3. Vaccination
• Takes advantage of immune memory
• Vaccines consist of various derivatives of infectious agents
that no longer cause disease but still immunogenic
• Types:
1. Whole vaccines: whole organisms used. consist of killed
and attenuated vaccines
Killed vaccines: high heat or chemical kills the pathogen but
leaves enough antigens intact to elicit an immune
response.
Attenuated vaccines: still living pathogens that no longer
express the toxin or proteins that cause disease. Can be
genetically engineered organisms to remove genes that
cause disease or can be related non-pathogenic strains of
the infectious agent.
4. - Advantage is that it does not have the same
risks as for live viruses.
- Disadvantages are that a lot of research has
to be done to identify pathogen causing genes
and also attenuated disease causing agents
might revert to the pathogenic version
especially if only one site is mutated.
6. • Subunit vaccines: one component or protein
of the disease agent is used.
• Can be:
DNA vaccines
Peptide vaccines
7. DNA Vaccines
• Bypass the need to purify antigens
• DNA that encodes appropriate antigens is
administered directly into muscle tissue
• The foreign genes are expressed for a few weeks
and the encoded protein is made in amounts
sufficient to trigger an immune response.
• Immune response localize to the muscle
therefore helps avoid side effects
• Cheaper to prepare
• Can be stored dry at RT thereby avoiding the
need for refrigeration
8. • A disadvantage of DNA vaccines is that certain
DNA sequence motifs found in bacterial DNA
may elicit strong immune responses, which in
turn may cause the body to target its own
DNA resulting in autoimmune responses.
10. Making vector vaccines using
homologous recombination
• Genetic engineering is used to express disease
causing antigens on the surface of a non-
pathogenic virus or bacterium. This induces
immunity to both the vector and the attached
antigen.
• The genes are added using homologous
recombination – two segments of a similar or
homologous DNA align, and one strand of each
DNA helix is broken and exchanged to form a
crossover.
11. Reverse Vaccinology
• Uses expressed genomic sequences to find new
potential vaccines instead of using the pathogenic
organisms.
• It takes advantage of the fact that many genomes
of infectious agents have now been sequenced.
• A library of the genes is made and then the
proteins are screened in mice for immune
responses.
• Proteins that elicit the best response can either
be combined into a subunit vaccine or used as
separate vaccines.
12. Edible vaccines
• Many susceptible to heat
• Needless and qualified personnel needed to
administer injected vaccines
• As a result, an alternative is needed
(i) Oral vaccines
(ii) Edible vaccines
• Oral vaccines
- In liquid form or pill taken by mouth
- E.g. polio - consists of live attenuated polio virus.
The injected form consists of inactivated virus
13. • Edible vaccines
- Expressed in plants that can be used as
vegetables or fruit
- Heat-stable and cheap to produce (usually in
large quantities
- Easy to distribute and storage is the same as
for standard crops
- E.g. genetically engineered potatoes
containing Hepatitis B vaccines
