The challenges and progress in target selection for a methanogen vaccine

<p dir="ltr">An effective vaccine to reduce methane emissions from farmed ruminant livestock will need to produce high levels of antibodies in the saliva of the animals. This saliva enters the rumen where the antibodies must impact on the activity of the methane-forming methanogens. Progress is being made on developing a vaccine, but there are challenges for target selection, some of which are specific to different types of vaccines. There are a large number of potential candidates. Many of these have no known function and there is limited literature to assist with selection and prioritisation of candidates for evaluation. The rumen is populated with a wide diversity of methanogens, which further complicates candidate evaluations. </p><p dir="ltr">The search for effective vaccine targets has been assisted by the increased availability of methanogen genomes and by rumen metagenomic data. We used bioinformatics to identify more than 300 possible targets for evaluation. This approach was combined with empirical methods to rule out unsuitable candidates. Antibodies have been produced in ruminants, against more than 60 targets. These antibodies have been tested for their interaction with methanogen cells using a range of methodologies including ELISA, western blotting, flow cytometry and their impact on methanogen cultures. To date, our findings have led to approximately 20 candidates being prioritised for testing. Prototype vaccines are being assessed by measuring methane emissions from animals in closed circuit respiration chambers, and by determining their effects on rumen methanogen community composition.</p>