mRNA-based prime-and-pull vaccination combines benefits of subcutaneous and mucosal BCG vaccination

Pulmonary vaccination has been proposed as a strategy to improve protection against tuberculosis, due to the generation of immune cells that more efficiently survey and eliminate infected cells within the lung. However, uncontrolled replication and excessive inflammation associated with mucosal delivery of live-attenuated vaccines highlight the need for alternative strategies that balance efficacy and safety. Here, we describe a prime-and-pull vaccination approach in which systemic immunity is established by subcutaneous BCG vaccination, followed by the induction of local lung immunity through mucosal delivery of lipid nanoparticle-formulated multi-antigen mRNA. Proof-of-concept studies using a model antigen demonstrated the induction of polyfunctional antigen-specific T cells in the lung with minimal inflammatory cell infiltration, compared with mucosal BCG vaccination. Eight Mycobacterium tuberculosis- and BCG-derived proteins were subsequently selected to generate four multi-antigen mRNA constructs. In vivo vaccination and challenge experiments demonstrated that this prime-and-pull strategy is well tolerated and confers protective immunity against tuberculosis in a murine model. Collectively, these data support a modular mRNA-based prime-and-pull vaccination strategy as a translational approach that bridges the improved immunogenicity and efficacy of mucosal BCG vaccination with the safety profile of parenteral BCG administration. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/739464v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@c0635borg.highwire.dtl.DTLVardef@bb0357org.highwire.dtl.DTLVardef@1d87243org.highwire.dtl.DTLVardef@135bcd7_HPS_FORMAT_FIGEXP M_FIG C_FIG