A training network for the design of new synthetic carbohydrate-based vaccines to combat antibiotic resistant Pseudomonas aeruginosa

Project Information

PAVax

Grant agreement ID: 861194

DOI

10.3030/861194

Project closed

EC signature date 29 November 2019

Start date 1 March 2020

End date 31 August 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 1 054 239,12

EU contribution

€ 1 054 239,12

Coordinated by

UNIVERSITEIT LEIDEN
Netherlands

Periodic Reporting for period 2 - PAVax (A training network for the design of new synthetic carbohydrate-based vaccines to combat antibiotic resistant Pseudomonas aeruginosa)

Reporting period: 2022-03-01 to 2024-08-31

Summary of the context and overall objectives of the project

The Covid-19 pandemic has shown the massive impact that life threatening pathogens and infectious diseases have on life as we know it. Besides the viral infections that have plagued the world the last years, bacterial infections represent a continuous threat, with bacterial arms becoming more and more resistant against the armoury that we have at our disposal: antibiotics. With ever developing resistance against antibiotics and the rise of multi-drug resistant bacteria new ways for therapeutic intervention have to be brought forward. The ongoing pandemic has also shown the power of vaccination in fighting infectious diseases and indeed vaccination against viral and bacterial infections has been one of the great medical successes. However, many bacterial infections remain that cannot yet be prevented by vaccination. The goal of the PAVax program was to train young scientists in the development of glycoconjugate vaccines, targeting two bacteria that are on the WHO-list of most acute antibiotic-resistant bacteria: Pseudomonas aeruginosa and Staphylococcus aureus. These two bacteria cause life threatening infections, especially in a hospital setting, where they are often found side-by-side in poly bacterial infections. The program has aimed to generate novel vaccine entities, building on the use of polysaccharides found on the exterior of the bacteria, that can be targeted by our immune system. P. aeruginosa and S. aureus express unique glycans that they use to colonize the host and build up a protective biofilm in which they hide from the host immune system. PAVax has aimed to use of these glycans to train our immune system to recognize these glycans and mount an effective immune response. Because it has been shown that glycans by themselves are only weakly immunologically active, they have to be connected to a so-called carrier protein to generate a conjugate vaccine. PAVax has generated ‘designer’ carrier proteins that in combination with P. aeruginosa and S. aureus glycans can elicit a powerful immune response. The glycans that are to be used are isolated from the bacteria, but because this represents a great challenge, organic synthesis has been called upon to deliver the target glycans. This has led to the development of innovative chemistry to assemble the target bacterial glycans of unprecedented complexity and length and the first demonstration that these glycans can be used in anti-Stapylococcal vaccines. The PAVax program has trained four PhD students in a multi-sectorial environment and multidisciplinary program and by performing research in both industry and academia, they have been trained in state-of-the-art of bacterial vaccine development.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The PAVax project has delivered several novel model glycoconjugate vaccines directed at combating Pseudomonas aeruginosa and Staphylococcus aureus. The research of the PAVax program was centred around glycoconjugate vaccines, that are built up of a carrier protein and a bacterial carbohydrate. The carbohydrate in these vaccines represents the antigen, which is presented by the target bacteria on the outside of their cells. But because stand-alone carbohydrates do not work well as a vaccine, they are connected to a protein to generate glycoconjugate vaccines. These can be taken up and processed by cells of our immune system to initiate a powerful and long-lasting immune response. The model vaccines were generated to provide proofs-of-principle for novel working mechanisms of these vaccines or for the components that they were built up from. As a first example, a model vaccine was generated by combining different proteins from P. aeruginosa and S. aureus to create a novel designer carrier protein. This was combined with a polysaccharide, isolated from S. aureus to generate the glycoconjugate vaccines. It was shown that all three components in these designer vaccines (the two proteins in the novel carrier protein and the bacterial carbohydrate) were processed and recognized well in an initial immunization experiment, indicating that the novel three-component-dual target vaccine modality can be an attractive modality to target both P. aeruginosa and S. aureus with a single vaccine. The PAVax program has also investigated the isolation, characterisation, synthesis and application of P. aeruginosa polysaccharides. While isolation of these saccharides proved very challenging, it was shown that organic synthesis could be used to generate well-defined fragments of the polysaccharides. These could be used to generate novel conjugate vaccines to target P. aeruginosa. Finally, several S. aureus glycans were targeted by organic synthesis. As these complex structures represent major synthetic hurdles, novel synthetic strategies had to be developed. Eventually effective synthetic routes were exposed and the PAVax program has delivered fragments of unprecedented length and complexity. These were then used to show how what structure these oligosaccharides adopt and what parts are required for adequate immune recognition.
The work of the PAVax consortium has been published in several peer-reviewed journals and many publications are in preparation. At least three PhD thesis manuscripts are in preparation.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The developed synthetic chemistry has pushed the boundaries of the complexity and length of bacterial glycans that can be achieved. No synthetic vaccines have been reported so far that can target the glycans against which this project has been directed. Because of the synthetic successes achieved, for the first time an effective antibody response could be generated by the synthetic glycans. The designer carrier proteins have broken new ground in the development of designer carriers, and they will inspire the development of the next-generation carriers, that can be used to generate glycoconjugates with tailor-made immune stimulating properties. The availability of the well-defined synthetic fragments will be indispensable for these endeavours.


This work was supported by the European Union’s Horizon 2020 Research and Innovation programme under the Marie Skłodowska-Curie grant agreement No 861194 coordinated by the University of Leiden.
ESRs are Ph.D fellows and are enrolled at Leiden University and, as per grant, have participated in a postgraduate PhD program at GSK. The supervisors are Professor Jeroen Codée of Leiden University and Drs Roberto Adamo and Maria Romano, employees of the GSK group.

PAVax combines designer carrier proteins and synthetic glycans in the development of vaccines