A chimeric glycoprotein formulated with a combination adjuvant induces protective immunity against both human respiratory syncytial virus and parainfluenza virus type 3

Abstract Human respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV3) are major causes of serious lower respiratory tract disease in infants. Currently there is no licensed vaccine against RSV or PIV3. To make an effective bivalent subunit vaccine, a chimeric truncated F R HN protein containing the N-terminal ectodomain of the RSV fusion (F) protein linked to the C-terminal ectodomain of the PIV3 haemagglutinin-neuraminidase (HN) protein was produced in HEK293T cells. Mice, cotton rats and hamsters were immunized intramuscularly (IM) with both RSV F and PIV3 HN (F R +HN) or F R HN, formulated with TriAdj, which consists of poly(I:C), innate defense regulator peptide and poly[di(sodium carboxylatoethylphenoxy)]-phosphazene. Both formulations were immunogenic and elicited full protection from RSV; however, animals vaccinated with F R HN/TriAdj were significantly better protected from PIV3 than animals vaccinated with F R +HN/TriAdj. To develop a potentially more effective subunit vaccine, a chimeric glycoprotein (F RipSc HN), encoding the RSV F ectodomain stabilized in the pre-fusion form linked to PIV3 HN was generated. Intramuscular vaccination with F RipSc HN/TriAdj induced virus neutralizing antibodies followed by complete protection from RSV and PIV3 replication in the lungs of challenged cotton rats. Furthermore, intranasal vaccination with F RipSc HN/TriAdj significantly reduced both RSV and PIV3 replication in cotton rats. Mucosal immunization with F RipSc HN/TriAdj also elicited strong antigen-specific mucosal and systemic immune responses in a lamb model. In conclusion, the chimeric F RipSc HN protein combined with TriAdj has potential for development of a safe, effective, bivalent vaccine against both RSV and PIV3.