Vaccinology Flashcards
vaccine
- something originating from a microorganism that elicits a protective immune response
vaccine outcomes (2)
- can lead to resistance to the disease, but not necessarily resistance to infection
- can protect against the disease, but not necessarily against transmission
herd immunity
- if most of the population is immune, it will slow down spread of disease and protect those who are susceptible
vaccination: goal (2)
- prevention
- want to prime the immune response so that the response to the pathogen takes 1-2 days instead of weeks
concentration of antibody response
- first exposure
- second exposure
- during first exposure, the primary immune response has a moderate [Ab]
- during secondary exposure, the secondary immune response has a high [Ab]
importance of herd immunity: no vaccination (2)
- infection passes from individuals with disease to susceptible individuals
- spreads throughout the population
importance of herd immunity: vaccine coverage below threshold for herd protection (3)
- infection can still pass too susceptible individuals
- infection spreads throughout population
- those vaccinated will be protected
importance of herd immunity: vaccine coverage above threshold for herd protection (2)
- infection cannot spread in the population
- susceptible individuals are indirectly protected by vaccinated individuals
adjuvants
- compounds that increase or modulate intrinsic immunogenicity of a particular antigen
adjuvants: how can they modulate immunogenicity (3)
- stimulate innate immunity
- result in potent and persistence immune response
- influence type of immune response (Th1 vs Th2)
which adjuvants can result in potent and persistent immune response (2)
- Alum
- TLR agonists (DNA, MPLA)
why type of immune response does Alum elicit
- Th2 response
what topics are included in the study of vaccinology (6)
- what the protective immune response is
- the correct timing and place for the immune response
- pathogen serotypes
- stability of the vaccine
- age of recipients
- side-effects and complications
what are possible routes of vaccines (4)
- injection
- inhalation
- ingestion
- subcutaneous
generation of immune response to a vaccine: initial injection (3)
- adjuvant is bound by PRR
- vaccine antigen is taken up by a DC and presented on MHC CII
- DC is activated and trafficked to the lymph node
generation of immune response to a vaccine: CD8+ T cell pathway (2)
- DC presents MHC CI:Ag complex to CD8+ T cell, with some help from activated CD4+ T cell
- CD8+ T cell is activated and differentiates into CD8+ effector T cell or CD8+ memory T cell
generation of immune response to a vaccine: CD4+ T cell pathway (6)
- DC present MHC CII: Ag complex to CD4+ T cell
- B cell’s BCR detects soluble vaccine Ag and is activated with CD4+ T cell help
- B cell undergoes proliferation and maturation of the antibody response
- memory B cell proliferation occurs
- plasma cell differentiation and antibody production occurs
- long-live plasma cells remain in the bone marrow for future infection
design of vaccines: Pasteur’s Philosophy (3)
- isolate the organism
- inactivate or cripple the organism
- inject the inactivated microbe
Pasteur’s Philosophy for vaccine design: inactivation of the organism (2)
- attenuated strains
- inactivate the microbe by killing it
attenuated strains (2)
- passaging of the microbe on different media or treatment with chemicals
- strain is alive, but crippled
design of vaccines: subunit vaccines (2)
- purified or inactivated proteins (toxoids)
- conjugate vaccines
vaccine types: common (4)
- live, attenuated
- killed, whole organism
- toxoid
- subunit
vaccine types: less common (5)
- virus-like particle
- outer membrane vesicle
- protein-polysaccharide conjugate
- viral vectored
- nucleic acid vaccine
vaccine types: experimental (2)
- bacterial vectored
- antigen presenting cell
subunit vaccines (4)
- purified protein
- recombinant protein
- polysaccharide
- peptide
viral vectored vaccine
- pathogen gene and viral vector gene contained inside a viral vector
bacterial vectored vaccine
- pathogen gene inside a bacterial vector
new vaccine approaches (3)
- reverse vaccinology
- DNA and RNA vaccines
- directed /DNA shuffling
reverse vaccinology (3)
- bioinformatic identification of candidate genes
- produce and express genes synthetically
- screen in infections models
reverse vaccinology: candidate gene examples (3)
- extracellular location
- association with B cell epitopes
- outer membrane proteins
directed evolution
- design and co-screen
what is the conventional method of vaccine development (4)
- cultivate the microbe
- purify the components (antigens)
- test for immunogenicity
- clone genes, express proteins, and purify the proteins
what are the downsides of the conventional method of vaccine development (5)
- time consuming
- bias toward antigens that can be made in large quantities
- bias as not all antigens expressed during infection will be expressed in lab media
- may not be able to culture certain microbes
- hypothesis driven
in silico
- experimentation performed by computer
reverse vaccinology: step 1 (2)
- rely on bioinformatics for initial screen of pathogen genome
- in silico, identify putative vaccine candidates
what is the difference between the first step of conventional vaccine development vs reverse vaccinology
- conventional methods starts with the pathogen, whereas reverse starts with the pathogen genome
what are examples of in silico for reverse vaccinology (3)
- using pSORTB to analyze predicted amino acid sequences to predict protein localization
- using programs to predict antigenicity and immunogenicity
- search the epitope database and analysis resource
what types of surfaces are usually linked to antigenicity and immunogenicity
- hydrophilic surfaces
reverse vaccinology: step 2 (3)
