Page 863 - Veterinary Immunology, 10th Edition

with the leukotoxoid show greater efficacy than conventional
VetBooks.ir bacterins.

One problem encountered, especially when using coliform and
Campylobacter vaccines, is strain specificity. Several different strains

of each organism commonly occur, and successful vaccination
requires immunization with appropriate strains. This is sometimes
not possible if a commercial vaccine must be employed. One
method of overcoming this difficulty is to use autogenous vaccines.

These are vaccines that contain organisms obtained either from
infected animals on the farm where the disease problem is
occurring or from the infected animal itself. These can be very
successful if carefully prepared since the vaccine will contain all the

antigens required for protection in that specific location. As an
alternative to the use of autogenous vaccines, some manufacturers
produce polyvalent vaccines containing a mixture of antigenic
types. For example, leptospirosis vaccines commonly contain up to

five different serovars.
An alternative approach to the development of vaccines against
Gram-negative bacteria is the use of common core antigens. As
pointed out in Chapter 2, the outer layer of the Gram-negative

bacterial cell wall consists of lipopolysaccharide. This
lipopolysaccharide consists of a variable oligosaccharide (O
antigen) bound to a highly conserved core polysaccharide and lipid
A. The O antigen varies greatly among Gram-negative bacteria so

that an immune response against one O antigen confers no
immunity against bacteria expressing other O antigens. In contrast,
the underlying core polysaccharide is similar between Gram-
negative bacteria of different species and genera. Thus an immune

response directed against this common core structure has the
potential to protect against a wide variety of different Gram-
negative bacteria.
Mutant strains of E. coli (J5) and S. enterica Minnesota and

Typhimurium (Re) have been used as sources of core antigen. J5 is a
rough mutant that is deficient in uridine diphosphate galactose 4-
epimerase. As a result, the organism makes an incomplete
oligosaccharide side chain, having lost most of the outer
lipopolysaccharide structure (see Fig. 2.2). Immunization with J5

thus provides protection against E. coli, K. pneumoniae, A.

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