IL2-PE40 is a chimeric protein composed of human interleukin 2 (IL2) genetically fused to the amino terminus of a truncated form of pseudomonas exotoxin lacking its cell recognition domain (PE40). IL2-PE40 is extremely cytotoxic to IL2 receptor positive cells. This chimeric protein was found to be an effective and selective immunosuppressive agent for IL2 receptor targeted therapy in many models of disorders of the immune response where activated T-cells play a crucial role. In an attempt to produce an improved IL2-PE40 chimeric protein, we constructed new IL2-PE derivatives. This was done by inserting defined DNA sequences within the chimeric gene encoding IL2-PE40. Inserted sequences represent motifs of other proteins known to be targeted and/or sorted to specific compartments inside or outside the cell. One of the proteins, IL2-PE40(LAP+DUP), containing a targeted signal for lysosomal membrane, was 2-3-fold more active than IL2-PE40. The insertion of the LAP sequence also increased the cytotoxicity of another IL2-PE derivative, IL2-PE664Glu. Our results suggest that a selective targeting of IL2-PE chimeric proteins to lysosomes may enable the proteins to reach the cytosol more efficiently, thus improving its specific cytotoxicity. The LAP (lysosomal alkaline phosphatase) sequence may be used as a common motif for increasing the cytotoxicity of other chimeric proteins to be used for targeted immunotherapy.

Steinberger I, Ben-Bassat H, Hochberg E, Lorberboum-Galski H. Interleukin-2 (IL-2) Receptor a, b and g Subunit Expression as a Function of B-Cell Lineage Ontogeny: the Use of IL-2-PE66 4Glu to Characterize Internalization via IL-2 Receptor Subunits. Scand J Immunol 1997;46:129-136 Interleukin-2 (IL-2) is a pluripotent cytokine which plays a crucial role in the immune system response. Although the IL-2/IL-2 receptor (IL-2R) system has been well characterized in cells of the T lineage it is less known in B lymphocytes. The authors therefore studied the expression of the IL-2Ra, b and g subunits in human B-cell lines at different stages of maturation, by the polymerase chain reaction technique. The authors found that the a and b subunits are expressed in the final stages of B-cell lineage maturation, whereas the g subunit is constitutively expressed during B-lymphocyte differentiation. The results indicate that the IL-2/ IL-2R system, most probably, does not have a role in the early stages of B-cell differentiation, but may be involved only in the final stages of B-cell lineage ontogeny. Moreover, the ability of the different forms of IL-2R to internalize the IL-2 ligand was investigated, using the chimeric protein IL-2-PE66 4Glu . Cell lines bearing the ag, bg and abg forms of IL-2R were inhibited by the chimeric protein, while those bearing the g subunit alone did not respond to the chimera. Thus, internalization of IL-2 is most likely mediated via the ag form of the IL-2R, as shown here for the first time, as well as through the bg and abg IL-2R forms. However, IL-2 cannot be internalized through the IL-2R g subunit alone.

No abstract

No abstract

No abstract