Biochemical nature and mapping of PSMA epitopes recognized by human antibodies induced after immunization with
K Todorova1, S Zoubak, M Mincheff
1Institute of Biology and Immunology of Reproduction, Bulgarian Academy of Sciences, Sofia, Bulgaria.
Background:
A possible new target for immunotherapy is the prostate-specific membrane antigen (PSMA). The aim of the present study was to define potential PSMA epitopes for antibody binding using sera from patients immunized with gene-based anti-PSMA vaccines.
Materials And Methods:
Sera from prostate cancer patients, immunized repeatedly with plasmid and adenoviral vectors, each encoding for the extracellular portion of human PSMA, were tested for anti-PSMA antibodies by Western blot. PSMA-producing LNCaP cells were used as a control. Recombinant PSMA protein cleaved with different proteinases was used for epitope mapping. Different enzymes were used to cleave the PSMA molecule.
Results:
Specific anti-PSMA antibodies were detected in the studied patients' sera, mainly against the PSMA protein core. An alignment of the predicted enzyme-cleavage fragments was compared with Western blot results and several antibody epitopes were determined.
Conclusion:
These data demonstrate that multiple gene-based vaccinations induce an anti-PSMA humoral immune response. The antibodies are predominantly specific for the PSMA protein core.
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