Construction And Immunogenicity Of Virus-like Particles Displaying H5N1 Avian Influenza Virus HA Or Respiratory Syncytial Virus G Protein

H5N1 avian influenza virus (H5N1 AVI), which was first isolated from humans in Hong Kong, China, in 1997, causes highly morbidity and mortality in infected humans. Untill March 2015, the World Health Organization (WHO) had recorded 784 confirmed H5N1 cases with 429 dead, which represents over 50% case-fatality rate.Due to the high pathogenicity, lowerpropagated efficiencyin embryo and high mutanted rate of virus, it is difficult to develop vaccines against H5N1 infection by conventional approaches.Thus, it is imperative to develop novel safe arid effective vaccines against H5N1 viruses.Respiratory syncytial virus (RSV), a major respiratory pathogen, is the leading cause of severe bronchiolitis or even death in infants. To date, no RSV vaccines are available partially due to vaccine enhanced disease (VED) with conventional formalin inactivated RSV vaccines.Virus-like particles (VLPs) platforms have been identified as efficient tools for development of novel vaccines against many different viruses. In this study, two viral structure proteins, which can self-assemble into VLPs, are exploited as platforms for heterologous antigen expression for H5N1 AIV and RSV.Firstly, wild-type (wt) WhNVc protein and its tructed mutants, WhNvc?N and WhNvc?NC, were expressed in E. coli BL21 (DE3), respectively. After purification via Ni+-affinity chromatography, the purified proteins were renatured in vitro. TEM observation suggested that both WhNvc?N and WhNvc?NC protein could efficiently self-assemble into VLPs compared with the wt WhNVc.Secondly, the chimeric protein WhNvc?NC-HAe (which contained the HAlaa47-301 of A/VN/1194/H5N1) and WhNvc?NC-HA2 (which contained the HA2aal-130 of A/VN/1194/H5N1) were expressed in E coli BL21 (DE3) and purified by Ni+-affinity chromatography.TEM observation suggested that both of the two chimeric proteins could efficiently self-assemble into VLPs, respectively and ELISA analysis showed that both of the chimeric VLPs had specific antibody-binding activity in vitro.Thirdly, the immugenictiy and protective efficiency of the chimeric VLPs WhNvc?NC-HAe and WhNvcANC-HA2 were investigated respectively in a mouse model. Both of the two chimeric VLPs could elicit high levels of HA-specific antibodies and potent cellular immune response. The WhNvc?NC-HAe VLPs could completely protected mice from homologous H5N1 AIV leathal challgene, and the WhNvc?NC-HA2 VLPs could provide cross protection against the heterologous A/Hubei/489/H5Nl infection.Fourthly, a chimeric HBc?-tG protein, which contained the tructed Hepatitis B virus core protein (HBcA, aal-149) and the fragment of RSV G (aal44-204) was expressed in E coli. And a second chimeric HBc?-tG/M2 protein with a CTL epitope of RSV M2 (aa82-90) fused to HBc?-tG was also prepared. Both chimeric proteins could efficiently self-assemble into VLPs.Finally, the potential of the two VLPs (HBc?-tG and HBc?-tG/M2) were evaluated in a mouse model. The results suggested that both chimeric VLPs elicited high levels of RSV-specific antibodies and cellular immune responses. Sera antibody isotype (IgG2a/IgGl) and cytokines profile of immunized mice suggested that HBc?-tG VLPs stimulated a Thl/Th2 mixed but Th2-biased immune response and led to lung tissue pathology damage after RSV challenge. HBc?-tG/M2 VLPs induced a Thl-like predominated response and protedted mice from RSV challenge without enhanced lung pathology.Our results provide bases for the development of novel VLPs vaccines against H5N1 AIV and RSV.