Leptospira interrogans Bat proteins impair host hemostasis by fibrinogen cleavage and platelet aggregation inhibition

Leptospiral adhesins: from identification to future perspectives

Leptospirosis is a significant zoonosis worldwide, with disease severity ranging from a mild non-specific illness to multi-organ dysfunction and hemorrhage. The disease is caused by pathogenic bacteria of the genus Leptospira, which are classified into pathogenic and saprophytic clades. Bacterial binding to host molecules and cells, coordinated by adhesin proteins, is an important step in pathogenesis. While many leptospiral adhesins have been identified, the vast majority have not been characterized in vivo. Herein, we present an overview of the current methodologies and successes in identifying adhesins in Leptospira, including known biological roles in vivo. We will also identify and discuss potential areas for future research.

The dangerous liaisons in innate immunity involving recombinant proteins and endotoxins: Examples from the literature and the Leptospira field

Endotoxins, also known as lipopolysaccharides (LPS), are essential components of cell walls of diderm bacteria such as Escherichia coli. LPS are microbe-associated molecular patterns that can activate pattern recognition receptors. While trying to investigate the interactions between proteins and host innate immunity, some studies using recombinant proteins expressed in E. coli reported interaction and activation of immune cells. Here, we set out to provide information on endotoxins that are highly toxic to humans and bind to numerous molecules, including recombinant proteins. We begin by outlining the history of the discovery of endotoxins, their receptors and the associated signaling pathways that confer extreme sensitivity to immune cells, acting alone or in synergy with other microbe-associated molecular patterns. We list the various places where endotoxins have been found. Additionally, we warn against the risk of data misinterpretation due to endotoxin contamination in recombinant proteins, which is difficult to estimate with the Limulus amebocyte lysate assay, and cannot be completely neutralized (e.g., treatment with polymyxin B or heating). We further illustrate our point with examples of recombinant heat-shock proteins and viral proteins from severe acute respiratory syndrome coronavirus 2, dengue and HIV, for which endotoxin contamination has eventually been shown to be responsible for the inflammatory roles previously ascribed. We also critically appraised studies on recombinant Leptospira proteins regarding their putative inflammatory roles. Finally, to avoid these issues, we propose alternatives to express recombinant proteins in nonmicrobial systems. Microbiologists wishing to undertake innate immunity studies with their favorite pathogens should be aware of these difficulties.

MPL36, a major plasminogen (PLG) receptor in pathogenic Leptospira, has an essential role during infection

Leptospirosis, a zoonosis with worldwide distribution, is caused by pathogenic spirochetes belonging to the genus Leptospira. Bacterial outer membrane proteins (OMPs), particularly those with surface-exposed regions, play crucial roles in pathogen dissemination and virulence mechanisms. Here we characterized the leptospiral Membrane Protein L36 (MPL36), a rare lipoprotein A (RlpA) homolog with a C-terminal Sporulation related (SPOR) domain, as an important virulence factor in pathogenic Leptospira. Our results confirmed that MPL36 is surface exposed and expressed during infection. Using recombinant MPL36 (rMPL36) we also confirmed previous findings of its high plasminogen (PLG)-binding ability determined by lysine residues of the C-terminal region of the protein, with ability to convert bound-PLG to active plasmin. Using Koch's molecular postulates, we determined that a mutant of mpl36 has a reduced PLG-binding ability, leading to a decreased capacity to adhere and translocate MDCK cell monolayers. Using recombinant protein and mutant strains, we determined that the MPL36-bound plasmin (PLA) can degrade fibrinogen. Finally, our mpl36 mutant had a significant attenuated phenotype in the hamster model for acute leptospirosis. Our data indicates that MPL36 is the major PLG binding protein in pathogenic Leptospira, and crucial to the pathogen's ability to attach and interact with host tissues during infection. The MPL36 characterization contributes to the expanding field of bacterial pathogens that explore PLG for their virulence, advancing the goal to close the knowledge gap regarding leptospiral pathogenesis while offering a novel potential candidate to improve diagnostic and prevention of this important zoonotic neglected disease.

Next Generation Sequencing for Diagnosis of Leptospirosis Combined With Multiple Organ Failure: A Case Report and Literature Review

Introduction

Leptospirosis poses a major threat to human life. The disease spectrum ranges from a nearly undetectable presentation to severe multi-organ dysfunction and death. Leptospirosis is difficult to diagnose by traditional antibody and culture tests. We here present a case of multiple organ failure associated with leptospirosis.

Material and Methods

A 64-year-old woman presented with fatigue and arthralgia, which developed rapidly into multiple organ injuries, and she eventually died of cerebral hemorrhage. Serum antibody test and cultures of blood, sputum, urine, and feces samples were all negative. The patient was diagnosed with leptospirosis by the next-generation sequencing (NGS).

Conclusion

We conclude that leptospirosis is a neglected zoonosis caused by pathogenic Leptospira species. New techniques such as NGS are highlighted for early diagnosis. Surveillance for pathogens during diagnosis can provide guidance for clinical treatment and improves prognosis.

