Résumé
Jacalin is a plant lectin known to specifically induce the proliferation of CD4+ T lymphocytes in human. We demonstrate here that jacalin completely blocks human immunodeficiency virus type 1 (HIV‐1) in vitro infection of lymphoid cells. Jacalin does not bind the viral envelope glycoprotein gp120. Besides other T cell surface molecules, it interacts with CD4, the high‐affinity receptor to HIV. Binding of jacalin to CD4 does not prevent gp120‐CD4 interaction and does not inhibit virus binding and syncytia formation. The anti‐HIV effect of the native lectin can be reproduced by its separated a‐subunits. More importantly, we have defined in the a‐chain of jacalin a 14‐amino acid sequence which shows high similarities with a peptide of the second conserved domain of gpl20. A synthetic peptide corresponding to this similar stretch also exerts a potent anti‐HIV effect. This peptide is not mitogenic for peripheral blood mononuclear cells and does not inhibit anti‐CD3‐induced lymphocyte proliferation. These results make jacalin a chain‐derived peptide a potentially valuable therapeutic agent for acquired immunodeficiency syndrome.