2 DIFFERENT 8 KDA MONOMERS ARE INVOLVED IN THE OLIGOMERIC ORGANIZATION OF THE NATIVE ECHINOCOCCUS-GRANULOSUS ANTIGEN-B

The present work describes the purification and characterization of an tigen B (AgB), the thermostable lipoprotein from E. granulosus. Native AgB was purified to homogeneity by a new strategy involving adsorptio n on DEAE-Sepharose, followed by immunopurification. The purified anti gen was analysed using mapped monoclonal antibodies (MoAbs) and peptid e isolation by in situ digestion in gels after SDS-PAGE. Epitope mappi ng of 7 MoAbs using PEPSCAN, synthetic peptides and competition studie s, revealed that six of them defined epitopes which clustered the N-te lminal extension of a 8 kDa subunit of AgB, whilst the remaining one r eacted against the stretch RGLIAEGE, corresponding to the C-terminus. The epitopes defined by the seven MoAbs were found to be present in al l the subunits. Furthermore, the similarities of the peptide finger pr ints obtained by HPLC analysis and amino acid sequencing of tryptic pe ptides isolated from the 8, 16 and 24 kDa subunits, indicated that the y have most if not all the amino acid sequence in common. We also foun d evidence that the band representing a component of an apparent molec ular weight of 8 kDa in SDS-PAGE, believed to be the smallest subunit of AgB, contained at least two components, which may constitute the bu ilding blocks of the higher molecular weight subunits.