Establishing Preferred Product Characterization for the Evaluation of RNA Vaccine Antigens

Abstract

The preferred product characteristics (for chemistry, control, and manufacture), in addition to safety and efficacy, are quintessential requirements for any successful therapeutic. Messenger RNA vaccines constitute a relatively new alternative to traditional vaccine development platforms, and thus there is less clarity regarding the criteria needed to ensure regulatory compliance and acceptance. Generally, to identify the ideal product characteristics, a series of assays needs to be developed, qualified and ultimately validated to determine the integrity, purity, stability, and reproducibility of a vaccine target. Here, using the available literature, we provide a summary of the array of biophysical and biochemical assays currently used in the field to characterize mRNA vaccine antigen candidates. Moreover, we review various in vitro functional cell-based assays that have been employed to facilitate the early assessment of the biological activity of these molecules, including the predictive immune response triggered in the host cell. Messenger RNA vaccines can be produced rapidly and at large scale, and thus will particularly benefit from well-defined and well-characterized assays ultimately to be used for in-process, release and stability-indications, which will allow equally rapid screening of immunogenicity, efficacy, and safety without the need to conduct often lengthy and costly in vivo experiments.

Keywords: antigen presenting cells; capping; dendritic cells; product characteristics; therapeutics.

Figure 1

Tools for the quality control and cell-based functional evaluation of mRNA vaccine antigens.

Figure 2

Comparison between in vitro, ex vivo, and in vivo approaches to mRNA vaccine evaluation in terms of cost and time. mRNA monitoring: Green—mRNA transfection and translation can be monitored by flow cytometry and western blotting. Red—no easy tracking possible. #—Number of cells available. PBMC—Peripheral Blood Monocytes Cells, BMDC—Bone-Marrow Derived Cells, NHP—Non-human Primates.