Immunogenicity of Recombinant Adenovirus-Respiratory Syncytial Virus Vaccines with Adenovirus Types 4, 5, and 7 Vectors in Dogs and a Chimpanzee

Recombinant adenovirus type 4, 5, and 7 expressing the fusion glycoprotein (F) gene, the attachment glycoprotein (G) gene, or both F and G genes of respiratory syncytial virus (RSV) was constructed. Intratracheal immunization of dogs with Ad7F induced moderate titers of RSVneutralizing antibodies. After booster immunization with Ad4F, the dogs developed high titers of RSV-specific antibody. Subsequently, three two-dose vaccination regimens, Ad4F/Ad5F, Ad7G/Ad4G, and Ad7FG/Ad4FG, were compared with Ad7F/Ad4F for immunogenicity and protective efficacy. The results indicated that Ad4F/Ad5F was equal or greater in immunogenicity to Ad7F/Ad4F, but Ad7G/Ad4G and Ad7FG/Ad4FG were less effective than Ad7F/Ad4F in inducing RSV-neutralizing antibody. All vaccination regimens completely protected the lungs of dogs from RSV infection. A chimpanzee was sequentially immunized orally with Ad7F, Ad4F, and Ad5F. A low-level antibody response to RSV was induced after the primary immunization, but no significant increases were observed after booster immunizations.