Efficient and sustained transgene expression in human corneal cells mediated by a lentiviral vector

The development of vectors and techniques able to transfer potentially therapeutic genetic information to corneal tissues efficiently may have broad clinical applications. Although a variety of vectors have been tested for their ability to transduce corneal tissue, these systems have been ineffective at transducing all cell types or have been associated with a relatively short duration of transgene expression. Towards the implementation of efficient, long-term transgene expression in all corneal cell types, we have studied the ability of a recombinant lentiviral vector, containing the enhanced green fluorescent protein (eGFP), to mediate gene transfer into human corneal tissue in vitro and in situ. Human primary keratocytes, cultured in vitro, were efficiently transduced by a lentiviral vector as determined by fluorescent-activated cell sorting (FACS) and by fluorescent microscopy. Transduction efficiency was found to be dependent upon multiplicity of infection (MOI); 92% of keratocytes were transduced at an MOI of 1000. The proportion of eGFP-positive cells remained unchanged throughout continuous culture for 60 days, indicating stable expression and a lack of selective pressure for or against transduced cells. Human corneal tissue, obtained at the time of penetrating keratoplasty, demonstrated efficient in situ transduction with this vector. Endothelial cells, epithelial cells and stromal keratocytes at the exposed cut edge of the corneal tissue in situ demonstrated eGFP expression. Underlying stromal cells not in direct contact with vector-containing media, were not transduced, implying that virus-cell contact is required for transduction. Transduced corneal tissues expressed eGFP in situ for the life of the corneal button in extended organ culture (60 days). These results imply that lentiviral vectors may prove to be useful tools, able to transduce corneal tissue efficiently, and that transgene expression is temporally stable.