Characterization of the microtranscriptome of macrophages infected with virulent, attenuated and saprophyte strains of Leptospira spp

Molecular Characterization of Leptospira Species Detected in the Kidneys of Slaughtered Livestock in Abattoirs in Gauteng Province, South Africa

Leptospira was investigated in kidneys (n = 305) from slaughtered livestock in the Gauteng Province abattoirs, South Africa, using a culture medium to isolate Leptospira, followed by the LipL32 qPCR to detect Leptospira DNA. The SecY gene region was amplified, sequenced, and analyzed for LipL32 qPCR-positive samples or Leptospira isolates. The overall frequency of isolation of Leptospira spp. was 3.9% (12/305), comprising 4.8% (9/186), 4.1% (3/74), and 0% (0/45) from cattle, pigs, and sheep, respectively (p > 0.05). However, with LipL32 qPCR, the overall frequency of Leptospira DNA was 27.5%, consisting of 26.9%, 20.3%, and 42.2% for cattle, pigs, and sheep, respectively (p = 0.03). Based on 22 SecY sequences, the phylogenetic tree identified the L. interrogans cluster with serovar Icterohaemorrhagiae and the L. borgpetersenii cluster with serovar Hardjo bovis strain Lely 607. This study is the first molecular characterization of Leptospira spp. from livestock in South Africa. The reference laboratory uses an eight-serovar microscopic agglutination test panel for leptospirosis diagnosis, of which L. borgpetersenii serovar Hardjo bovis is not part. Our data show that pathogenic L. interrogans and L. borgpetersenii are circulating in the livestock population. Diagnostic use of molecular methods will eliminate or reduce the under-reporting of leptospirosis in livestock, particularly sheep, in South Africa.

Going Micro in Leptospirosis Kidney Disease

Leptospirosis is a zoonotic and waterborne disease worldwide. It is a neglected infectious disease caused by Leptospira spp., as well as a reemerging disease and global public health problem with respect to morbidity and mortality both in humans and animals. Leptospirosis emerges as a leading cause of acute febrile illness along with hepatorenal injury in many countries, including Thailand. While most affected persons are symptomatic in acute disease, which is always difficult to differentiate from other tropical diseases, there is growing evidence of subtle manifestations that cause unrecognized chronic symptoms. The kidney is one of the common organs affected by Leptospires. Although acute kidney injury in the spectrum of interstitial nephritis is a well-described characteristic in severe leptospirosis, chronic kidney disease from leptospirosis is widely discussed. Early recognition of severe leptospirosis leads to reduce morbidity and mortality. Thus, in this review, we highlight the spectrum of characteristics involved in leptospirosis kidney disease and the use of serologic and molecular methods, as well as the treatments of severe leptospirosis.

Identification and validation of circulating miRNAs as potential new biomarkers for severe liver disease in patients with leptospirosis

Background

Leptospirosis, a global zoonotic infectious disease, has various clinical manifestations ranging from mild self-limiting illness to life-threatening with multi-organ damage, including liver involvement. This study was aimed at identifying circulating microRNAs (miRNAs) as novel biomarkers for predicting severe liver involvement in patients with leptospirosis.

Methods

In a discovery set, 12 serum samples of patients with anicteric and icteric leptospirosis at initial clinical presentation were used for miRNA profiling by a NanoString nCounter miRNA assay. In a validated cohort, top candidate miRNAs were selected and further tested by qRT-PCR in serum samples of 81 and 16 individuals with anicteric and icteric leptospirosis, respectively.

Results

The discovery set identified 38 significantly differential expression miRNAs between the two groups. Among these, miR-601 and miR-630 were selected as the top two candidates significantly up-regulated expressed in the icteric group. The enriched KEGG pathway showed that these miRNAs were mainly involved in immune responses and inflammation. In the validated cohort, miR-601 and miR-630 levels were significantly higher in the icteric group compared with the anicteric group. Additionally, these two miRNAs displayed good predictors of subsequent acute liver failure with a high sensitivity of 100%. On regression analysis, elevated miR-601 and miR-630 expression were also predictive of multi-organ failures and poor overall survival.

