Genetic and subunit vaccines based on the stem domain of the equine influenza hemagglutinin provide homosubtypic protection against heterologous strains.

The study investigates the effectiveness of new genetic and subunit influenza virus vaccines made from recombinant proteins, aimed at increasing the immunogenic response to heterologous strains of equine influenza.

Research Context

• Equine influenza, caused by H3N8 strains of the influenza virus, is a global issue that affects horse populations.
• While current vaccines trigger a humoral immune response, they have shown poor effectiveness against different, non-matching strains.

Research Focus

• The researchers have developed a novel recombinant protein vaccine (ΔHAp) and a genetic vaccine (ΔHAe), focusing on the conserved stem region of the influenza virus’ hemagglutinin (HA), which is responsible for virus infection in host cells.
• The H3N8 virus is the source of these vaccines’ HA stems.

Research Methodology

• The team administered the developed immunogens to mice in unique combinations and regimes.
• The mice’s serum was analyzed for reactivity against numerous, vastly divergent strains of the influenza virus, part of either phylogenetic group 1 (H1 subtype) or group 2 (H3 subtype).

Key Findings

• The vaccines provided strong 100% protection against the matching equine strain and 70-100% protection against the homosubtypic human strain A/Victoria/3/75 (H3N2).
• However, animals vaccinated with the same vaccines but exposed to the human strain A/PR/8/34 (H1N1), from phylogenetic group 1, did not show significant protection (0-33%).
• A combination of protein and DNA immunogens showed higher reactivity against non-matching strains compared to protein alone though all vaccines allowed for lung infection.

Research Implications

• This study’s findings demonstrate that the newly developed vaccines could provide a more significant immune response against various equine influenza virus strains, potentially overcoming the limited effectiveness of existing vaccines that are poorly inducing of cross-reactive antibodies.
• Despite these promising results, it is worth noting that the vaccines were unable to significantly protect against all strains, indicating room for further improvements and research.