CD4 DELETION MUTANTS EVALUATED FOR HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INFECTIVITY IN A HIGHLY EFFICIENT SYSTEM OF EXPRESSION AND DETECTIONBASED ON LTR-DEPENDENT REPORTER GENE ACTIVATION

The human CD4 glycoprotein is thought to be involved at several stages of the infection process with the human immunodeficiency virus type 1 . To pursue this line of investigation with CD4 deletion mutants, we c ombined a system of high transient cell-surface expression of the targ et molecule with an assay of HIV-1 infectivity based on induction of L TR-linked luciferase activity. The approach was also designed to disti nguish between defects in gp120 binding and postbinding events. Optima l assay conditions were established with wild-type CD4 and the previou sly characterized CD4 mutant, d367-371. New deletions of CD4 domains D 3 and D4 were then designed from a rat model of the D3D4 atomic coordi nates with the concern of maintaining overall structural integrity. Wh ile all CD4 mutants were found to be defective towards HIV, it was dem onstrated that the mutations affected different stages of the entry pr ocess. These data indicate that the system is well suited for studying the intricacy of molecular interactions involving HIV envelope glycop roteins and its receptors. (C) 1997 Elsevier Science B.V.