CELL-SURFACE PROTEINS BINDING TO RECOMBINANT SOLUBLE HIV-1 AND HIV-2 TRANSMEMBRANE PROTEINS

Objective: To further characterize cell surface proteins binding to re combinant soluble (rs) forms of the transmembrane glycoproteins gp41 o f HIV-1 (rsgp41) and gp36 of HIV-2 (rsgp36). Methods: Various human an d murine cell lines of different lineages were surface-labelled with I -125. rsgp41 and rsgp36 were bound to CnBr-Sepharose and used as an af finity matrix for the surface-labelled cell lysates. The bound cell su rface proteins were separated on sodium dodecyl sulphate polyacrylamid e gel electrophoresis under reducing conditions. A rabbit serum was pr oduced against one of the cell surface proteins and flow cytometry use d to compare the results with those obtained from affinity chromatogra phy. Results: We have confirmed and extended the results obtained by Q ureshi et al. [1]. In addition to the 44 kD protein, we identified cel l surface proteins with molecular, weights of 98 and 106 kD binding wi th high affinity to both rsgp41 and rsgp36. We have demonstrated diffe rences between human and murine cell lines in the expression of the ce ll surface proteins that interact with rsgp41 and rsgp36. Furthermore, a correlation between the level of rsgp41 and rsgp36 binding proteins , detected either by affinity chromatography or by reactivity with an antiserum directed against one of the cell surface binding components was shown. Conclusions: Three cell surface proteins, with molecular we ights of 44, 98 and 106 kD, bind with high affinity to rs forms of gp4 1 and gp36. Their expression decreases from a T-lymphoid cell line, to a monoblastoid cell line, to a cell line representing mature monocyte s. Human T-cell lymphotropic virus-infected cell lines show a predomin ance of the 44 kD protein. There are species-specific differences, in that murine cell lines lack the 44 kD protein.