Lec 7 - Viruses and CNS Flashcards
for which viruses is neural spread a definitive characteristic of pathogenesis
rabies
alphaherpes
in which viruses is CNS spread ‘accidental’
polio
only 1% of cases
mostly spread by haematogenous route
where must viruses go in neurone for it to replciate
to cell body via microtubules and motor proteins
Neurotropic
virus can infect neural cells via neural or haematogenous route.
Neuroinvasive
virus can enter the central nervous system after infection of a peripheral site
Neurovirulent
virus can cause disease of nervous tissue cause neurological symptoms and often death.
2 types of movement a virus can have in neuron
retrograde
anterograde
what motor protein is used for retrograde and anterograde movement
r= dyenin
a = kinesin
3 main serotypes of polio virus
- brunhilde
- lansing
- leon
proportion of symptoms people get with polio
90% subclinical
5-10% = nonparalytic
1% = paralytic
what is incubation period for polio and why so variable
3-35 days
depends on number of virions you’re exposed to, how long it takes for them to replicate and cause damage
why the paralysis with polio
viral replication in motor neurons
cell lysis = destroys motor neurons
depending on how much destruction, might or might not be able to recover
where are the motor neurones that polio affects
anterior horn and brain stem
how does polio enter body
via faecal oral route
first place polio replicates
oralpharync
and in intestinal muscosal surfaces
in those with polio paralysis, where does virus go after primary viremia
- reticuloendothelial cells
- spleen
- liver
- muscle
- brown fat tissue
polio receptor
CD155
can only infect cells that express this
replacing polio IRES with rhinovirus IRES allows what>
- minimal replication in neural tissue
- can inject into glioblastoma
- trigger immune repsonse
rabies virus type
ssRNA
membrane bound
2 glycoproteins that rabies has
- adhesin
- matrix protein
2 types of rabeis transmission
- mostly animal to human
- very rarely iatrogenic (cornea translpant)
why does incubation vary sm in rabies
depends of severity of wound
location of wound
inoculum size
how does rabies travel in neurones
retrograde
after rabies in CNS, how does it spread
in anterograde manner via efferent and afferent neural pathways
what is prodome period
period of subclinical signs and symptoms that precedes the onset of psychosis
symptoms of rabies
furious form = fever, anorexia, nausea
then
acute encephalitic phase = hydrophobia, hallucinations, excitement, shedding of virus in slaiva
OR
numb (paralytic form) = 20% of infecctions
= flaccid paralysis
where does rabies adhesin glycoprotein target on muscle cells
nAChR on post synaptic muscle membrane
how does rabies move from muslce to neurone
via neural cell adhesion molecule (NCAM)
virulence stragetegies of rabies virus
-prevent cell death:
- immune unresponsiveness
- limit T cell proliferation
- keep blood brain barrier closed
- abolish apoptotic capability of the cell
