Viruses Affecting the Central Nervous System Flashcards Preview

MD1 Neuroscience > Viruses Affecting the Central Nervous System > Flashcards

Flashcards in Viruses Affecting the Central Nervous System Deck (97):
1

What is a neurotropic virus?

Capable of replicating in nerve cells

2

What is a neuroinvasive virus?

Capable of entering/infecting CNS

3

What is a neurovirulent virus?

Capable of causing disease within nervous system

4

What is encephalomyelitis?

Inflammation of brain and spinal cord

5

What is primary viral encephalitis/acute viral encephalitis?

Direct viral infection of spinal cord and brain
Can be focal or diffuse

6

What is secondary encephalitis/post-infectious encephalitis?

From complications of current viral infection
Virus spreads to brain

7

What is the most common route viruses take to the brain?

Blood

8

What is more common: viral or bacterial meningitis?

Viral

9

What is more severe: viral or bacterial meningitis?

Bacterial

10

What is the presentation of meningitis?

Headache
Fever
Neck stiffness
+/- vomiting
+/- photophobia

11

What is the main viral cause of meningitis?

Enteroviruses

12

How do enteroviruses enter the body?

Via mouth

13

What are some other viral causes of meningitis, that aren't enteroviruses?

Mumps
VZV
Influenza
HIV
HSV 2

14

What is more severe: viral or bacterial encephalitis?

Viral

15

What is the presentation of encephalitis?

Like meningitis, but also
- Personality and behavioural changes
- Seizures
- Partial paralysis
- Hallucinations
- Altered state of consciousness
- Ultimately coma and death

16

What are the most common causes of viral encephalitis?

HSV 1 and 2
Rabiesvirus
Arboviruses (insect-borne)
Enteroviruses

17

Can mumps virus meningitis also cause encephalitis?

Yes but is generally mild

18

What is post-infectious encephalomyelitis?

Occurs few days after infections
No virus present but
- Inflammation
- Demyelination
Possibly autoimmune in nature

19

Which viruses can cause post-infectious encephalomyelitis?

Measles
Chickenpox
Rubella
Mumps

20

What is Guillain-Barre syndrome?

Acute inflammatory demyelinating disease after infection with several viruses
Partial/total paralysis in 75% of people
Full recovery within weeks
Doesn't need active infection

21

Which viruses can cause Guillain-Barre syndrome?

EBV
CMV
HIV

22

What is Reye's syndrome?

Post-infection with influenza or chickenpox in children
25% case-fatality rate
Cerebral oedema but no inflammation
Association with administration of aspirin during initial fever

23

What are chronic demyelinating diseases?

Very rare
Eg: sub-acute sclerosing panencephalitis (SSPE)
- Late sequel (30 yrs) to measles infection

24

What is AIDS encephalopathy/AIDS dementia complex?

HIV infection > immunodeficiency > neurovirulent
50% of patients develop progressive dementia

25

How do some viruses avoid the blood-brain-barrier and enter the CNS?

Travel up axon fibres of peripheral nerves to CNS

26

What are some viruses that infect the CNS via peripheral nerves?

Rabiesvirus
Yellow fever virus
HSV 1 and 2

27

How are virions transported in the peripheral nerves?

Whole virions or uncoated nucleocapsids carried passively via anterograde or retrograde transport

28

Why aren't viruses found by CD8 T cells?

Nerve cells express very few MHC I molecules

29

Where do viruses replicate in a neuron?

In cell body

30

How do virions travel from neuron to neuron?

Can cross synapse

31

Which viruses use blood to enter the CNS?

Poliovirus
Mumps virus
Measles virus
Coxsackievirus

32

How does HIV reach the CNS?

Via monocytes

33

What structures carry viruses into the CNS?

Cerebral blood vessel
Direct spread from adjacent structures
Meningeal blood vessel
Peripheral nerve ending
Nasal mucosa
Blood vessel in choroid plexus

34

Which viruses enter through the olfactory bulb?

Coronavirus
HSV

35

Which viruses cause inflammatory diseases?

Those that directly kill neurons

36

What are the sequelae of extensive loss of neurons because of a viral infection?

Mental retardation
Epilepsy
Paralysis
Deafness
Blindness

37

Which cells do viruses replicate in that cause demyelination?

Oligodendrocytes

38

Does the immune response also cause damage during inflammation?

Yes

39

Does rabiesvirus need nerve cells for its life cycle?

Yes

40

What is the neuroinvasiveness and neurovirulence of rabiesvirus?

High neuroinvasiveness
High neurovirulence

41

Describe the structure of rabiesvirus

Bullet shaped
-ve ssRNA
Helical capsid
Envelope

42

Does rabiesvirus hide from the immune system when it's in nerve cells?

No, rabies glycoproteins displaced on cell surface because exits cell via budding

43

What kind of rabies is present in Australia?

Classical rabies not present
Related lyssavirus of bats

44

What are the symptoms of rabies?

Aggression - causes animal to bite and spread virus
Thirst
Muscle spasm and terror upon attempt to drink water

45

What is the pathogenesis of rabies?

