Revisiting the development of vaccines against pathogenic leptospira: innovative approaches, present challenges, and future perspectives

Human vaccination against leptospirosis has been relatively unsuccessful in clinical applications despite an expressive amount of vaccine candidates has been tested over years of research. Pathogenic Leptospira encompass a great number of serovars, most of which do not cross-react, and there has been a lack of genetic tools for many years. These obstacles have hampered the understanding of the bacteria’s biology and, consequently, the identification of an effective antigen. Thus far, many approaches have been used in an attempt to find a cost-effective and broad-spectrum protective antigen(s) against the disease. In this extensive review, we discuss several strategies that have been used to develop an effective vaccine against leptospirosis, starting with Leptospira-inactivated bacterin, proteins identified in the genome sequences of pathogenic Leptospira, including reverse vaccinology, plasmid DNA, live vaccines, chimeric multi-epitope, and toll- and nod-like receptors agonists. This overview should be able to guide scientists working in the field to select potential antigens and to choose the appropriate formulation to administer the candidates.

Identification of leptospiral protein antigens recognized by WC1+ γδ T cell subsets as target for development of recombinant vaccines

Pathogenic Leptospira species cause leptospirosis, a neglected zoonotic disease recognized as a global public health problem. It is also the cause of the most common cattle infection that results in major economic losses due to reproductive problems. γδ T cells play a role in the protective immune response in livestock species against Leptospira while human γδ T cells also respond to Leptospira. Thus, activation of γδ T cells has emerged as a potential component in the optimization of vaccine strategies. Bovine γδ T cells proliferate and produce IFN-γ in response to vaccination with inactivated leptospires and this response is mediated by a specific subpopulation of the WC1-bearing γδ T cells. WC1 molecules are members of the group B scavenger receptor cysteine rich (SRCR) superfamily and are composed of multiple SRCR domains, of which particular extracellular domains act as ligands for Leptospira. Since WC1 molecules function as both pattern recognition receptors and γδ TCR coreceptors, the WC1 system has been proposed as a novel target to engage γδ T cells. Here, we demonstrate the involvement of leptospiral protein antigens in the activation of WC1+ γδ T cells and identified two leptospiral outer membrane proteins able to interact directly with them. Interestingly, we show that the protein-specific γδ T cell response is composed of WC1.1+ and WC1.2+ subsets, although a greater number of WC1.1+ ???? T-cell respond. Identification of protein antigens will enhance our understanding of the role γδ T cells play in the leptospiral immune response and in recombinant vaccine development.

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.

The leptospiral LipL21 and LipL41 proteins exhibit a broad spectrum of interactions with host cell components

Leptospirosis is a globally prevalent zoonotic disease, and is caused by pathogenic spirochetes from the genus Leptospira. LipL21 and LipL41 are lipoproteins expressed strongly on the outer membrane of pathogenic Leptospira spp. Many studies have shown that both proteins are interesting targets for vaccines and diagnosis. However, their role in host–pathogen interactions remains underexplored. Therefore, we evaluated the capacity of LipL21 and LipL41 to bind with glycosaminoglycans (GAGs), the cell receptors and extracellular matrix, and plasma components by ELISA. Both proteins interacted with collagen IV, laminin, E-cadherin, and elastin dose-dependently. A broad-spectrum binding to plasma components was also observed. Only LipL21 interacted with all the GAG components tested, whereas LipL41 presented a concentration-dependent binding only for chondroitin 4 sulphate. Although, both proteins have the ability to interact with fibrinogen, only LipL21 inhibited fibrin clot formation partially. Both proteins exhibited a decrease in plasminogen binding in the presence of amino caproic acid (ACA), a competitive inhibitor of lysine residues, suggesting that their binding occurs via the kringle domains of plasminogen. LipL41, but not LipL21, was able to convert plasminogen to plasmin, and recruit plasminogen from normal human serum, suggesting that the interaction of this protein with plasminogen may occur in physiological conditions. This work provides the first report demonstrating the capacity of LipL21 and LipL41 to interact with a broad range of host components, highlighting their importance in host–Leptospira interactions.

