Résumé : Human recombinant myeloperoxidase was evaluated in a cell-free system for its inactivation properties on the replication of human immunodeficiency virus, HTLV-III(B). In the presence of a hydrogen peroxide generating system (glucose and glucose oxidase) and sodium thiocyanate, the recombinant enzyme inhibited virus-induced syncytium formation and viral replication without causing any cytopathic effects on SupT1 reporter cells. In addition, U937 monocytoid cells, chronically infected with HIV1, were exposed to recombinant myeloperoxidase (10 U/ml) and monitored during 48 h for the accumulation of intracellular p24 viral antigen. Under these conditions, the recombinant enzyme significantly reduced intracellular viral replication without affecting cell viability.