- use PCR to amplify the open reading frames (genes)
- clone gene into an expression vector to make proteins
- purify proteins
reverse vaccinology: step 3
- immunize model host
- test for immunogenicity (eg. antibodies)
reverse vaccinology: advantages (5)
- relatively fast
- can be used for non-culturable bacteria
- no bias as to where/when an antigen is expressed
- allows us to find low abundance antigens
- discovery driven research, avoiding limitations of hypothesis driven research
reverse vaccinology: disadvantages
- protein folding issues
- antigen post translational modifications
how was reverse vaccinology used to make the meningococcal B vaccine (6)
- candidates predicted in the whole genome sequence of Neisseria meningitidis
- in silico predicted surface expressed proteins
- genes expressed, purified and used to immunize mice
- genes identified as surface exposed
- genes identifies to induce bactericidal antibodies
- 3 antigens selected
DNA vaccines: advantages (6)
(class slides)
- elicit protective immunity
- general conformation (shape) of antigen that is expressed is preserved
- simple, just a plasmid DNA
- stable compared to protein or RNA
- cheap
- low-risk
DNA vaccine scheme (6)
- origin of replication
- eukaryotic promoter
- antigen genes
- cytokine and co-stimulatory molecule genes
- terminator
- selectable marker to help with cloning
DNA vaccine mechanism (4)
- delivered via injection (DNA in saline) into muscle cells
- DNA gets endocytosed
- DNA goes into the nucleus where it is transcribed
- mRNA goes to cytosol, can be found on cell surface, or can be secreted from the cell
what kind of immune responses are DNA vaccines good at eliciting (2)
- Ab immune response
- CMI immune response
why can bacterial DNA be used as an adjuvant (3)
- bacterial DNA has CpG dinucleotides
- 1/16 dinucleotides in bacteria are CpGs (not methylated)
- CpGs are rare and methylated in vertebrates
what roles does bacterial DNA play as an adjuvant (3)
- bacterial DNA CpGs are strong activators of B cells
- strong activators of monocytes
- can induce Th1 response
why are DNA bacterial plasmids considered low-risk (2)
- non-infectious
- do not replicate in humans or animals
how can DNA vaccines be improved (3)
- methods to improve gene expression
- delivery systems to antigen presenting cells
- target dendritic cell delivery
improving DNA vaccines: methods to improve gene expression (2)
- better promoters
- correcting for codon bias
improving DNA vaccines: delivery systems to APCs (2)
- Langerhans cells (type of DC) residues just under skin
- gene guns, microneedles, tattoo guns to target these cells
improving DNA vaccines: targeting DC delivery
- fusing a gene encoding an antibody to a DC receptor to the antigen
DNA vaccine delivery: gene gun (2)
- carries multiple genes by coating them onto microcarriers
- microcarriers are dense enough to enter target tissues (APCs)
gene gun: microcarriers (4)
- spheres
- nontoxic
- subcellular-sized
- often positively charged gold
mRNA vaccines: safety (2)
- mRNA is non-infectious and non-integrating; no potential risk of infection or insertional mutagenesis
- mRNA is degraded by normal cell processes
what are some disadvantages to mRNA vaccines (2)
(class slides)
- can be unstable
- can be difficult to translate
how can the disadvantages of mRNA vaccines be overcome
- various modifications can be made to the mRNA to make it more stable and highly translatable
mRNA vaccines: how can efficient in vivo delivery be achieved
- formulating mRNA into carrier molecules
- allows for rapid uptake and expression in cytoplasm
mRNA vaccines: production advantages (4)
(class slides)
- rapid
- inexpensive
- scalable manufacturing
- high yields of in vitro transcription reactions
mRNA vaccines: production steps (5)
- cloning to produce cDNA
- transcription of cDNA into mRNA
- capping and co-transcriptional capping of mRNA
- purification to produce purified and capped mRNA
- storage as a mRNA-LNP
mRNA vaccines: how is mRNA made more stable (5)
- 5’ cap is added to mRNA
- optimized codon usage
- enrichment of G+C content
- modification of vaccine immunogen coding region
- storage in a lipid carrier
why doesn’t human mRNA elicit an immune reaction
- many modifications naturally found in human RNA reduce it immunostimulatory potential
what kinds of modifications are naturally made to human RNA to reduce immunostimulatory potential (3)
- reduced synthesis of antisense RNA
- altering interaction with RNA secondary structure
- altering interaction with single-stranded RNA immune receptors
mRNA vaccines: what kind of modifications can be made to the immunogen coding region to increase stabilization
- m1Ψ
mRNA vaccines: m1Ψ modification (2)
- alteration to uridine of endogenous mRNA produces m1Ψ
- done through isomerization of C-glycoside; a steric “bump”
DNA and RNA vaccines: advantages (4)
(outside chart)
- simple, scalable manufacturing
- rapid deployment
- safety (no change of infection compared to live/attenuated pathogen vaccines)
- better cellular and humoral immune response (compared to only subunit vaccines)
DNA vaccines: advanatges (4)
(outside chart)
- persistence
- prolonged expression
- stable under normal conditions
- ease of storage
RNA vaccines: advantages (5)
(otside chart)
- short half-life allows controlled expression kinetics
- amplification during manufacturing
- no need to enter nucleus
- no change of genomic integration
- cell-free, in vitro synthesis
DNA and RNA vaccines: disadvantages
(outside chart)
- immunogenicity below expectations in human clinical trials
DNA vaccines: disadvantages (2)
(outside chart)
- theoretical possibility of adverse events from genomic integration
- nuclear delivery required
RNA vaccines: disadvantages (2)
(outside chart)
- additional steps required in productions
- susceptible to degradation ex vivo and in vivo
