Transient detection of E1‐containing adenovirus in saliva after the delivery of a first‐generation adenoviral vector to human parotid gland

Abstract

Background Radiation-induced salivary hypofunction is a common side-effect of treatment for head and neck cancers. Patients suffer significant morbidity and there is no suitable conventional therapy. We are conducting a Phase I clinical trial, using a first-generation serotype 5 adenoviral (Ad5) vector encoding human aquaporin-1 (AdhAQP1) to treat such patients. One week after the administration of AdhAQP1 to an enrolled, generally healthy patient, E1-containing adenovirus was detected in parotid saliva. Methods The real-time quantitative polymerase chain reactuion (PCR) was used to measure the Ad5 E1 gene and AdhAQP1 in saliva and serum. PCR and sequencing were used to characterize viral/vector DNA extracted from saliva. The presence of infectious adenovirus was assessed by the inoculation of A549 cells with aliquots of saliva. Serum Ad5 neutralizing antibodies were measured by the inhibition of 293-cell transduction with an Ad5 vector encoding luciferase. Multiple clinical evaluations were performed. Results On day 7 after AdhAQP1 delivery, low levels of the Ad5 E1 gene were detected in parotid saliva (82 copies/μl). In addition, significant levels of AdhAQP1 were also detected (1.5 × 103 copies/μl). The patient was asymptomatic and subsequent analysis of parotid saliva samples prior to day 7 and after day 7 until day 42 was negative for both virus and vector. No virus or vector was detected in serum at any time. Detailed PCR analyses of DNA extracted from the day 7 parotid saliva sample suggested the absence of a recombination event, and no infectious virus was found. Conclusions The patient most likely had a latent Ad5 infection in the targeted parotid gland that was activated after gene transfer and was without clinical consequence. Published in 2009 by John Wiley & Sons, Ltd.

Early responses to adenoviral-mediated transfer of the aquaporin-1 cDNA for radiation-induced salivary hypofunction

“…On day 7 after vector administration, his saliva, but not serum, was positive for both replication competent adenovirus (RCA; per protocol, required stopping rule) and AdhAQP1. As reported (12), this resulted from activation of a latent Ad5 infection in the targeted gland, was without clinical consequence, and was judged a mild adverse event. No other subject had saliva or serum samples positive for RCA or AdhAQP1, and none developed serum antibodies to hAQP1.…”

“…One, RCA in one subject's saliva, required us to invoke a stopping rule temporarily. This situation was extensively described earlier (12), occurred because of latent Ad5 infection in the targeted gland, and is likely an uncommon occurrence, difficult to predict prospectively. However, it was reassuring that the event was temporary, resulted in no viremia, and resolved without sequalae or need for intervention.…”

A Novel Hybrid Adenoretroviral Vector with More Extensive E3 Deletion Extends Transgene Expression in Submandibular Glands

“…In the present study, however, vectors primarily were delivered locally by salivary duct cannulation and retrograde infusion, i.e., the vectors thus delivered do not have a significant opportunity to transduce and modulate immune cells directly, unlike the circumstances of earlier in vivo studies. As we have shown, the salivary glands provide an enclosed, somewhat protected mucosal immune system target for the Ad5 vectors with little to no access to the circulation (Zheng et al, 2010). Conversely, following use of intramuscular injections, no differences were found when comparing E1-and E3-deleted vectors.…”

Advances in salivary gland gene therapy – oral and systemic implications

“…If any of the transgene encoding vector somehow escaped from the targeted gland it could either stimulate growth of the SCCA (hKGF) or enhance the tumor’s vascular supply (hFGF2). Although these concerns are reasonable, albeit theoretical, it is important to recognize that we previously have shown it is highly unlikely that vectors delivered to human salivary glands can escape from the glands and be found systemically [31]. In that study, a single subject enrolled in the above described phase I/II clinical trial was administered AdhAQP1 to one parotid gland.…”