Flashcards in Viruses affecting the CNS Deck (22):
What is a neurotropic virus
capable of replicating in nerve cells
What is a neuroinvasive virus?
capable of entering or infection the CNS
What is a neurovirulent virus?
a virus capable of causing disease anywhere within the nervous system
What viruses enter the CNS via the olfactory bulb?
coronavirus, herpes simplex virus)
What viruses enter the CNS via the blood stream
poliovirus, mumps virus, measles virus, coxsackievirus; also HIV in monocytes
Where do viruses affecting the nervous system replicate?
Cell body (uses host machinery -> site of protein synthesis)
Why aren't viruses travelling in nerve axons removed by the immune system?
nerve cells do not have class 1 molecules -> Tc cells cannot attack
What viruses travel via axon fibres of the PNS to the CNS?
Rabies virus, yellow fever virus, HSV1&2
What is sub-acute sclerosis panencephalitis?
late sequalae to measles infection -> causes chronic demyelination and dementia
What is Reye's syndrome? what is it associated with
occurs post infection with influenzaV or chickenpox in children, resulting in cerebral oedema -> associated with aspirin use for initial fever
What is Guillane-Barre syndrome?
acute inflam demyelinating disease following infection with EBV, CMV, HIV. Results in partial/total paralysis that recovers
What is postinfectious encephalomyelitis? how does it occur?
occurs a few days post measles/chickenpox, rubella or mumps. No virus but inflammation and demyelination -> possibly autoimmune
What are the most common causes of viral encephalitis?
HSV1&2, rabiesvirus, arboviruses, enteroviruses
what is encephalitis
inflam of brain
Rabies virus has high neuro what?
neuroinvasiveness and neurovirulence
How does the rabies virus cause nervous cell damage?
does not hide from immune system, replication causes rabies glycoproteins to be displaced on cell surface -> B cells come and kill
Describe rabies pathogenesis - how it is contracted and symptoms it causes
rabid raccoon/dog bites a human transferring rabis virus from the saliva to the muscle, replicates and gets to a peripheral nerve which it uses to travel to the CNS (takes time). Causes aggression and thirst but also muscle spasm and terror on attempt to drink water (virus doesn't want to be diluted out of saliva)
Alpha herpesviruses (HSV1, 2, VZV) have night neuro what but low neuro what?
-> causes disease in the nervous system but less likely in the CNS
Describe how HSV can cause encephalitis
RARE. if virus enter the blood it can replicate in the liver and spleen then get into the brain and spinal cord to cause severe encephalitis
Which virus does not have to grow in nerve cells?
What is the pathogenesis of poliovirus?
enterovirus (ingested) replicates in regional lymph nodes then gets into the blood (free virus) enters the spinal cord and replicates in motor neuron cells - cytocidal virus -> paralysis (commonly of lower limbs)