Broadly active intranasal influenza vaccine with a nanocomplex particulate adjuvant targeting mast cells and toll-like receptor 9.

Flumist is the only FDA-approved intranasal influenza vaccine. Although it has recently been approved for at-home use, it has significant limitations. These include reduced effectiveness in generating a protective immune response in patients with extensive influenza exposure, safety concerns due to its live attenuated virus formulation, and reduced efficacy due to viral drift/shift. To address this limitation, we have developed a nanocomplex comprised of a mast cell (MC) agonist and toll-like receptor 9 (TLR9) ligand to adjuvant a broadly acting influenza antigen. The newly reported MC agonist was identified by screening mastoparan-7 analogs for MC degranulation activity, which led to a more active peptide analog, MP12W. Positively charged MP12W spontaneously forms nanoparticulate complexes (NPs) with CpG 1826 that were then used to intranasally vaccinate mice with a computationally optimized broadly reactive antigen (COBRA) hemagglutinin (HA) protein. The NPs were further optimized by substituting CpG 1826 with CpG 55.2, a TLR-9 agonist identified by machine learning to be more active in humans. MP12W-CpG 1826 NPs showed an increased pro-inflammatory response and decreased cytotoxicity in vitro compared to M7 complexes, translating into a safer profile in a model of increased hypersensitivity, collaborative cross mice 027 (CC027). Intranasal vaccination with this complex and broadly reactive HA resulted in higher mucosal antibody concentration and increased cytokine production with antigen recall. These responses were enhanced with MP12W-CpG 55.2 NP vaccination. MP12W-CpG NPs provided similar protection in an influenza challenge model. This study demonstrates the potential of this novel intranasal nanocomplex for vaccination.