. Vesicles = fluid filled elevations
  2. Ulcer = opening in skin by sloughing of necrotic tissue past the epi
  3. Nodule/tumor = solid elevated mass w borders & deep into dermis
  4. Warts = benign skin growth appear when viruses infect top layer of skin
  5. Papule = solid elevation without sharp borders
  6. Erythema = red skin due to systemic viral inf
17
Q

Describe virus injury to organs/tissues in the GIT.

A
18
Q

Describe virus injury to organs/tissues in the respiratory tract.

A

-loss of ciliary activity
-loss of integrity of lining of mucus layer
-multi focal destruction of epi
-inflammation
-exudation
-influx of inflam cells
-obstruction of air passages
-hypoxia & respiratory distress
-2ndary bacterial inf

19
Q

Describe virus injury to organs/tissues in the CNS.

A

-encephalitis or encephalomyelitis characterized by neuronal necrosis
-phagocytosis of neurons (neuronophagia)
-perivascular infiltrations of inflam cells (perivascular cuffing)
-neuronal vacuolation
-progressive demyelination (k9 distemper)

20
Q

Describe virus injury to organs/tissues in the hemopoietic system.

A

-petechial (pinpoint) & ecchymotic (larger areas w ill defined margins) hemorrhages
-disseminated IV coagulation (DIC)
>clots form in small blood vessels thru out body -> organs dont get blood -> organ failure
>late stage: raw material for clot exhausted bc over use -> no clot forms = hemorrhage thru out body
-edema
-infarction
>ischemic necrosis

21
Q

Describe teratogenesis VS arthrogryposis.

A
  1. Teratogenesis
    -abnormal development or arrest in development of embryo or fetus
    >may result in death or malformations fur antenatal period
  2. Arthrogryposis
    -joint malformations
22
Q

Describe virus injury to organs/tissues in the fetus.

A
  1. Porencephaly
    -BVDV
  2. Congenital hydraencephaly
    -calf showing recumbence, depression, dome shaped skull
    -BVDV
23
Q

Describe virus injury to organs/tissues - virus induced immunopathology.

A

-tissue injury mediated by host immune response to virus inf (price paid by host to clear viral inf)
-depends on balance between protective & destructive effects of the host immune response to viruses
-immunopathology = cause of damage w viruses that are non cytolytic & persistent (ex. Infected cells not immediately destroyed & immune response becomes chronic)
>if immune response clears inf by destroying small # of virus inf cells = host survives w min symptoms & no permanent damage
>if lg # of cells inf before immune induction = same immune mediated destruction can cause severe or fatal path consequences

24
Q

Describe immunopathology.

A

-tissue damage mediated by hypersensitivity reactions
-autoimmune disease (ex. Moon blindness in horses)
-inflam mediated tissue damage (ex. Fibrosis)
-immunodeficiency disorders

25
Q

Describe virus injury to organs/tissues - the role of T cells.

A

-cytotoxic cell mediated lysis/killing of infected host cells
-release of cytokines from T cells (CD4+ & CD8+) & other cells that cause inflam & tissue damage that becomes chronic against persistent virus inf

26
Q

Describe virus injury to organs/tissues - the role of the innate immunity.

A

-toll like receptors (TLR)
>persistent activation of receptors of innate host cells by viruses causes production of pro inflam cytokines & interferons + signals that recruit & activate cells involved in inflam
>injury mediated by free radicals like NO, & superoxide

27
Q

Describe virus injury to organs/tissues - toxicity from antibody responses.

A

-antibody responses to viruses contribute to tissue damage
-when antibody binds to infected cell = activates complement & causes inflam reaction
-antibody mediated inflam reactions involving toxicity following:
>engagement of IgG w Fc receptors on inflam cells which causes inflam mediator release
>deposition of viral Ag-Ab complex in capillary beds, leading to activation of the complement cascade

28
Q

Describe immunosuppresion.

A

a type of virus induced immunopathology
-infectious bursal disease:
>virus replication causes atrophy of bursa & deficiency of B lymphocytes
>infected birds become sus to other pathogens

29
Q

Describe the different types of viral infections.

A
  1. In apparent
    -CS & symptoms not evident
    -too few cells may be infected
    -stim host immune response
    -poss source of virus spread
  2. Acute (short term)
    -short clinical course
    -rapid clearance from host immune response
  3. Latent (persistent)
    -infectious virus not demonstrable except when reactivation occurs
    >stim by immunosuppression or action of cytokine or hormone
  4. Chronic (persistent)
    -acute inf followed by chronic inf where the virus is continuously shed from or is present in infected tissue
  5. Slow (persistent)
    -prolonged incubation period (months, yrs)
    -slow progressive lethal disease

Virology (24 decks)

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