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MICR > L13 > Flashcards

L13 Flashcards

1
Q

Three requirements to ensure successful infection of host:

A
  • Sufficient virions available to initiate infection
  • Cells at site of infection need to be physically accessible to virions, must be susceptible (bear receptors for entry), and permissive (contain intracellular gene products needed for viral replication)
  • Local host antiviral defense systems must be absent or initially ineffective
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2
Q

Requirements for a successful infection simple

A
  • Dose
  • Access to target cells: be susceptible an permissive
  • Absent or insufficient host immunity (innate not good enough for virus)
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3
Q

Transmission

A

Spread of virus from one susceptible host to another

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4
Q

Two patterns of virus transmission

A
  • Perpetuation of transmission in one species (measles only in humans (are reservoir))
  • Alternate infection of insect and vertebrate host (rabies from animals to humans but maintains in animals)
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5
Q

What is the term for a viral disease shared by humans and animals/insects

A

Zoonoses

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6
Q

The number of virus particles required to initiate and maintain infection depend on what three things?

A
  • particular virus (how many virions needed to infect)
  • Site of infection
  • Age/physiology of host
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7
Q

A ___ virus particle can initiate an infection; complexity of the infectious cycle, and probability of a single virus particle completing the cycle is_____ 100%

A

single
not

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8
Q

In the initiation of an infection can defective virus particles be produced?

A

Yes

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9
Q

How can virus infectivity be determined?

A
  • Tissue culture infectious dose
  • Plaque assays
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10
Q

Virus entry into the respiratory tract

A
  • Common
  • large absorptive area (140m2) and high ventilation rate (6 Lair/in)
  • So many foreign particles and aerosolized droplets introduced to the lungs with every breath
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11
Q

Respiratory tract defence mechanism

A
  • mechanical barriers like the
  • mucociliary blanket of ciliated cells
  • Mucous-secreting goblet cells
  • Subepithelial mucous secreting glands
    All trap foreign particles and swallow or move them from lungs to throat.
  • Macrophages that line alveoli ingest and destroy particle
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12
Q

What form do virus enter the respiratory tract

A

Aerosolized form
The aero droplets expelled by an infected person cough or sneeze

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13
Q

What do goblet cells do

A
  • secrete mucous that acts like a barrier to virus attachment
  • Virions will pass though barrier and multiply in ciliated cells or pass between them
  • Will then reach the basement membrane and virions taken to lympathic capillaries and reach blood
  • Macrophages patrol tissue fluids and ingest foreign particles
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14
Q

Viruses can replicate that different levels of the respiratory tract

A

yes

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15
Q

What is the Alimentary Tract

A

Stomach

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16
Q

Virus Entry: Alimentary Tract

A
  • Common route of infection and dispersal
  • Extremely hostile environment for virions – stomach = acidic, intestine = alkaline
  • Many digestive enzymes and bile detergents, intestine is lined by mucous, lumenal surface includes antibodies and phagocytes
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17
Q

What virus can replicate in lowpH of stomach

A

Poliovirus

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18
Q

Changes in capsid that occur under acid conditions are fully ___; low pH induces ____ disassembly of the rhinovirus capsid

A

reversible
irreversible

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19
Q

The intestine wall is made up of what?

A

epithelial, connective, and muscle tissues, made up of different cell types within an extracellular matrix.

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20
Q

What does a typical M cell have

A

surrounded by 2 enterocytes. Lymphocytes and macrophages move in and out of invagina&ons on basolateral side of M cell

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21
Q

Virus Entry Through Skin

A
  • Skin of most animals is an effective barrier against viral infection – dead outer layer cannot support viral replication
  • Entry through skin mostly occurs when integrity has been breached by breaks or punctures:
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22
Q

Entry through skin mostly occurs when integrity has been breached by breaks or punctures:

A
  • Mechanical transmission eg.
    1. by insect vectors such as arthropods, introducing virus into highly vascularized dermis
    2. by hypodermic needle puncture into tissues below dermis.
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23
Q

Urogenital tract mucosal cells are protected by what?

A

mucous and low pH

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24
Q

Minute abrasions allow viruses to enter – may produce local lesions, spread to other organs

A

fact

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25
Q

Transplacental infection

A
  • ZIKV infection can occur during any pregnancy stage
  • By mosquitos
  • ZIKV can breach the placenta barrier
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26
Q

Virus infect targets cells where

A

at site of entry

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27
Q

Progeny viruses remain localised and is contained within what

A

Epithelium by immune response and by physical structure of tissue

28
Q

Virus spread: disseminated

A

They are spread beyond primary site and can lead to systemic infections

29
Q

Virus spread: systemic infection

A

Many organs are infected

30
Q

Polarized (directional) release of virus from cells

A
  • Directional release of virus from polarised cells at a mucosal surface permits avoidance of shot immune response
  • Will facilitate and spread within the body
31
Q

