H1n1pdm09 Influenza Virus And Its Descendants Lack Extra-Epitopic Amino Acid Residues Associated With Reduced Recognition By M1(58-66)-Specific Cd8(+) T Cells

Extra-epitopic amino acid residues affect recognition of human influenza A viruses (IAVs) by CD8(+) T-lymphocytes (CTLs) specific for the highly conserved HLA-A*0201 restricted M M1(58-66) epitope located in the matrix 1 (M1) protein. These residues are absent in the M1 protein of the 2009-pandemic IAV (H1N1pdm09). Consequently, stimulation with M1 protein of H1N1pdm09 IAV resulted in stronger activation and lytic activity of M1(58-66)-specific CTLs than stimulation with seasonal H3N2 IAVs. During > 6 years of circulation in the human population, descendants of the H1N1pdm09 virus had accumulated 4 other amino acid substitutions. However, these did not affect M1(58-66)-specific CTL activation.