HIV-1 GP41 BINDS TO 2 PROTEINS IN CELL-CULTURE SUPERNATANT OF HUMAN B-CELL LINE RAJI AND MONOCYTE CELL-LINE U937

Based on our findings that HIV-1 gp41 can bind independently of CD4 to the human T cell line H9, B cell line Raji and monocytic cell line U9 37, as well as human peripheral blood mononuclear cells preferentially to B lymphocytes and monocytes, we examined whether soluble protein f or HIV-1 gp41 binding exists in the cell culture supernatant of Raji a nd U937. Using HIV-1 recombinant soluble gp41 (sgp41; Env amino acid 5 39-654) attached to sepharose beads, the cell culture supernatants of Raji and U937 were absorbed. By SDS-PAGE of sgp41-eluates of these cel l culture supernatants three protein bands of 70, 75 and 92kD were sta ined with Coomassie blue. By Western blot (ligand blot) analysis using sgp41, two protein bands of 70 and 75kD were observed in sgp41 eluate s from Raji and U937 cell culture supernatants. These sgp41-eluates co uld inhibit the sgp41 binding to Rail and U937 cells. Our data indicat e that Raji and U937 cells produce two soluble binding proteins for HI V-1 gp41.