Identification ofE. coliK88 Receptor in Porcine Intestinal Mucus using Anti-idiotypic Antibodies

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Abstract
Escherichia coli K88 receptors were purified from porcine intestinal mucus by affinity chromatography using a K88 fimbrial antigen attached to Sepharose 4B. Receptor eluate from the column was identified using anti-idiotypic antibodies that bore an internal image to K88. They were produced in chickens against both mouse anti-K88 monoclonal and rabbit anti-K88 polyclonal antibodies. The anti-idiotypic antibodies were tested against purified receptors using an indirect ELISA. Higher absorbance values (1.3 and 1.2) were observed for the anti-polyclonal anti-idiotypic antibodies than those for anti-monoclonal anti-idiotypic antibodies (0.95 and 0.56). Analysis of purified receptors by SDS-PAGE electrophoresis and immunoblotting with K88 fimbriae revealed several bands corresponding to 40, 45, 50 and 70 kDa. However, the anti-polyclonal anti-idiotypic antibodies recognized only the 70 kDa protein while the anti-monoclonal anti-idiotypic antibodies failed to recognize any of these proteins. Sugar staining suggested that only the 50 kDa protein contained a sugar moiety. This study indicated that a 70 kDa protein in the intestinal mucus of pigs may be a dominant receptor for K88 and demonstrated that anti-idiotypic antibodies are useful tools for receptor identification.