Intro to Vaccines and Immunotherapy Flashcards
What is smallpox?
Infection focused on small blood vessels in the skin and mouth/throat
Transmitted by inhalation
What is the aim of vaccination?
Protect the individual and the population against disease - known as herd immunity
What are the types of vaccines?
Living organisms - natural or attenuated
Intact but non-living organisms - viruses or bacteria
Subcellular fragments - capsular polysaccharides or surface antigens
Toxoids
Recombinant DNA-based - gene cloned & expressed, gene expressed in vectors or naked DNA
Give examples of living organism vaccines
Natural = vaccinia for smallpox, vole bacillus for TB
Attenuated = Sabin for polio, MMR, yellow fever 17D, varicella-zoster, BCG for TB
Give examples of intact but non-living organism vaccines
Viruses - Salk for polio, Rabies, influenza, hepatitis A, typhus
Bacteria - pertussis, typhoid, cholera, plague
Give examples of subcellular fragment vaccines
Capsular polysaccharides - pneumococcus, meningococcus, Haemophilus influenzae
Surface antigen - hepatitis B
Give examples of toxoid vaccines
Tetanus, diphtheria
Give examples of recombinant DNA-based vaccines
Gene cloned and expressed = hepatitis B yeast-derived
Genes expressed in vectors = experimental
Naked DNA = experimental
Why are live vaccines not popular?
Risk of causing disease if mutations in the weakened pathogen
Too risky but research being done into knocking out genes to render the live virus safe e.g. new Rotavirus vaccine
Why are attenuated vaccines better?
Continuous culture in non-human species
No selective pressure to maintain human virulence genes or human to human transfer genes
What was the first attenuated vaccine?
BCG for TB by Calmette and Guerin
How effective are dead vaccines?
Range of effectiveness - rabies and Salk polio are good; flu, typhoid and cholera less effective; plague questionable effectiveness
What are dead vaccines being replaced with?
Attenuated and subunit vaccines
What is a toxin?
Usually a bacterial exotoxin which has been inactivated by heat or chemical action
Active against toxin-induced illness
What are pseudoviruses?
Non-replicative virus-like particles that can be used to deliver DNA or RNA from an antigen of choice
They are recombinant viruses - surface proteins of one virus are combined with core genome/genetic material of a different deactivated virus e.g. vesicular stomatitis virus (VSV) or a retrovirus
How are pseudoviruses used to develop vaccines?
Success of vaccines and antibody therapies are measured in the lab by a neutralisation assay by testing an antibody for its ability to neutralise the pseudovirus entry
What are pseudoviruses used for?
Widely used for study of cellular tropism, receptor recognition, drug discovery and for development and evaluation of antibodies and vaccines
What determines the delivery route of a pseudovirus?
The choice of pseudovirus used
e.g. Papilloma virus pseudovirus delivered to mucosa
What is meant by prophylactic?
Prevents disease
Most vaccines are prophylactic
What is the difference between prophylactic and therapeutic vaccines?
Prophylactic prevents disease = cautionary measure
Therapeutic vaccines administered post-infection to destroy pathogens that have already entered host cells
Describe how therapeutic dendritic cell therapy is used in cancer?
Monocytes from the patient are isolated
Immature DCs generated
DCs loaded with whole cell tumour-lysate (made by isolating tumour cells and preparing lysate)
Mature, antigen-presenting DCs acquired and patient is vaccinated
What do adjuvants do?
Boost the immunogenicity of poor antigens
Initiate an inflammatory response
What do adjuvants cause after vaccination?
Side-effects such as pain and swelling
What is the Depot effect?
Concentration/trapping of antigens at the site where lymphocytes are exposed to it
What are the different types of adjuvants?
