Trimeric, APC-Targeted Subunit Vaccines Protect Mice against Seasonal and Pandemic Influenza

J Virol. 2023 Feb 28;97(2):e0169422. doi: 10.1128/jvi.01694-22. Epub 2023 Jan 31.


Viral subunit vaccines contain the specific antigen deemed most important for development of protective immune responses. Typically, the chosen antigen is a surface protein involved in cellular entry of the virus, and neutralizing antibodies may prevent this. For influenza, hemagglutinin (HA) is thus a preferred antigen. However, the natural trimeric form of HA is often not considered during subunit vaccine development. Here, we have designed a vaccine format that maintains the trimeric HA conformation while targeting antigen toward major histocompatibility complex class II (MHCII) molecules or chemokine receptors on antigen-presenting cells (APC) for enhanced immunogenicity. Results demonstrated that a single DNA vaccination induced strong antibody and T-cell responses in mice. Importantly, a single DNA vaccination also protected mice from lethal challenges with influenza viruses H1N1 and H5N1. To further evaluate the versatility of the format, we developed MHCII-targeted HA from influenza A/California/04/2009(H1N1) as a protein vaccine and benchmarked this against Pandemrix and Flublok. These vaccine formats are different, but similar immune responses obtained with lower vaccine doses indicated that the MHCII-targeted subunit vaccine has an immunogenicity and efficacy that warrants progression to larger animals and humans. IMPORTANCE Subunit vaccines present only selected viral proteins to the immune system and allow for safe and easy production. Here, we have developed a novel vaccine where influenza hemagglutinin is presented in the natural trimeric form and then steered toward antigen-presenting cells for increased immunogenicity. We demonstrate efficient induction of antibodies and T-cell responses, and demonstrate that the vaccine format can protect mice against influenza subtypes H1N1, H5N1, and H7N1.

Keywords: DNA vaccines; adaptive immunity; influenza; influenza vaccines; subunit vaccine.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibodies, Viral
  • Antigen-Presenting Cells / immunology
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • Influenza A Virus, H1N1 Subtype
  • Influenza A Virus, H5N1 Subtype
  • Influenza A Virus, H7N1 Subtype
  • Influenza Vaccines* / immunology
  • Mice
  • Mice, Inbred BALB C
  • Orthomyxoviridae Infections* / prevention & control
  • Seasons
  • T-Lymphocytes / immunology
  • Vaccines, DNA / immunology
  • Vaccines, Subunit / immunology


  • Antibodies, Viral
  • Hemagglutinin Glycoproteins, Influenza Virus
  • Influenza Vaccines
  • Vaccines, Subunit
  • Vaccines, DNA