The Fc epsilon similar to Fc gamma fusion protein (AAFP) is considered as a promising drug candidate for IgE-mediated allergic diseases by bridging REM and Fc gamma RII together on mast cells and basophils. The coaggregation depends on the flexible IgG1 hinge in AAFP with a necessary spatial relationship between AAFP and its two receptors. In this work, a mouse homolog of AAFP (mAAFP) was designed and transiently expressed in Chinese hamster ovary cells to facilitate the evaluation of its efficacy in mouse. The parameters affecting transient gene expression (TGE) were optimized in 6-well plates, and then the process was conducted to produce 2 mg mAAFP in the batch culture in 1.31 bioreactor. To improve the production yield, fed-batch and hypothermic fed-batch cultures were adopted to achieve 5.5- and 14-fold increases, respectively. The obtained mAAFP was assayed in vivo in a mouse passive cutaneous anaphylaxis (PCA) model. The results showed that mAAFP significantly inhibited IgE-mediated allergic reaction and its efficacy lasted for at least 24 days. It is indicated that the IgG1 hinge could coaggregate Fc epsilon RI with the inhibitory receptor Fc gamma RII on mast cells and basophils, and thus activate the inhibitory signaling pathway of Fc gamma RII. This work shows AAFP has great potential for allergy therapy. (c) 2010 Elsevier Ltd. All rights reserved.