The Viromer® IN VIVO mRNA transfection reagents enable effective delivery of messenger RNA (mRNA) through various routes, i.e. systemic or local applications, thus facilitating targeted protein expression in living model animals. These reagents are available as lyophilized material that simply needs to be rehydrated with the mRNA of interest in solution before injection.
As shown with cells in culture, mRNA provides a very productive template for translation and significantly increases the transfection efficiency of the Viromer® reagents compared to plasmid DNA. That is true for most of cells but it presents a particular interest for specific cells poorly transfectable with plasmid: e.g. mononuclear phagocytes with strong DNase activity, primary cells with low division rates, and highly specialized cells (neurons, skeletal muscle cells). This improvement is also related to current modified mRNA chemistries that have solved much of the instability associated with its native form and its capacity to elicit innate immune responses.
Translated to in vivo conditions, the Viromer® technology provides an incomparable protecting and delivery system for mRNA, usable in a broad range of applications such as mRNA-vaccination, study of inflammatory diseases, functional studies in immunology, oncology or metabolic research.
Upon systemic injection (e.g. into the tail vein of mice), Viromer® delivers payloads predominantly to the spleen followed by the liver, in a dose-dependent manner. It results in rapid local protein expression, supposedly by targeting resident macrophages and dendritic cells.
When formulated with Viromer®, up to 10µg Luciferase encoding mRNA are completely adsorbed in spleen. It results in the local production of 150ng protein per gram of spleen tissue 6 hours post-injection. Substantial activity is detectable as early as 2 hours post-injection and the signal can be tracked for up to 44 hours.
Figure 1: Luciferase signal 6h after a single dose of 10µg mRNA i.v.
Intravenous injections of 20 to 40µg mRNA per mouse saturate the spleen and target the liver.
Typical levels of expression are 50 and 400ng luciferase per gram of liver or spleen tissue, respectively.
Figure 2: Mice received a single dose of 40µg luciferase encoding mRNA:Viromer complexes i.v. (6h after application)
Proteins having an export sequence or signal peptide are excreted into the circulation. For instance with erythropoietin, serum levels of 60 ng EPO /mL have been measured as early as 2h after the injection of a single dose of 10µg mRNA (reaching 160 ng/mL with 30µg mRNA).
The Kit has been shown to work in all local applications tested so far. We started from intra-muscular or dermal applications and can demonstrate protein expression or subsequent vaccination results. Expression of mRNA was also achieved for lung, brain, in the peritoneum and even upon local injection within the intestine.