Developing a convenient large animal model for gene transfer to salivary glands in vivo

BACKGROUND: Localized gene transfer to salivary glands has great potential for the treatment of salivary gland, systemic, and oral diseases. The minipig parotid gland, given its volume and morphological similarities to the human parotid gland, may be useful as a large animal model for pre-clinical gene transfer experiments. The purpose of this study was to perform an initial assessment of the efficacy and safety of adenoviral-vector-mediated gene transfer to parotid glands of miniature pigs. METHODS: AdCMVluc, a recombinant type 5 adenoviral (rAd5) vector containing a luciferase reporter gene, was administered to miniature pig parotid glands by intraductal cannulation. Five regions of gland tissue were obtained to measure the distribution of luciferase activity. The effects of time, viral dose, infusate buffer volume, and gland anatomical region on transgene expression were determined. Detailed serum chemistry and hematological analyses were performed. In addition, AdCMVlacZ, a similar rAd5 vector encoding beta-galactosidase, was also delivered to determine the parotid gland cell types transduced. RESULTS: Luciferase assays indicated that gene transfer to miniature pig salivary glands could be readily accomplished using rAd5 vectors. Highest transgene expression was found in the center of glands, which was > posterior > inferior > anterior > superior tissue regions. Expression was maximal on day 2 and declined to background by day 14, and observed in both acinar and ductal cells. Several serum chemistry and hematology parameters were transiently changed following rAd5 administration. CONCLUSIONS: Transgene expression by, and inflammatory response to, rAd5 vectors in minipig parotid glands are similar to results seen earlier in rodent studies. This suggests that results of salivary gland gene transfer from rodent studies can be extended to a larger animal model, and supports the value of using minipigs for pre-clinical applications of gene transfer to these tissues. Published in 2004 by John Wiley & Sons, Ltd.