title: Cre-LoxP-regulated expression of monoclonal antibodies driven by an ovalbumin promoter in primary oviduct cells.
abstract: BACKGROUND
  A promoter capable of driving high-level transgene expression in oviduct cells is important for developing transgenic chickens capable of producing therapeutic proteins, including monoclonal antibodies (mAbs), in the whites of laid eggs. Ovalbumin promoters can be used as oviduct-specific regulatory sequences in transgenic chickens, but their promoter activities are not high, according to previous reports.
  
  
  RESULTS
  In this study, while using a previously characterized ovalbumin promoter, we attempted to improve the expression level of mAbs using a Cre/loxP-mediated conditional excision system. We constructed a therapeutic mAb expression vector, pBS-DS-hIgG, driven by the CMV and CAG promoters, in which the expression of the heavy and light chains of humanized immunoglobulin G (hIgG) is preceded by two floxed stuffer reporter genes. In the presence of Cre, the stuffer genes were precisely excised and hIgG expression was induced in pBS-DS-hIgG-transfected 293T cells. In chicken oviduct primary culture cells, hIgG was expressed after transfection of pBS-DS-hIgG together with the ovalbumin promoter-driven Cre expression vector. The expression level of hIgG in these cells was increased 40-fold over that induced directly by the ovalbumin promoter. On the other hand, hIgG was not induced by the ovalbumin promoter-driven Cre in chicken embryonic fibroblast cells.
  
  
  CONCLUSIONS
  The Cre/loxP-based system could significantly increase ovalbumin promoter-driven production of proteins of interest, specifically in oviduct cells. This expression system could be useful for producing therapeutic mAbs at high level using transgenic chickens as bioreactors.
authors.affiliation: Health Research Institute, National Institute of Advanced Industrial Science and Technology, 1-8-31, Midorioka, Ikeda, Osaka 563-8577, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Oishi
authors.forename: Sungtae
authors.initials: S
authors.lastname: Kim
authors.forename: Kyoko
authors.initials: K
authors.lastname: Yoshii
authors.forename: Concepcion Rodriguez
authors.initials: CR
authors.lastname: Esteban
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Izpisua Belmonte
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D002645:Chickens; D005260:Female; D005822:Genetic Vectors; D057809:HEK293 Cells; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000378:metabolism; D019426:Integrases / Q000235:genetics; D010047:Ovalbumin / Q000235:genetics*; D010057:Oviducts / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D011994:Recombinant Proteins; D010047:Ovalbumin; C045073:Cre recombinase; D019426:Integrases