Vaccines Flashcards
Live vaccines
living but not able to cause disease
killed vaccines
killed by heating or chemical exposure
Naked DNA vaccines
encodes and makes proteins after injection
Sub-unit vaccines
fragments of the micro-organism, e.g. proteins or polysaccharides.
Antibody-mediated immunisation
Toxin
Diphtheria toxin (corynebacterium diphtheriae). Anthrax toxin (Bacillus anthracis). Tetanus (clostridium tetani).
formaldehyde detoxification
cross-link proteins molecules so the toxicity is abolished but the immunogenicity is maintained
genetic toxoids
genetically modify toxin but maintain immunogenecity
e-toxin
Causes enterotoxaemia in livestock. caused by Clostridium perfingens. Infection in gut, crosses over to cause damage in kidneys and brain.
Formaldehyde-treated bacterial culture filtrates
current treatment for enterotoxaemia.
production requires C. perfingens. Low yield. Immunogenicity is low and variable.
Indirect assay to test neutralizing antibody
Cature toxin on plate and incubate with monoclonal antibody directed towards toxin. Can sheep serum displace the monoclonal Ab - measure the reduction in signal from monclonal Ab
Direct assay to measure neutralizing antibody
Get serum from sheep and incubate with the toxin - mix for 1hr. Use cell culture system to see whether the the toxin is neutralized
Y30 -Y196-A168F vaccine
triple mutant genetic toxoid. Y30 and Y196 are in binding domain. A168F are in pore-forming domain
advantages of genetic toxoids
not reversible. reproducible. more similar to the molecular structure of the toxin. able to be produced using a less harmful bacterium e.g. E coli. high yield.
Diphtheria CRM197 genetic toxoid
Single mutation in the catalytic A-subunit. Glycine to glutaminic acid at residue 52.
Plague
Yersinia pestis
Subunit vaccine against plague
Multiple subunit. F1 antigen (forms capsule around bacterium). V-antigen (found at the tip of the needle that is in the type III system to inject toxin)
F1 and V-antigens
Produced in E.coli by genetic engineering. Need both - seen in mice that they’re not as effective on their own.
Antiserum protects mice from plague
Immunise mice with mixture of F1 and V antigens. Allow development of antibodies. Remove serum. Transfer to mice that have not been immunised. Test these mice’s protection. YES.
Meningitis B
Neisseria meningitidis B. Traditional vaccinology has failed.
Men B reverse technology
Identify 570 ORFs that code for putative secreted/expressed proteins. Purify 350 proteins. Immunise mice and harvest sera. Test for bactericidal activity.
Men B vaccine
4CMenB. Bexsero (2013).
Polysaccharide subunit vaccimnes
e.g. Streptococcus pneumoniae (pneumonia), haemophilus influenzae (pneumonia), neisseria meningitidis (meningitis) , salmonella typhi (typhoid)
23-valent vaccine
pick serotypes that are most likely to cause disease and isolate the polysaccharides from these serotypes
polysaccharides are T cell independent antigens
Don’t require CD4 or CD8. polysaccharides directly signal to B cells - clonal proliferation of B cells to produce IgM
Problem with polysaccharide subunit vaccines
polysaccharide diversity.
at risk populations have a weak response (elderly and children). no memory
Link polysaccharide to protein
Polysaccharide from Streptococcus pneumoniae serotype 9A. + CDM197 (diphtheria genetic toxoid) - protein-polysaccharide conjugate vaccine.
glycoconjugates
boost Ab response. Type III polysaccharide of Streptococcus (III). Ovalbumin protein carrier (OVA). conjugate (III-OVA)
mechanism of T cell activation by glycoconjugate vaccines
Glycoconjugate is internalised into an endosome of an APC e.g. B cell. Proken down into glycanp-pepties and presented with MHCII. Picked up by alphabeta receptors of CD4+ cells. Activate into Tcarb cells which release cytokines (IL2 and IL4) to mature B cells into memory B cells.
CD8-T cell response in vaccines
Live, attenuated microbes (balance between under- and over-attenuation) - use microbes that can invade host cells e.g. tuberculosis (BCG), measles, mumps, yellow fever, polio, influenza).
