Adeno-associated and herpes simplex viruses as vectors for gene transfer to the corneal endothelium

We examined the efficacy and cytopathogenicity of adeno-associated (AAV) and herpes simplex viruses (HSV) as vectors for gene transfer to corneal endothelial cells (CECs).

Recombinant AAV and HSV were examined for their ability to deliver a lacZ histochemical marker gene to whole-thickness rabbit and human corneas ex vivo. Transgene expression was detected with histochemistry and quantified by a colorimetric assay.

Rabbit and human corneas transduced with AAV showed increasing numbers of cells expressing marker gene over a 3- to 4-week period. Using 2.5 x 10(6) or 1.5 x 10(7) infective units for rabbit and human corneal specimens, respectively, approximately 2% of CECs expressed the reporter gene. HSV (10(6) plaque-forming units/specimen) transduced approximately 5% of rabbit and human CECs but showed cytotoxicity. In contrast to the duration of recombinant AAV-mediated lacZ expression, recombinant HSV expression was maximal at day 1 and declined to low levels at day 7.

AAV is a promising vector, but its usefulness for corneal transduction is currently limited by the technical difficulties preparing high titres. The HSV vector examined is efficient but needs further genetic modification to prolong transgene expression and reduce its toxicity.