Combination Adjuvants to Program Durable Immunity to Respiratory Viral and Fungal Pathogens

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ABSTRACT: Respiratory infections with viruses and fungi constitute major public health problems globally. Except for influenza virus, there are no licensed vaccines against viruses or fungi. It is generally agreed that induction of T-cell memory is critical for defense against viruses and fungi in the respiratory tract. We and others have shown that induction of tissue-resident memory (TRM) CD8 and CD4 T cells and systemic migratory memory CD4 T cells are essential for protection against influenza A virus (IAV) and inhaled fungi, respectively. However, both TRM cells and systemic memory CD4 T cells undergo attrition, leading to short-lived immunity, which is especially true for TC1/TH1 cells. Therefore, induction of durable T-cell immunity poses major challenges for vaccinologists. As compared to TH1 cells, TH17 cells display sought-after attributes of stem-ness, durability and functional plasticity. We propose to tailor combination adjuvants to harness T17 programming and induce durable and protective lung TRM cells and migratory memory CD4 T cells against viruses and fungi. We find that Adjuplex, a nano-emulsion adjuvant, when combined with the TLR4 agonist glucopyranosyl lipid A (GLA), evokes antigen-specific CD8 and CD4 T-cell responses in the lung that are: (i) durable and multifaceted (TC1/TC17/TH1/TH17), and (ii) confer heterosubtypic immunity against IAV that persists >400 days. We further find that combining those adjuvants with fungal CLR ligands Blastomyces endoglucanase 2 (Bl-Eng2; Dectin-2 agonist) and b-glucan particles (Dectin-1 agonist) augments antiviral TC17/TH17/TC1/TH1 and elicits migratory memory T cells that protect against fungal pneumonia. By single-cell RNAseq, we found that our combined adjuvants induce memory antiviral and antifungal CD8 and CD4 T-cell clusters that express ICOS (Inducible T Cell Co-stimulator), the transcription factor c-Maf, and a transcriptome that fosters tissue residency, stem cell-ness and non-pathogenic T17 programming. Cyclic dinucleotides also promote T17 programming in lungs. This, we postulate that programming stem cell-like, functionally plastic, non-pathogenic TC17/TH17 memory cells with our combination adjuvants (that engage TLR-4, Dectin-1/2 and STING pathways) will foster durable protective immunity to viral and fungal pathogens in the lung. Our specific aims will test three hypotheses: Aim 1: Combination adjuvants that evoke TC17/TH17 stem cell-like functionally-plastic TRM or systemic migratory memory will engender durable immunity to respiratory viral and fungal pathogens; Aim 2: Functional plasticity of TC17/TH17 memory is important for protective immunity to viruses and fungi; Aim 3: The ICOS/c-Maf pathway is integral to establishment and/or maintenance of durable vaccine-induced protective immunity to respiratory viral and fungal infections. The proposed work is significant and of high impact because it has the potential to create a tractable adjuvant system/tool kit that will advance the formulation of vaccines: (i) targeted for mucosal or parenteral administration; (ii) designed to induce TRM or systemic T-cell memory; and (iii) tailored to elicit CD8 and CD4 T cells that protect against diverse pathogens such as viruses and fungi.