Conclusion

Our data indicated that miRNA expression profiles were significantly differentiated between the icteric and anicteric groups. Serum miR-601 and miR-630 at presentation could potentially serve as promising biomarkers for predicting subsequent acute liver failure and overall survival in patients with leptospirosis.

Protective efficacy of whole-cell inactivated Leptospira vaccines made using virulent or avirulent strains in a hamster model

Whole-cell inactivated vaccines remain the only licensed vaccines used to control human and animal leptospirosis worldwide. Although they are protective against lethal infections, the efficacy of these vaccines has been divergent. The manufacturing process often involves the use of standard bacterial strains subjected to serial in vitro passages, with a risk of loss of virulence, and may affect the immunogenicity and consequently decrease protection. Thus, the objective of this study was to perform a comparative analysis of the efficacy of in-house bacterins produced with standard (avirulent) and virulent strains. Hamsters were immunized with killed bacteria produced using avirulent and virulent strains of L. interrogans serovars Copenhageni and Canicola. Vaccine efficacy was determined in terms of protection against lethal homologous or heterologous challenges. The results showed that immunization with both avirulent and virulent Canicola strains resulted in 100% protection against homologous challenge. Conversely, Copenhageni bacterins produced using an avirulent strain conferred only 25-37.5% protection against homologous challenge (P > 0.05), while virulent Copenhageni bacterin conferred 100% protection (P < 0.001). A single vaccine dose was sufficient to induce protection, and administration of a prime boost significantly reduced the bacterial load in the kidneys and improved the humoral immune response to the virulent Copenhageni strain. These findings suggest that the maintenance of virulent strains in bacterin formulations is essential for improving the immunogenicity and efficacy of leptospirosis vaccines.

Circulating microtranscriptome profiles reveal distinct expression of microRNAs in severe leptospirosis

Biomarkers to predict the severity of leptospirosis are still lacking. This study aimed to identify and validate microRNAs in patients with severe leptospirosis, that could potentially be used as biomarkers for predicting an unfavorable outcome. Serum samples were collected from participants with definite diagnosis of leptospirosis. The participants were divided into two groups, non-severe and severe leptospirosis, as defined by the Specific Organ Sequential Organ Failure (SOFA) Score of more than two in any organ. Microtranscriptome analysis was performed using the NanoString miRNA Expression Assay. The expression level of candidate miRNAs was then validated by quantitative RT-PCR. Based on the NanoString, the microtranscriptome profile of the severe group was significantly different from that of the non-severe group. Upregulation of miR155-5p, miR362-3p, miR502-5p, miR601, miR1323, and miR630 in the severe group were identified, and further investigated. A total of 119 participants were enrolled in the validation cohort. Serum miR155-5p and miR630 levels were significantly higher in the severe group compared to the non-severe group. The combined use of miR155-5p or miR-630 with serum bicarbonate levels had an AUC of 0.79 (95%CI; 0.69-0.89, p<0.001) in identifying the severity of the disease. This data provides the first evidence that the microtranscriptome profiles of patients with severe leptospirosis were different from the non-severe group. Serum miR155-5p and miR630 levels might be novel biomarkers for identifying severe leptospirosis.

MicroRNAs Regulated by the LPS/TLR2 Immune Axis as Bona Fide Biomarkers for Diagnosis of Acute Leptospirosis

Here, we used miRNAs that are differentially regulated by the LPS/TLR2 immune axis to devise a miRNA-based diagnosis for leptospirosis. The study established the role of the circulating stable miRNAs (miR-21-5p, miR-144-3p, and miR-let-7b-5p) as an early diagnostic marker for leptospirosis. These miRNAs can be used to diagnose acute leptospirosis and also to differentiate leptospiral infection from other bacterial and spirochetal infections, as proved by the use of human clinical samples. Thus, our findings indicate that miRNAs can play a crucial role in the diagnosis of infectious diseases, like leptospirosis, that are generally misdiagnosed.