Application of CRISPR interference (CRISPRi) for gene silencing in pathogenic species of Leptospira

Leptospirosis is a global neglected zoonosis, responsible for at least 1 million cases per year and almost 60 thousand deaths. The disease is caused by pathogenic and virulent bacteria of the genus Leptospira, either by direct contact with the bacteria or indirectly by exposure to contaminated water or soil. Domestic and wild animals act as reservoir hosts of infection, shedding leptospires from colonized renal tubules of the kidney, via urine, into the environment. The generation of mutant strains of Leptospira is critical to evaluate and understand pathogenic mechanisms of infection. CRISPR interference (CRISPRi) has proven to be a straightforward, affordable, and specific tool for gene silencing in pathogenic Leptospira. Therefore, the methodological details of obtaining the plasmid constructs containing both dCas9 and guide RNA, delivery of plasmids to Leptospira by conjugation with the E. coli strain β2163, and transconjugant recovery and evaluation, will be described. In addition, the recently described Hornsby-Alt-Nally (HAN) media allows for the relatively rapid isolation and selection of mutant colonies on agar plates.

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.

Strategies for the production of soluble interferon-alpha consensus and potential application in arboviruses and SARS-CoV-2

Biopharmaceutical production is currently a multibillion-dollar industry with high growth perspectives. The research and development of biologically sourced pharmaceuticals are extremely important and a reality in our current healthcare system. Interferon alpha consensus (cIFN) is a non-natural synthetic antiviral molecule that comprises all the most prevalent amino acids of IFN-α into one consensus protein sequence. For clinical use, cIFN is produced in E. coli in the form of inclusion bodies. Here, we describe the use of two solubility tags (Fh8 and DsbC) to improve soluble cIFN production. Furthermore, we analyzed cIFN production in different culture media and temperatures in order to improve biopharmaceutical production. Our results demonstrate that Fh8-cIFN yield was improved when bacteria were cultivated in autoinduction culture medium at 30 °C. After hydrolysis, the recovery of soluble untagged cIFN was 58% from purified Fh8-cIFN molecule, fourfold higher when compared to cIFN recovered from the DsbC-cIFN, which achieved 14% recovery. The biological activity of cIFN was tested on in vitro model of antiviral effect against Zika, Mayaro, Chikungunya and SARS-CoV-2 virus infection in susceptible VERO cells. We show, for the first time, that cIFN has a potent activity against these viruses, being very low amounts of the molecule sufficient to inhibit virus multiplication. Thus, this molecule could be used in a clinical approach to treat Arboviruses and SARS-CoV-2.

Genetic manipulation of pathogenic Leptospira: CRISPR interference (CRISPRi)-mediated gene silencing and rapid mutant recovery at 37 °C

Leptospirosis is a neglected, widespread zoonosis caused by pathogenic species of the genus Leptospira, and is responsible for 60,000 deaths per year. Pathogenic mechanisms of leptospirosis remain poorly understood mainly because targeted mutations or gene silencing in pathogenic Leptospira continues to be inherently inefficient, laborious, costly and difficult to implement. In addition, pathogenic leptospires are highly fastidious and the selection of mutants on solid agar media can take up to 6 weeks. The catalytically inactive Cas9 (dCas9) is an RNA-guided DNA-binding protein from the Streptococcus pyogenes CRISPR/Cas system and can be used for gene silencing, in a strategy termed CRISPR interference (CRISPRi). Here, this technique was employed to silence genes encoding major outer membrane proteins of pathogenic L. interrogans. Conjugation protocols were optimized using the newly described HAN media modified for rapid mutant recovery at 37 °C in 3% CO2 within 8 days. Complete silencing of LipL32 and concomitant and complete silencing of both LigA and LigB outer membrane proteins were achieved, revealing for the first time that Lig proteins are involved in pathogenic Leptospira serum resistance. Gene silencing in pathogenic leptospires and rapid mutant recovery will facilitate novel studies to further evaluate and understand pathogenic mechanisms of leptospirosis.

In silico structural and functional characterization of HtrA proteins of leptospira spp.: possible implications in pathogenesis

Leptospirosis is a zoonosis caused by the pathogenic bacteria of the genus Leptospira. The identification of conserved outer membrane proteins among pathogenic strains is a major research target in elucidating mechanisms of pathogenicity. Surface-exposed proteins are most probably the ones involved in the interaction of leptospires with the environment. Some spirochetes use outer membrane proteases as a way to penetrate host tissues. HtrA is a family of proteins found in various cell types, from prokaryotes to primates. They are a set of proteases usually composed of a serine protease and PDZ domains, and they are generally transported to the periplasm. Here, we identified four genes—annotated as HtrA, LIC11111, LIC20143, LIC20144 and LIC11037—and another one annotated as a serine protease, LIC11112. It is believed that the last forms a functional heterodimer with LIC11111, since they are organized in one operon. Our analyses showed that these proteins are highly conserved among pathogenic strains. LIC11112, LIC20143, and LIC11037 have the serine protease domain with the conserved catalytic triad His-Asp-Ser. This is the first bioinformatics analysis of HtrA proteins from Leptospira that suggests their proteolytic activity potential. Experimental studies are warranted to elucidate this possibility.

