CNS Virus

Question 1

Define Neurotropic

Answer 1

capable of replicating in nerve cells

Question 2

Define neuroinvasive

Answer 2

capable of entering or infecting the CNS

Question 3

Define neurovirulent

Answer 3

capable of causing disease within the nervous system

Question 4

What’s myelitis?

Answer 4

infection of the spinal cord

Question 5

What are the most common causes of viral meningitis?

Answer 5

herpes simplex virus
rabiesvirus
arbovirus
enteroviruses

Question 6

What’s the pathophysiology of postinfectious encephalomyelitis

Answer 6

inflammation and demyelination due to possible autoimmune damage

Question 7

What’s the pathophysiology of Guillain-Barre syndrome?

Answer 7

post-infectious (viral) inflammation and demyelination leading to partial or total paralysis

Question 8

T/F Most people can recover completely from guillain barre

Answer 8

True, 75% of people recover within weeks

Question 9

What are the presenting symptoms of Reye’s syndrome

Answer 9

cerebral oedema, and a lot of swelling but not inflammation

Question 10

what’s Reye’s syndrome caused by

Answer 10

post-infection with influenza or chickenpox

Question 11

T/F Reye’s syndrome may be associated with administration of paracetamol to treat fever

Answer 11

False, it is linked to aspirin administration

Question 12

What’s the pathophysiology of chronic demyelinating disease?

Answer 12

A late sequel to measles, which the antibody selects a specific strain of measles to infect CNS neurons, causing very slow onset sub-acute sclerosing panencephalitis

Question 13

How does virus get into the CNS?

Answer 13

infect PNS neuron
enter directly via blood stream, commonly the choroid plexus
via olfactory bulb

Question 14

Why can’t we our immune system get rid of the virus inside PNS neurons

Answer 14

nerve cells don’t express MHCI to activate CD8 T cells’, and the intracellular pathogen cannot be cleared

Question 15

Where does the replication of virus in nerves occur?

Answer 15

at the soma of nerve, where virus can utilise host machinery

Question 16

How does virus cause damage in the CNS?

Answer 16

direct killing of neurons
replicate in non-neuronal cells to cause demyelination
induce inflammation to allow entry of lymphocyte via BBB

Question 17

T/F Rabiesvirus must grow inside a nerve cell

Answer 17

True

Question 18

describe the shape and virus type of rabiesvirus

Answer 18

bullet shaped with helical capsid and envelop

It’s a -ve stranded RNA virus

Question 19

How does a virus exit the cell if it has an envelop?

Answer 19

budding

Question 20

T/F Rabiesvirus actively evades the immune system

Answer 20

False, it displays glycoprotein on the cell surface and can be targeted by antibody

Question 21

What are the symptoms associated with rabies

Answer 21

aggression

thirst but unable to drink water

Question 22

Why does rabiesvirus cause muscle spasm upon attempt to drink water (what’s the logic of it)

Answer 22

Rabies spread via the saliva, and water will dilute the viral load

Question 23

Describe the life cycle of rabiesvirus

Answer 23

entry via a site of penetrated skin
contaminated saliva infect muscle cell
eventually reaches a PNS nerve 
works its way up to the CNS 
invades the salivary gland to spread

Question 24

T/F Vaccines are only useful prophylactically

Answer 24

False, there is a window to use vaccine against rabies virus after being infected (before virus enters the CNS)

Question 25

Describe the shape and type for alpha herpesvirus

Answer 25

large envelope, icosahedral shape

linear dsDNA genome

Question 26

What’s the primary infection site of herpes

Answer 26

mouth or the lip

Question 27

How does herpes infect body’s organs

Answer 27

hide in PNS nerve cells or spread as viremia to different organs. They can then spread to the CNS

Question 28

T/F Proteins are actively produced in latent herpes infection

Answer 28

False, there is no structural gene expression

Question 29

What keeps the herpes virus in the latent stage

Answer 29

CD8 T cells, hence virus can reactivate when immune system is compromised

Question 30

What is the reactivation phage called in herpes

Answer 30

Shingles, painful blisters that follow dermatome distribution

Question 31

T/F Poliovirus must grow in a nerve cell as part of the life cycle

Answer 31

false, they just accidentally get into nerve cells

Question 32

describe the shape and type of poliovirus

Answer 32

+ve stranded RNA virus with icosahedral capsid

no envelope

Question 33

How does poliovirus cause damage?

Answer 33

it’s cytocidal, killing cells in which they replicate

Question 34

Where does poliovirus typically replicate in the CNS?

Answer 34

anterior horn cells because there is a receptor for polio

Question 35

What kind of CNS symptoms can polio cause?

Answer 35

acute paralysis