Development of probiotic Lactobacillus producing hGH fused with Fc fragment of IgG

Abstract

It has been understood that the MHC class-I related IgG receptor has mutiple functions such as the passive delivery of immunoglobulin (Ig)Gs from mother to young and the regulation of serum IgG levels. In addition, FcRn expression in tissues such as liver, mammary gland, and adult intestine suggests that it may modulate IgG transport at these sites. These diverse functions are apparently brought about by the ability of FcRn to bind IgGs and transport them within and across cells. Futhermore, it is well understood that the Fc amino acids are highly conserved in rodents and man and interact with residues primarily located on the alpha2 domain of FcRn and rodent FcRn has affinity to human IgG. As information about the MHC class-I related IgG receptor is revealed more and more, people have interested in developing the Fc fragment of IgG-based therapeutics. Therefore we produced the lactobacillus producing a fusion protein , consisting of the mature part of hGH and Fc fragment of human IgG1 fused to the secretional signal of the S-layer protein of Lactobacillus. brevis. Because Lactobacillus has capability to colonize on the mammalian intestine and to secret the human GH coupled human Fc , the lactobacillus producing the human GH coupled Fc could deliver the fusion protein across intestinal barrier to the blood stream. The expressed fusion protein was analysed by western-blotting and ELISA method. To show that the hGH-Fc fusion protein have transcytosis activity of IgG and growth promoting activity of hGH, We tested the biological activities of the fusion protein through in vitro transcytosis assay and in vivo test. As a result, lactobacillus to producing the fusion protein , hGH-Fc showed that Lb.brevis could efficiently secrete biological active candidate fusion protein and that the fusion protein have two functional activities of hGH and transcytosis.