Abstract
Foot-and-mouth-disease (FMD) remains the most infectious livestock disease worldwide. Although commercially available inactivated or adenovirus-vectored-vaccines (Ad5-FMD) are effective, they require 5-7 days to induce protection. Therefore, new control strategies that stimulate rapid immune responses are needed. Expression of bovine interferon lambda 3 using the Ad5-vector platform (Ad5-boIFN lambda 3) is able to delay disease in cattle, but clinical signs appear at 9 days after challenge. We hypothesized that combination of Ad5-boIFN lambda 3 and Ad5-FMD could induce immediate and lasting protection against FMD. Cattle were vaccinated with an Ad5-FMD, Ad5-boIFN lambda 3, or the combination of both, followed by challenge at three days post-immunization. All animals treated with Ad5-FMD combined with Ad5-boIFN lambda 3 were fully protected against FMD, despite the absence of systemic neutralizing antibodies or antiviral activity at the time of challenge. Induction of a strong cell-mediated immune response suggested that Ad5-boIFN lambda 3 is able to act as an adjuvant of Ad5-FMD vaccine in cattle.