Vladimir Perkov, a Scientist at Sanofi, has led the development of a bioimaging lab at Sanofi. He focused on imaging mRNA vaccines after delivery. Drawing on his bioimaging expertise, he used techniques such as bioluminescence and fluorescence imaging in mouse models to study biodistribution and protein expression.
mRNA is important because its coding region can provide the desired antigens/ protein of interest. Once this mRNA is obtained, it will be encapsulated within an LNP (lipid nanoparticle), which acts as a delivery system. Perkov discussed finding and quantifying mRNA within cells, quantifying lipids, and the desired protein.
He presented an in vitro example that demonstrated that human skeletal muscles show high protein expression, which correlates with mRNA accumulation rather than with LNP accumulation. For instance, lipid 4 showed moderate LNP accumulation but high mRNA and protein expression.
Moving on to in vivo studies, mouse models were injected intramuscularly with mRNA encoding luciferase. Perkov used IVIS technology, which performs bioluminescence or fluorescence imaging. The IVIS system covers several routes of administration, such as intranasal, sublingual, intradermal, subcutaneous, and intramuscular.
Once the IVIS technology was used for biodistribution, particularly protein quantification, RT-qPCR was used to quantify the number of mRNA copies. MALDI MSC imaging and LC-MS revealed insights into the distribution and internalization of mRNA and lipids post-injection. Over a 28-day period, imaging was performed, and the findings suggested that peak protein expression occurred between 6 and 24 hours post-injection, with signal declining over time.
Perkov’s study observed immune cell infiltration at the injection site and the formation of germinal centres in lymph nodes, indicating the immune response triggered by the mRNA vaccine. Future steps include phenotyping immune cells and understanding mRNA internalisation.
The take-home message from Perkov was that biodistribution studies are essential for predicting safety and efficacy. He also mentioned that immune cell infiltration and lymph node activity were observed, with further work planned to phenotype these cells.
