WEEK 12: RABIES VIRUS Flashcards
How long do you wait until you get symptoms from first getting bitten?
- 20-90 days will pass before getting symptoms
Does Rabies virus kill 100% of the time once the symptoms begin?
- YES
Is there a sensation at the original bite site?
-YES
When symptoms begin, what are they similar to in general?
- the flu–> flu like symptoms
What is the most common clinical feature of rabies occurring in 80% of cases?
- The furious type
What clinical feature of rabies occurs in 20% of cases?
- Paralytic
What are the 6 clinical symptoms of rabies?
- Fever, moth salivates, convulsions
- Hydrophobia–> can’t drink a cup of water
- Hallucinations
- Hypersexual behaviour (ejaculating once per hour)
- Moments of clarity
- Coma, death
Which clinical symptoms is UNIQUE to rabies?
- Hydrophobia (can’t drink a cup of water)
- Body rejects water–> unknown why
Is there any record for human-human transmission?
-NO
What is the rough timeline of rabies?
- Exposure–> 20-90 days
- First symptoms –> prodrome (Early symptom) (1-2 days)
- Clinical expression –> Acute neurological phase (1-4 days)
- Coma –> death (1-7 days)
Who was the rabies vaccine developed by?
-Louis Pasteur and Pierre Roux in 1885
What was done for the first rabies virus?
- Weaken a virulent rabies virus by aging and drygin spinal cords of rabies infected rabbits –> administered to 9y r old boy
How was the rabies vaccine improved from the first one?
- It was inactivated and –> recombinant vaccines (G protein)
Can the rabies virus be applied post-exposure (before symptoms)?
- YES
- 5 vaccination course
How many deaths a year roughly occur from rabies?
- > 55 000 deaths
Which types of animals can be infected by rabies?
- Zoonotic–> almost all warm blooded animals
- This includes bats, dogs, foxes, raccoons, skunks etc
What do 99% of rabies cases come from (which animal)?
- Bats
How come rabies is almost impossible to eliminate?
- Due to so many wildlife reservoirs
How can we control rabies?
- Vaccination of dogs, pets
- Wild-life oral bating (herd immunity)
What is meant by humans being a ‘dead-end host’ for rabies?
- no-human-human transmission
- they are dead, don’t pass on
If you were bitten by a dog, would it be better to be bitten on the face or the foot?
- Better to be bitten on the foot
- Because it has more time to travel to the brain compared to already being on the face
Is rabies only caused by rabies virus?
NO
- Also caused by lyssaviruses (“greek spirit for mad rage’)
How many members of the lyssavirus genus is there?
- About 14
Does Australia have rabies?
- We have something very similar
- ABLV–> Australian Bat Lyssavirus
- 3 human cases recorded –> fatal
What is ABLV found in?
- flying foxes and bats
What is the treatment for ABLV?
- Same as for rabies–> rabies Ig and Rabies vaccine protects against lyssavirus
Is there any prevention for ABLV?
- Avoid handling bats
What are the 6 non molecular steps of the rabies virus?
- Animal bite or scratch (virus in saliva)
- Infects muscle (replicates), transmitted to peripheral nerves, then CNS
- Virus particles transport in along neuronal axons (i.e. retrograde) in vesicles using MICROTUBULES
- When at neuronal cell body, released from vesicle, replicate, assemble, new virus particles, then infect the next neuron.
- travels up SC–> to brain–> encephalitis
- Spreads to other organs (e.g. salivary glands, eyes)
How does rabies virus travel to the CNS?
- Via microtubules as part of retrograde transport
When rabies virus travels up the neurons, does it damage them?
- NO
- Very little cytoplasmic effect
How does the rabies virus kill if it doesn’t ‘damage’ neurons?
- Inhibits apoptosis
- Immunosuppressive strategies (immune evasion)
Which two types of polymerases must host viruses provide that aren’t in host cells?
- RNA polymerase –> (RNA dependent RNA polymerase)
- Reverse transcriptase (RNA dependent DNA polyemrase)
What type of RNA does rabies virus use?
- Negative sense RNA
In rabies virus, because it uses negative sense RNA, what does this mean for the replication?
- It must BRING and make its own RNA polymerase
- this allows it to make the +ve sense RNA strand
- The +ve sense RNA strand can now be used to translate the viral RdRP which can allow for replication of RNA (+ve and -ve sense produced)
In a normal virus such as polio that uses +ve sense RNA, what are the steps in replication?
- Easier than rabies
- Ribosome translates protein in form of RNA dependent RNA polymerase
- This then allows for +ve RNA to be translated directly and replicated to both +ve and -ve sense
In rabies virus, what are the steps in the RNA replication (-ve sense RNA)?
- -ve sense RNA must bring with it a viral RdRp to allow +ve sense RNA to be made
- This then follows the same steps as polio where ribosome translates into protein and allows for replication
Which type of nucleic acid do Lyssaviruses use?
- RNA
Does rabies virus have to make its own RNA polymerase?
- YES
What are some features of the lyssaviruses genome?
- Mutates quickly –> no proofreading
- Small genome
What strand and sense of RNA is involved in lyssaviruses?
- ss -ve sense
How many segments does the genome of lyssaviruses have?
- ONE
- Non-segmented (unlike influenza which has lots of segments)
Which class in the Baltimore scheme is it?
- V
What is the rough size of the Lyssavirus genome?
- 11kb
How many genes does the Lyssavirus genome contain?
- 5
- N, P, M, G, L
What order is Lyssaviruses in?
- Monoegavirales
Apart from Rabies (Rhabdoviridae), what are some other viruses that are under the monoegavirales order, and do they have similar pathways to rabies?
- Ebola (Filoviridae)
- Hendra, Measles, Mumps, Respiratory syncytial virus
- YES they all have similar pathways; if you understan the steps of lyssaviruses then you will understand the steps of ALL Mononegaviruses
What shape is the rabies particle/virion?
- Bullet
Is the rabies particle enveloped?
- YES
What are the 5 common steps to all viral life cycles?
- Attachment
- Entry
- Synthesis
- Assembly
- Release
Which part of the Rabies virion is helical?
- The RNP (Ribonuccelocapsid)
Are all 5 proteins in the Rabies particle?
- YES
- N, P, M, G (on surface), L
What is the function of the N protein in the Rabies virion?
- Binds and covers (encapsidates) RNA genome (nucleoprotein)
Where is the G protein present in Rabies virus?
- On the surface (spikes)
Do viruses have their own translational machinery?
- NO
- They must ALWAYS use the host cells ribosomal machinery to make proteins
Are proteins made by the host cell ribosomes (not the virus)?
- YES
What is the function of the nucleoprotein (N) in Lyssaviruses?
- Encapsidates the genome (nucleocapsid) –> required for transcription, replication