Biomedical Engineering Reference
In-Depth Information
cells/cellular debris. The antigen-containing supernatant is then treated with β-propiolacetone in
order to inactivate viral particles present. The antigen is not subjected to subsequent high-resolu-
tion chromatographic purifi cation steps, and hence is not purifi ed to homogeneity. The product is
then formulated as an oil-in-water emulsion.
13.5 Adjuvant technology
Administration of many vaccines on their own stimulates a poor host immunological response. This is
particularly true of the more recently developed subunit vaccines. An adjuvant is defi ned as any mate-
rial that enhances the cellular and /or humoral immune response to an antigen. Adjuvants thus generally
elicit an earlier, more potent and longer-lasting, immunological reaction against co-administered anti-
gen. In addition, the use of adjuvants can often facilitate administration of reduced quantities of antigen
to achieve an adequate immunological response. This implies consequent economic savings, as vac-
cines (particularly subunit and vector vaccines) are far more expensive to produce than the adjuvant.
A number of different adjuvant preparations have been developed (Table 13.13). Most prep-
arations also display some associated toxicity and, as a general rule, the greater the product's
adjuvanticity, the more toxic it is likely to be. A few different adjuvants may be used in veteri-
nary medicine; however (for safety reasons), aluminium-based products are the only adjuvants
routinely used in human medicine. Application of many of the aggressive adjuvant materials is
reserved for selected experimentation purposes in animals.
An ideal adjuvant should display several specifi c characteristics. These include:
•
safety (no unacceptable local/systemic responses);
•
elicit protective immunity, even against weak immunogens;
Table 13.13
Overview of the adjuvant preparations that have been developed to date, or are under
investigation. Of these, aluminium-based substances are the only adjuvants used to any signifi cant degree
in humans. Calcium phosphate and oil emulsions fi nd very limited application in human medicine
Mineral compounds Aluminium phosphate (AlPO
4
)
Aluminium hydroxide (Al(OH)
3
)
Alum (AlK(SO
4
)
2
.
12H
2
O)
Calcium phosphate (CaPO
4
)
Bacterial products Mycobacterial species
Mycobacterial components, e.g. trehalose dimycolate (TDM),
muramyl dipeptide (MDP)
Corynebacterium
species
B. pertussis
LPS
Oil-based emulsions
Freund's complete/incomplete adjuvant (FCA/FIA)
Starch oil
Saponins
Quil A
Liposomes
Immunostimulatory complexes (ISCOMs)
Some cytokines
IL-1 and -2
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