title: A model system for studying the transcriptomic and physiological changes associated with mammalian host-adaptation by Leptospira interrogans serovar Copenhageni.
abstract: Leptospirosis, an emerging zoonotic disease with worldwide distribution, is caused by spirochetes belonging to the genus Leptospira. More than 500,000 cases of severe leptospirosis are reported annually, with >10% of these being fatal. Leptospires can survive for weeks in suitably moist conditions before encountering a new host. Reservoir hosts, typically rodents, exhibit little to no signs of disease but shed large numbers of organisms in their urine. Transmission occurs when mucosal surfaces or abraded skin come into contact with infected urine or urine-contaminated water or soil. In humans, leptospires can cause a variety of clinical manifestations, ranging from asymptomatic or mild fever to severe icteric (Weil's) disease and pulmonary haemorrhage. Currently, little is known about how Leptospira persist within a reservoir host. Prior in vitro studies have suggested that leptospires alter their transcriptomic and proteomic profiles in response to environmental signals encountered during mammalian infection. However, no study has examined gene expression by leptospires within a mammalian host-adapted state. To obtain a more faithful representation of how leptospires respond to host-derived signals, we used RNA-Seq to compare the transcriptome of L. interrogans cultivated within dialysis membrane chambers (DMCs) implanted into the peritoneal cavities of rats with that of organisms grown in vitro. In addition to determining the relative expression levels of "core" housekeeping genes under both growth conditions, we identified 166 genes that are differentially-expressed by L. interrogans in vivo. Our analyses highlight physiological aspects of host adaptation by leptospires relating to heme uptake and utilization. We also identified 11 novel non-coding transcripts that are candidate small regulatory RNAs. The DMC model provides a facile system for studying the transcriptional and antigenic changes associated with mammalian host-adaptation, selection of targets for mutagenesis, and the identification of previously unrecognized virulence determinants.
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America; Department of Pediatrics, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Caimano
authors.affiliation: Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventative Medicine, Trinity College Dublin, Dublin, Ireland.
authors.forename: Sathesh K
authors.initials: SK
authors.lastname: Sivasankaran
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Anna
authors.initials: A
authors.lastname: Allard
authors.affiliation: School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Hurley
authors.affiliation: Department of Genetics, School of Genetics and Microbiology, Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland.
authors.forename: Karsten
authors.initials: K
authors.lastname: Hokamp
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America; Unidade de Biotecnologia, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Pelotas, Rio Grande do Sul, Brazil.
authors.forename: André A
authors.initials: AA
authors.lastname: Grassmann
authors.affiliation: Department of Microbiology, School of Genetics and Microbiology, Moyne Institute of Preventative Medicine, Trinity College Dublin, Dublin, Ireland; Department of Functional and Comparative Genomics, Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom.
authors.forename: Jay C D
authors.initials: JC
authors.lastname: Hinton
authors.affiliation: School of Veterinary Medicine, University College Dublin, Belfield, Dublin, Ireland; Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin, Ireland.
authors.forename: Jarlath E
authors.initials: JE
authors.lastname: Nally
mesh_terms: D000818:Animals; D005798:Genes, Bacterial / Q000235:genetics*; D054884:Host-Pathogen Interactions / Q000502:physiology*; D015151:Immunoblotting; D007921:Leptospira interrogans / Q000472:pathogenicity* / Q000502:physiology*; D007922:Leptospirosis / Q000235:genetics*; D008954:Models, Biological; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D059467:Transcriptome