Project P12

Development of an efficient cure against a CoV-2 infection

Thomas Carell, Milda Nainyte, Franziska Traube
Department of Chemistry, LMU Munich

Cells possess innate immune systems that allow them to fight against invading pathogens like viruses. One of these processes is RNA interference (RNAi), which is a conserved sequence-specific gene silencing mechanism. The RNAi machinery allows cells to destroy invading double-stranded RNA (dsRNA) molecules, which are often of viral origin, and single-stranded RNA transcripts thereof that serve as a template for (viral) protein expression. The process requires small dsRNA molecules (siRNAs) that are complementary to the invading RNA. These small siRNA duplexes, which can be externally added to the cells, are loaded into a multicomponent nuclease, the RNA-induced silencing complex (RISC). The active complex then utilizes the sequence information of the siRNA to recognize the complementary sequence and subsequently induces an RNA cutting processes that ultimately leads to the full destruction of the invading dsRNA and its transcripts. SARS-CoV-2 possesses a single-stranded positive-sense RNA genome that is fully and partially copied during various stages of the viral life cycle. We designed and screened a large number of siRNAs against different genomic regions of SARS-CoV-2. Screening was performed with a special reporter system and in cell cultures after virus infection. Chemical modification chemistry was used to improve the stability and the cell penetrating properties of the externally added siRNA (Fig. 1). We discovered that externally added, chemically modified siRNA can indeed protect the cells from virus infection. Importantly, infected cells could be fully cured (99.97%) with our siRNAs. These promising cell culture data are currently transferred to 3D organoids and human lung tissue models. Our goal is to develop chemically modified, targetable siRNA to protect lung tissue from a CoV-2 infection and to cure an existing CoV-2 infection, by training the innate RNAi immune system.

Figure 1: Depiction of an siRNA molecule together with the chemical modification unit