ChAd155-RSV vaccine is immunogenic and efficacious against bovine RSV infection-induced disease in young calves
Abstract Respiratory syncytial virus (RSV) infection causes a substantial lower respiratory-tract disease burden in infants, and is a global priority for vaccine development. We evaluated the immunogenicity, safety and efficacy of a chimpanzee adenovirus (ChAd)-based vaccine candidate, ChAd155-RSV, in a bovine RSV (bRSV) challenge model. This model closely reproduces the pathogenesis/clinical manifestations of severe pediatric RSV disease. In seronegative calves, ChAd155-RSV elicited robust neutralizing antibody responses against human RSV. Two doses protected calves from clinical symptoms/lung pathological changes, and reduced nasal/lung virus loads after both a short (4-week) and a long (16-week) interval between the last immunization and a subsequent bRSV challenge. The one-dose regimen also conferred near-complete or significant protection after the short-term or long-term intervals before challenge, respectively. Importantly, immunized calves presented no clinical signs of enhanced respiratory disease. Collectively, the data supported the development of ChAd155-RSV as an RSV vaccine candidate for infants.