ASSOCIATION OF AUTOANTIBODIES AGAINST PLATELET GLYCOPROTEINS IB IX AND IIB/IIIA, AND PLATELET-REACTIVE ANTI-HIV ANTIBODIES IN THROMBOCYTOPENIC NARCOTIC ADDICTS/

The levels of platelet-associated Igs (PAIgs) and plasma circulating a ntiplatelet antibodies were evaluated by a now cytometric immunofluore scence assay (FCIFA), an enzyme-linked immunoassay (ELISA), and a plat elet radioactive antiglobulin test (PRAT), in a group of 45 human immu nodeficiency virus (HIV)-infected intravenous drug users (IVDUs), with or without thrombocytopenia (TCP). Direct tests demonstrated an incre ased amount of PAIgs in 40% of the patients, irrespective of their pla telet count. These PAIgs were mainly of IgG class and could not be elu ted with ether, Plasma IgG with antiplatelet activity was found in 70% of the thrombocytopenic individuals, whereas it was detected in only one patient without TCP. The relative frequencies of antibodies agains t the platelet glycoproteins (GPs) Ib/IX and IIb/IIIa were assessed in plasma from all patients by means of the monoclonal antibody-specific immobilization of platelet antigens assay (MAIPA), Plasmas from all n on-thrombocytopenic patients were negative when tested by indirect MAI PA. In contrast, 10/23 plasmas from thrombocytopenic patients reacted with either GP IIb/IIIa, GP Ib/IX, or both GPs. Finally, aiming to inv estigate whether HIV antibodies from these patients are reactive with normal platelets, we performed absorption-elution experiments, followe d by evaluation of HIV antibodies in the indirect eluates by ELISA and Western blot. Interestingly, we detected anti-HIV antibodies that bin d to normal platelet antigens in 50% of the ether eluates prepared fro m control platelets sensitized with plasma from patients with TCP, but in only 5% of eluates obtained from platelets sensitized with plasma from non-thrombocytopenic patients. The present study provides direct evidence that specific autoantibodies against platelet membrane GPs Ib /IX and IIb/IIIa are common in HIV positive thrombocytopenic individua ls. The finding in these patients of HIV antibodies crossreactive with normal platelets, suggests that mimicry of human antigens by HIV coul d play a key role in the pathophysiology of the HIV-related TCP.