Immunoprotective activity induced by leptospiral outer membrane proteins in hamster model of acute leptospirosis

Leptospirosis is a zoonotic disease of worldwide distribution, affecting both humans and animals. The development of an effective vaccine against leptospirosis has long been pursued but without success. Humans are contaminated after direct contact with the urine of infected animals or indirectly by contaminated water or soil. The vaccines available consist of inactivated whole-bacterial cells, and the active immunoprotective antigen is the lipopolysaccharide moiety, which is also the basis for serovar classification. However, these vaccines are short-lasting, and protection is only against serovars contained in the preparation. The search for prevalent antigens, present in pathogenic species of Leptospira, represents the most cost-effective strategy for prevention of leptospirosis. Thus, the identification of these antigens is a priority. In this study, we examined the immunoprotective effect of eight leptospiral recombinant proteins using hamster as the challenge model. Animals received subcutaneously two doses of vaccine containing 50 μg of each recombinant protein adsorbed on alum adjuvant. Two weeks after the booster, animals were challenged with virulent leptospires and monitored for 21 days. All proteins were able to induce a specific immune response, although significant protective effects on survival rate were observed only for the proteins Lsa14, rLIC13259, and rLIC11711. Of these, only rLIC13259 and rLIC11711 were found to be highly prospective in promoting renal clearance. The sterilizing potential of both proteins will be further investigated to elucidate the immunoprotective mechanisms involved in leptospirosis control. These are the first proteins involved with human complement components with the capacity to protect against virulent challenge and to eliminate the bacteria from the host.

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.

Structural analysis of CACHE domain of the McpA chemoreceptor from Leptospira interrogans

Leptospira is a genus of spirochete bacteria highly motile that includes pathogenic species responsible to cause leptospirosis disease. Chemotaxis and motility are required for Leptospira infectivity, pathogenesis, and invasion of bacteria into the host. In prokaryotes, the most common chemoreceptors are methyl-accepting chemotaxis proteins that have a role play to detect the chemical signals and move to a favorable environment for its survival. Here, we report the first crystal structure of CACHE domain of the methyl-accepting chemotaxis protein (McpA) of L. interrogans. The structural analysis showed that McpA adopts similar α/β architecture of several other bacteria chemoreceptors. We also found a typical dimerization interface that appears to be functionally crucial for signal transmission and chemotaxis. In addition to McpA structural analyses, we have identified homologous proteins and conservative functional regions using bioinformatics techniques. These results improve our understanding the relationship between chemoreceptor structures and functions of Leptospira species.

Heterologous expression of the pathogen-specific LIC11711 gene in the Saprophyte L. biflexa increases bacterial binding to laminin and plasminogen

Leptospirosis is a febrile disease and the etiological agents are pathogenic bacteria of the genus Leptospira. The leptospiral virulence mechanisms are not fully understood and the application of genetic tools is still limited, despite advances in molecular biology techniques. The leptospiral recombinant protein LIC11711 has shown interaction with several host components, indicating a potential function in virulence. This study describes a system for heterologous expression of the L. interrogans gene lic11711 using the saprophyte L. biflexa serovar Patoc as a surrogate, aiming to investigate its possible activity in bacterial virulence. Heterologous expression of LIC11711 was performed using the pMaOri vector under regulation of the lipL32 promoter. The protein was found mainly on the leptospiral outer surface, confirming its location. The lipL32 promoter enhanced the expression of LIC11711 in L. biflexa compared to the pathogenic strain, indicating that this strategy may be used to overexpress low-copy proteins. The presence of LIC11711 enhanced the capacity of L. biflexa to adhere to laminin (Lam) and plasminogen (Plg)/plasmin (Pla) in vitro, suggesting the involvement of this protein in bacterial pathogenesis. We show for the first time that the expression of LIC11711 protein of L. interrogans confers a virulence-associated phenotype on L. biflexa, pointing out possible mechanisms used by pathogenic leptospires.

