Human immunodeficiency virus-infected T cells and monocytes are killed by monoclonal human anti-gp41 antibodies coupled to ricin A chain

Two human monoclonal antibodies specific for the envelope glycoprotein (gp), gp41, of the human immunodeficiency virus were conjugated to deglycosylated ricin A chain. These immunotoxins killed human immunodeficiency virus-infected H9 (T cell) and U937 (monocyte) cell lines but were nontoxic to the uninfected cell lines or to class II-positive Daudi cells. Specific killing of infected H9 cells could be completely blocked by recombinant gp160 and partially blocked by unconjugated anti-gp41 antibody but was not blocked by recombinant gp120 or human IgG demonstrating specificity for gp41. The specific toxicity of the immunotoxins for infected U937 cells was markedly potentiated by chloroquine.