CNS Virus Flashcards
Define Neurotropic
capable of replicating in nerve cells
Define neuroinvasive
capable of entering or infecting the CNS
Define neurovirulent
capable of causing disease within the nervous system
What’s myelitis?
infection of the spinal cord
What are the most common causes of viral meningitis?
herpes simplex virus
rabiesvirus
arbovirus
enteroviruses
What’s the pathophysiology of postinfectious encephalomyelitis
inflammation and demyelination due to possible autoimmune damage
What’s the pathophysiology of Guillain-Barre syndrome?
post-infectious (viral) inflammation and demyelination leading to partial or total paralysis
T/F Most people can recover completely from guillain barre
True, 75% of people recover within weeks
What are the presenting symptoms of Reye’s syndrome
cerebral oedema, and a lot of swelling but not inflammation
what’s Reye’s syndrome caused by
post-infection with influenza or chickenpox
T/F Reye’s syndrome may be associated with administration of paracetamol to treat fever
False, it is linked to aspirin administration
What’s the pathophysiology of chronic demyelinating disease?
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
How does virus get into the CNS?
infect PNS neuron
enter directly via blood stream, commonly the choroid plexus
via olfactory bulb
Why can’t we our immune system get rid of the virus inside PNS neurons
nerve cells don’t express MHCI to activate CD8 T cells’, and the intracellular pathogen cannot be cleared
Where does the replication of virus in nerves occur?
at the soma of nerve, where virus can utilise host machinery
How does virus cause damage in the CNS?
direct killing of neurons
replicate in non-neuronal cells to cause demyelination
induce inflammation to allow entry of lymphocyte via BBB
T/F Rabiesvirus must grow inside a nerve cell
True
describe the shape and virus type of rabiesvirus
bullet shaped with helical capsid and envelop
It’s a -ve stranded RNA virus
How does a virus exit the cell if it has an envelop?
budding
T/F Rabiesvirus actively evades the immune system
False, it displays glycoprotein on the cell surface and can be targeted by antibody
What are the symptoms associated with rabies
aggression
thirst but unable to drink water
Why does rabiesvirus cause muscle spasm upon attempt to drink water (what’s the logic of it)
Rabies spread via the saliva, and water will dilute the viral load
Describe the life cycle of rabiesvirus
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
T/F Vaccines are only useful prophylactically
False, there is a window to use vaccine against rabies virus after being infected (before virus enters the CNS)
Describe the shape and type for alpha herpesvirus
large envelope, icosahedral shape
linear dsDNA genome
What’s the primary infection site of herpes
mouth or the lip
How does herpes infect body’s organs
hide in PNS nerve cells or spread as viremia to different organs. They can then spread to the CNS
T/F Proteins are actively produced in latent herpes infection
False, there is no structural gene expression
What keeps the herpes virus in the latent stage
CD8 T cells, hence virus can reactivate when immune system is compromised
What is the reactivation phage called in herpes
Shingles, painful blisters that follow dermatome distribution
T/F Poliovirus must grow in a nerve cell as part of the life cycle
false, they just accidentally get into nerve cells
describe the shape and type of poliovirus
+ve stranded RNA virus with icosahedral capsid
no envelope
How does poliovirus cause damage?
it’s cytocidal, killing cells in which they replicate
Where does poliovirus typically replicate in the CNS?
anterior horn cells because there is a receptor for polio
What kind of CNS symptoms can polio cause?
acute paralysis
