Adjuvant effects of a sequence-engineered mRNA vaccine: translational profiling demonstrates similar human and murine innate response

Abstract

BackgroundProphylactic and therapeutic vaccines often depend upon a strong activation of the innate immune system to drive a potent adaptive immune response, often mediated by a strong adjuvant. For a number of adjuvants immunological readouts may not be consistent across species.MethodsIn this study, we evaluated the innate immunostimulatory potential of mRNA vaccines in both humans and mice, using a novel mRNA-based vaccine encoding influenza A hemagglutinin of the pandemic strain H1N1pdm09 as a model. This evaluation was performed using an in vitro model of human innate immunity and in vivo in mice after intradermal injection.ResultsResults suggest that immunostimulation from the mRNA vaccine in humans is similar to that in mice and acts through cellular RNA sensors, with genes for RLRs [ddx58 (RIG-1) and ifih1 (MDA-5)], TLRs (tlr3, tlr7, and tlr8-human only), and CLRs (clec4gp1, clec2d, cledl1) all significantly up-regulated by the mRNA vaccine. The up-regulation of TLR8 and TLR7 points to the involvement of both mDCs and pDCs in the response to the mRNA vaccine in humans. In both humans and mice activation of these pathways drove maturation and activation of immune cells as well as production of cytokines and chemokines known to attract and activate key players of the innate and adaptive immune system.ConclusionThis translational approach not only allowed for identification of the basic mechanisms of self-adjuvantation from the mRNA vaccine but also for comparison of the response across species, a response that appears relatively conserved or at least convergent between the in vitro human and in vivo mouse models.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-1111-6) contains supplementary material, which is available to authorized users.

mRNA vaccines — a new era in vaccinology

“…For example, the RNActive (CureVac AG) vaccine platform 52,53 depends on its carrier to provide adjuvant activity. In this case, the antigen is expressed from a naked, unmodified, sequence-optimized mRNA, while the adjuvant activity is provided by co-delivered RNA complexed with protamine (a polycationic peptide), which acts via TLR7 signalling 52,54 . This vaccine format has elicited favourable immune responses in multiple preclinical animal studies for vaccination against cancer and infectious diseases 18,36,55,56 .…”

“…This vaccine format has elicited favourable immune responses in multiple preclinical animal studies for vaccination against cancer and infectious diseases 18,36,55,56 . A recent study provided mechanistic information on the adjuvanticity of RNActive vaccines in mice in vivo and human cells in vitro 54 . Potent activation of TLR7 (mouse and human) and TLR8 (human) and production of type I interferon, pro-inflammatory cytokines and chemokines after intradermal immunization was shown 54 .…”

“…A recent study provided mechanistic information on the adjuvanticity of RNActive vaccines in mice in vivo and human cells in vitro 54 . Potent activation of TLR7 (mouse and human) and TLR8 (human) and production of type I interferon, pro-inflammatory cytokines and chemokines after intradermal immunization was shown 54 . A similar adjuvant activity was also demonstrated in the context of non-mRNA-based vaccines using RNAdjuvant (CureVac AG), an unmodified, single-stranded RNA stabilized by a cationic carrier peptide 57 .…”

“…Potential safety concerns that are likely to be evaluated in future preclinical and clinical studies include local and systemic inflammation, the biodistribution and persistence of expressed immunogen, stimulation of auto-reactive antibodies and potential toxic effects of any non-native nucleotides and delivery system components. A possible concern could be that some mRNA-based vaccine platforms 54,166 induce potent type I interferon responses, which have been associated not only with inflammation but also potentially with autoimmunity 167,168 . Thus, identification of individuals at an increased risk of autoimmune reactions before mRNA vaccination may allow reasonable precautions to be taken.…”

Expression kinetics and innate immune response after electroporation and lipid nanoparticle mediated delivery of a self-amplifying mRNA in the skin of mice

“…Indeed, if the innate immune response has not faded away at the moment of the next mRNA injection a chronical inflammatory condition will be established. The duration of the innate immune response after in vivo delivery of mRNA is not well studied and most information comes from studies that used RT-PCR or ELISA to quantify key innate immune proteins [22][23][24]. Although RT-PCR is a very sensitive technique, the correlation between mRNA levels and protein expression are not always linear [25].…”