Viral Pathogenesis and Host Resp Flashcards

1
Q

Tissue Tropism

A

the likeliness of a virus to infect tissues and not others; aka tissue specificity.

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2
Q

Which virus is hardier, enveloped ones, or non-enveloped ones?

A

□ Enveloped viruses: fragile and sensitive
- thus needs to be transmitted via close contact

□ Non-enveloped: hardier, can withstand stresses
- thus often transmitted via- viral associated objects or fomites ( objects) and use respiratory or fecal/ oral routes.

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3
Q

acute local disease (ie: common cold)

  • incubation period
  • virus shedding and transmission
  • host responses
  • likelihood of re-infection
A
  • incubation period: short
  • virus shedding and transmission: many serotypes are rapidly mutating, resulting in short lived immunity
  • host responses: secretory IgA
  • likelihood of re-infection: common
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4
Q

acute systemic disease (ie: measles)

  • incubation period
  • virus shedding and transmission
  • host responses
  • likelihood of re-infection
A
  • incubation period: long
  • virus shedding and transmission: primary infxn in epithelium but can result in 2nd replication sites
  • host responses: secretory IgA and serum IgG
  • likelihood of re-infection: low
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5
Q

Types of viral diseases

Examples

A
  1. Acute local: common cold
  2. Acute systemic: Smallpox, measles
  3. Chronic: rubella in neonate
  4. Latent: VZV in nerves
  5. Slow/Progressive: AIDS
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6
Q

Effects of viruses on infected cells:

A
  1. CPE (Cytopathic effects)
  2. Syncytia
  3. Growth
  4. Apoptosis
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7
Q

CPE (Cytopathic effects)

A

any detectable morphological changes or inclusion bodies in host cell.

  • Direct cell damage: *think what things virus can interfere with in the cytoplasm
  • Indirect cell damage: integration of viral genome→ induction of mutations in host genome →inflammation and host immune response.
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8
Q

Explain the interferon response and “anti-viral state”.

A

When the host cell is infected (bound) with the virus, it induces IFNs (interferes with viral infection of neighboring cells) which induces the anti-viral state.

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9
Q

When a host cell is infected with a virus, what factors does it induce? What does that do?

A

IFNs → antiviral state

  • results in some blockade of cell division, reduction of cell metabolism, increase in NK activity including IFNg production, ¬ expression of APC, and may lead to apoptosis and more.
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10
Q

What two ways are IFNs activated by viruses?

A
  1. facilitated by dsRNA (virus)

2. TLRs and RLHs (retinoic acid inducible gene- like helicases)

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11
Q

What does innate response to viruses depend on?

A

TLRs and Helicases (RLHs)

non specific, but immediate

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12
Q

Type I IFNS and Type II IFNS

  • what do they each consist of?
  • Are they apart of innate or adaptive responses?
A

Q
Type I IFNS: alpha and beta
Type II IFNS: gamma
- Both are innate

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13
Q

What produces:
Type I IFNS
Type II IFNS

A

Type I IFNs (IFN alpha and beta) produced by most infected cells within hours of infection

Type II IFNs (IFN gamma) produced by T cells and NK cells, (more restricted)

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14
Q

IFNs induce the antiviral state how? (mechanism)

A

IFNs bind to specific receptors on cells → signal through JAK/State pathway and control Type I and Type II genes → induce transcription of genes = antiviral state.

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15
Q

IFNs induce the antiviral state how? (mechanism)

IFNs can involve mediators such as PKR and OAS when activating the antiviral state. What do each of them do?

A

□ PKR (protein kinase): phosphorylate and inactivate translation (tln) initiation factor to decrease protein synthesis

□ OAS: activates a cellular ribonuclease that degrades mRNA

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16
Q

2 types of viral Adaptive Responses

A
  1. humoral

2. cell mediated

17
Q

Humoral Response:

A

Ab produced during primary virus infections are usually of lower affinity. It is not until later that they bind with higher affinity, most Ab being IgM (unswitched).

§ BIG PICTURE: humoral response is important for recognition of virions.

18
Q

Which Ig inhibits fusion of enveloped viruses with host membranes

A

IgG

19
Q

Cell-Mediated Response:

A

CTLs lyse/clear virus-infected cells

NK and macrophages kill infected cells directly or by Ab-dependent cell-mediated cytotoxicity (ADCC)

20
Q

Between Th1 and Th2 which one “skews” toward humoral response and which towards cell-mediated?

A

Q

Th1 differentiation skews towards cell-mediated immunity and inflammation

Th2 differentiation skews toward humoral response

21
Q

Compare antibodies produced in primary and secondary responses.

A
  • 1° response: Abs are usually of lower affinity than those produced later.
  • 2° Response: Already has Abs of greater affinity and there is a faster increase in that AB both due to immunological memory.
22
Q

List and describe major cell types involved in anti-viral responses.

A
  1. Mononuclear phagocytes: phagocytosis, release of inflammatory mediators, Ag presentation
  2. DC: APC, stimulate B cell diff and prof, modulator of development of adaptive immune response, secrete antoviral and immunoregulatory cytokines.
  3. NK cells- serve to contain infection while
    CTL cells are produced by adaptive immune response which can then clear infection.
  4. Granulocytes- PMNs, basophils, and eosinophils
23
Q

Which Ig inhibits virion/host attachment, neutralizes toxins and enzymes

A

IgA