Durable and broad airway immunity through next-generation intranasal boosters

PROJECT SUMMARY Intramuscular SARS-CoV-2 mRNA-LNP do not reliably nor durably elicit respiratory mucosal IgA. Moreover, vaccinated individuals who become infected are more durably protected and this is thought to be mediated by respiratory mucosal IgA. Currently, there are no mucosal respiratory vaccines for human use. We identified a mucosal booster vaccine admixed with a mast cell agonist adjuvant, mastoparan-7, and a toll-like receptor 9 agonist adjuvant, CpG, that elicits durable mucosal IgA. Importantly, mice intranasally boosted with a multivalent nanoparticle vaccine adjuvanted with mastoparan-7 and CpG are protected from bat SARS-like virus challenge. We propose to study the mechanism of mast cell and antigen-presenting cell signaling modulated by this novel mucosal adjuvant combination. We will pursue our central objective which is to understand how mucosal IgA is elicited and maintained following respiratory mucosal vaccination with our exciting universal vaccines to ultimately achieve durable and broadly protective immunity against zoonotic coronaviruses. To achieve this objective, we will complete these aims: Aim 1: Test the hypothesis that mast cells and antigen-presenting cells elicit specific cytokines and chemokines that modulate durable IgA. We propose to study the impact of intranasal boost dose and interval on IgA kinetics and durability. We will also define if the mastoparan-7 and CpG adjuvant combination requires mast cell and antigen presenting cells that signal through CpG via the TLR-9 pathway. We will then define gene expression profiles from respiratory tract mast cells and antigen presenting cells that are activated by mastoparan-7 and CpG and modulate durable mucosal IgA responses. Aim 2: Test the hypothesis that M7/CpG nanoparticle vaccine elicits durable IgA secreting cells and IgA memory B cells in the respiratory tract using lineage-tracing, fluorescent reporter mice pre- immune with common-cold CoV. We will determine how intranasal boosting modulates IgA-secreting plasma cells and IgA memory B cells that home back to the respiratory mucosa in SARS-CoV-2 immune mice and in mice immune against common-cold coronaviruses. We will use cre-lox inducible, IgA-secreting cell and IgA memory B cell fluorescent reporter mice to define how intranasal boosting modulates mucosal IgA immunity. We will also test adjuvant and intranasal safety using a human lymph node organoid model from upper- respiratory tract draining lymph tissue from humans. Aim 3: Test the hypothesis that durable mucosal IgA can protect against transmissible SARS-CoV-2 variants in hamster transmission models and protect against SARS-related coronaviruses. We will determine if the mastoparan-7 and CpG adjuvanted nanoparticle intranasal booster reduces transmission of SARS-CoV-2 variants in hamster models. We will also use IgA knockout mice to determine if IgA is required for protection against SARS-like viruses.