H2020 MycoSynVac Project: Engineering Mycoplasma pneumoniae as a broad-spectrum animal vaccine

WUR developed a dynamic whole-cell model for M. pneumoniae metabolism and, based on these models, developed a genome-scale constraint-based model for M. hyopneumoniae for vaccine optimization. WUR also implemented its metabolic models to assess the genome-wide metabolic capabilities of several Mycoplasmas for the purpose of designing a tailored vaccine portfolio.

CRG developed two genome engineering methods for M. pneumoniae. The result was a non-pathogenic chassis that can survive in mouse lungs as long as WT Mycoplasma pneumoniae, does not trigger lung injury, and exhibits a reduced inflammatory response. This chassis can express heterologous proteins and protein adjuvants for vaccination on its surface. The genes essential for survival in mouse lungs that cannot be eliminated from the chassis were determined.

ICL designed, optimized, and tested its biosecurity circuits in the WT strain, which showed good elimination efficiency when activated. Furthermore, the integration of redundancy improves the biosecurity system. Very promising results have been obtained in pairwise competitions that tested the different biosecurity systems developed in vivo using mouse models. The biosecurity circuits were also transformed into chassis strains. In this case, the circuits had to be reoptimized, and not all cases were successful. The best strain generated is a CV2 with two copies of the reoptimized KS1 circuits.

INRA developed a method called Genomic Transfer-Recombinase-Mediated Cassette Exchange (GT-RMCE). This new technology allows for large-scale genomic modifications at specific M. pneumoniae loci. It allows for insertion and replacement of large DNA fragments and gene deletions, and could be extended to introduce point mutations. All these new tools made it possible to inactivate known M. pneumoniae virulence factors and led to the construction of prototype vaccine chassis.

ATG completed the selection of candidate peptides for inclusion in chimeric proteins for vaccine production; 44 were selected for Mycoplasma hyopneumoniae and 23 for Mycoplasma bovis. Furthermore, analysis of 64 porcine reproductive and respiratory syndrome virus (PRRSV) strains by peptide microarrays allowed the selection of an additional 20 candidate peptides for this virus. The peptides were combined into 8 chimeric proteins for M. hyopneumoniae, 6 for M. bovis, and 4 for PRRSV.

Merck conducted eight large animal experiments to evaluate the various vaccines generated in the project. Expression of heterologous antigens on the surface of an attenuated M. pneumoniae chassis, grown in serum-free medium, is safe in food animals as an inactivated vaccine and produces seroconversion to all exposed antigens. Preliminary results also indicate that the chassis variants could be safe as a live attenuated vaccine, as the bacteria cannot be detected in body parts other than the injection site. Additional animal experiments would be necessary to conclude on the efficacy of these vaccines.

The work conducted by UCPH on societal concerns has also established that, while there is generally broad acceptance of the use of a synthetic cattle vaccine in Europe, there are significantly different perceptions of such a vaccine across countries. Their internal dialogue activities helped our researchers reflect on how their work might be perceived by other relevant stakeholders.

Biofaction developed a wide variety of different types of public engagement, ranging from in-person interactions at science cafés, high school visits, and public science communication events to online activities such as five-character animation videos, a short science documentary, and the science game 'Battle for Cattle' for web and mobile devices.