Vaccine Platforms Flashcards
outline the different vaccine platforms
- live (attenuated)
- killed (inactivated)
- purified proteins ( including Mabs) and toxoids
- recombinant proteins
- virus like particle
- polysaccharide
- glycoconjugate
- viral vector
- mRNA vaccines
what are monovalent vaccines
designed to immunise against a single antigen or single microorganism
what is a multivalent vaccine
designed to immunise against 2 or more strains/isolates of the same microorganism
what is a combination vaccine
designed to immunise against multiple organisms
what is a heterologous vaccine
confers protective immunity against a pathogen that shares cross reacting antigens with the micro-organisms in the vaccine
what are the properties of inactivated vaccines
- virus/bacteria grown in culture
- organism inactivated physically (heat, radiation) or chemically (formalin)
- test for inactivation before use
- usually no cold chain
what are the properties of attenuated vaccines
- virus/bacteria repeatedly passaged in cells or chick embryos until virulence lost
- or genome specifically modified
- test for virulence before use
- requires cold chain
- attenuation due to mutation of specific genes when cultured in non human cells
compare the safety between inactivated and attenuated vaccines
- killed- safe, cannot revert to virulence
- attenuated- target groups only, potential for infection
compare the stability between inactivated and attenuated vaccines
- killed- stable, may not require cold chain
- attenuated- varies, often requires cold chain
compare the target groups between inactivated and attenuated vaccines
- killed- all ages and can use in immunosuppressives
- attenuated- mature immune system only and less use in immunosuppressives
compare the response between inactivated and attenuated vaccines
killed has a weaker response than attenuated
compare the dosage between inactivated and attenuated vaccines
- killed- multi dose and booster, parenteral
- attenuated- fewer doses, oral
compare the modifications between inactivated and attenuated vaccines
- killed- purified protective antigens
- attenuated- genetic modifications
give an example of an attenuated vaccine
oral polio vaccine (OPV)
give an example of an inactivated vaccine
inactivated poliovirus vaccine (IPV)
- chemically inactivated
what are the 2 types of purified protein vaccines
- natural protein antigen purified from the bug itself
- eg. inactivated diphtheria and tetanus toxoids - recombinant protein antigen created by genetic engineering and produced in an expression system
- eg. recombinant Hep B surface antigen produced in yeast
describe how toxoids are produced
- pathogenicity of some bacteria lead to secreted bacterial toxins
- exotoxins - exotoxins induce T h 2 type response but cannot be used as vaccines
- inactivated by treating with formalin - inactivated toxins= toxoids
- safe to use for vaccines - can be created by genetic engineering
what occurs with immunisation with toxoids
- creates memory B cells
- on recall, B cells produce neutralising antibodies
what is the mechanism of action of toxoids
toxoid specific neutralising antibodies bind to and complex the bacterial toxins, inactivating them
what is ronapreve
- two neutralising mAbs
- binds to 2 different sites on the SARs-COV-2 spike protein, neutralising the virus’ ability to infect cells
what are subunit vaccines
specific antigen/epitopes that induce potent and specific protective humoral or CTL responses
- example of recombinant proteins
how are subunit vaccines manufactured once key antigens/epitopes are identified
- chemical fractionation of intact microbe
- purification and stabilisation of key antigens
- chemical linkage of antigens - if key epitopes known, manufacture as peptides
- 3d amino acids created using scaffolds - using recombinant DNA technology, genetic construct coding for antigen is conducted and express as soluble proteins/glycoproteins
- recombinant subunit vaccines
describe the case of bordetella pertussis
- used for whooping cough in children
- whole cell vaccine (killed)- effective but serious side effects
- redness, pain and swelling at injection site - infanrix hexa now used- reduced side effects
give an example of a vaccine using virus like particles
Gardisil
- a HPV vaccine
- prevents HPV binding to cell surface entry receptors on epithelial basal cells and induces high serum HPV type specific neutralising antibodies
what is the major antigen in HPV
L1 capsid protein
- expressed as a recombinant protein in yeast cells
- L1 protein spontaneously assembles into 3d virus like protein
- cannot cause disease and mild side effects
what are polysaccharide vaccines
- have a capsule layer around them and composed of polysaccharides
- polysaccharide is highly antigenic- used as vaccines
- polysaccharide is sugar not protein antigens
- immune response is T cell independent - provide little protective immunity to infants/young children as they can’t induce T cell independent humoral responses or create memory cells
give examples of encapsulated bacteria
- neisseria meningitidis
- streptococcus pneumonaie
- haemophilus influenzae
give an example of a polysaccharide vaccine and what it is used for
pneumovax 23- capsule components from 23 pathogenic serotypes of streptococcus pneumoniae
- routinely offered to elderly patients
- not recommended for children >2
describe the structure of glycoconjugate vaccines
- formed by chemically coupling the polysaccharide capsular antigens from Neisseria meningitidis, haemophilus influenzae or streptococcus pneumoniae to a carrier protein
- carrier protein is toxoid from tetanus or diphtheria organisms
give an example of a glycoconjugate vaccine
- Hib conjugate vaccine
- DTaP/IPV/Hib
- infanrix hexa
- meningococcal ACWY vaccine
give examples of new viral and bacterial vaccines introduced into clinic
- viruses: Zika (phase II), HIV (phase III)
- bacteria: typhoid conjugate vaccine (phase III)
what are viral vector vaccines
- use genetically modified viruses that are not pathogenic as vectors to get heterologous genetic material into a cell
- this material encodes for pathogen antigens
- once inside the cell, the viral genes produce new chimeric non pathogenic viruses or just pathogen antigens
- APCs then process these to generate adaptive immunity
give examples of viral vectors
- measles virus
- adenovirus
what are mRNA vaccines and how are they used
- prime immune system which is then boosted by a viral vector
- eg. Covid mRNA vaccine
