Med Micro 8 - Vaccines Flashcards
What is a vaccine?
suspension of attenuated or killed microorganisms, or of antigenic proteins derived from them, administered for prevention, amelioration, or treatment of infectious diseases
Types of vaccines
Attenuated (live - attenuated virulence), Killed (inactivated and avirulent), Toxoid (inactivated and avirulent), Others (nucleotide, conjugate, Viral like particle)
Attenuated
Weakened so they cannot cause disease. Stripped of essential virulence factors, heat killed, etc.
What type of vaccine would you use to generate as large an immune response as possible? What cell would you target? How?
It is an open question. One way: target APC with attenuated vaccine. It stimulates release of cytokines, chemokines, interleukin, GF, so antigens will be presented to T helper cells to activate adaptive immune response. Polyclonal response
What would you do if you couldn’t produce an attenuated vaccine to generate as large an immune response as possible? What cell would you target? How?
It is an open question. One answer: Target a Pro APC using a PAMP with a linked specific antigen (conjugated vaccine). Stimulates the immune response.
Changing face of vaccine development
Conventional development and reverse vaccinology
Conventional vaccine development
take some pieces of a pathogen (ie flagella, cell surface), test in convalescent sera, test immunogenicity (agglutination), purify, identify, clone genes, test in animal models. 10-15 years
Reverse vaccinology
aka reverse genetics. Based on DNA, identify potential candidates based on homology and function (computer prediction). Way faster.
Convalescent sera
Serum from someone recovering from a disease. They have Ab so you can test.
Why is ELISA so important?
Test for Ab binding an antigen. If people have the Ab, they’ve been exposed to the antigen
Use of LD50?
Not so good to identify pathogen etc; Tell you whether or not vaccine candidate is protective
Hydropathy plots
help us know where in membrane. Can focus on one place and make conjugated vaccines.
Process of attenuation for virus (classic)
Isolate virus from infected human and grown in human tissue culture; grow in tissue culture of another species; virus gains mutations to grow there, but no longer can infect humans
Process of attenuation for bacteria (classic)
Culture under weird conditions or genetic manipulation
Attenuated vaccine - reverse genetics method
Insert genes from a virulent strain into a the coat of a non-virulent strain ***
What is a potential concern with vaccines even if they are avirulent? Why?
May generate an allergic reaction (rare) or inflammatory response,
Killed/Inactivated Vaccine
Deactivated whole microbes or subunit. When killing we need to maintain antigen structure. Formaldehyde - causes cross-linking of proteins and nucleic acids
Adjuvants
Goal is to stimulate an immune response. Ex. slow down processing of antigen so immune response has more time to be activated
Elements of gene
Start site (Met), stop site, promoter (RNA polymerase binding), transcriptional start and stop, translational start and stop (not same as transcript), regulatory sequences (operator - b/w promoter and start, used to stop RNA poly). Genes produce polypeptide.
Do all genes have a promoter?
No, operons are several genes but have only one promoter
How do we express a gene outside of its normal host?
Plasmid in E. coli for example.
How do we express the protective parts of a gene?
Cut out parts that will be exposed on outside, then link the piece to other pieces or something else. Need a promoter
How can we define what parts of a gene would be protective?
Something that is exposed that the immune system would recognize if there was an infection, so we can protect ourselves against it. Hydropathy plots.
If protective parts are too small to make a immune response what do you do?
Make conjugate vaccines! Lots of
How would you develop a new Influenza vaccine knowing that it mutates so fast? (final exam question)
Look for something that is very conserved
Consider the different route of administration of the two flu vaccines, and then type of immune response each would generate
Live attenuated: given nasally, infects through normal route; creates humoral and cell-mediated response (to kill infected cells). Killed: only antibody (humoral) response; prevents spreading to new cells
Diagram killed whole cell vaccine
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Toxoid (inactivated) vaccines
chemically or thermally modified toxins. Must try to retain original shape. Generates what type of response???
Why is attenuated better than toxoid
??
HIV subunit vaccines
Inactivated HIV subunit vaccines do not maintain their 3D structure; and it changes its antigens so rapidly that we cannot form vaccine
Heptavalent conjugate vaccine (polysaccharide)
7 components against 7 strains with slightly different polysaccharide attached to a protein (for S pneumoniae)
What kind of immune response would subunit vaccine generate?
Antibody response (T-dependent humoral). Won’t infect cells, just get taken up.
Polynucleotide vaccination
Taking the DNA that codes for a pathogen’s antigen and put it in a DNA plasmid, which is injected into a patient’s cell. Presented on MHCI (could use another gene to be exported too…) so cell-mediated.
Pros of attenuated vaccine
Lots and lots of epitopes - huge response and long lasting. Normal pathway. Possibly mild infection but no disease. Viral ones cause cell-mediated and humoral response. Vaccinated individuals can infect those around them with the attenuated virus (contact immunity)
Cons of attenuated vaccine
Possible for vaccine to revert or and begin to cause damage again. Can only enter host cells. Not suitable for certain people (age, pregnant, immunocompromised)
What kind of response would an attenuated vaccine cause?
Virus can infect cells, just no damage. So largely a cell-mediated response (Th1 and Tc)
Pros of killed vaccine
Safer (subunit and whole cell)
Cons of killed vaccine
Weak antigenically. Can cause allergic responses (adjuvants), especially with high or multiple doses (ie second and third time gets worse) - if not cleared by adaptive immunity, innate immune response is
Pros of conjugated vaccine
Safer, not monoclonal
Cons of conjugated vaccine
Not as strong of a polyclonal response (fewer epitopes) - require booster shots sometimes. Doesn’t affect via normal route.
Pros of subunit vaccine
Can protect against several strains by targeting a common subunit
Pros of Polynucleotide vaccination
inexpensive, safe, induces broad range of immune responses, long lived immunity
Cons of Polynucleotide vaccination
Integration into DNA (hasn’t happened yet), Limited to protein vaccines, autoimmunity (not yet)
How does polynucleotide vaccination induces a broad range of immune responses? Be able to show this
Broad = cell-mediated and humoral. Transcript translated in cytoplasm causes cell mediated immune response; use another gene to be exported to outside would generate humoral.
What type of immune response does each vaccine type cause?
Working on it
Reverse genetics
Delete virulence gene - cannot revert; express in yeast etc.; ex HPV gardasil - VLP has some components but not complete virus, vaccine delivery system - goes through main expression, cause cell-mediated
Active vs passive immunization
Active: get disease, vaccination; passive: injection of antibodies produced commercially (antitoxins); we generate response against passive Ab; can be contaminated with viral pathogens; short lived
