Characterization of amyloid protein from mice infected with alveolar hydatid cyst: isolation, purification, and amino acid composition.

The physicochemical properties of alveolar hydatid cyst-induced amyloid (AHCA) were investigated. The AHCA was extracted from spleens, livers, and kidneys of C57BL/6J mice at 12 weeks postinfection and purified on Sephadex G-100 and G-50 gel columns. By using SDS-PAGE and isoelectric focusing techniques the purified AHCA protein showed a molecular weight (MW) of approximately 8,700 and a pI value of 5.3, respectively. The azocasein-induced AA amyloid from C57BL/6J mice had a similar MW but a pI value of 5.8. Unlike mouse AA amyloid, the AHCA was resistant to KMnO4-trypsin treatment, and was shown to cross-react with antisera raised against mouse AA amyloid. The immunologic cross-reactivity between mouse AA, serum amyloid A protein, and AHCA as determined by immunoperoxidase, indirect immunofluorescence, and gel diffusion tests indicated antigenic similarity between AHCA and mouse AA. The amino acid composition of purified AHCA presented both similarities and differences when compared with published data from mouse AA and spontaneously developed mouse amyloid proteins. We report here for the first time the presence of small amounts of methylated basic amino acids and amino sugars in AHCA protein.