Viruses affecting the CNS Flashcards
Under what circumstances do lymphocytes cross the BBB?
During inflammation of the CNS
At what point does HIV become neurovirulent?
Once immunodificiency presents
Is it more common for alpha herpes viruses to travel to the CNS via the blood or through peripheral nerves?
Peripheral nerves
How does the rabies virus interact with the immune system?
It doesn’t try to hide, rather its glycoprotein is displayed on the cell surface
What is Guillain-Barre syndrome?
An acute inflammatory demyelinating disease following viral infection - commonly EBV, CMV, and HIV
T/F Viral replication occurs at the synapses in the nerve cells so they can quickly infect other cells
False, they replicate in the cell body as they require the protein synthesis machinery
What type of virus is rabies?
-sense RNA virus
Where is a common location for viral entry into the parenchyma of the CNS?
The choroid plexus
How does poliovirus get into the spinal cord?
Gut > regional lymph nodes > blood > spinal cord
How do young children with HSV 1 present?
Gingivostomatitis (cold sores)
In which is the virus still present, postinfectious encephalomyelitis or postinfectious encephalitis.
Postinfectious encephalitis
What type of virus is poliovirus?
+RNA with isosahedral capsid and no envelope
Does Guillain-Barre syndrome require an active infection?
No, as show by the outbreak that followed a vaccination program for influenza that used an inactivated virus
T/F Growth in nerve cells is obligatory part of the lifecycle or alphaherpes viruses and poliovirus
False, not for poliovirus
How does rabies virus get to the salivary glands?
Travels via the peripheral nerves and brain and down into them
What is the case fatality rate of HSV encephalitis?
70%
In which structure do HSV typically establish a latent infection?
Sensory nerve ganglia of the trigeminal or sacral nerve
What is Reye’s syndrome?
Post-infectious cerebral oedema in children. Influenza or chicken pox
What are the most common causes of viral encephalitis?
HSV 1 and 2
Rabies virus
Arboviruses
Enteroviruses
In what form is the HSV genome maintained in latent infections?
Episome coated with histones
What is secondary encephalitis (aka post-infectious encephalitis)
Secondary viral infection of the CNS, usually via the blood
True or false, rabies replicates in the salivary glands only
False, it also replicates in the muscle adjacent to its entry point
What is so problematic about viruses traveling in peripheral nerves?
They’re protected from attack by CTLs
How does varicella-zoster virus enter the body?
Respiratory transmission
What is the sequelae of viral infection of oligodendrocytes?
Demyelination
In which cells does poliovirus infect in that leads to paralysis?
Anterior horn cells in the spinal cord
Why aren’t peripheral nerves targeted by CTLs?
They don’t MHC class I
What are neuroinvasive viruses capable of?
Entering or infecting the CNS
What immune mechanism may be responsible for keeping the HSV genome in a latent state?
CD8+ T cells
Why is the fear of water in rabies?
Evolutionary adaptation of the virus to avoid dilution of the virus in the saliva
What are neurotropic viruses?
Viruses capable of replicating in nerve cells
Describe HSV 1 and 2 in terms of neuroinvasiveness and neurovirulence
Low neuroinvasiveness
High neurovirulence
What is myelitis?
An infection of the spinal cord
Are alpha herpesviruses non-enveloped or enveloped?
Enveloped
How is HSV 1 transmitted?
Via saliva
What are neurovirulent cells capable of?
Causing disease within the nervous system
What are two stategies of entering the CNS used by viruses?
Traveling up peripheral nerves
Crossing the BBB
Which virus causes a mild encephalitis?
Mumps virus
At what point during varicella-zoster infection does virus enter peripheral nerves?
After entering rashes
What is the mechanism of damage postulated to cause postinfectious encephalomyelitis?
Autoimmune demyelination
Does rabies infect neurones or oligodendrocytes?
Neurones, it’s highly neuroinvasive and neurovirulent
Coronavirus and herpes simplex virus share this route of entry to the CNS, what is it?
Via the olfactory bulbs
