Polystyrene nanoparticles induce stronger cellular and more durable humoral immune responses against an inactivated bovine herpesvirus 1 isolate
Authors: Liu Xingbo , Xin Zhihao , Zhang Fan , zhang Luyao , Yan Hanyu , Gu Liwei , Ni Hongbo 
Published: February 2020

Abstract
The inactivated bovine herpesvirus type 1(BoHV-1) vaccines are generally safe and suitable for use in dairy and pregnant cattle, but induces weaker cellular immune responses and shorter antibody responses compared with the modified live virus vaccine. In this study, we used polystyrene (PS) nanoparticles (100 nm) as a carrier for purified inactivated broken BoHV-1 to improve cellular and humoral immune responses compared with the traditional inactivated vaccine. Mice were injected intramuscularly with the inactivated complex mixed with ISA206 adjuvant. Transmission electron microscopy showed that the PS nanoparticles displayed broken BoHV-1 on their surfaces. After validation of BoHV-1 and gB gC gD gE tegument proteins, it proved that the BoHV-conjugated PS nanoparticles induced higher-titer and more durable antibody responses. The inactivated BoHV-PS nanoparticle complex elicited neutralizing antibodies (titer ~2 6 ) in 5 weeks post-immunization in mice. The CD4/CD8 ratio was higher in mice immunized with PS nanoparticles compared with other groups. However, this ratio reached its maximum 1 week later than in mice immunized with ISA206+BoHV-1 or BoHV-1. Levels of interleukin (IL)-4, IL-6, and interferon-γ in followed similar patterns. In conclusion, this pilot study demonstrated that PS nanoparticles can adjuvant inactivated BoHV-1 vaccines, enhancing both cell-mediated immune responses and the duration of antibody responses. This study provides the foundation for a new development platform for inactivated vaccines, which can elicit potent cellular and humoral immune responses in animals and humans.The inactivated bovine herpesvirus type 1(BoHV-1) vaccines are generally safe and suitable for use in dairy and pregnant cattle, but induces weaker cellular immune responses and shorter antibody responses compared with the modified live virus vaccine. In this study, we used polystyrene (PS) nanoparticles (100 nm) as a carrier for purified inactivated broken BoHV-1 to improve cellular and humoral immune responses compared with the traditional inactivated vaccine. Mice were injected intramuscularly with the inactivated complex mixed with ISA206 adjuvant. Transmission electron microscopy showed that the PS nanoparticles displayed broken BoHV-1 on their surfaces. After validation of BoHV-1 and gB gC gD gE tegument proteins, it proved that the BoHV-conjugated PS nanoparticles induced higher-titer and more durable antibody responses. The inactivated BoHV-PS nanoparticle complex elicited neutralizing antibodies (titer ~2 6 ) in 5 weeks post-immunization in mice. The CD4/CD8 ratio was higher in mice immunized with PS nanoparticles compared with other groups. However, this ratio reached its maximum 1 week later than in mice immunized with ISA206+BoHV-1 or BoHV-1. Levels of interleukin (IL)-4, IL-6, and interferon-γ in followed similar patterns. In conclusion, this pilot study demonstrated that PS nanoparticles can adjuvant inactivated BoHV-1 vaccines, enhancing both cell-mediated immune responses and the duration of antibody responses. This study provides the foundation for a new development platform for inactivated vaccines, which can elicit potent cellular and humoral immune responses in animals and humans.