The delivery of genetic information has emerged as a valid therapeutic approach. Various reports have demonstrated that mRNA, besides its remarkable potential as vaccine, can also promote expression without inducing an adverse immune response against the encoded protein. In the current study, we set out to explore whether our technology based on chemically unmodified mRNA is suitable for passive immunization. To this end, various antibodies using different designs were expressed and characterized in vitro and in vivo in the fields of viral infections, toxin exposure, and cancer immunotherapies. Single injections of mRNA–lipid nanoparticle (LNP) were sufficient to establish rapid, strong, and long‐lasting serum antibody titers in vivo, thereby enabling both prophylactic and therapeutic protection against lethal rabies infection or botulinum intoxication. Moreover, therapeutic mRNA‐mediated antibody expression allowed mice to survive an otherwise lethal tumor challenge. In conclusion, the present study demonstrates the utility of formulated mRNA as a potent novel technology for passive immunization.

While active immunization elicits a lasting immune response by the body, passive immunotherapy transiently equips the body with exogenously generated immunological effectors in the form of either target-specific antibodies or lymphocytes functionalized with target-specific receptors. In either case, administration or expression of recombinant proteins plays a fundamental role. mRNA prepared by in vitro transcription (IVT) is increasingly appreciated as a drug substance for delivery of recombinant proteins. With its biological role as transient carrier of genetic information translated into protein in the cytoplasm, therapeutic application of mRNA combines several advantages. For example, compared to transfected DNA, mRNA harbors inherent safety features. It is not associated with the risk of inducing genomic changes and potential adverse effects are only temporary due to its transient nature. Compared to the administration of recombinant proteins produced in bioreactors, mRNA allows supplying proteins that are difficult to manufacture and offers extended pharmacokinetics for short-lived proteins. Based on great progress in understanding and manipulating mRNA properties, efficacy data in various models have now demonstrated that IVT mRNA constitutes a potent and flexible platform technology. Starting with an introduction into passive immunotherapy, this review summarizes the current status of IVT mRNA technology and its application to such immunological interventions.

No abstract

SUMMARYPost-transcriptional gene silencing often limits the over-expression of transgenes in transgenic plants. It involves RNA-DEPENDENT RNA POLYMERASE 6 (RDR6), which recognizes aberrant transcripts, such as inaccurately processed or uncapped mRNA, and triggers silencing of target transcripts. Here, we describe the isolation and characterization of an Arabidopsis mutant displaying increased transgene silencing (its1). Reduced accumulation of transgene mRNA in the its1 mutant background was accompanied by accumulation of transgene-specific siRNAs and was overcome by potyvirus infection. We therefore speculated that ITS1 is a suppressor of post-transcriptional gene silencing. Map-based cloning and subsequent complementation revealed that ITS1 encodes DECAPPING 2 (DCP2), which is crucial for decapping, a prerequisite for mRNA degradation. In agreement with the proposed function of DCP2, we found a reduced accumulation of uncapped mRNA in the its1 mutant. Furthermore, silencing in the its1 mutant was dependent on RDR6 function, suggesting that reduced decapping leads to accumulation of aberrant capped mRNA. Hence, we provide evidence for a class of aberrant mRNA that accumulates upon impaired mRNA decapping and triggers posttranscriptional gene silencing in Arabidopsis. As DCP2 knockouts cause post-embryo lethality, we isolated a hypomorphic dcp2 allele, providing insights into mRNA degradation and its interplay with post-transcriptional gene silencing.

The ongoing SARS-CoV-2 pandemic necessitates the fast development of vaccines. Recently, viral mutants termed variants of concern (VOC) which may escape host immunity have emerged. The efficacy of spike encoding mRNA vaccines (CVnCoV and CV2CoV) against the ancestral strain and the VOC B.1.351 was tested in a K18-hACE2 transgenic mouse model. Naive mice and mice immunized with a formalin-inactivated SARS-CoV-2 preparation were used as controls. mRNA-immunized mice develop elevated SARS-CoV-2 RBD-specific antibody and neutralization titers which are readily detectable, but significantly reduced against VOC B.1.351. The mRNA vaccines fully protect from disease and mortality caused by either viral strain. SARS-CoV-2 remains undetected in swabs, lung, or brain in these groups. Despite lower neutralizing antibody titers compared to the ancestral strain BavPat1, CVnCoV and CV2CoV show complete disease protection against the novel VOC B.1.351 in our studies.