Dysregulated Proteolysis in Aids

Plasmin activity induced by different concentrations of added urokinase (UK) in serum from 20 patients with AIDS (P) and 10 healthy control (HC) subjects was measured using the fibrin plate assay. 125I-fibrin coated 24 well plates were exposed to UK (0.34-6.8 ng/ml) or to trypsin (T) (2.5 ug/ml) in the presence of serum (10%) from P or HC. Control wells were exposed to either T or tris buffer (pH 8.1) alone. Volumes were adjusted to 1 ml with buffer and after 1 hr at 37°C, radioactivity (cpm) released into the medium was determined using a gamma counter. Data are expressed as % plasmin activity or as % inhibition of plasmin activity. All sera from HC totally abrogated (>98%) the plasmin activating ability of UK (1.7 ng/ml). In contrast, sera from −50% of P were less able to inhibit plasmin activation (to 26%). The inability of P sera to inhibit plasmin activation was specific since P and HC sera were equally capable of inhibiting T. Mixing experiments using P and HC sera demonstrated that P sera did not block the ability of HC sera to inhibit plasmin activation. The inhibitory activity of HC and active P sera eluted in the void volume of a spehadex G100 column (MW >100,00 daltons) and is acid sensitive, however HC sera also contains an acid stable inhibitor(s) of plasmin activation not detected in P sera. These data suggest dysregulation of UK dependent proteolysis may be associated with AIDS.