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CELL MICRO S1 > Viruses of NS > Flashcards

Viruses of NS Flashcards

1
Q

what is the route of entry for viruses into the NS?

A

via skin or alimentary tract

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2
Q

what are the 2 components of the PNS?

A

sensory and motor neurones

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3
Q

how do viruses spread into CNS using the PNS? what are names of the two types of transport?

A

1) infect peripheral NS
- travel up neuron AWAY from cell body to CNS/back to peripheral
- ANTEROGRADE VIRAL TRANSPORT
2) infect peripheral NS
- travel up neuron TOWARDS the cell body
- RETROGRADE VIRAL TRANSPORT

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4
Q

how do viruses use BBB to spread to the CNS?

A
  • tight junctions joining endothelial cells which form BBB
  • only small mol & few immune cells can cross
  • viruses cross by infecting the endotheliium, or by infecting monocytes that can cross the barrier
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5
Q

what is a neurotropism?

A

hundreds of viruses that exhibit tropism for CNS or PNS

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6
Q

give an example of a virus that has evolved to enter PNS and exploit neuronal biology?

A

alphaherpesvirus

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7
Q

give an example of a virus that has no advantage for it to infect the CNS?

A
  • often a ZOONOTIC INF

- eg rabies

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8
Q

give an example of a virus that causes OPPORTUNISTIC infection of CNS?

A

HIV, human cytomegalovirus

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9
Q

what are the key symptoms of viral inf of CNS?

A

1) Aseptic meningitis- inflammation of meninges w/ sterile CSF
2) Encephalitis- infection of brain
3) Meningoencephalitis- inflammation of brain AND meninges
4) Myelitis- inflammation of the spinal cord—>long term paralysis

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10
Q

what are the symptoms of meningitis?

A
  • severe headache
  • photophobia
  • stiff neck
  • nausea vom
  • fever
  • confusion
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11
Q

what are the symptoms of encephalitis?

A
  • hallucinations
  • confusion
  • seizures
  • paralysis (face/body)
  • muscle weakness
  • speech problems
  • loss of consciousness
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12
Q

what can cause meningitis?

A
  • HSV2 (herpes virus type 2)
  • mumps
  • HIV
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13
Q

what can cause encephalitis?

A
  • HSV1
  • measles
  • insect borne viruses
  • rabies
  • polio
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14
Q

what is a lesser known way that viruses can enter the body?

A

olfactory route- - olfactory cell layer only 1 CELL DEEP before NS

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15
Q

which viruses use motor route to infect?

A

RABV (rabies) and polio

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16
Q

which viruses use sensory route to infect?

A

Herpes (HSV)

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17
Q

which human alphaherpesviruses?

A

HSV1, HSV2, VZV (varicella-zoster virus)

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18
Q

which animal alphaherpesviruses?

A
  • pseudorabies virus (pigs)
  • bovine herpesvirus 1
  • equine herpesvirus 1
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19
Q

which part of the NS do alphaherpesviruses infect?

A

in PNS

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20
Q

are alphaviruses species specific or not?

A

yes- species specific

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21
Q

HSV1 infection comes from where?
describe pathogenesis
where does it lie dormant?

A

inside AND outside
- once replicated, transmits into neurons that are innervating the initial infection
- travels RETROGRADE into cell body
- lies dormant in TRIGEMINAL NERVE
- becomes REACTIVATED
- travels ANTEROGRADE to initial infection
OR can travel to CNS (rare)

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22
Q

what type of infection do alphaherpesviruses cause?

A

latent infection O infected for life

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23
Q

what causes reactivation of Herpes?

A
  • sunlight (UV)

- hormonal (menstrual cycle)

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24
Q

primary HSV causes what?

A
  • white coating on tongue, or asymptomatic
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25
Q

reactivated HSV causes what? occurrence is affected by?

A

cold sores, these are periodic

affected by: genetics

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26
Q

primary VZV causes what?

A

chickenpox, then transport into the SACRAL GANGLIA causing reactivation

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27
Q

reactivated VZV causes what? how common is this?

A

shingles (zoster) only occurs ONCE in a lifetime

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28
Q

can HSV cause encephalitis?

A

yes (HSE)

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29
Q

how is HSE HSV encephalitis caused?
how common is it?
who does this normally affect?

A
  • neural invasion, the virus DOESN’T travel back to skin to cause cold sore, it travels to CNS
  • the MOST COMMON non-epidemic viral encephalitis
  • mostly affects elderly (immunocompromised)
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30
Q

how dangerous is HSE HSV encephalitis? how is it treated?

A

VERY dangerous, often fatal

- must have antiviral treatment, this can leave brain damage

31
Q

rabies virus is part of which family?

A

rhabdovirus family

32
Q

the rabies virus has what kind of a genome?

A

RNA- O can change very easily

33
Q

how is rabies virus transmitted? who are the common infected animals?

A
  • via SALIVA of infected animals (dogs, bats, foxes)
34
Q

what is the route of infection of rabies?

A

bite from infected animal

35
Q

what is the pathogenesis of rabies?

