Page 801 - Veterinary Immunology, 10th Edition

have been licensed as vaccine adjuvants. (Squalene is a triterpene
VetBooks.ir oil.) They are more potent than alum-based vaccines but may

induce mild local reactions by triggering the local release of TNF-α
and IL-1β, but their mechanism of action remains unclear.

Particulate Adjuvants

The immune system can trap and process particles such as bacteria
or other microorganisms much more efficiently than soluble

antigens. As a result, successful adjuvants may incorporate antigens
into readily phagocytosable particles (Fig. 24.12). These adjuvants
include emulsions, microparticles, ISCOMs, and liposomes, and all
are designed to deliver antigen efficiently to antigen-presenting
cells. The particles are usually of similar size to bacteria and are

readily endocytosed. Liposomes are lipid-based synthetic
microparticles 200 to 1000 nm in size containing encapsulated
antigens that are effectively trapped and processed yet are also

protected from rapid degradation. ISCOMs, described above, are
complex lipid-based microparticles about 40 nm in size. All of these
particulate adjuvants may be made more potent by incorporating
microbial immunostimulants. They are not yet widely employed in
veterinary vaccines.

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