Detection of urinary biomarkers in reservoir hosts of Leptospirosis by capillary electrophoresis mass spectrometry

Authors: Nally, Jarlath; MULLEN, W - University Of Glasgow; CALLANAN, J - Ross University; MISCHAK, H - University Of Glasgow; ALBALAT, A - University Of Stirling

Submitted to: Proteomics Clinical Applications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/26/2015
Publication Date: 4/17/2015
Citation: Nally, J.E., Mullen, W., Callanan, J.J., Mischak, H., Albalat, A. 2015. Detection of urinary biomarkers in reservoir hosts of Leptospirosis by capillary electrophoresis mass spectrometry. Proteomics Clinical Applications. 9(5-6):543-551. DOI: 10.1002/prca.201400205.

Interpretive Summary: Pathogenic leptospires colonize the kidney of reservoir hosts of infection and are excreted via urine into the environment where they can survive in suitable moist conditions. In contrast to incidental hosts of infection, reservoir hosts of infection typically do not show any clinical signs of disease. Reservoir hosts include a wide range of domestic and wild animal species and include cattle, dogs and rats which can persistently excrete large numbers of pathogenic leptospires over many months, despite mounting a humoral and cellular immune response. Since reservoir hosts of leptospirosis do not show clinical signs of infection, the gold standard diagnostic assay is culture. Leptospira are highly fastidious bacteria with relatively long generation times so culture is typically restricted to those laboratories with specialized personnel and facilities and is not routinely practiced. The microscopic agglutination test (MAT) is considered to be the gold standard serological diagnostic assay which requires a panel of isolates of live leptospires representative of locally circulating serovars and with which test sera are incubated to identify reacting samples. A positive MAT confirms exposure to leptospires but has limited efficacy for detecting reservoir hosts of infection; MAT negative animals may be culture positive, whilst MAT positive animals can be culture negative. The goal of this study was to determine if urinary biomarkers could be used as a diagnostic assay to identify reservoir hosts of leptospirosis using an experimental model of infection. Results confirm that a panel of urinary peptides can discriminate urine from experimentally infected rats and further suggests that analysis of the urinary proteome can provide insights into host-pathogen interactions.

Technical Abstract: Pathogenic leptospires colonize the renal tubules of reservoir hosts of infection and are excreted via urine into the environment. Reservoir hosts include a wide range of domestic and wild animal species and include cattle, dogs and rats which can persistently excrete large numbers of pathogenic leptospires over many months. A similar presentation has been observed in humans categorized as ‘‘long-term asymptomatic individuals” as they excreted pathogenic or intermediate-pathogenic leptospires, in the absence of any clinical symptoms or positive serology. In this study, the urine of experimentally infected rats, which showed no clinical symptoms or positive serology, was analyzed by capillary-electrophoresis mass spectrometry to identify urinary biomarkers of chronic infection. A discriminating peptide pattern of 43 polypeptides provided a sensitivity of 86%, a specificity of 83% and an accuracy of 90% for the identification of urine from chronically infected rats (p<0.05, AUC >90%). The majority of discriminating peptides were decreased in abundance in urine of chronically infected rats, including a peptide derived from neprilysin, a membrane metalloendopeptidase, the expression of which has previously been shown to be diminished in infected urine. Results highlight the diagnostic capabilities for urinary biomarkers to identify reservoir hosts of leptospirosis using capillary electrophoresis coupled to mass spectrometry (CE-MS).