Antibody class-specific immune responses in ovine milk measured by
ELISA
A.J. Hodgkinson, M.R. McQuoid, S.C. Hodgkinson
AgResearch, Ruakura Agricultural Centre, Private Bag 3123,
Hamilton, New Zealand
Proceedings of the New Zealand Society of Animal Production. 1995,
55: 218-220
Diseases affecting mucosal surfaces, especially gastrointestinal
disorders, cause high mortality rates in young domestic livestock.
Hyperimmune milk products, using milk secretions from ruminants
immunised systemically with enteric pathogens, have been shown to confer
passive immunity against such disorders but the results are variable. To
study the type and titre of immunoglobulin (Ig) classes produced in milk
secretions after immunisation with gut pathogens, we have developed
ELISAs for the estimation of ovine IgG and IgA antibodies directed against
E. coli. Utilising an indirect ELISAs technique, the method involved
coating antigen onto microtitre plates then sequential addition of test sample
dilutions (containing primary antibody), anti-class-specific antibody and anti-
species horse radish peroxidase labelled antibody. Colorimetric end point
detection employed 3, 3í, 5, 5í-tetramethylbenzidine and measurement of
optical density at 450 nm. Colostrum sampled from normal untreated ewes
(n=7) had low titres of both anti-E. coli IgG (0.87 ± 0.3; mean x 10-3
±s.e.m.) and IgA (0.25 ± 0.1), while colostrum from ewes (n=7) systemically
immunised with E. coli during late pregnancy had high titres of anti-
E. coli IgG (417.6 ± 169.4) but low titres of anti-E. coli IgA
(3.2 ± 1.5). It can be seen that systemic immunisation with gut pathogens
does not induce an IgA response in milk, although IgA is the predominant Ig
of gut mucosal surfaces. Immunisation procedures to induce better IgA
responses in ruminant milk secretions are currently being investigated which
may result in more effective hyperimmune milk products.
Keywords: NZSAPAB;
ELISA; immune responses; IgA; IgG; E. coliM antibodies;
hyperimmune milk
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Last Updated 25-01-1997
