Recent outbreaks of a novel H7N9
avian influenza virus in humans in China raise pandemic concerns and underscore an urgent need to develop effective
vaccines. Theoretically, live
influenza vaccines are of multiple advantages over traditional inactivated
influenza vaccines to be used in a pandemic, because they can be produced rapidly, safely, and inexpensively. However, studies on live
vaccines against the novel H7N9 virus are limited. In this study, we evaluated a potential live
influenza vaccine candidate using an H7N3
avian influenza virus isolated from ducks with controls of two recombinant viruses generated through reverse genetics. The potential candidate could be produced efficiently using chicken embryonated eggs, and is homogenous to the novel H7N9 virus in their
viral hemagglutinin genes. The potential candidate is likely low pathogenic to birds and mammals, and likely sensitive to
oseltamivir and
amantadine, as suggested by its genomic sequences. Its low pathogenicity was further supported through inoculation in mice, chicken embryonated eggs and chickens. Specific
antibodies elicited in mice were detectable at least during the period between day 14 and day 56 after
intranasal administration of the candidate for one time. Titers of the specific
antibodies increased significantly with a boost
intranasal administration or a higher inoculation dose. The induced specific
antibodies were of substantial cross-reactivity with the novel H7N9 virus. These primary but promising evaluation data suggest that the duck influenza virus could be used as a potential live
vaccine candidate, favorably through a prime-boost route, to mitigate the severity of the possible pandemic caused by the newly emerging H7N9 virus, and is valuable to be further evaluated.