Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

VII. Interpretation of Serum Protein Profiles
143
but these aspects are more fully explored in Chapter 4
lipids.
F . Other Serum Proteins
A number of other serum proteins of domestic animals
have been studied but have not been fully investigated for
diagnostic purposes.
The antiproteases, α 1 -antitrypsin and α 1 -antichymotrypsin
have moderate acute phase responses in cattle and dogs,
and an antielastin was also identified in dogs ( Conner et al. ,
1988b ). Ceruloplasmin, a copper-containing serum protein
that has inherent oxidase activity, is involved in iron metabolism
and is also a moderate APP ( Ceron and Martinez-
Subiela, 2004 ; Martinez-Subiela et al. , 2002b ).
Among the collectins ( Gabius, 1997 ), mannan-binding
protein, conglutinin, and collectin-43 have been investigated
in cattle ( Kawai et al. , 1997 ; Krogh-Meibom et al. ,
2004a, 2004b ). A low level of conglutinin was found to be
associated with reduced resistance to disease and could be
used as a breeding trait to produce animals with increased
resistance ( Holmskov et al. , 1998 ). Lipopolysaccaridebinding
protein, which as its name suggests is able to
bind to bacterial endotoxin (lipopolysaccharide), has been
shown to be a moderate APP in cattle ( Horadagoda et al. ,
1995 ; Schroedl et al. , 2001 ).
G . Multiplex Assays, Protein Arrays, and
Acute Phase Index
Advances in proteomics and in genomics have stimulated
investigations of multiple analytes in an organism, cell, tissue,
or biological fluid. Gene arrays have been developed
that can monitor the expression of several thousand genes
in a tissue sample at the same time. An objective of proteomics
is to be able to perform a similar feat for protein,
but the technology is still some distance from use in the
clinical biochemistry laboratory ( Anderson and Anderson,
2002 ). A step toward the examination of the complete
serum proteome would be made if it were possible to measure
the concentration of a number of proteins in the same
aliquot of sample. To achieve this goal, multiplex assay
systems are being developed in which numerous immunoassays
can be run simultaneously. One such system uses
fluorescently labeled beads with differing emission characteristics
for different proteins, which can be quantified
simultaneously ( Pang et al. , 2005 ). Another novel multiplex
system uses an array of antibody-based reagent s for
different protein analytes immobilized on a biochip surface
( Molloy et al. , 2005 ). These multiplex assays may find a
role in the clinical biochemistry of domestic animals if
they can be developed and validated for individual species.
Interpretation of data from multiple assays will be a
challenge for the clinical biochemist involved in serum
protein analysis. It is possible that the relative change in
concentrations of groups of proteins will provide more
useful diagnostic information than that obtained by simply
interpreting the changes in concentration of individual
proteins. Advanced statistical methods—for instance,
using neural network analysis ( Chen et al. , 2004 )—may
be needed for implementation of such analysis, but bioinformatics
is exploiting the application of mathematics,
statistics, and computing to biological systems. However,
combination of results from individual analyte tests is not
new. Use of the albumin-globulin ratio to improve diagnosis
is a simple example of this approach. Combination of
results from individual acute phase proteins can increase
the diagnostic value of the tests involved. This has been
developed as an “ acute phase index ” with a formula proposed
of (major positive APP) (moderate positive APP)
divided by (major negative APP) (moderate negative
APP), which increased the sensitivity and specificity of
analysis ( Toussaint et al. , 1995 )
VII . INTERPRETATION OF SERUM
PROTEIN PROFILES
The determinations of serum proteins and their SPE profiles
are important diagnostic aids in clinical biochemistry,
even though a specific diagnosis can seldom be made
with SPE. Abnormal serum protein profiles can be identified
with general types of disease processes and in this way
provide the rationale for further definitive studies of the
patient. Various electrophoretograms illustrating some common
applications in different species are given in Figures
5-8 and 5-9 . Inclusion of total protein and albumin assays in
automated systems to provide the albumin-to-globulin ratio
(A:G) enhances the analysis . A change in the A:G ratio is
often the first signal of a protein dyscrasia, which leads to
further study of the proteins by SPE. Reference values for
total serum protein and its fractions in animals and birds are
given in Appendices VIII, IX, and X.
A . Physiological Influences
Abnormalities of SPE must be interpreted in light of the
many influences not associated with disease. However,
normal physiological variations within an individual are
relatively constant over a considerable period of time;
therefore, even minor changes in the SPE profile can be of
significance and warrant close scrutiny.
1 . Infl uence of Age, Development, and Breed
In the fetus, the concentration of total protein and albumin
progressively increases with little change in total globulins
and an absence of γ -globulin. After birth, and with colostral
uptake during the first 24 hours, the SPE changes to reflect