A Review on Host-Leptospira Interactions: What We Know and Future Expectations

Leptospirosis is a widespread zoonosis caused by pathogenic Leptospira spp. It is considered a neglected infectious disease of human and veterinary concern. Our group has been investigating proteins annotated as hypothetical, predicted to be located on the leptospiral surface. Because of their location, these proteins may have the ability to interact with various host components, which could allow establishment of the infection. These proteins act as adherence factors by binding to host receptor molecules, such as the extracellular matrix (ECM) components laminin and glycosaminoglycans to help bacterial colonization. Leptospira also interacts with the host fibrinolytic system, which has been demonstrated to be a powerful tool for invasion mechanisms. The interaction with fibrinogen and thrombin has been shown to reduce fibrin clot formation. Additionally, the degradation of coagulation cascade components by secreted proteases or by acquired surface plasmin could also play a role in reducing clot formation, hence facilitating dissemination during infection. Interaction with host complement system regulators also plays a role in helping bacteria to evade the immune system, facilitating invasion. Interaction of Leptospira to cell receptors, such as cadherins, can contribute to investigate molecules that participate in virulence. To achieve a better understanding of the host-pathogen interaction, leptospiral mutagenesis tools have been developed and explored. This work presents several proteins that mediate binding to components of the ECM, plasma, components of the complement system and cells, to gather research achievements that can be helpful in better understanding the mechanisms of leptospiral-host interactions and discuss genetic manipulation for Leptospira spp. aimed at protein function validation.

A Novel Leptospira interrogans Protein LIC13086 Inhibits Fibrin Clot Formation and Interacts With Host Components

Leptospirosis is a neglected zoonosis, caused by pathogenic spirochetes bacteria of the genus Leptospira. The molecular mechanisms of leptospirosis infection are complex, and it is becoming clear that leptospires express several functionally redundant proteins to invade, disseminate, and escape the host’s immune response. Here, we describe a novel leptospiral protein encoded by the gene LIC13086 as an outer membrane protein. The recombinant protein LIC13086 can interact with the extracellular matrix component laminin and bind plasminogen, thus possibly participating during the adhesion process and dissemination. Also, by interacting with fibrinogen and plasma fibronectin, the protein LIC13086 probably has an inhibitory effect in the fibrin clot formation during the infection process. The newly characterized protein can also bind molecules of the complement system and the regulator C4BP and, thus, might have a role in the evasion mechanism of Leptospira. Taken together, our results suggest that the protein LIC13086 may have a multifunctional role in leptospiral pathogenesis, participating in host invasion, dissemination, and immune evasion processes.

Phagocyte Escape of Leptospira: The Role of TLRs and NLRs

The spirochetal bacteria Leptospira spp. are causative agents of leptospirosis, a globally neglected and reemerging zoonotic disease. Infection with these pathogens may lead to an acute and potentially fatal disease but also to chronic asymptomatic renal colonization. Both forms of disease demonstrate the ability of leptospires to evade the immune response of their hosts. In this review, we aim first to recapitulate the knowledge and explore the controversial data about the opsonization, recognition, intracellular survival, and killing of leptospires by scavenger cells, including platelets, neutrophils, macrophages, and dendritic cells. Second, we will summarize the known specificities of the recognition or escape of leptospire components (the so-called microbial-associated molecular patterns; MAMPs) by the pattern recognition receptors (PRRs) of the Toll-like and NOD-like families. These PRRs are expressed by phagocytes, and their stimulation by MAMPs triggers pro-inflammatory cytokine and chemokine production and bactericidal responses, such as antimicrobial peptide secretion and reactive oxygen species production. Finally, we will highlight recent studies suggesting that boosting or restoring phagocytic functions by treatments using agonists of the Toll-like or NOD receptors represents a novel prophylactic strategy and describe other potential therapeutic or vaccine strategies to combat leptospirosis.

Virulent Leptospira interrogans Induce Cytotoxic Effects in Human Platelets in vitro Through Direct Interactions

Leptospirosis is a prevalent zoonotic disease, caused by bacteria of the genus Leptospira. Leptospirosis frequently leads to hemostatic disturbances, and the severe cases are marked by hemorrhages and low platelet number in circulation, which is associated with the patients’ poor outcomes. Nevertheless, Leptospira-platelet interactions remain poorly explored. In this study, we performed a series of in vitro experiments evaluating whether leptospires induce human platelet aggregation, activation, and morphological changes. Platelets were incubated with virulent L. interrogans and the platelet outcomes were assessed by aggregometry, flow cytometry, and scanning and transmission electron microscopy. Our results show that leptospires alone do not induce platelet aggregation and activation, and induce platelet cytotoxic effects instead, by clearly inducing platelet disruption and detachment. We show for the first time that virulent leptospires do interact directly with platelets, an event that could trigger pathophysiological effects during the infection. This study might serve as a basis for the development of novel treatments for the disease.