A parainfluenza virus 5 (PIV5)-vectored intranasal vaccine for Lyme disease provides long-lasting protection against tick transmitted in mice.

Lyme disease (LD) is the most prevalent vector borne disease in North America and Europe and its geographic range continues to expand. Strategies for disease control are necessary to effectively reduce incidence of LD including development of safe vaccines for human use. Parainfluenza virus 5 (PIV5) vector has an excellent safety record in animals and PIV5-vectored COVID-19 and RSV vaccines are currently under clinical development. We constructed PIV5-vectored LD vaccine candidates expressing OspA from sensu stricto (OspA) and a chimeric protein containing sequences from and (OspA). Immunogenicity and vaccine efficacy were analyzed in C3H-HeN mice after prime-boost intranasal (IN) vaccination with PIV5-OspA and PIV5-OspA, subcutaneous (SC) vaccination with rOspA+Alum as well as the respective controls. Mice vaccinated with either PIV5-A or PIV5-A intranasally had high endpoint titers of serum antibody against OspA antigen beyond 1 year post vaccination, similar to levels detected in mice vaccinated SC with rOspA. Flowcytometric analysis of spleen cells at 9-months post-immunization demonstrated that immunization with the intranasal PIV5 vaccine candidates led to an overall increase in the number of memory B cells, cytotoxic T and cytotoxic effector T cells compared to SC groups. Borreliacidal activity measured by neutralization assay was maintained up to 18 months post-immunization, with the response greater in intranasal PIV5-delivered OspA vaccines, than that induced by SC rOspA. Challenge with infected ticks (10-19 strains of ) performed at 4-, 9- or 15-months post-immunization showed increased breakthrough infections in mice vaccinated with SC rOspA compared to IN PIV5-A or IN PIV5-A at 9- and 15-months, as determined by qPCR of in tissues, culture of from tissues, and antibodies against protein VIsE. These data demonstrate that intranasal PIV5-based immunization is superior to parenteral immunization with the same recombinant protein and provides long-lasting protection (> 1 year) against Lyme disease.