Immediate inflammatory responses to adenovirus-mediated gene transfer in rat salivary glands

Although replication-deficient adenoviruses can efficiently transfer genes to the salivary glands, the current vectors precipitate an immediate, transient decrease in salivary function. To study the cause of this salivary hypofunction, 10(6)-10(10) plaque-forming units (pfu) of the vector AdCMV beta gal were delivered by retrograde ductal infusion to the submandibular glands (SMGs) of rats. Microscopic analysis of infected glands showed a dose-related, rapidly developing inflammatory response, which at the highest amount of virus was characterized by a predominantly neutrophil-containing infiltrate, focal necrosis, and edema. Moreover, the glands of nude rats developed similar morphologic changes to those of immunocompetent rats. After 3 days, the volume of stimulated saliva secreted from SMGs receiving AdCMV beta gal (6.75 x 10(9) pfu) was approximately 20% that of controls. UV-inactivated virus caused a similar decrease in saliva output. We evaluated to what extent the anti-inflammatory glucocorticoid, dexamethasone, could suppress inflammation and preserve salivary function. Three days after infusion with a high dose of AdCMV beta gal (6.75 x 10(9) pfu), the glands from dexamethasone-treated animals showed markedly less inflammation and no necrosis. Furthermore, there was no significant difference in the average amount of saliva secreted from the infected glands (105 +/- 17 microliters) compared to the control glands (123 +/- 18 microliters). In addition, dexamethasone extended the expression of beta-galactosidase in the SMGs. These results suggest that the adenovirus-mediated acute inflammation in rat SMG is responsible for diminished gland function and transgene expression. Furthermore, we demonstrate a useful role for glucocorticoids in controlling acute inflammation during experimental gene transfer with current adenovirus vectors.