Influenza is a highly infectious disease caused by the influenza virus. Previous research has shown that Indigenous Australians are at higher risk of developing severe cases of influenza infection than non-Indigenous Australians. In the event of a pandemic outbreak, Indigenous Australians are more likely (16%) to be hospitalised due to influenza infection than non-Indigenous Australians, despite only making up a small portion (2.5%) of the total population. The underlying immunological reason is still unclear but may be due to the distinct Human Leukocyte Antigen (HLA) profile of Indigenous Australians. The HLA type restricts the targets of anti-viral T cells, which play a critical role in the eradication of the virus.
We have focused our work on HLA-A*24:02, a dominant HLA allele in the Indigenous Australian population. In order to understand the correlation between these distinct HLA molecules and severity of influenza infection, we have identified novel HLA-A*24:02-restricted influenza-specific epitopes using immunopeptidomics and functional validation determined their structures using X-ray crystallography. Structural analyses of these HLA complexes with immunogenic epitopes provides insight into their ability to stimulate T cells.
For structural characterisation of the HLA-A*24:02-bound influenza epitopes, the HLA heavy chain and beta-2-microglobulin were produced as insoluble proteins in bacteria, solubilised and refolded with the newly identified influenza peptides. The HLA-peptide complexes were then purified, and crystallised using the Monash university crystalmation platform. The crystals were then manually optimised to obtain large, good quality diffracting crystals that were used for X-ray diffraction at the Australian Synchrotron.