The Leptospira interrogans LIC10774 is a multifunctional surface protein that binds calcium and interacts with host components

Leptospirosis is a global re-emerging zoonosis, caused by pathogenic bacteria of the genus Leptospira. Humans are infected mainly through contact with contaminated water or soil. The understanding of the molecular mechanisms of leptospirosis through the characterization of unknown outer membrane proteins may contribute to the development of new treatments, diagnostic methods and vaccines. We have identified using bioinformatics analysis a protein that is encoded by the gene LIC10774, predicted to be localized at the leptospiral outer membrane and exhibit beta-roll folding. Surface exposure was confirmed by flow cytometry, ELISA and immunofluorescence-based confocal microscopy. Through circular dichroism spectroscopy and hydrophobic dye binding we have shown that rLIC10774 binds calcium ions, which imposes changes to secondary and tertiary structures. The recombinant protein was capable of binding to several host extracellular matrix and serum components. Therefore, we describe LIC10774 as a calcium-binding protein exposed in the outer surface of pathogenic leptospires with possible multifunctional roles in adhesion to host tissues, evasion of the immune system and participation in dissemination processes during leptospirosis. In addition, we hypothesize that the calcium binding is important for temperature-dependent functional roles during leptospirosis

Identification of a novel protein in the genome sequences of Leptospira interrogans with the ability to interact with host's components

Background Leptospirosis is an infectious disease that affects humans and animals worldwide. The etiological agents of this disease are the pathogenic species of the genus Leptospira. The mechanisms involved in the leptospiral pathogenesis are not full understood. The elucidation of novel mediators of host-pathogen interaction is important in the detection of virulence factors involved in the pathogenesis of leptospirosis. Objective This work focused on identification and characterization of a hypothetical protein of Leptospira encoded by the gene LIC10920. Methods The protein of unknown function was predicted to be surface exposed. Therefore, the LIC10920 gene was cloned and the protein expressed in Escherichia coli BL21 (DE3) Star pLysS strain. The recombinant protein was purified by metal affinity chromatography and evaluated with leptospirosis human serum samples. The interaction with host components was also performed. Results The recombinant protein was recognized by antibodies present in leptopsirosis human serum, suggesting its expression during infection. Immunofluorescence and intact bacteria assays indicated that the bacterial protein is surface-exposed. The recombinant protein interacted with human laminin, in a dose-dependent and saturable manner and was named Lsa24.9, for Leptospiral surface adhesin, followed by its molecular mass. Lsa24.9 also binds plasminogen (PLG) in a dose-dependent and saturable fashion, fulfilling receptor ligand interaction. Moreover, Lsa24.9 has the ability to acquire PLG from normal human serum, exhibiting similar profile as observed with the human purified component. PLG bound Lsa24.9 was able of generating plasmin, which could increase the proteolytic power of the bacteria. Conclusions This novel leptospiral protein may function as an adhesin at the colonization steps and may help the invasion process by plasmin generation at the bacterial cell surface.

The interplay between host haemostatic systems and Leptospira spp. infections

Hemostasis is a defence mechanism that protects the integrity of the vascular system and is comprised of the coagulation cascade, fibrinolysis, platelet aggregation, and vascular endothelium. Besides the primary function in preserving the vascular integrity, the haemostatic system cooperates with immune and inflammatory processes to eliminate invading pathogens during microbial infections. Under pathological manifestations, hemostasis must therefore interact in a coordinated manner with inflammatory responses and immune reactions. Several pathogens can modulate these host-derived countermeasures by specifically targeting certain haemostatic components for their own benefit. Thus, the ability to modulate host defence systems has to be considered as an essential bacterial virulence mechanism. Complications that bacterial pathogens can induce are therefore often the consequence of evoked host responses. A comprehensive understanding of the molecular mechanisms triggered in infectious processes may help to develop prophylactic methods and novel therapies for the patients suffering from a particular infectious disease. This review aims to provide a critical updated compiling of recent studies on how the pathogenic Leptospira can interact with and manipulate the host haemostatic systems and the consequences for leptospirosis pathogenesis.

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

Leptospirosis is a worldwide spread zoonosis, caused by pathogenic Leptospira. Evidences suggest that compromised hemostasis might be involved in the leptospirosis pathophysiology. In the genome of L. interrogans serovar Copenhageni, we found two genes coding for proteins which comprise von Willebrand factor (VWF) A domains (BatA and BatB). As VWF A domains exhibit multiple binding sites which contributes to human VWF hemostatic functions, we hypothesized that the L. interrogans BatA and BatB proteins could be involved in the hemostatic impairment during leptospirosis. We have cloned, expressed in Escherichia coli, and purified recombinant BatA and BatB. The influence of recombinant BatA and BatB on different in vitro hemostatic assays evaluating the enzymatic activity, platelet aggregation and fibrinogen integrity was investigated. We describe BatB as a new serine protease which is able to cleave thrombin chromogenic substrate, fibrin, fibrinogen, gelatin and casein; while BatA is active only towards fibrinogen. BatA and BatB interfere with the platelet aggregation induced by VWF/ristocetin and thrombin. Our results suggest an important role of the L. interrogans serovar Copenhageni Bat proteins in the hemostasis dysfunction observed during leptospirosis and contribute to the understanding of the leptospirosis pathophysiological mechanisms.

