Viruses & Vaccines Flashcards
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What is a virus and what makes it different from other types of cell?
The key thing that separate viruses and cells is how they divide and reproduce
- viruses don’t grow or reproduce like prokaryotes and eukaryotes
- they enter a cell and assemble new virus cells and the cell exit the cell, they hijack the resources and make cells make more viruses
What is the viral life cycle
you have a virus and inside the virus is nucleic acid, (some viruses can use RNA as their genome)
First thing that happens
- the virus binds to the receptor
- the cell has a receptor and it is not for the virus it is to pump out the antibiotics out of the cell but the virus has evolved to bind to it
-the interaction is dependent on if the virus has the receptor key and thus this is what determines if the virus can infect a bacteria or not
Second thing, the nucleic acid needs to be delivered into the cell (this is called penetration)
- the nucleic acid comes rushing into the cell because there is a lot of pressure
Third thing, the nucleic acid is inside the host cell then it will tell the host cell to replicate it
Fourth thing, the only way for the virus to get out is to bust the cell open, and in bacteria this is not easy since the cell wall is so tough so the viruses make a chemical that will help break down the cell wall
What are the bacteriophage lifestyles?
Two lifestyles
- lytic life cycle
- lysogenic life cycle
What is lytic life cycle
virulent phages
- as soon as they enter the cell they don’t do anything else they just making viruses, they need to gain control, so they prevent the cell from defending itself by inhibiting cellular polymerase
so they first attack the early genes –> early proteins –> regulate process
then they attack the late genes –> late proteins structural –> assemble into progeny
- these are the proteins that make the head and tails
they also never integrate into the chromosome or the genes (hence making them lytic)
viral enzyme lyses the cell to release progeny viruses
if the environment is not optimal the cell can die at any moment then the virus will make as much as it possible can, does not affect genes, just adds its viral DNA
What is lysogenic lifestyle?
temperate phages
they enter lysogenic life cycle (phage I) alternate between lytic life cycle and integrate as a prophage
it integrates itself into the gene and then when the cell undergoes translation and divsion it is with the gene and it creates viral genome this way
if there is stress to the cell then the gene will excised
how does the bacteria defend itself?
three ways
- mutation
- CRISPR
- DNA restriction and modification
Mutation defensive
bacterias replicate so fast that they can become immune to viruses as mutations pop up and bacteria that is immune will survive
DNA restriction and modification defense mechanism
it is an innate system, it is always active and present and ready, it does not require prior infection
you need a matched pair enzyme of:
- Restriction endonuclease
- Methylase
What do restriction endonuclease do?
apart of the bacterial DNA restriction and modification defenses
endo means inside and it cuts the ends of the genes
enzymatic cleavage of foreign DNA
they cut a palindromic sequence
what does methylase do?
apart of the bacterial DNA restriction and modification defenses
methylation of bacterial DNA
this methylation (adds Me to the sequence) helps the bacteria recognize itself so when a virus adds its DNA it is not methylated and thus it will be cleaved (cut)
Phage therapy
IPATH (innovative phage applications and therapeutics )
how do we find phages
- by using a petri dish containing bacteriophage assay
- the light beige cloudy background on the petri dish is the bacteria
- the clearings circles = areas where phage killed the bacteria
phage infect bacteria like the key opens a lock
- one type of phage infects one type of bacteria
Resistance to phage how does this happen?
The phage binds to a protein on the cell surface, viral receptor, but some bacteriophage the efflux pump is the protein
Although since the phage binds to the protein, the bacteria evolves and stop expression and changes the shape so it can’t bind to it anymore
it evolves under pressure, but when the protein changes shape, it cannot be bounded by the bacteriophage yet the antibiotic cannot be pumped out anymore, so the antibiotic kills it
Resistance to antibiotics, how does this happen?
Normal efflux pump is what helps contribute to antibiotic resistance since it helps push out toxins and antibiotics out of the bacterial cell
but the phage binds to the efflux pump and the bacteria is killed by the phage
Why is combining both antibiotics and phages effective at fixing the antibiotic resistance epidemic?
A normal efflux pump will pump out the antibiotics but the phage will kill the bacteria by attaching itself to the pump, so bacteria mutates and changes the efflux pump shape so the phage cannot bind anymore, yet antibiotics cannot be pumped out thus killing the bacteria
having both antibiotics and bacteriophage in combination helps antibiotic resistance since it put pressure on the cell, to evolve
what are vaccines? and how do they work?
Vaccines mimic natural infection without causing harm of the real infection
When you get a vaccine you always produce B cell response
They help produce an immune response in two steps
in initial exposure to the pathogen you get:
1. primary immune response
- this is the 1st response
- it is slow
- it has moderate intensity, it helps the cells know what the pathogen looks like so the B cells and T cells are ready as they have already seen it
then the adaptive immune response goes down and decreases but when you have a secondary exposure to the pathogen then you response in:
2. secondary response
- subsequent responses
- this is a fast response
- it has high intensity and causes immunity (either total or partial)
immunity isn’t always all or nothing, you can have complete immunity
what are B cells and T cells?
B cells are the cell type that makes antibodies
T cells contribute a different aspect of immunity and you only get a T cell response for some vaccines not all
What are antibodies?
Antibodies are proteins that attach and disable bacteria viruses
They are made by white blood cells and meant to bind to things on your body
What is an adaptive immune response? and why is it not innate?
It is an adaptive immune response because you are adapting to the exposure during the secondary exposure
adaptive immune responses are long term and they produce T cells and antibodies
innate immune responses are not antigen specific
What does it mean for a vaccine to “work”
Vaccine sometimes protects against infection
- not for polio or diphtheria or tetanus
but it does protect against disease
- it produces a T cell response and it helps prevent you from dying
How did the prevention of smallpox occur?
the smallpox epidemic killed many people, 1 in 4 children died of small pox, and killed 500 million people, it was the disease that killed the most people
Edward Jenner was the person to come up with a vaccine for it
He came up with the cowpox vaccine as he noticed that women who would milk cows would get infected with cowpox and he decided to get cowpox pus and injected to a kid (James Phipps) and challenged the kid with small pox and the kid was immune, he gained immunity
it provided cross protection
what is variolation or inoculation?
This was coined in the middle east, Africa, India
They took pus from smallpox blisters and scratched into skin
this caused a mild case of smallpox and killed 1-2% of people
What is cowpox virus called?
Vaccinia virus
What is insufflation?
It was done in China in 1500s, where they would take dried scabs and ground them into powder
then they would put the powder in the nose and it would cause mild case of smallpox and conferred immunity
what famous person lost a son to smallpox for not wanting to inoculate them?
Benjamin franklin
In 1736 his son was four years old and smallpox took his life
there is a risk benefit to it when taking vaccines, they arent completely safe
