Viruses Affecting the Central Nervous System

Question 1

What is a neurotropic virus?

Answer 1

a virus capable of replicating in nerve cells

Question 2

What is a neuroinvasive virus?

Answer 2

a virus capable of entering the CNS

Question 3

What is a neurovirulent virus?

Answer 3

a virus capable of causing serious disease in the CNS

Question 4

What is the main cause of viral meningitis?

Answer 4

enteroviruses

Question 5

What are the main causes of viral encephalitis?

Answer 5

HSV type 1 and 2, rabiesvirus, arboviruses or enteroviruses

Question 6

What is post infectious encephalomyelitis?

Answer 6

after an infection with measles, chickenpox, rubella or mumps there is inflammation and demyelination - no virus is present so the mechanism is possibly autoimmune

Question 7

What is Guillain Barre syndrome?

Answer 7

an acute inflammatory demyelinating disease following infection from EBV, CMV, HIV - results in partial or total paralysis that usually recovers

Question 8

What is Reye’s syndrome?

Answer 8

cerebral oedema post infection with influenza or chicken pox - associated with aspirin - 25% fatality rate

Question 9

What is chronic demyelinating disease?

Answer 9

30 years after measles the patient becomes demented - because the measles virus infects the neurons

Question 10

What is AIDS encephalopathy?

Answer 10

with immunodeficiency the HIV virus becomes neurovirulent and causes a progressive dementia

Question 11

How can a virus spread to the brain?

Answer 11

travel via axon fibres from the periphery, or can enter via the blood, or can enter via the olfactory bulb

Question 12

Why are viruses in neurons protected from cytotoxic T cells?

Answer 12

nerve cells dont have class I MHC

Question 13

What ways can viruses cause damage in the brain?

Answer 13

can kill neurons directly and cause inflammatory disease, can replicate in oligodendrocytes and cause demyelination, can cause break down of the blood brain barrier

Question 14

Is growth in nerve cells an obligatory part of the replication cycle of rabiesvirus?

Answer 14

yes

Question 15

What is the structure of rabiesvirus?

Answer 15

-ve RNA genome in an enveloped helical capsid

Question 16

What is the pathogenesis of rabies?

Answer 16

a rabid animal bites another animal, the virus is present in the saliva, the virus replicates in myocytes until it gets to a peripheral nerve where it can gain access to the spinal cord and brain

Question 17

What are the symptoms of rabies?

Answer 17

aggresion, thirst, muscle spasm and terror upon attempt to drink water

Question 18

Why can you vaccinate against rabiesvirus after the bite?

Answer 18

because the virus takes up to 60 days to get into the central nervous system

Question 19

Which viruses are alpha herpesviruses?

Answer 19

HSV type 1 and type 2 and varicella-zoster

Question 20

Is growth in nerve cells an obligatory part of the alpha herpesvirus life cycle?

Answer 20

yes

Question 21

What is the structure of alpha herpesviruses?

Answer 21

linear dsDNA - icosahedral surrounded by an envelope

Question 22

How do alpha herpesviruses get into the CNS?

Answer 22

the blood or via peripheral nerves