Virus released at the apical surface will:

A

Establish localised infection where the underlying lymphatic and circulatory vessels rarely invade

32
Q

Virus released at the basolateral surface of polarized epithelial cells are:

A

distant from def of the lumenal surface and can access underlying tissues and facilitate systemic spread

33
Q

Haematogenous Spread

A
  • Entry of virus to bloodstream results in disseminated infection
  • Virus replicates at entry site and is released into extracellular fluid, which can be taken up by local lymphatic vascular system
  • Lymphatic vessels drain into circulatory system -> viruses enter bloodstream
  • In lymphatic system viruses pass through LN where they encounter migratory immune cells -> infected immune cells release virus into plasma or tissues
34
Q

How can a virus enter the bloodstream

A
  • directly through capillaries
  • By replicating in endothelial cells
  • by inoculation by a vector bite
35
Q

Viremia

A

: presence of infectious virus in blood [virions may be free in blood or contained within infected cells, such as lymphocytes]

36
Q

Ac.ve viremia:

A

when there is replicating virus in blood

37
Q

Passive viremia:

A

introduc&on of virions into blood without replication at site of entry

38
Q

Primary viremia:

A

progeny virions are released into blood aRer ini&al replication at site of entry

39
Q

Secondary viremia:

A

Delayed appearance of high concentra&on of infectious virus in blood, following dissemina&on from initial entry site

40
Q

Neural spread

A
  • Virus spread from primary by entering local nerve ending
  • If they infect NS - neurotropic
  • Virus repliation first in non-neural cells to afferent (sense) or effected (motor) fibres that innervate infected tissue
    Non- PNS then SC then brain
41
Q

Herpes latency in PNS

A

Reactivationfromlatencyresultsinviralreplicationin primary neuron and transport of progeny virions back to peripheral tissue (to form a cold sore) , or to the CNS (to cause lethal viral encephalitis)

42
Q

Organ invasion

A
  • After spread from primary into blood virus needs to invade new tissue/cell
  • Continuous endothelium and basement membranes
  • fenestrated epithelium
  • sinusoid
43
Q
A
44
Q

Found in CNS, CT, muscle, skin and lungs

A

Contin. endothelium and basement membranes

45
Q

Found in choroid plexus, intestinal vili, renal glomerulus, pancreas, endocrine galnd

A

Fenestrated epithelium

46
Q

Adrenal glands liver spleen and bone marrow

A

Sinusoid lined with macrophages of reticuloendothelial system

47
Q

Adrenal glands liver spleen and bone marrow characterised by sinusoid with macrophages

A

Macrophage infected by virus present in blood will infect underlying cells
Kupfer inected (line liver) infect hepatocytes and cause hepatitis

48
Q

Found in CNS, CT, muscle, skin and lungs characterised by dense basement membrane

A
  • CNS basement mem is foundation of BBB
  • Virus pass thru capiliary endothelium and enter stroma of choroid plexus, cross epithelium to CSF and infeact brain tissue
  • Cross BBB or via transcytosis
49
Q

Skin rashes

A
  • made when virions leave blood
  • In systemic infections (V)
    *
50
Q

Macules and papules

A

Small and flat non elevated
Small and swollen bumps

51
Q

Macules and papules develop when

A

Infection in dermis with lesion confined in or near vascular bedV

52
Q

Vesicles and pustules occur when

A

virus spread from capillary to superficial skin

53
Q

Rash in mucosal tissue (mouth and throat)

A

Mealses infect vesicles of mouth and breakdown to become ulcers like koplik spots

54
Q

Vasicular rash

A

Varicella zoster virus (chicken pox and shingles)

55
Q

Maculopapular rash

A

Measules and zika

56
Q

latrogenic

A

activity of health care worker leads to infection of patient

57
Q

Nosocomial:

A

individual is infected while in a hospital or health care facility

58
Q

Vertical:

A

transfer of infection between parents and offspring

59
Q
  • Horizontal:
A

all other forms of transmission

60
Q

Germ line: transmission as part of host genome (eg. Integrated proviral DNA)

A

transmission as part of host genome (eg. Integrated proviral DNA)

61
Q

How infection is a virus

A

*Viral infectiousness is quantified and viruses are assigned a reproduction number (Ro)
* Ro = average number of secondary cases generated by one primary case in a susceptible community (with no control measures)

62
Q
  • The higher the Ro value, the more persons can be infected from one case
  • However, the incubation period in the host (and the vector where relevant) is also important
A
63
Q
  • Viruses with longer incubation periods and low Ro gives time for possible use of_____ to stop an outbreak eg. SARS
A

quarantine

64
Q
  • Viruses with high Ro and short incubation period are significant public health problems eg. Influenza
A

asdf

65
Q

RO
hep C
Ebola
HIV
SARS
Measles

A

2
2
4
4
18

MICR (23 decks)

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