Essential and Virulence Genes of Coxiella burnetii

Abstract

Coxiella burnetii is an intracellular pathogen responsible for causing Q fever in humans, which has been classified as a potential category B bioterrorism agent by the CDC. There is a requirement for the identification of possible drug and vaccine targets for C. burnetii due to the lack of a licenced vaccine in the UK, and lengthy drug regimens with undesirable side effects. Until the recent development of axenic media for C. burnetii, its obligate intracellular lifestyle has meant there is a paucity of information on the virulence mechanisms of C. burnetii. In this project the Galleria mellonella insect model was further characterised to aid its use in the identification of C. burnetii virulence determinants. It was found that in G. mellonella, C. burnetii proliferates quicker than in axenic media, and forms a vacuole comparable to that seen in mammalian cells. To identify essential and virulence determinants in a high-throughput manner, a transposon library containing > 10,000 unique transposon mutants was created. Axenic media was used to identify essential genes, and significant steps were taken in the use of G. mellonella as a screen for the high-throughput identification of virulence determinants. Finally, a transposon mutant in CBU_1468, a gene which confers a hypothetical protein of unknown function, was discovered to be attenuated in the G. mellonella model. Potentially identifying a further virulence factor and giving scope for further investigation.