JACALIN, A LECTIN WITH ANTI-HIV-1 PROPERTIES, AND HIV-1 GP120 ENVELOPE PROTEIN INTERACT WITH DISTINCT REGIONS OF THE CD4 MOLECULE

Jacalin is a multimeric plant lectin able to interact with the lymphoc yte cell-surface molecule CD4, a known receptor for the human immunode ficiency virus type 1 (HIV-1). Moreover, jacalin is able to block HIV- 1 infection of CD4(+) lymphoblastoid cells. Here we studied whether ja calin prevents HIV-1 gp120-CD4 interactions. We found (i) that jacalin did not inhibit HIV-1 Lai-induced syncytium formation that requires g p120-CD4 interactions; (ii) that jacalin prevented neither rgp120 bind ing to cell-surface CD4 nor sCD4 binding to viral envelope proteins ex pressed at the surface of HIV-1-infected lymphoblastoid cells; (iii) t hat jacalin did not compete for binding to CD4 with anti-CD4 mAb speci fic for the CDR2- or CDR3-like regions of the D1 domain of CD4; (iv) t hat jacalin did not bind a recombinant soluble molecule containing the D1/D2 domains of CD4; and, (iv) that jacalin binding to CD4 is inhibi ted by sugars known to interact with the lectinic-site of jacalin. The se data have implications for the understanding of the mechanism by wh ich jacalin blocks HIV-1 infection of CD4(+) cells.