A combination TLR7/8 and RIG-I agonist adjuvant reverts asthmatic allergic sensitization and prevents aggravated influenza infection in OVA-sensitized mice

Allergen-specific immunotherapy (AIT) is the only disease-modifying treatment currently available to treat allergy. However, it has limitations, as most allergens are poorly immunogenic, resulting in an AIT process that can take years. Therefore, adjuvant selection becomes critical to achieve a more efficacious therapy. Our group has developed and tested an amphiphilic TLR7/8 agonist (IMDQ) and a RIG-I agonist (SDI) that used alone, or in combination, have demonstrated strong adjuvant activity for influenza and SARS-CoV-2 vaccines in preclinical models. Here we describe the effect of these adjuvants in the sensitization of preclinical models with the ovalbumin (OVA) asthmatic allergic model via an in-depth humoral and cellular immune profiling. We assess their immune skewing and tolerance inducing capacities in previously sensitized preclinical models with different genetic backgrounds (C57BL/6 vs. BALB/c mice). Moreover, we evaluate their effect in an unrelated antigenic challenge with influenza. Finally, we investigate the role of IgG subclasses and T-cell subpopulations in the protection against OVA challenge conferred by the combination of IMDQ and SDI. We demonstrate that OVA-immunization in combination with IMDQ+SDI prevents allergic sensitization via the induction of a balanced Type 1/Type 2 response. Furthermore, it can revert the allergic phenotype in mice previously sensitized with OVA-Alum, through reducing lung eosinophilia, as well as IL-4 and IL-5 production. However, this was dependent on genetic background. IMDQ+SDI sensitization also led to reduced morbidity of a secondary influenza challenge in OVA-sensitized mice. Finally, we demonstrated that IgG2c, by itself, cannot protect from allergic sensitization and that both CD4 ⁺ and CD8 ⁺ T-cells are needed for IMDQ+SDI prevention of eosinophil recruitment and activation upon intranasal OVA-challenge.