Inorganic salts
Delivery systems
Bacterial products
Natural mediators (cytokines)
Give examples of inorganic salt adjuvants routinely used in humans
Aluminium hydroxide
Aluminium phosphate
Calcium phosphate
All cause depot and inflammation
Give an example of an inorganic salt adjuvant that is too toxic for human use
Beryllium hydroxide
Give examples of delivery system adjuvants too toxic to use in humans
Liposomes
Immune-stimulating complexes (ISCOMs)
Block polymers
Slow release formulations
Give examples of bacterial product adjuvants routinely used in humans
Bordetella pertussis with diphtheria and tetanus toxoids
Give examples of bacterial product adjuvants that are experimental or too toxic for human use
BCG
Mycobacterium bovis and oil
Muramyl dipeptide (MDP)
Give examples of cytokine adjuvants that are experimental or too toxic for human use
IL-1
IL-2
IL-12
IFN-g
Name some new adjuvants being developed
Monophosphoryl lipid A - detoxified form of endotoxin lipopolysaccharide (LPS); first of a new generation of TLR agonists
MPL and alum (AS04) - used in HPV vaccine, Cervarix
MPL and Saponin (AS02) - may be useful in malaria vaccines
TLR ligand-based adjuvants
What are some TLR ligand-based adjuvants?
BCG - ligates TLR2 and TLR4
Poly IC - ligates TLR3
Aldara (TLR7 agonist) / R848 (TLR7 and 8 agonist)
What does TLR ligation do?
May shift Th1/Th2 balance (as might cytokines)
How can vaccines be administered?
Injection
Intramuscular
Cutaneous
What cells do vaccines target?
Langerhans cells
What is the danger of using needlesticks for vaccination?
HIV can be transmitted
Some people may have a phobia of needles
What are jet injectors?
Medical device used for vaccination that uses high pressure, narrow stream of fluid to penetrate the skin instead of a needle
May be powered by compressed gas or springs
What is a problem with using jet injectors?
Possible cross-contamination, however now may be disposable single-use carts
What is a microneedle array patch?
New delivery system for vaccine delivery
It is a solid array of microneedles made form different metals and silicon then further coated with a drug or mixture of drugs
Once applied to the skin the coated material becomes absorbed into the skin
Why is mucosal immunisation good?
Mimics natural exposure route
e.g. polio, cholera and rotavirus
What kind of vaccines are used for mucosal immunisation?
Attenuated vaccines work well
Killed vaccines do not
How do mucosal vaccines work?
Vaccine needs to penetrate through the gut wall and use and adjuvant such as partially inactivated toxins
Should be balance between some and too much inflammation
What needs to be overcome with mucosal vaccines?
Overcome the tolerance that is usually associated with food antigens - when food is ingested and passed through the gut, tolerance response is generated so same happens for mucosal vaccination due to the administration pathway
What is the significance of recombinant vaccines used for mucosal immunisation?
Recombinant vaccines transfected into bacteria can work if the bacteria had the right level of pathogenicity
- If non-pathogenic then the vaccine will not work
- If too pathogenic then has no use as it will cause infection
What is meant by parenteral administration?
Non-oral administration
Generally interpreted as injecting directly into the body. bypassing skin and mucous membranes
Describe the nasal trivalent flu vaccine
Consists of 3 live attenuated trivalent flu stains
Licenced since 2003 USA
Nasally delivered
Safe and well tolerated
This vaccine strain is unable to replicate in any cell other than the nasopharyngeal epithelium
Why is the trivalent flu vaccine an exception for nasal administration?
Usually there is a safety concern with nasal administration due to proximity of nasal compartment to the brain so inactivated vaccines would require an adjuvant and associated inflammation
e.g. Swiss inactivated flu vaccine withdrawn due to safety concerns about the adjuvant used as it caused Bell’s palsy
What type of vaccine is better to use than others?
Live vaccines better because they induce appropriate immune response and have many antigens to target
Killed vaccines do not produce a prolonged antigenic stimulus
Subunit vaccine may need adjuvants and small antigens may have issues with MHC restriction
Polysaccharide antigens do not stimulate T cells
Describe a case that highlights the issues in vaccine safety
In 1990 infant David Salamone received routine polio vaccine
Became weak and unable to crawl - he had polio
Contracted polio from the vaccine as he had a weakened immune system and was therefore immunocompromised
Known risk of polio vaccine causing one case of disease in 2.4 x 10^6 doses
Describe some other issues with vaccine safety
Vaccines may get contaminated
Killed viruses may not be dead
Attenuated viruses may revert to wild type
Patient may be hypersensitive to trace contaminants
Patient may be immunocompromised
Describe MMR
Measles risk of death = 0.2-10%
Mostly in under 5s
9/10 people sharing space with an infected individual will contract measles
Mortality is 30% in HIV+ adults
What are potential safety problems with attenuated vaccines?