The Leptospira interrogans LIC10774 is a multifunctional surface protein that binds calcium and interacts with host components

Leptospirosis is a global re-emerging zoonosis, caused by pathogenic bacteria of the genus Leptospira. Humans are infected mainly through contact with contaminated water or soil. The understanding of the molecular mechanisms of leptospirosis through the characterization of unknown outer membrane proteins may contribute to the development of new treatments, diagnostic methods and vaccines. We have identified using bioinformatics analysis a protein that is encoded by the gene LIC10774, predicted to be localized at the leptospiral outer membrane and exhibit beta-roll folding. Surface exposure was confirmed by flow cytometry, ELISA and immunofluorescence-based confocal microscopy. Through circular dichroism spectroscopy and hydrophobic dye binding we have shown that rLIC10774 binds calcium ions, which imposes changes to secondary and tertiary structures. The recombinant protein was capable of binding to several host extracellular matrix and serum components. Therefore, we describe LIC10774 as a calcium-binding protein exposed in the outer surface of pathogenic leptospires with possible multifunctional roles in adhesion to host tissues, evasion of the immune system and participation in dissemination processes during leptospirosis. In addition, we hypothesize that the calcium binding is important for temperature-dependent functional roles during leptospirosis

Identification of a novel protein in the genome sequences of Leptospira interrogans with the ability to interact with host's components

Background Leptospirosis is an infectious disease that affects humans and animals worldwide. The etiological agents of this disease are the pathogenic species of the genus Leptospira. The mechanisms involved in the leptospiral pathogenesis are not full understood. The elucidation of novel mediators of host-pathogen interaction is important in the detection of virulence factors involved in the pathogenesis of leptospirosis. Objective This work focused on identification and characterization of a hypothetical protein of Leptospira encoded by the gene LIC10920. Methods The protein of unknown function was predicted to be surface exposed. Therefore, the LIC10920 gene was cloned and the protein expressed in Escherichia coli BL21 (DE3) Star pLysS strain. The recombinant protein was purified by metal affinity chromatography and evaluated with leptospirosis human serum samples. The interaction with host components was also performed. Results The recombinant protein was recognized by antibodies present in leptopsirosis human serum, suggesting its expression during infection. Immunofluorescence and intact bacteria assays indicated that the bacterial protein is surface-exposed. The recombinant protein interacted with human laminin, in a dose-dependent and saturable manner and was named Lsa24.9, for Leptospiral surface adhesin, followed by its molecular mass. Lsa24.9 also binds plasminogen (PLG) in a dose-dependent and saturable fashion, fulfilling receptor ligand interaction. Moreover, Lsa24.9 has the ability to acquire PLG from normal human serum, exhibiting similar profile as observed with the human purified component. PLG bound Lsa24.9 was able of generating plasmin, which could increase the proteolytic power of the bacteria. Conclusions This novel leptospiral protein may function as an adhesin at the colonization steps and may help the invasion process by plasmin generation at the bacterial cell surface.

The interplay between host haemostatic systems and Leptospira spp. infections

Hemostasis is a defence mechanism that protects the integrity of the vascular system and is comprised of the coagulation cascade, fibrinolysis, platelet aggregation, and vascular endothelium. Besides the primary function in preserving the vascular integrity, the haemostatic system cooperates with immune and inflammatory processes to eliminate invading pathogens during microbial infections. Under pathological manifestations, hemostasis must therefore interact in a coordinated manner with inflammatory responses and immune reactions. Several pathogens can modulate these host-derived countermeasures by specifically targeting certain haemostatic components for their own benefit. Thus, the ability to modulate host defence systems has to be considered as an essential bacterial virulence mechanism. Complications that bacterial pathogens can induce are therefore often the consequence of evoked host responses. A comprehensive understanding of the molecular mechanisms triggered in infectious processes may help to develop prophylactic methods and novel therapies for the patients suffering from a particular infectious disease. This review aims to provide a critical updated compiling of recent studies on how the pathogenic Leptospira can interact with and manipulate the host haemostatic systems and the consequences for leptospirosis pathogenesis.