Expression of the human autoantigen of Wegener's granulomatosis (PR3) in a baculovirus expression system.

Proteinase 3 (PR3) is a multifunctional serine protease found in myeloperoxidase-positive granula of PMN. It is also the main target antigen for antineutrophil cytoplasmic antibodies (ANCA) found in Wegener's granulomatosis (WG). There is ample evidence that these autoantibodies play an active role in the pathogenesis of this disease. We have established the expression of the autoantigen (PR3) in a baculovirus expression system using insect cells. Recombinant PR3 was identified by IIF, direct ELISA using 3 different MoAbs and by catching ELISA using a MoAb and a rat polyclonal Ab or cANCA-positive WG patient sera. As purification of human PR3 from blood-derived PMNs has been shown to be difficult and very inefficient, insect cell-derived recombinant PR3 offers new possibilities for obtaining sufficient amounts of this protein to facilitate further biochemical characterizations.