Analysis of prostate specific antigen and alpha1-antichymotrypsin interaction using antipeptide monoclonal antibodies.
OBJECTIVE
The synthetic peptides E30D and D10P that correspond to prostate specific antigen (PSA) sequences 60-91 and 78-89, respectively, and contain the kallikrein loop were used to immunize mice to obtain anti-PSA monoclonal antibodies (mAbs).


METHODS
Antipeptide mAb characteristics were studied using biosensor technology and enzyme-linked immunosorbent assay, and analyzing the mAb effects on PSA-alpha1-antichymotrypsin (ACT) complex formation and PSA enzymatic activity. Epitope mapping of these mAbs was performed using overlapping peptide synthesis on nitrocellulose membrane.


RESULTS
Anti-E30D mAbs bound PSA coated on the solid phase only, whereas anti-D10P mAbs recognized PSA in detection as well as in capture. However, these mAbs appeared to be anti-total PSA mAbs. Anti-E30D and anti-D10P mAbs were directed against linear epitopes corresponding to residues H74-Y77 and N84-R88, respectively, of the PSA sequence. Anti-D10P mAb recognition of PSA and PSA-ACT complex was equimolar, although an existing molecular model suggested that the sequence corresponding to anti-D10P mAb epitope was involved in the interaction site of PSA with ACT. Furthermore, we were unable to inhibit the enzymatic activity of PSA as well as PSA-ACT complex formation. Finally, the epitope N84-R88 overlapped the cleavage site R85-F86 of PSA.


CONCLUSIONS
The linear anti-D10P mAb epitope is located outside of the PSA-ACT binding site. However, these mAbs may be of value for evaluating the presence of different molecular PSA forms in sera.
Michel
S
S
Département R&D unité Immunoessais, bioMérieux, Marcy L'etoile, Lyon, France.
Charrier
J P
JP
Deleage
G
G
Battail-Poirot
N
N
Jolivet
M
M
Jolivet-Reynaud
C
C
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D004797:Enzyme-Linked Immunosorbent Assay; D018604:Epitope Mapping; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D017430:Prostate-Specific Antigen / Q000276:immunology / Q000378:metabolism*; D000514:alpha 1-Antichymotrypsin / Q000276:immunology / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D000514:alpha 1-Antichymotrypsin; D017430:Prostate-Specific Antigen