Reversion to wild type - esp. polio types 2 and 3
Severe disease in immunodeficient patients - vaccinia, BCG, measles
Persistent infection - varicella-zoster
Hypersensitivity to viral antigens - measles
Hypersensitivity to egg antigens - measles, mumps
What are potential safety problems with killed vaccines?
Vaccine not killed - polio accidents in the past
Yeast contaminant - hepatitis B
Contamination with animal viruses - polio
Contamination with endotoxin - pertussis
What vaccine is given for TB and who are the eligible groups?
BCG vaccine
In the tropics given at birth
UK = 10-14 years
USA = at-risk groups only
What vaccine is given for hepatitis B and who are the eligible groups?
Surface antigen vaccine
At risk groups e.g. medical and nursing staff
Drug addicts
Male homosexuals
Known contacts of carriers
What is the vaccine for rabies and who are the eligible groups?
Killed vaccine
At risk groups e.g. animal workers
Post-exposure groups
What is the vaccine for meningitis and who are the eligible groups?
Polysaccharide vaccine
Travelers
What is the vaccine for yellow fever and who are the eligible groups?
Attenuated vaccine
Travelers
What is the vaccine for typhoid and cholera and who are the eligible groups?
Killed or mutant vaccine
Travelers
What is the vaccine for hepatitis A and who are the eligible groups?
Killed or attenuated vaccine
Travelers
What is the vaccine for influenza and who are the eligible groups?
Killed vaccine
At risk groups or elderly
What is the vaccine for pneumococcal pneumonia and who are the eligible groups?
Polysaccharide vaccine
Elderly
What is the vaccine for varicella zoster and who are the eligible groups?
Attenuated vaccine
Leukemic children
What are the main issues with development of future vaccines?
Huge expense - development costs in USA in 2013 was $200-400
Even is cost of vaccine is low there are other costs - cold-chain, transport, personnel etc. which makes it uneconomic
What are additional issues with future vaccine development?
Carrier state e.g. Hep B
Variation of effectiveness between countries e.g. BCG
Safety issues
Free living forms and animal hosts constitute the reservoirs e.g. tetanus and yellow fever
Pandemic e.g. flu novel antigenicity
How can passive immunisation be done?
Pre exposure as in tetanus and diphtheria
Post exposure as in bites
Describe the process of passive immunisation in production of the funnel-web antivenom
Spider is milked
Venom is injected to immunise a rabbit
Blood is collected from the immunised rabbit’s ear and allowed ot clot
The serum is passed through a chromatography column to remove unwanted substances
The column retains the antibodies and the fluid is discarded
Antibodies are washed from the column
Abs are freeze dried and stored in ampoules
Reconstituted antivenom is injected into an individual that has been envenomated by the same initial spider with care to avoid anaphylactic effects
What are is immunotherapy used in?
Cancer
Autoimmunity
Allergy
Infectious disease
What are immunomodulators associated with cancer?
Coley’s toxins
Cytokines
PRR agonists
Heat shock proteins (HSP)
Ab therapy
Inflammation
What are Coley’s toxins?
William B Coley was a bone sarcoma surgeon and he injected streptococcal organisms into a cancer patient to cause erysipelas (skin infection) and stimulate the immune system
The patient’s tumour was found to have disappeared, presumably because it was attacked by the immune system
How is cytokine therapy used in cancer?
Different cytokines can be used to activate and expand certain populations of cells
IL-2 for T cell stimulus, NK cells and NKT cells
GM-CSF for APC stimulus
Type 1 IFN activates a number of immune cells and upregulates MHC
Others include IL-1, IL-4, IL-7, IL-12 and IFN-g
What are the roles of HSPs?
Generally involved in refolding of misfolded proteins and contributing to maintenance of cellular homeostasis
How do HSPs work?
