Distinct transcriptional profiles of Leptospira borgpetersenii serovar Hardjo strains JB197 and HB203 cultured at different temperatures

Authors: Putz, Ellie; SIVASANKARAN, SATHESH - Iowa State University; FERNANDES, LUIS - Butantan Institute; Brunelle, Brian; Lippolis, John; Alt, David; Bayles, Darrell; Hornsby, Richard; Nally, Jarlath

Submitted to: PLOS Neglected Tropical Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2021
Publication Date: 4/7/2021
Citation: Putz, E.J., Sivasankaran, S.K., Fernandes, L.G., Brunelle, B.W., Lippolis, J.D., Alt, D.P., Bayles, D.O., Hornsby, R.L., Nally, J.E. 2021. Distinct transcriptional profiles of Leptospira borgpetersenii serovar Hardjo strains JB197 and HB203 cultured at different temperatures. PLOS Neglected Tropical Diseases. 15(4). Article e0009320. https://doi.org/10.1371/journal.pntd.0009320.
DOI: https://doi.org/10.1371/journal.pntd.0009320

Interpretive Summary: Leptospirosis is a global zoonotic, neglected tropical disease. Interestingly, a high level of species specificity (both bacteria and host) plays a major role in the severity of disease presentation which can vary from asymptomatic to multi-organ failure. Leptospira colonize the kidneys of infected individuals and are shed in urine into the environment where they can survive until they are contracted by another host. This study looks at two strains of L. borgpetersenii, HB203 and JB197 which are genetically very similar, and identical by serotyping as serovar Hardjo, yet HB203 causes a chronic infection in the hamster while JB197 causes organ failure and mortality. To better characterize bacterial factors causing different disease outcomes, we examined the gene expression profile of these strains in the context of temperatures that would reflect natural Leptospira life cycles (environmentally similar 29 degrees C and 37 degrees C which is more indicative of host environment). We found vast differences in gene expression both between the strains and within strains between temperatures. Characterization of the transcriptome of L. borgpetersenii serovar Hardjo strains JB197 and HB203 provides insights into factors which can determine acute versus chronic disease in the hamster model of infection. Additionally, these studies highlight strain to strain variability within the same species, and serovar, at different growth temperatures, which needs to be considered when serovars are selected and propagated for use as bacterin vaccines, the current strategy used to immunize domestic animal species.

Technical Abstract: Background: Leptospirosis is a zoonotic, bacterial disease, posing significant health risks to humans, livestock, and companion animals around the world. Symptoms range from asymptomatic to multi-organ failure in severe cases. Complex species-specific interactions exist between animal hosts and the infecting species, serovar, and strain of pathogen. Leptospira borgpetersenii serovar Hardjo strains HB203 and JB197 have a high level of genetic homology but cause different clinical presentation in the hamster model of infection; HB203 colonizes the kidney and presents with chronic shedding while JB197 causes severe organ failure and mortality. This study examines the transcriptome of L. borgpetersenii and characterizes differential gene expression profiles of strains HB203 and JB197 cultured at temperatures during routine laboratory conditions (29 degrees C) and encountered during host infection (37 degrees C). Methodology/Principal Findings: L. borgpetersenii serovar Hardjo strains JB197 and HB203 were isolated from the kidneys of experimentally infected hamsters and maintained at 29 degrees C and 37 degrees C. RNAseq revealed distinct gene expression profiles; 440 genes were differentially expressed (DE) between JB197 and HB203 at 29 degrees C, and 179 genes were DE between strains at 37 degrees C. Comparison of JB197 cultured at 29 degrees C and 37 degrees C identified 135 DE genes while 41 genes were DE in HB203 with those same culture conditions. The consistent DE of ligB which encodes the outer membrane virulence factor LigB, was validated by immunoblotting and 2D-DIGE. Differential expression of lipopolysaccharide was also observed between JB197 and HB203. Conclusions/Significance: Investigation of the L. borgpetersenii JB197 and HB203 transcriptome provides unique insight into the mechanism between acute and chronic disease. Characterizing the nuances of strain to strain differences and investigating the environmental sensitivity of Leptospira to temperature is critical to the development and progress of preventative and treatment technologies. This is an important consideration when serovars are selected and propagated for use as bacterin vaccines as well as for the identification of novel therapeutic targets.