Poster Presentation 8th Australasian Virology Society Meeting and 11th Annual Meeting of the Australian Centre for Hepatitis & HIV Virology Meeting 2015

Pre- versus Post-fusion: The effect of protein conformation on the induction of a neutralising antibody response to the influenza hemagglutinin (#167)

Christopher McMillan 1 , Keith Chappell 2 , Daniel Watterson 2 , Paul R Young 2
  1. School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD, Australia
  2. Australian Infectious Disease Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia

Despite our best efforts to vaccinate against influenza viruses, they remain a major cause of morbidity and mortality worldwide, causing millions of severe infections and resulting in more than 250,000 deaths annually. Due to continual antigenic change between circulating strains, vaccinations against influenza virus must be updated and readministered annually to provide protection against the predominant circulating strains. This approach is time-consuming, labour-intensive, costly and predictions of circulating strains are not always accurate, resulting in delays in vaccine release that do not always afford effective protection. Recent discoveries of broadly neutralising antibodies directed against the highly conserved stem region of the influenza hemagglutinin protein (HA) suggest this is a promising target for a universal influenza vaccine. Here, we present our studies using a novel approach to stabilise the HA in its native, trimeric pre-fusion conformation by the addition of a stabilisation clamp to the membrane-proximal region of the HA ectodomain. This stabilisation constrains HA into a conformation that exposes the conserved stem region, which is otherwise hidden by the adoption of rosette-like, post-fusion structures likely to predominate in current subunit influenza vaccines. Correct conformation of the trimeric pre-fusion structure of the stabilised HA protein was confirmed by interaction with pre-fusion specific monoclonal antibodies FI6v3, CR6261 and CR8043, with unstabilised proteins showing no reactivity. Size-exclusion chromatography revealed the stabilised HA protein exists as a soluble trimer, whereas unstabilised proteins form high molecular weight oligomers. Vaccination studies are currently underway in mice to compare the immune response to influenza HA in its pre- and post-fusion conformation. Mouse sera will be assessed for neutralisation of H1N1 and H3N2 virus in vitro, thereby allowing us to determine the effect of protein conformation on the induction of a broadly cross-protective immune response.