Anti-native and recombinant myeloperoxidase monoclonals and human autoantibodies

Area of Science:

• Immunology
• Rheumatology
• Biochemistry

Background:

• Anti-neutrophil cytoplasmic antibodies (ANCA) are key in systemic vasculitides.
• Myeloperoxidase (MPO) is a primary target for ANCA.
• Previous research suggested anti-MPO antibodies might recognize a single epitope on recombinant MPO.

Purpose of the Study:

• To investigate the epitope recognition profile of anti-MPO autoantibodies using both native and recombinant MPO.
• To determine if the human anti-MPO autoantibody response is restricted to a single epitope.
• To assess the utility of recombinant MPO in reflecting native MPO epitopes for potential therapeutic strategies.

Main Methods:

• Epitope mapping was performed on native and recombinant MPO.
• Fifty patients with anti-MPO autoantibodies were analyzed.
• Competition assays using mouse monoclonal antibodies against MPO were conducted.

Main Results:

• At least four distinct epitopes were identified on native MPO.
• Only two of these epitopes were conserved on recombinant MPO.
• Human anti-MPO autoantibody response was found to be polyclonal, targeting multiple epitopes on native MPO.
• 30% of patient sera with anti-native MPO antibodies did not recognize recombinant MPO.

Conclusions:

• The human anti-MPO autoantibody response is not restricted to a single epitope on native MPO.
• Recombinant MPO is a limited model for studying the full epitope diversity of native MPO.
• Findings suggest complexity in targeting MPO for therapeutic interventions in ANCA-associated vasculitis.