Anti-Human IAV H3N2 chimeric monoclonal antibody, clone Ms3C8

Author summary Annual influenza infections cause significant morbidity and morbidity globally. Established T-cell immunity directed at conserved viral regions provides some protection against influenza viruses and promotes rapid recovery, leading to better clinical outcomes. Killer CD8(+)T-cells recognising viral peptides in a context of HLA-I glycoproteins, provide the broadest ever reported immunity across distinct influenza strains and subtypes. We asked whether the expression of certain HLA-I alleles affects CD8(+)T cells responses. Our study clearly illustrates altered immunodominance hierarchies and immunodomination within broadly-cross-reactive influenza-specific CD8(+)T-cells in individuals expressing two or more universal HLA-I alleles, key for T cell-directed vaccines and immunotherapies. Seasonal influenza virus infections cause 290,000-650,000 deaths annually and severe morbidity in 3-5 million people. CD8(+)T-cell responses towards virus-derived peptide/human leukocyte antigen (HLA) complexes provide the broadest cross-reactive immunity against human influenza viruses. Several universally-conserved CD8(+)T-cell specificities that elicit prominent responses against human influenza A viruses (IAVs) have been identified. These include HLA-A*02:01-M1(58-66)(A2/M1(58)), HLA-A*03:01-NP265-273, HLA-B*08:01-NP225-233, HLA-B*18:01-NP219-226, HLA-B*27:05-NP(383-391)and HLA-B*57:01-NP199-207. The immunodominance hierarchies across these universal CD8(+)T-cell epitopes were however unknown. Here, we probed immunodominance status of influenza-specific universal CD8(+)T-cells in HLA-I heterozygote individuals expressing two or more universal HLAs for IAV. We found that while CD8(+)T-cell responses directed towards A2/M1(58)were generally immunodominant, A2/M1(58)(+)CD8(+)T-cells were markedly diminished (subdominant) in HLA-A*02:01/B*27:05-expressing donors followingex vivoandin vitroanalyses. A2/M1(58)(+)CD8(+)T-cells in non-HLA-B*27:05 individuals were immunodominant, contained optimal public TRBV19/TRAV27 TCR alpha beta clonotypes and displayed highly polyfunctional and proliferative capacity, while A2/M1(58)(+)CD8(+)T cells in HLA-B*27:05-expressing donors were subdominant, with largely distinct TCR alpha beta clonotypes and consequently markedly reduced avidity, proliferative and polyfunctional efficacy. Our data illustrate altered immunodominance patterns and immunodomination within human influenza-specific CD8(+)T-cells. Accordingly, our work highlights the importance of understanding immunodominance hierarchies within individual donors across a spectrum of prominent virus-specific CD8(+)T-cell specificities prior to designing T cell-directed vaccines and immunotherapies, for influenza and other infectious diseases.

Influenza A virus (IAV) infection is a major cause of morbidity and mortality. Retinoic acid-inducible protein I (RIG-I) plays an important role in the recognition of IAV in most cell types, and leads to the activation of interferon (IFN). We investigated mechanisms of RIG-I and IFN induction by IAV in the BCi-NS1.1 immortalized human airway basal cell line and in the A549 human alveolar epithelial cell line. We found that the basal expression levels of RIG-I and regulatory transcription factor (IRF) 7 were very low in BCi-NS1.1 cells. IAV infection induced robust RIG-I and IRF7, not IRF3, expression. siRNA against IRF7 and mitochondrial antiviral-signaling protein (MAVS), but not IRF3, significantly inhibited RIG-I mRNA expression and IFN induction by IAV infection. Most importantly, even without virus infection, IFN-beta alone induced RIG-I, and siRNA against IRF7 did not inhibit RIG-I induction by IFN-beta. Similar results were found in the alveolar basal epithelial A549 cell line. RIG-I and IRF7 expression in humans is highly inducible and greatly amplified by IFN produced from virus infected cells. IFN induction can be separated into two phases, that initially induced by the virus with basal RIG-I (the first phase), and that induced by the subsequent virus with amplified RIG-I from the first phase IFN (the second phase). The de novo synthesis of IRF7 is required for the second phase IFN induction during influenza virus infection in human lung bronchial and alveolar epithelial cells.