When there is a non-lethal increase in temperature above the physiological normal level of a species, protein synthesis is suppressed
This activates heat shock factor (HSF) and enhances the transcription of heat shock genes
HSPs inhibit apoptosis and provide cells with thermal stability to prevent irreversible aggregation of unfolded proteins and help to restore them to their normal structure
After stress has been removed from the cell, HSF transforms to its inactive state and is transported to the cytoplasm
How are HSPs significant in cancer?
Main role is to stabilise the active functions of overexpressed and mutated cancer genes
HSPs isolated from tumours can be used to induce protection in the recipient
What are the ways therapeutic antibodies can be used in cancer?
Growth factor blocking
Apoptosis induction
Immunomodulation
Delivery
Describe growth factor blocking as a cancer therapy
- Trastuzumab (Herceptin) targets ERBB2 (human epidermal growth factor) on breast cancer cells
It blocks ERBB2 signalling by binding to ERBB2 receptors to stop them from receiving growth signals and allow targeting of ADCC to kill the cancer cells - Bevacizumab (Avastin) targets VEGF and upon binding to circulating VEGF, causes reduction in microvascular growth of tumour blood vessels, limiting blood supply to tumour tissues; used against colon cancer, non-small cell lung cancer, glioblastoma and kidney cancer
Describe apoptosis induction as a cancer therapy
Rituximab is an anti-CD20, used for CD20 positive B cell non-Hodgkin’s lymphoma and chronic lymphocytic lymphoma - rituximab binds to CD20 proteins to mark them for immune cell killing
Alemtuzumab (Campath) is an anti-CD52 used for B cell chronic lymphocytic lymphoma - the drug binds to CD52 proteins and marks them for immune system killing
Describe immunomodulation as a cancer therapy
Ipilimumab (anti CTLA-4) - binds CTLA-4 to stop the inhibitory signals, used in metastatic melanomas
What are the problems with ipilimumab?
Non-specific actions
Immune related adverse events
Mainly skin and GI and treated alongside corticosteroids
Possible autoimmunity
Describe delivery as a cancer therapy
Yttrium-labelled ibritumomab tiuxetan is and antibody to CD20 and delivers radiotherapy to follicular B cell NHL
Brentuximab vedotin binds to CD30 receptor and is internalised into the cell via endocytosis, auristatin (MMAE) is then released to prevent the cancer cell from dividing
How is innate immunity targeted as cell-based immunotherapy in cancer?
LAK cells - lymphokine activated killer cells, mostly NK cells
NKT cells activated with alpha galactosyl ceramide
Gamma delta T cells via use of zoledronic acid
DCs by therapeutic vaccination
How is adaptive immunity targeted for immunotherapy in cancer?
Tumour infiltrating lymphocytes (TILs) - tumours have high infiltration of CD8+ T cells so these can be extracted, expanded and put back into the patient to cause a TIL response
Chimeric Ab receptors - take TCR off from T cell and replace with antibody receptor that has multiple signalling domains to activate the T cell; has high specificity and affinity but can also be dangerous e.g. in case study where patient with colon carcinoma developed acute autoimmune response possibly due to low levels of antigen on lung epithelium
What are some ways of treating autoimmunity?
Immunosuppressive therapy
Targeting autoreactive cells
Tolerance therapy
What is used for immunosuppressive therapy?
NSAIDs
Steroids
Anti-inflammatory Abs e.g. anti-TNF alpha
How are autoreactive cells targeted?
Rituximab and RA, anti-CD20 targets B cells
Campath and RA, anti CD52/anti CD4 and lymphodepletion
What is tolerance therapy?
Re-training effector T cells to avoid recognising autoantigens
Ag desensitisation trialled in SLE, MS and Grave’s disease
How are allergies controlled?
Anti-histamines and corticosteroids
Mast-cell stabilisers = sodium chromoglycate
Allergen insensitivity = progressive increase in dose of allergen to densensitise response, best if started early in life
Describe monoclonal antibody therapy for infectious disease
Palivizumab is used for prophylaxis in RSV disease
Humanised antibody against the RSV F protein blocks fusion of the virus and host cell
It is effective in protecting high-risk individuals and premature infants
