ALiCE beyond the cell: a plant-based cell-free protein synthesis system for pandemic preparedness

The significance of recombinant protein production has increased greatly over the years given the relevance of countless proteins in medical and industrial applications. One such case are protein-based vaccines. The recent global pandemic caused by SARS-CoV-2 has revealed the susceptibility of humanity to new and re-emerging diseases. Despite of the scientific and commercial endeavour in rapidly developing and releasing a safe and effective vaccine against SARS-Cov2, the first vaccines were available only after one year of the discovery of the virus. Therefore, the capability of vaccines to prevent the spread, morbidity and mortality of SARS-CoV-2 was hindered. Additionally, with the rise of new viral variants the fear of vaccines becoming less effective could become a reality. A niche thus exists for versatile vaccine and therapeutic production platforms capable of rapidly adapting to the ever-changing pathogenic threat.
Cell-Free Protein Synthesis (CFPS) systems could serve as promising platforms for pandemic preparedness. In contrast to traditional recombinant expression platforms, CFPS systems use cell-lysates that include all the elements required for protein production (ribosomes, DNA, amino acids etc.). Protein production can thus occur without the constraints of maintaining live cells and without the natural barrier of cellular walls and membranes, which in turn provides CFPS systems with several advantages: CFPS reactions can be readily optimized, altering the reaction substrates and parameters at will whilst having rapid synthesis and simple protein purification processes. The supplementation with, or production of toxic substances is plausible. CFPS systems lack the tedious process of selecting cell clones with the highest protein yield, making them directly applicable once a new protein sequence is discovered. Moreover, gene cloning is simplified, due to the possibility of using PCR amplicons as template for the synthesis reactions, thus accelerating the process from sequence discovery to protein production. The open reaction conditions also allow to parallelize the production of different variants to rapidly find the most effective vaccine or therapeutic candidates.
The Almost Living Cell-free Expression (ALiCE®) system is an emerging eukaryotic CFPS platform that has shown increased potential compared to many other CFPS systems given its high recombinant protein yields, production of complex proteins and post-translational modifications. Furthermore, the production of the ALiCE lysate is faster and simpler than other eukaryotic CFPS. More importantly, the ALiCE synthesis reaction has shown potential to be scaled-up far beyond any other eukaryotic CFPS, which is a requirement of the utmost importance to rapidly produce any putative vaccine or therapeutic in the event of a new/re-emerging pandemic. Given these characteristics, ALiCE poses as one of the most promising CFPS systems to serve as a platform for pandemic preparedness.
In my PhD project, the ALiCE CFPS system will be explored to produce a variety of vaccine candidates alongside therapeutics, including peptides and antibodies. Special focus will be put into creating a versatile system capable of delivering rapid solutions to new or re-emerging diseases.