mRNA - lipid nanoparticle (LNP) vaccines developed against SARS-CoV-2 are a transformative technology and saved millions of lives during the COVID-19 pandemic. In this vaccine platform, LNPs function as both a delivery agent and a powerful adjuvant. However, the relationship between LNP composition and adjuvanticity is not fully understood, hindering future vaccine design.
In this study, we focus on the impact of the Polyethylene-glycol conjugated lipid (PEG-lipid) which is one of the four standard lipids used to make LNPs. PEG-lipids are known to give stability to nanoparticles in solution, control particle size, and impact circulation half-life. We designed mRNA-LNP vaccines that encode SARS-CoV-2 spike as a model antigen, and we modulate the amount of PEG-lipid within the LNP. A comparative vaccination study was performed using BALB/c mice.
We demonstrate that the amount of PEG-lipid used in the LNP formulation has a significant impact on humoral immune responses to mRNA-LNP vaccines in mice and can impact memory B cell responses.
These findings support the rational design of novel LNPs to create more tailored and effective mRNA vaccines against both existing and emerging infectious pathogens.
NIAID, R01AI153064
Vaccines and Immunotherapy (VAC)
Emily F. Daley, Máté Vadovics, F. Coirada et al.· Journal of Immunology· 0 citations
The modification of RNA by the incorporation of N-methyl pseudo-uridine (N1mψ) renders the mRNA less inflammatory, resulting in durable cellular and humoral responses. Interestingly, mRNA-LNP vaccines still elicit strong innate immune activation and stimulate the production of type I interferons (IFN-I) by antigen-presenting cells (APCs). IFN-I is critical in the induction of CD8 T-cell responses to mRNA vaccines; however, the mechanisms underlying this process are poorly understood.
We determined protection from lethal infection with ectromelia virus in mice with cell-specific deletion of IFNAR1, as well as in mice deficient in specific IFN-I, following vaccination with a previously described EVM158 mRNA-LNP vaccine containing an immunodominant CD8 T-cell epitope.
We demonstrate that the optimal induction of CD8 T-cells requires IFN-I signaling in multiple myeloid cell types, not just in CD8 T-cells, dendritic cells, or monocytes. We also show that at optimal vaccine doses, IFN-β- and IFN-α-deficient mice generate protective CD8 T-cell responses. However, at suboptimal doses, male mice deficient in IFN-β and in IFN-α4, which are regulated by constitutive transcription factors, do not generate completely protective CD8 T cells. Moreover, mice deficient in the NF-κB binding site in the IFN-β promoter and the transcription factor IRF7 generate poorly protective responses.
Our results indicate that optimal induction of protective CD8 T-cell responses by mRNA LNP vaccines requires IFN-I signaling in myeloid cells but not in CD8 T-cells, that IFN-β and IFN-α can individually provide the signals required for protection, and that regulation of IFN-β by NF-κB and all IFN-I subtypes by IRF is required to induce protective CD8 T-cells.
NIAID, NIH
Vaccines and Immunotherapy (VAC)
Samit Kafle, Brian Montoya, Carolina R. Melo-Silva et al.· Journal of Immunology· 0 citations
mRNA vaccines have transformed vaccinology in recent years, shortening timelines and enabling precise response to infectious diseases. One key modification that made this platform so successful is the replacement of uridine (U) with N1-methylpseudouridine (m¹ψ), which improved antigen expression and tolerability. The use of adjuvants for mRNA platforms represents a promising approach to increase immunogenicity of these vaccines, lowering the doses and offering more potent CD8+ T cell priming. However, successful adjuvant strategies remain largely undefined.
Here, we developed a novel and structurally defined double-stranded RNA (dsRNA) and evaluated its immunogenic potential to induce immune responses against infectious diseases using an mRNA encoding influenza hemagglutinin (HA) as a model. C57BL/6 mice were immunized with 3 doses of HA m¹ψ mRNA-LNP (HA-LNP) alone or in co-administered with dsRNA-LNP using intramuscular-prime/ intravenous-boost administration. Peripheral blood mononuclear cells (PBMCs) were collected after each dose and stimulated ex vivo with HA peptides for intracellular cytokine staining (ICS) or ELISpot. Sera was collected 21 days after immunization for humoral analyses.
Co-administration of HA-LNP and dsRNA-LNP induces more robust humoral responses with ∼3-fold higher specific IgG-antibody titers and increased neutralizing ability compared to HA-LNP alone. Evaluation of cellular arm showed that dsRNA-LNP potentializes the cellular immune responses with enhanced frequency of IFNγ production by CD4+ and CD8+ subsets, T cell activation (CD69+), CD8+ T cell polyfunctionality (IFNγ/TNFα), and higher cytotoxic profile (Granzyme B+/ Perforin+).
Overall, the dsRNA-LNP acts as a potent adjuvant for nucleoside-modified mRNA vaccination, inducing a strong immune activation, representing a potent platform for eliciting balanced, durable antiviral immunity.
This work was supported by the National Institute of Allergy and Infectious Disease (NIAID) and National Cancer Institute (NCI) of the US National Institutes of Health (NIH) under award numbers R01AI153064 (NP) and R01CA283736 (NP and CGR), respectively.
Vaccines and Immunotherapy (VAC)
F. Coirada, Nelson Cortes Oliveira, Emily F. Daley et al.· Journal of Immunology· 0 citations
It is demonstrated that antigenic clade-matching is likely critical for protection against H5N1 and suggest that currently stockpiled H5N1 vaccines may not protect against contemporary viruses.
E. Gary, Nicholas J. Tursi, Casey E. Hojecki et al.· Journal of Immunology· 0 citations
The V1V2 mRNA-LNP vaccine is highly immunogenic in mice and rhesus macaques, eliciting cross-clade functional antibodies capable of recognizing native Env, and may provide insights relevant to vaccine testing against other pathogens.
Catarina E. Hioe, Xiao-Mei Liu, C. Yengo et al.· Journal of Immunology· 0 citations
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