A replication-competent adenovirus -free Ad5 vector encoding pathogen antigens thus potentially can confer seamless protection against mucosal pathogens as a DVD in a wide variety of clinical settings. RCA-free Ad5 vectors can be rapidly mass-produced in serum-free PER.C6 suspension cells; painlessly mass-administered by nasal spray ; . In the case of an influenza DVD, the chance to generate drug-resistant IFV is minimal since Ad5 particles conceivably induce an anti-influenza state without directly attacking the IFV. In contrast to a live attenuated IFV vaccine, an Ad5-vectored DVD is non-replicating and does not reassort with wild IFV. It is expected that nasal spray of an Ad5-vectored influenza DVD can confer broad protection against heterosubtypic IFV strains for several weeks as a prophylactic drug; followed by elicitation of strain-specific protective immunity as a vaccine for months or even years before the druginduced protection declines away. This novel regimen may add a rapid-response tool to the public health arsenal against influenza and other diseases if the DVD’s protective effects should be reproduced in human subjects. Pre-exposure to Ad5 has been associated with loss of Ad5’s potency when this vector is i.m. injected. However, emerging evidence shows that an Ad5-vectored nasal vaccine can bypass pre-existing Ad5 immunity in mice, macaques, and humans probably due to high-efficiency gene delivery into cells in the superficial layer along the mucosal Vorinostat HDAC inhibitor barrier in conjunction with potent antigen presentation associated with this immunocompetent interface tissue. The synergy between primary and booster applications induced by the AdE double-dose regimen shows that the rapid anti-influenza responses induced by AdE were additive in the presence of pre-existing Ad5 immunity. These findings hold promise that this nasal influenza DVD not only is able to induce rapid and sustained protection against influenza in a single-dose regimen but also may be administered repeatedly without losing potency. Although prophylactic influenza therapy can be performed by i.n. administration of complex bacterial lysates or bacterial toxins, the bacterial component-induced anti-influenza state was very transient with its protective effects declining within a few days post-therapy. The finding that AdE-induced protective effects could persist for at least 3 weeks and up to 47 days in a single-dose regimen suggests that the underlying mechanisms between bacterial component- and Ad5- induced anti-influenza states may differ.