1. Virus entry: day 0
- Bite of rabid animal
- Infected saliva injected
2. Striated muscle: day 1-60
- Virus replicates in myocytes
3. Peripheral nerves: day 10-60
- Enters nerve endings
- Nucleocapsid carried by fast axonal transport to spinal cord
4. CNS: day 12-60
- Travels along neurons processes > spreads > replicates
- Neuronal dysfunction
- Clinical rabies: day 50-70
- Death
5. Peripheral nerves: day 30-70
- Travels from CNS
- Invades salivary gland
6. Salivary gland: day 40-70
- Replicates in acinar cells
- Discharged in saliva

46

Can you vaccinate against rabies after infection?

Yes

47

At what stage can you vaccinate against rabies without sequelae?

When in striated muscle

48

At what stage can you vaccinate against rabies with minor sequelae?

When in peripheral nerves but not in CNS

49

Which virus causes coldsores?

HSV 1

50

Which virus causes genital warts?

HSV 2

51

What are some viruses that belong to the herpesvirus family?

HSV 1 and 2
VZV

52

Do herpesviruses need nerve cells for their life cycle?

Yes

53

What is the neuroinvasiveness and neurovirulence of herpesviruses?

Low neuroinvasiveness
High neurovirulence

54

Describe the structure of herpesviruses?

Linear dsDNA
Icosahedral
Envelope

55

What is the normal maintenance cycle of HSV?

Primary infection in mucosal surfaces >
Latent infection in sensory and autonomic ganglia >
Reactivation from ganglia to mucosal surfaces

56

What are the pathways leading to serious disease with HSV?

Viremia from primary infection > disseminated infection in organ systems > latent infection in ganglia OR deadly CNS infections
Latent infection in ganglia > deadly CNS infections

57

How does HSV 1 enter the body?

Contact with infected saliva
Enter via cut/abrasion

58

What site do primary infections of HSV 1 typically involve?

Mouth and/or throat

59

What is the possible presentation of HSV 1 in children?

Gingivostamatitis
- Ulceration in mouth
- can spread to other areas of face in severe cases

60

Is infection with HSV 1 always apparent?

No

61

Where does skin/mucous membrane break to allow HSV entry?

HSV 1: mouth, throat, eyes
HSV 2: genital region

62

What proportion of HSV infections cause primary disease?

10-15%

63

What proportion of HSV infections cause inapparent infection in the lymph nodes?

85-90%

64

What ganglia does HSV inhabit?

HSV 1: trigeminal
HSV 2: sacral

65

What can reactivate a latent HSV infection?

Stress
UV
Declining immunity

66

Where does HSV infect in the CNS?

Neurons and glia in temporal lobe

67

What is the case fatality rate of HSV encephalitis?

70%

68

What causes most cases of HSV encephalitis: reactivated or primary infections?

Reactivated

69

How many people have a latent infection with HSV in their ganglia?

20%

70

How is the HSV genome maintained in a latent infection?

As episome coated with histones

71

What does the latent genome of HSV express?

Latency activated mRNA transcripts (LATs)

72

How do CD8 T cells help maintain the HSV genome in a latent state?

Kill any viruses that move out of latent state

73

How does VZV spread during chickenpox?

Haematogenously

74

How does VZV enter the nerves?

Via vesicular rash

75

How does VZV enter the body?

Conjuctiva and/or mucosa of URT

76

Where does VZV first replicate?

Regional lymph nodes

77

What happens during the incubation period in a VZV infection?

Replication in regional LNs
Primary viremia
Replication in liver and spleen
Secondary viremia

78

What is the incubation time for VZV?

4-6 days

79

When does the vesicular rash appear in VZV?

Day 10 after infection

80

Where does VZV reside during its latent phase?

Dorsal root ganglia

81

What causes shingles?

Reactivation of VZV in a dermatome

82

Why is shingles more likely in older people?

CD8 T cells deplete with age

83

Does poliovirus need nerve cells as part of its life cycle?

No

84

What is the neuroinvasiveness and neurovirulence of poliovirus?

Low neuroinvasiveness
High neurovirulence

85

What is the structure of poliovirus?

+ve ssRNA
Icosahedral
No envelope

86

What is the genus of poliovirus?

Enterovirus

87

What familydoes poliovirus belong to?

Picornavirus

88

Is poliovirus cytocidal?

Yes

89

What is the pathogenesis of poliovirus?

1. Faecal-oral spread - ingested: day 0
2. GALT: day 0-3
- Tonsils and Peyer's patches
- Invades possibly via M cells
- Possibly replicates in monocytes
3. Regional LNs: day 3-5
- Replicates
4. Blood: day 5-15
- Viremia
5. BBB: day 8-12
- Rarely
- Crosses
6. Spinal cord: day 10-30
- Replicates in anterior horn cells
- Cell destruction
- Paralysis
7. Gut: day 5-45
- Normally stays here
- Excreted in faeces

90

How quickly can poliovirus cause total paralysis if it enters the CNS?

Hours

91

How many cases of polio occur before 3?

50%

92

How many poliovirus infections lead to irreversible paralysis?

Less than 1%

93

Which limbs are affected more in polio?

Lower > acute flaccid paralysis

94

What happens in the most severe cases of polio?

Attacks motor neurons of brainstem
- Reduced breathing capacity
- Increased difficulty swallowing
- Impedes speech

95

What is the route of transmission of enteroviruses?

Faecal-oral

96

What causes enterovirus meningitis?

All coxsackie B types
Coxsackie A7 and A9
Many echoviruses

97

When does enterovirus meningitis often occur?

Summer
Autumn

Decks in MD1 Neuroscience Class (55):