Identification of Linear Peptide Immunogens with Verified Broad-spectrum Immunogenicity from the Conserved Regions within the Hemagglutinin Stem Domain of H1N1 Influenza Virus.

BACKGROUND

Influenza A viruses (IAVs) induce acute respiratory disease and cause severe epidemics and pandemics. Since IAVs exhibit antigenic variation and genome reassortment, the development of broad-spectrum influenza vaccines is crucial. The stem of the hemagglutinin (HA) is highly conserved across IAV strains and thus has been explored in broad-spectrum influenza vaccine studies. The present study aimed to identify viral epitopes capable of eliciting effective host immune responses, which can be explored for the development of broad-spectrum non-strain specific prophylactic options against IAV.

METHODS

In this study, a series of conserved linear sequences from the HA stem of IAV (H1N1) was recognized by sequence alignment and B/T-cell epitope prediction after being chemically coupled to the Keyhole Limpet Hemocyanin (KLH) protein. The predicted linear epitopes were identified by enzyme-linked immunosorbent assay (ELISA) after animal immunization and then fused with ferritin carriers.

RESULTS

Three predicted linear epitopes with relatively strong immunogenicity, P3, P6 and P8 were fused with ferritin carriers P3F, P6F and P8F, respectively to further improve their immunogenicity. Antibody titre of the sera of mice immunized with the recombinant immunogens revealed the elicitation of specific antibody-binding activities by the identified sequences. While hemagglutinin-inhibition activities were not detected in the antisera, neutralizing antibodies against the H1 and H3 virus subtypes were detected by the microneutralization assay.

CONCLUSION

The linear epitopes fused with ferritin identified in this study can lay the foundation for future advancements in development of broad-spectrum subunit vaccine against IAV (H1N1), and give rise to the potential future applicability of ferritin-based antigen delivery nanoplatforms.