Recombinant nucleic acids – DNA or RNA – and their manipulation and manufacturing are the starting point of many research and development projects. DNA or RNA largely serve to express foreign genes in cells or organisms, either permanently or temporarily. This function of nucleic acids is thereby referred to as vectors, shuttling genes into cells. At TRON the units VECTORS, CLONING and GENE TRANSFER cover the complete workflow from the initial design of a specific vector, the molecular cloning to the transfer into cells. All state-of-the-art technologies are available to colleagues within TRON and to external partners and customers.
The VECTORS Unit has been focusing for on self-amplifying RNA (saRNA) vectors. saRNA is engineered from the genomes of plus-stranded RNA viruses (mostly alphaviruses), as these naturally resemble messenger RNA. As such saRNAs are capped and poly-adenylated leading to efficient translation once they enter the cell cytoplasm. In addition to the transgene, saRNA encodes the enzymatic machinery of the parental virus that serves to replicate the transfected RNA, thus ‘self-amplifying’ the RNA. This process leads to very high expression from very low starting amounts of RNA, making it an attractive vector for vaccines.
The VECTORS unit at TRON aims to advance the saRNA platform by introducing new properties, or using unusual formats as a vaccine. These efforts have led to what we called trans-amplifying RNA (taRNA), our proprietary vector platform that joins a non-replicating replicating mRNA to a replicating RNA.
Achieving uniformly efficient gene transfer to a wide variety of target cells is challenging. For this reason, the Gene Transfer unit works with a modular set of tools comprising specialized vector backbones, various envelope proteins and optimized protocols. This unit’s key expertise is on retroviral gene transfer within a spectrum of expanding methods which includes transposons and CRISPR vectors.
The cloning of target genes into various vector backbones is often essential for the validation of these genes as possible targets, e.g. in cancer therapy. The Cloning Unit performs state-of-the-art cloning from the development of a suitable cloning strategy to the delivery of purified, quality-controlled plasmid DNA in different scales. Additionally, linearization yielding linearized, purified DNA as ready-to-use templates for RNA synthesis is available to partners and customers. All our standard methods are established as standard operating procedures (SOPs) and are implemented into our internal quality assurance system.
Tools & Platforms
- saRNA. A single very long synthetic RNA encoding replicase and the gene of interest. saRNA requires in vitro capping and poly-adenylation. Synthesis requires adaptation to the length of the RNA.
- taRNA. A split-vectors system engineered from saRNA encoding replicase on a non-amplifying mRNA, and the trangene on a short second RNA called trans-replicon. Trans-replicons require no capping, and short oligo-A tails. Trans-replicons synthesis is handy and flexible.
- Retro. 2nd generation vector derived from the retrovirus MLV, suitable for stable gene transfer into proliferating cells. Allows work under BSL-1 conditions if particles do not transduce human cells.
- Lenti. 2nd generation vector derived from the retrovirus HIV-1. Suitable for stable gene transfer into resting and proliferating cells.
Key Contributions & Publications
Beissert T, Perkovic M, Vogel A, Erbar S, Walzer KC, Hempel T, Brill S, Haefner E, Becker R, Türeci Ö, Sahin U. (2020) A Trans-amplifying RNA Vaccine Strategy for Induction of Potent Protective Immunity. Mol Ther. 28(1):119-128. PMID: 31624015
Vogel AB, Lambert L, Kinnear E, Busse D, Erbar S, Reuter KC, Wicke L, Perkovic M, Beissert T, Haas H, Reece ST, Sahin U, Tregoning JS. (2018) Self-Amplifying RNA Vaccines Give Equivalent Protection against Influenza to mRNA Vaccines but at Much Lower Doses. Mol Ther. 26(2):446-455. PMID: 29275847
Beissert T, Koste L, Perkovic M, Walzer KC, Erbar S, Selmi A, Diken M, Kreiter S, Türeci Ö, Sahin U. (2017) Improvement of In Vivo Expression of Genes Delivered by Self-Amplifying RNA Using Vaccinia Virus Immune Evasion Proteins. Hum Gene Ther. 28(12):1138-1146. PMID: 28877647