A
  • bite
  • replication of virus in muscle
  • travels across neuro musc junction O gets into nerve cells
  • travels up axons
  • replicates in these neuorns & spinal cord
  • enters brain via spinal cord
  • spreads back out to skin
36
Q

what are the symptoms of rabies virus?

A
  • fever
  • headache
  • nausea/vomiting
  • agitation
  • anxiety
  • confusion
  • hyperactivity
  • difficulty swallowing, excessive salivation
  • fear of water(due to difficulty in swallowing)
  • hallucinations, insomnia, partial paralysis
37
Q

how long is the incubation period for rabies virus? what is the length of the incubation period dependent on?

A
  • can be as long as ONE YEAR O no symptoms for a year

- the further the CNS the initial bite, the longer the incubation period

38
Q

at what point does rabies become fatal?

A

once symptoms appear

39
Q

how many people die a year from rabies?

A

almost 59000

40
Q

who does rabies affect most?

A

poor and disadvantaged

41
Q

how is rabies treated?

A
  • thorough washing of wound

- then vaccination (~15 million get post bite vaccination)

42
Q

how is rabies prevented?

A

vaccinate DOGS

43
Q

what type of virus is polio?

A

picornovirus

44
Q

what is the genus of poliovirus?

A

enterovirus

45
Q

is poliovirus a small or large virus?

A

small

46
Q

what form of genetic information is used by poliovirus?

A

RNA genome

47
Q

can poliovirus surivive for a long time outside the host?

A

yes

48
Q

what is the route of transmission for polio? how does it enter the body?

A

faecal-oral

ingestion of contaminated water

49
Q

how long is the incubation period for poliovirus?

A

6-10 days

50
Q

once ingested, where can polio replicate?

A

can be TONSILS, but predominantly in the GUT

  • transmitted from gut to form PRIMARY VIRAEMIA in bs
  • -> then SECONDARY viraemia when it spreads to other tissues (CNS)
51
Q

what can polio lead to?

A

meningitis, encephalitis & paralysis

52
Q

how does polio enter the brain?

A
  • orally ingested
  • passes low pH in stomach
  • blood circulation
  • crosses BBB
  • replicates in cell body of motor neurones
  • transmitted into skeletal muscle
  • causes paralysis (POLIO MYELITIS)
53
Q

what are the outcomes of polio infection?

A

95% no illness (asymptomatic, STILL transmittsable)
4% minor illness (ABORTIVE POLIOMYELITIS) - meningitis
1% major illness, paralysis (poliomyelitis) or non paralytic poliomyelitis

54
Q

how is polio prevented?

A

oral poliovirus vaccine (OPV)

  • attenuated vaccine, combination of 3 serotypes
  • for each serotype, there are around 20-50 nt within each attenuated virus
55
Q

what is used to transmit arboviruses (arthropod-borne) ?

A

vectors include mosquitos and ticks

56
Q

where does the problem arise with arboviruses?

A

when the vector infects HUMANS/HORSE (dead end hosts) etc

organisms that are not normally meant to be infected with this

57
Q

give 2 examples of new and emerging diseases?

A

Nipah and Hendra virus

58
Q

what is the reservoir host for Nipah and Hendra virus?

A

bat (flying fox)

59
Q

Nipah and Hendra are what type of virus?

A

paramyoxovirus

60
Q

what is the genome like of Nipah and Hendra?

A

enveloped RNA genome

61
Q

where did Nipah get transmitted from (spillover hosts)?

A

pigs –> humans

62
Q

where was Hendra transmitted from (spillover hosts)?

A

horses –> humans

63
Q

subacute sclerosing panencephalitis is caused by what?

A

measles virus

64
Q

how long after measles infection does subacute sclerosing panencephalitis occur?

A

late, 5-15 years after infection

65
Q

how common is subacute sclerosing panencephalitis?

A

v rare (2/100,000)

66
Q

what type of disease is subacute sclerosing panencephalitis?

A

progressive, degenerative disease of the CNS

67
Q

what is subacute sclerosing panencephalitis characterised by?

A

high levels of measles virus ANTIBODIES in serum and CSF

68
Q

how is subacute sclerosing panencephalitis protected /prevented against?

A

vaccinate against measles

69
Q

why is HIV inf in the brain known as ‘Trojan horse’ infection?

A
  • HIV infects macrophages

- goes on to infect microglia, other cell types in brain

70
Q

what are consequences of HIV in the brain? how quickly do these occur?

A
  • depression
  • cognitive disorders
  • HIV Associated dementia

very slow to progress

71
Q

who is most susceptible to infections of the brain?

A

immunocompromised individuals (transplant, chemotherapy, AIDS, genetic defects)

72
Q

which viruses can cross BBB?

A

human cytomegalovirus (hCMV) and HIV

73
Q

give an example of a genetic defect that leaves people predisposed to primary HSV infection?

A
  • mutation in TLR3 pathway individual (esp children)

- if infected with HSV infection, can lead to ENCEPHALITIS

CELL MICRO S1 (16 decks)

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