Leptospirosis remains a significant human health issue due to its systemic complications. Therefore, biomarkers that are more effective are urgently needed for the early diagnosis of leptospirosis. MicroRNAs (miRNAs) are evolutionarily conserved regulatory RNAs that have shown the potential to be used as biomarkers for diagnosis, prognosis, and therapy of infectious diseases. In this study, we performed an unbiased screen using the miRNome miRNA array to identify circulating miRNAs with the potential to serve as authentic biomarkers for early diagnosis of leptospirosis. Because leptospiral lipopolysaccharide (LPS) is the predominant leptospiral antigen and plays a vital role in immunological and biological activities, we used LPS treated and untreated in vitro (THP1 cells) and in vivo (BALB/c mice) surrogate models to identify the LPS-specific miRNAs. Differential expression analysis revealed 18 miRNAs to be associated strongly with LPS stimulation in THP1 cells. Of these, three (miR-let-7b-5p, miR-144-3p, and miR-21-5p) were observed to be present at increased levels in vivo. The identified miRNAs were validated for their biomarker potential using serum samples from leptospirosis-negative patients and patients with confirmed cases of leptospirosis. Identified miRNAs were able to discriminate the acute leptospiral infection from other febrile diseases with a test sensitivity and specificity of 93.2% and 88.19%, respectively. Gene functional enrichment and protein-protein interaction (PPI) network analysis revealed that the identified miRNAs play important roles in disease signal transduction, signaling by interleukins, the stress-activated protein kinase signaling cascade, the mitogen-activated protein kinase (MAPK) signaling pathway, and the cellular response to a transforming growth factor β (TGF-β) stimulus with a notable interconnection between these biological processes.

IMPORTANCE Here, we used miRNAs that are differentially regulated by the LPS/TLR2 immune axis to devise a miRNA-based diagnosis for leptospirosis. The study established the role of the circulating stable miRNAs (miR-21-5p, miR-144-3p, and miR-let-7b-5p) as an early diagnostic marker for leptospirosis. These miRNAs can be used to diagnose acute leptospirosis and also to differentiate leptospiral infection from other bacterial and spirochetal infections, as proved by the use of human clinical samples. Thus, our findings indicate that miRNAs can play a crucial role in the diagnosis of infectious diseases, like leptospirosis, that are generally misdiagnosed.

Gene expression is associated with virulence in murine macrophages infected with Leptospira spp

Leptospira genus contains species that affect human health with varying degrees of pathogenicity. In this context, we aimed to evaluate the differences in the modulation of host gene expression by strains of Leptospira varying in virulence. Our data showed a high number of differentially expressed transcripts in murine macrophages following 6h of infection. Leptospira infection modulated a set of genes independently of their degree of virulence. However, pathway analysis indicated that Apoptosis, ATM Signaling, and Cell Cycle: G2/M DNA Damage Checkpoint Regulation were exclusively regulated following infection with the virulent strain. Taken together, results demonstrated that species and virulence play a role during host response to Leptospira spp in murine macrophages, which could contribute to understanding the pathogenesis of leptospirosis.

microRNA profile datasets of murine macrophages infected with different strains of Leptospira spp

MicroRNAs play an important role in the regulation of immune responses. The influence of epigenetic mechanisms, particularly RNA-mediated post-transcriptional regulation of host immune responses has been proven vital following infections by different pathogens, and bacteria can modulated host miRNAs. Global miRNA expression analysis from macrophages infected in vitro with different strains of Leptospira spp was performed using miRNA 4.1 microarray strips. Leptospirosis is a bacterial zoonosis of global importance, responsible for significant morbidity and mortality worldwide. Despite considerable advances, much is yet to be discovered about disease pathogenicity, particularly in regards to host-pathogen interactions. We present here a high-quality dataset examining the microtranscriptome of murine macrophages J774A.1 following 8h of infection with virulent, attenuated and saprophyte strains of Leptospira. Metadata files were submitted to the Gene Expression Omnibus (GEO) repository.