Microbiology 6- Prevention and treatment of viral diseases Flashcards
Why was smallpox eradication successful (7)
No animal reservoir
No latent or persistent infection
Smallpox was an easily recognised disease
The vaccine was effective against all strains of virus
Vaccine properties. Potency, low cost, abundance, heat stability, easy administration
WHO determination
$250 million
Describe live attenuated virus vaccines and give examples (10)
A natural virus with its genome inside the capsid which has had its virulence reduced so it only produces a mild infection and kick starts the immune response.
Examples: Measles Adenovius Rotavirus Rubella Yellow fever
Influenza
smallpox
Mumps
Varicella
polio
(Marry is MVP)
Describe inactivated virus vaccines and give examples (5)
You take the parental virus and treat it with chemicals and heat to destroy the genome so it is no longer infectious
However, if injected into a person, the viral proteins will still be recognised and an immune response will be triggered
Examples Hep A Japanese encephalitis Polio Rabies Tick-borne encephaliti
Purified subunit vaccine
Original parental genome has been taken and treated with proteases to chop it into little pieces
These are subunits of the virus which contains antigens that can trigger an immune response
Example
Influenza
Cloning
3 types
virus vector vaccine,
DNA vaccine,
Virus-like particle vaccine
Parts of the original viral genome are cloned inside bacteria
You can put the DNA into virus-like particles (e.g. HPV vaccine)
You may just inject viral DNA into people
You may make a new virus which doesn’t make people ill but has a segment of virulent material from the original virus
examples
hep b
HPV
Describe the attenuation of Viruses to make Live Virus Vaccines (5)
Isolate pathogenic virus from patient
Grow in human cells
Take cultured virus and infect monkey cells
Gradually the genome of the virus will adapt to the monkey cells and it will become a monkey virus
The virus will no longer grow well in human cells
Pros(3) and cons(2) of live vaccine
Rapid broad, long lived immunity
Dose sparing
Cellular immunity
BUT
Requires attenuation
May revert
Pros(2) and cons (2) of inactivated vaccine
Safe
Can be made from wild type virus
BUT
Frequent boosting required
High doses needed
Explain the two types of vaccine used agasint influenza
Inactivated vaccine or the subunit vaccine consists only of the spike proteins (HA)
Given to people are risk - e.g. over 65, asthmatics, diabetes, CVD
Also given to healthcare workers
IT DOES NOT GIVE YOU FLU
Live Attenuated Influenza Vaccine
Cold Adapted - can replicate at 32 degrees (nose) but not at 37 degrees
Given as a nasal spray
Explain the two types of vaccine used agasint Polio
SALK inactivated vaccine
Preparation of virus which has been treated so it can no longer replicate
Isn’t a particularly good vaccine - need a large dose
SABINE live attenuated vaccine
This is better
1 in 7 million vaccinations result in poliomyelitis
If this vaccine was given to people who are immunosuppressed they get a PERSISTING INFECTION - they are reservoirs of live polio virus
We must stop using Sabine and switch to Salk for the end game
Making recombinant attenuated virus vaccines
Pathogenic virus genome typically consists of receptor-binding gene, virulence gene and capsid protein genes
You can either mutate the virulence gene or delete the virulence gene
You then get a virus which is IMMUNOGENIC but NOT VIRULENT
What can happen after the shingles infection has gone
pain could remain as Post Herpetic Neuralgia (PHN)
What are interferons and what are some problems with them
switch on a natural antiviral response
Problem with Interferons: switches on everything including inflammation and fever
By giving interferons - you would suppress the virus but you would make the patient feel even worse
What is acyclovir, what does it do and why does it only affect viral cells?
Chain Terminator
The modified nucleosides are incorporated into the DNA
Lack of a 3’ hydroxyl group (the part which the next nucleotide usually attaches onto) means that the chain terminates and a phosphodiester bond isn’t formed
You administer it as the pro-drug and it can only be phosphorylated by virus encoded enzyme - THYMIDINE KINASE
Furthermore, acyclovir has a higher affinity for Viral DNA polymerase than host DNA polymerase
Explain the action of neuraminidase inhibitors
virus produces neuraminidase which moves to the cell surface and destroys sialic acid so the virus can leave
We can make neuraminidase inhibitors which are substrate analgoues that can sit in the pocket and act as inhibitors stopping neuraminidase binding
Examples
Relenza
Tamiflu
