Basic study on a gene therapy for allergic diseases

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FcR expressed on mast cells have a critical role in allergic reaction. Inhibition of IgE binding to FcR could be a crucial target of allergy therapy. We cloned a mouse FceR gene from mouse spleen cDNA and introduced under two different promoters, CAG (pCAG-GS) and CMV (pSecTag2A) with immunoglobulin secretory signal and a MYC-tag to express soluble FceR protein.The expression plasmids were introduced to HEK293T cells. The protein of presumed molecular weight was successfully identified from the conditioned medium with anti-myc antibody by Western blot. The CAG promoter plasmid transfected cells produced ten times more proteins than CMV promoter one transfected cells. Incubation with IgE, the conditioned medium successfully inhibited the activity in PCA. This effect depended on the dose of the conditioned medium. The in vivo direct injection of expression plasmid successfully inhibited passive cutaneous anaphylaxis (PCA) response in rats. This finding provided us the promising possibility of gene therapy for human allergic diseases. However, the effect expired 96 hours after the injection. The route and site of administration may require improvement.In addition to those studies we investigated an immunoregulatory role of mast cells which IgE sensitize through FceR. The study revealed that mast cells are critical for Th2 development in mucosal immunity. Thus we now are conducting to modulate Th2 repnese based immune disease by FcR expression plasmid administration, which may provide another application of gene therapy to Th2 immune response based disorders, such as systemic lupus erythematosus.