Targeted elimination of cells expressing the high‐affinity receptor for IgE (FcϵRI) by a Pseudomonas exotoxin‐based chimeric protein

Abstract

The interaction between IgE and its high-affinity receptor Fc epsilon RI found on mast cells and basophils is the primary effector pathway in allergic response. To achieve a targeted elimination of cells expressing Fc epsilon RI receptors, we constructed a chimeric protein in which a Fc fragment of mouse IgE is attached to a truncated form of Pseudomonas exotoxin (PE). To prepare the targeting moiety, we used a DNA sequence corresponding to amino acids 301-437, representing 30 residues of domain 2 and domain 3 of the mouse IgE constant region. This sequence was fused at the 5' of a cDNA encoding PE40, a truncated form of PE lacking the cell binding domain. The chimeric protein, termed Fc(2'-3)-PE40, was expressed in Escherichia coli and partially purified. The protein is highly cytotoxic to mouse mast cell lines and bone marrow-derived primary mast cells. This cytotoxicity is specific, as it could be blocked upon addition of whole IgE. Moreover, the protein had no effect on other cell lines of hemopoietic origin. The Fc(2'-3)-PE40 chimeric protein offers a new approach to the treatment of allergic disorders.

Apoptosis-Inducing Human-Origin Fcε-Bak Chimeric Proteins for Targeted Elimination of Mast Cells and Basophils: A New Approach for Allergy Treatment

“…It has been shown that treatment with Fc⑀-PEA leads to mast cells elimination in vitro (2) and prevents passive coetaneous anaphylaxis in vivo (3). Moreover, Fc⑀-PEA does not cause degranulation in vitro or in vivo (2,3). These findings indicated that the targeting of mast cells and basophils by such chimeric proteins is a promising treatment for allergic diseases.…”

“…We recently described the in vitro and in vivo activity of the chimeric protein Fc⑀-PEA, which contains the bacterial Pseudomonas exotoxin A (PEA) 3 as a killing moiety (2,3). The chimera was designed to target mast cells and basophils, the main inducers of allergic responses.…”

“…Use of the Fc portion of the mouse IgE in the Fc⑀-PEA protein allowed specific targeting of the chimera to mast cells and basophils, because only these two types of cells exhibit relatively high levels of the Fc⑀RI. It has been shown that treatment with Fc⑀-PEA leads to mast cells elimination in vitro (2) and prevents passive coetaneous anaphylaxis in vivo (3). Moreover, Fc⑀-PEA does not cause degranulation in vitro or in vivo (2,3).…”

Pseudomonas aeruginosa Exotoxin A Induces Human Mast Cell Apoptosis by a Caspase-8 and -3-dependent Mechanism

“…Because of its potent cytotoxicity, ETA has been widely used to generate fusion proteins to kill target cells. For example, chimeric cytotoxins have been constructed by the fusion of growth factors or antibodies with the enzymatic region of ETA to specifically target and eliminate cancer cells, virally infected cells, or mast cells (7)(8)(9)(10)(11)(12). It is generally accepted that ETA is internalized by the cell surface receptor CD91 (the ␣2-macroglobulin receptor/low density lipoprotein receptor-related protein) (13) and asserts its cellular toxicity by blocking protein synthesis through ADP ribosylation of translation elongation factor 2 (14 -16).…”

“…Because mast cells play an essential role in allergy, several approaches have been used to deplete mast cells, including ETA (9,10). A chimeric protein composed of an Fc fragment of mouse IgE and a truncated form of ETA demonstrates potent mast cell cytotoxicity in vitro and prevents mast cell-dependent passive cutaneous anaphylaxis in mice in vivo (9, 10).…”