An oil-in-water nanoemulsion enhances immunogenicity of H5N1 vaccine in mice

To enhance the immunogenicity of the Influenza H5N1 vaccine, we developed an oil-in-water nanoemulsion (NE) adjuvant. NE displayed good temperature stability and maintained particle size. More importantly, it significantly enhanced IL-6 and MCP-1 production to recruit innate cells, including neutrophils, monocytes/macrophages and dendritic cells to the local environment. Furthermore, NE enhanced dendritic cell function to induce robust antigen-specific T and B cell immune responses. NE-adjuvanted H5N1 vaccine not only elicited significantly higher and long-lasting antibody responses, but also conferred enhanced protection against homologous clade 1 as well as heterologous clade 2 H5N1 virus challenge in young as well as in aged mice. The pre-existing immunity to seasonal influenza did not affect the immunogenicity of NE-adjuvanted H5N1 vaccine.

Graphical AbstractHighly pathogenic avian H5N1 influenza remains a serious public health threat. However, currently available H5N1 vaccines are poorly immunogenic and promising adjuvants are proprietary. Here, we developed an oil-in-water nanoemulsion (NE) adjuvant composed of squalene, α-Tocopherol and Tween 80. NE is stable and retained particle size at various storage temperatures for a long period of time. NE significantly enhanced the immunogenicity of H5N1 vaccine by recruiting monocytes to differentiate into dendritic cells which subsequently initiate robust antigen-specific adaptive immune responses. NE-adjuvanted H5N1 vaccine induces enhanced antibody responses and protective efficacy against both clade 1 and clade 2 H5N1 viruses.175