Adjuvantation of a SARS-CoV-2 mRNA vaccine with controlled tissue-specific expression of an mRNA encoding IL-12p70.

Messenger RNA (mRNA) vaccines were pivotal in reducing severe acute respiratory syndrome 2 (SARS-CoV-2) infection burden, yet they have not demonstrated robust durability, especially in older adults. Here, we describe a molecular adjuvant comprising a lipid nanoparticle (LNP)-encapsulated mRNA encoding interleukin-12p70 (IL-12p70). The bioactive adjuvant was engineered with a multiorgan protection (MOP) sequence to restrict transcript expression to the intramuscular injection site. Admixing IL-12-MOP (CTX-1796) with the BNT162b2 SARS-CoV-2 vaccine increased spike protein-specific immune responses in mice. Specifically, the benefits of IL-12-MOP adjuvantation included amplified humoral and cellular immunity and increased immune durability for 1 year after vaccination in mice. An additional benefit included the restoration of immunity in aged mice to amounts comparable to those achieved in young adult animals, alongside amplification with a single immunization. Associated enhanced dendritic cell and germinal center responses were observed. Together, these data demonstrate that an LNP-encapsulated IL-12-MOP mRNA-encoded adjuvant can amplify immunogenicity independent of age, demonstrating translational potential to benefit vulnerable populations.

Shaping Neonatal Immunization by Tuning the Delivery of Synergistic Adjuvants via Nanocarriers.

Adjuvanted nanocarrier-based vaccines hold substantial potential for applications in novel early-life immunization strategies. Here, via mouse and human age-specific in vitro modeling, we identified the combination of a small-molecule STING agonist (2'3'-cyclic GMP-AMP, cGAMP) and a TLR7/8 agonist (CL075) to drive the synergistic activation of neonatal dendritic cells and precision CD4 T-helper (Th) cell expansion via the IL-12/IFNγ axis. We further demonstrate that the vaccination of neonatal mice with quadrivalent influenza recombinant hemagglutinin (rHA) and an admixture of two polymersome (PS) nanocarriers separately encapsulating cGAMP (cGAMP-PS) and CL075 (CL075-PS) drove robust Th1 bias, high frequency of T follicular helper (TFH) cells, and germinal center (GC) B cells along with the IgG2c-skewed humoral response in vivo. Dual-loaded cGAMP/CL075-PSs did not outperform admixed cGAMP-PS and CL075-PS in vivo. These data validate an optimally designed adjuvantation system via age-selected small-molecule synergy and a multicomponent nanocarrier formulation as an effective approach to induce type 1 immune responses in early life.

The mRNA vaccine BNT162b2 demonstrates impaired TH1 immunogenicity in human elders in vitro and aged mice in vivo.

mRNA vaccines have been key to addressing the SARS-CoV-2 pandemic but have impaired immunogenicity and durability in vulnerable older populations. We evaluated the mRNA vaccine BNT162b2 in human in vitro whole blood assays with supernatants from adult (18-50 years) and elder (≥60 years) participants measured by mass spectrometry and proximity extension assay proteomics. BNT162b2 induced increased expression of soluble proteins in adult blood (e.g., C1S, PSMC6, CPN1), but demonstrated reduced proteins in elder blood (e.g., TPM4, APOF, APOC2, CPN1, and PI16), including 30-85% lower induction of TH1-polarizing cytokines and chemokines (e.g., IFNγ, and CXCL10). Elder TH1 impairment was validated in mice in vivo and associated with impaired humoral and cellular immunogenicity. Our study demonstrates the utility of a human in vitro platform to model age-specific mRNA vaccine activity, highlights impaired TH1 immunogenicity in older adults, and provides rationale for developing enhanced mRNA vaccines with greater immunogenicity in vulnerable populations.