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Soap bark tree discovery could revolutionize vaccine production

In a landmark development with far-reaching implications, a recent study from the John Innes Centre has opened doors to innovative bioengineering possibilities for vaccine adjuvants. 

This breakthrough centers around the soapbark tree (Quillaja saponaria), a critical yet environmentally taxing source for vaccine ingredients.

Unveiling new potential 

The key focus of the research is QS-21, a potent adjuvant derived from the bark of the Chilean soapbark tree. Adjuvants are crucial in vaccines, enhancing the body’s immune response, and QS-21 is a prime example used in vaccines against shingles, malaria, and more. 

However, sourcing QS-21 from soapbark trees raised sustainability concerns, given the environmental impact of harvesting this natural resource.

Breakthrough in bioengineering

The team at the John Innes Centre, using the recently published genome sequence of the soapbark tree, has successfully mapped the complex sequence of genes and enzymes required to produce QS-21. 

In a pioneering effort, the experts replicated this chemical pathway in a tobacco plant, marking the first instance of producing QS-21 outside of the tree. This method represents a significant leap towards sustainable production.

“Our study opens unprecedented opportunities for bioengineering vaccine adjuvants. We can now investigate and improve these compounds to promote the human immune response to vaccines and produce QS-21 in a way which does not depend on extraction from the soapbark tree,” said Professor Anne Osbourn.

Overcoming challenges

The quest to replicate QS-21 in an alternative host like tobacco or yeast has been challenging, primarily due to the molecule’s complex structure and the previously unknown biochemical pathway in the tree. 

Earlier efforts by Professor Osbourn’s group had identified part of this pathway, but the full sequence – particularly the acyl chain crucial for stimulating immune cells – remained elusive.

Advanced gene expression analysis

The recent study involved identifying approximately 70 candidate genes, which were then introduced into tobacco plants. Utilizing advanced gene expression analysis techniques, along with Metabolomic and Nuclear Magnetic Resonance (NMR) platforms, the researchers narrowed down to the final 20 genes and enzymes forming the QS-21 pathway.

Dr. Laetitia Martin, the first author of the study, expressed her excitement: “This is the first time QS-21 has been produced in a heterologous expression system. This means we can better understand how this molecule works and how we might address issues of scale and toxicity.”

Study implications 

By enabling more sustainable production of QS-21, the study not only advances scientific knowledge but also contributes positively to global health initiatives. 

“What is so rewarding is that this molecule is used in vaccines and by being able to make it more sustainably my project has an impact on people’s lives. It’s amazing to think that something so scientifically rewarding can bring such good to society,” said Dr. Martin.    

“On a personal level this research was scientifically extremely rewarding. I am not a chemist so I could not have done this without the support of the John Innes Centre metabolomics platform and chemistry platform.” 

The study is published in the journal Nature Chemical Biology.

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