Journal of Biotechnology 114 (2004) 89–97 Adenoviral vector mediates high expression levels of human growth hormone in the milk of mice and goats Oliberto S´ anchez ∗,1 , Jorge R. Toledo 1 , Mar´ ıa P. Rodr´ ıguez, F.O. Castro Department of Transgenesis and Animal Cloning, Animal Biotechnology Division, Centro de Ingenier´ ıa Gen´ etica y Biotecnolog´ ıa, P.O. Box 6162, Havana 10600, Cuba Received 22 April 2004; received in revised form 10 June 2004; accepted 29 June 2004 Abstract The production of large quantities of complex proteins with biopharmaceutical purposes is the main drawback for their more extensive use. Here we demonstrated that a direct instillation of a recombinant adenoviral vector containing an expression cassette for the human growth hormone gene into the mammary gland of mice and goats allowed for the efficient secretion of human growth hormone in the milk. Through this approach we were able to express human growth hormone at maximal levels of 2.8 mg/ml in the milk of mice and up to 0.3 mg/ml in goat milk. We found that the expression levels were closely dependent on both the degree of differentiation of the secretory epithelium and on the adenoviral dose used. Here we demonstrated that the direct transduction of mammary epithelial cells by means of a recombinant adenovirus could be a suitable alternative to transgenic technology for the production of recombinant proteins of biopharmaceutical interest. © 2004 Elsevier B.V. All rights reserved. Keywords: Adenovirus; Recombinant protein; Milk; Mammary gland 1. Introduction The mammary gland has been identified as a suit- able alternative to produce biopharmaceutical and nu- tritional proteins (Clark, 1998; Colman, 1998), that are synthesized in the mammary epithelial cells and there- after secreted into the milk from which the purification ∗ Corresponding author. Tel.: +53-7-2716022; fax: +53-7-331779. E-mail address: oliberto.sanchez@cigb.edu.cu (O. S´ anchez). 1 Oliberto S´ anchez and Jorge R. Toledo contributed equally to this work. process is relatively simple. Transgenesis has been ex- tensively used for the genetic modification of farm an- imals to produce human recombinant proteins in milk (Houdebine, 2000). However, drawbacks in this tech- nology include the technically difficult procedure re- quired, its inefficiency when applied to large livestock, the length of time between incorporating foreign DNA and harvesting the exogenous protein, and the health risk for animals due to the ectopic expression of trans- genes. The direct in vivo transfection of the mamm- ary gland has been proposed as a faster and more 0168-1656/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.jbiotec.2004.06.009