Epitope specificity of monoclonal and polyclonal antibodies to human elastin

Polyclonal (pAb) and monoclonal (mAb) anti-human aorta elastin antibodies were reacted with a series of overlapping hexapeptides along the human tropoelastin sequence covering exons 2-7 and 23-36 from the N-terminus to the C-terminus, advancing 1 amino acid residue each time. ELISA indicated reactive epitopes. mAb A2.1 recognized sequences containing Ala-Lys, mAb G8.1, A7.1 and pAb, hydrophobic sequences. None of them reacted with the hexapeptide VGVAPG, or with desmosine or isodesmosine. pAb L85 reacted with a His-containing sequence coded in exon 26A. pAb kappaE(L), kappaE(S) and L85 reacted with the Cys-containing sequence of exon 36. A synthetic 14-residue peptide containing the three proximal tyrosines coded in exon 13 did not react with any of the antisera tested. It appears therefore that the most frequently recognized epitopes are hydrophobic sequences. One polyclonal antibody detected several isoforms of tropoelastin in the medium of cultured vascular smooth muscle cells. Monoclonal and polyclonal antibodies stained elastic fibers on tissue sections, suggesting that the epitopes recognized are available on the native fibers for reaction with the antibodies.