Lecture 14 Flashcards
What is a virus
An infectious agent (toxin or poison)
Can a virus grow or reproduce itself?
No
What is the only characteristic of life that viruses have/can do
Evolution
How do viruses make more viruses
They use the host replication system
What do viral particles include
Genetic material (either rna or dna)
Capsid (protein coat, protects from enviro and immune syst)
Attachement proteins (allows virus to bind and enter host cells)
Three functions of capsid
Protects, attach to host cell, penetrates host cell membrane (to possibly inject its nucleic acid)
What do viruses attach to through attachment proteins
A specific receptor site on host cell membrane
Attachement of viruses to membrane determines what
The host and its cells that can be infected by a particular virus
Metaphor for virus attachment
Lock and key (only one fits specific one)
For a virus to infect the host cell, outer surface of virus must
chemically interact with receptor sites on surface of host cell
Viruses are host specific meaning
Binding proteins on virus bunds to specific receptors on specific cells in specific host species.
Once inside the cell, the viral nucleic acid can
Take over the cell and direct it
Once virus binds to receptor it either
Enters cell or injects its nucleic acid
In cell, protein coat released and viral nucleic acid will replicate by
Using machinery of cell
What are some of the smallest infectious agents known
Viruses
New copies of original virus are made by
Viral genes that take command of host metabolic pathways
When enough copies of viral nucleic acid and coat made,
Virus is assembled and released
When virus released,
Kills host cell and infects other cell
Examples of viral diseases
Cold, influenza, chicken pox, aids, hepatitis b
Most viral infections get resolved how
Without antiviral medications
Antivirals are prescribed tk treat
Chronic of life threatening viruses
(Ebola, flu, herpes…)
How antiviral medication works
- Prevents virus from attaching/entering healthy cell
- Prevents viral nuc acid from being copied
- Prevents viral proteins from being produced
Mechanism of action (moa) fusion inhibitors
Interfere with binding or entry of virus
Moa Genetic copying prevention
Prevents host cell from making viral nuc acid
Moa Viral prot production
Inhibits formation of viral proteins-> vital for reproduction of virus
Moa Viral release inhibitor
Keeps virus from leaving cell
First vaccine story
Material from cowpox virus injected in 8yo boy -> protection provided to save people from outbreaks
Vaccines work how
They train our immune system to detect and attack pathogens
When new pathogen enters body, it introduces what
Antigen, causes immun syst to form antibodies
What are antibodies
Body’s took for identifying and targeting invader
For every new pathogens/antigens, body needs to
Build specific antibodies
Person is susceptible to illness when
Immune syst needs time to respond/produce new antibodies to fight back
A vaccine is a substance that is designed to
Mimic a pathogen and its antigens
Immune syst triggers what when foreign microbes invade
Series of response in attempt to identify/remove from body
Signs that immune response is working
Coughing, sneezing, inflammation, fever…
Sings of sickness (cough, fever…) work to
Trap, deter and rid body of threats like bacteria
Immune responses trigger second line of defense called
Adaptive immunity
In adaptive immunity, what cells are recruited
B cells and T cells
B cells
Create antibodies
T cells
Detect and destroy pathogens
Adaptive immunity produces kong lived memory cells which results in
Immunity
What do memory cells do
Lie in wait ready to use right antibodies and killer T cells if pathogen is seen again
Vaccines trigger what
Body’s adaptive immune system
Vaccine isn’t infectious itself but has the job of
Teaching body to build specific antibody
Types of vaccines
- Inactive
- Live attenuated
- Subunit or recombinant
- DNA/mRNA
Inactive vaccine contain
Killed pathogen
Inactive vaccine mechanism
Take live pathogen, kill it, when introduced to human, inactivated pathogen is strong enough to create immune response but not cause disease
Inactive vaccine might need
Multiple doses
Live attenuated vaccines contain
Much weaker and tamer version of pathogen
How do pathogens in live attenuated vaccines work
Not strong enough to cause disease but can trigger strong immune response
Bc strong immune response in live attenuated vaccines (leaves behind memory cells),
Can provide lifetime protection after 1-2 doses
Downside of live attenuated vaccines
Weaker immune systems can’t have them and inactive vaccines dont create ling lasting protection
What does subunit/recombinant vaccine contain
Only part of the pathogen
Subunit/rec vaccines are good bc
Not infectious (lack genetic info to replicate) so safe for weak immune systems
Subunit/rec vaccines require
Multiple shots
Parts of virus used in subunit/rec vaccines
Proteins, polysaccharide chains or mix of the two
Rna/dna vaccines contain
Genes that make antigens needed to trigger immune response
In rna/dna vaccines, cells have machinery to take genetic material and
Use it to make antigens (pathogen proteins) which are displayed on outside of cell
When antigens displayed outside of cell in rna/dna vaccines, immune cells do what
See the pathogen proteins and reacts as if infected
Why dna/rna vaccin not dangerous
Bc only genetic material, no other ingredients that could develop into disease and harm
Scientists designed mrna molecules that
Use protein making machinery to train body to fight virus
For covid-19 vaccine, mrna molecule
Mimics one part of spike protein (cant give you virus)
Covid: spike mrna gets inside cell and is treated
Like any other mrna message in cells -> prot building machinery reads it and builds part of spike encoded by mrna vaccine
Covid: after builds spike protein from mrna vaccine, the spike prot is
Recognized by immune syst and makes antibodies. Spike mrna i eventually unstable and destroyed
Covid: over time, immune syst becomes less alert to spike prot if not infected, so
Another dose boosts alertness, longer lasting immune cells build memory of spike prot and recognize it faster and more efficiently
After multiple doses of mrna vaccine for covid, if gets infected,
quickly recognized and triggers large immune response by immune cells to prevent severe illness and successfully fight off infection
When virus replicates, undergoes copying errors which are
Mutations
Virus mutations alter virus surface proteins (antigens) so
Hard for immune syst to recognize
When virus mutates, how to fight it off
New vaccines (ex flu every year)
Herd immunity is when
Large percentage of population is immune to disease
How does herd immunity work
Disrupts chain of infection
How does herd immunity disrupt chain of infection
If virus tries to infect immune person, it dies -> chain is broken bc hard to reach vulnerable ones if keeps dying
If vaccination rates drops,
Risk that viruses reappear
Viruses can eradicate completely if
Herd immunity is maintained long enough
Example of eradicated virus
Smallpox
Who can’t get vaccines
Serious underlying health conditions that weaken immune syst (cancer, hiv)
Herd immunity protects those who
Can’t vaccinate
Flu virus characteristics
1, respiratory disease
2. Highly contagious
3. Can spread 1 day prior to symptoms/seven days after symptoms appear
4. Spread via cough/sneeze
Why flu season in winter 1
Bc indoors, more close contact which promotes transmission
Why flu season in winter 2
Influenza virus survives better in cold/drier (moisture from droplets evaporates more in dry air, so whisked away in air currents and floats around for days until gets breathed in)
Epidemic
-Outbreak affecting many people in population and spreads rapidly
-considered epidemic if certain nb of people within short time period (~2 weeks)
Pandemic
-larger epidemic, covers several countries/continents
-nb people doesn’t matter more than rate of spread and how far it spread
