Vaccination Flashcards
Why has it been so difficult to vaccinate against malaria; TB and HIV?
antibody responses are not sufficient for full protection
What is an attenuated organism?
organisms with reduced pathogenesis which stimulate protective immunity but don’t cause disease
Why do survivors of tetanus required vaccination to be protected against another attack?
the tetanus exotoxin is so powerful that the tiny amount needed for disease can be insufficient for a protective immune response
What are the criteria for effective vaccines?
safe; protective; gives sustained protection; induces neutralising antibody; induces protective T cells; practical- low cost; ease of administration; low SE profile
Why are inactivated vaccines less potent than live-attenuated vaccines?
inactivated have been treated so that they cannot replicate therefore do not produce proteins in the cytosol of infected cells so peptides are not presented on MHC-I moleules so CD8 T cells are not generated
How are attenuated vaccines generated?
pathogenic virus is isolated and grown in human cells then transferred to other animal cells where it then acquired mutations that allow it to grow well in monkey cells, then it no longer grows well in human cells
What is the problem with attenuated virus strains?
although they contain multiple mutations in genes, it may be possible for a pathogenic virus strain to reemerge by a furhter series of mutation; also in immunocompromised individuals
What method may supersede empirical approaches to attenuated virus generation?
recombinant DNA technology
How does recombinant DNA technology in developing attenuated vaccines work?
isolate virus; isolate virulence gene then mutate or delete the gene resulting a viable, immunogeneic but avirulent virus
Why is the route of vaccination an important determinant of success?
to induce host defense at the point of entry of the infectious agent- e.g in influenza, IgA antibodies are much more effective at preventing URT infection than systemic antibodies
What is the most effective defense against meningococcus; pneumococcus and H.influenzae?
opsonisation of the polysacchradie coat with antibody
How does conjugate vaccination work in Hib?
B cell binds polysaccharide epitope linked to tetanus toxin which is then internalised and processed; peptides from hte toxin are presented to the T cell which then stimualtes the B cell to produce antibody against polysaccharide
What are the problems with peptide-based vaccines?
a particular peptide may not bind to all the MHC molecules in a population as it is highly polymorphic; some direct exchange of short peptides can occur as processing isn’t required e.g if peptides loads onto cells other than DCs this can cause tolerance; need cross presentation by certain types of DC
What is an adjuvant?
a compoent which enhacne the immunogenicity of antigens
How was DNA vaccination discovered?
DNA encoding a viral immunogen when injected IM inducd antibody responses and cytotoxic T cells that could protect against subsequent infection from the live virus
