Leishmania infection modulates beta-1 integrin activation and alters the kinetics of monocyte spreading over fibronectin

Validation of an In-House ELISA Method in the Diagnosis of Cutaneous Leishmaniasis Caused by Leishmania donovani in Hambantota District, Sri Lanka

Clinical diagnosis has become a challenge amidst a surge of cutaneous leishmaniasis in Southern Sri Lanka. The routine diagnostic method, slit-skin smear (SSS), has variable sensitivity, leading to undiagnosed cases. Improved diagnostics are urgently needed. We assessed a new in-house ELISA method for its diagnostic capabilities against ITS-1 nested PCR (gold standard—Gs). A cohort of 190 clinical CL cases was examined by SSS microscopy, anti-rKRP42 IgG ELISA (serum- and urine-based), and rK39-Immunochromatographic strip test. Validation was done using non-endemic sera, and cutoffs were developed using the receiver operating curve. The sensitivity of SSS for case detection was 77.9% (authors) and 76.3% (technicians). ELISA vs. Gs demonstrated sensitivity (Sn) = 94.4%; specificity (Sp) = 50.0%; positive predictive value (PPV) = 97.1%; negative predictive value (NPV) = 33.3%; Kappa agreement (Kp) = 0.39/p < 0.01. Comparison of the combination method (SSS by technicians and ELISA) vs. Gs showed: Sn = 98.9%; Sp = 30.0; PPV = 96.2; NPV 60.0%; Kp = 0.378/p < 0.01. All methods performed better compared to SSS (29.4%) where the clinical diagnosis was doubtful (PCR = 94.15%; serum ELISA = 88.2%; combination = 94.1%; p < 0.01 for all). High serum anti-rKRP42 titers were seen in those with multiple lesions. Anti-rKRP42 urine ELISA was suboptimal as a diagnostic test. A 9% rate of positivity was seen for rk39-ICT, and positives recorded high anti-rKRP42 titers. The diagnostic accuracy can be increased above the level of the Gs by combining SSS and ELISA. Advanced studies are required to understand the association between rk39-ICT positivity and high anti-rKRP42 titers.

Identification of the Recombinant Plasmodium vivax Surface-Related Antigen as a Possible Immune Evasion Factor Against Human Splenic Fibroblasts by Targeting ITGB1

Plasmodium vivax–infected erythrocytes can enter the spleen and evade spleen clearance to establish chronic infections. However, the mechanism underlying P. vivax immune evasion in the spleen is still unclear. Human splenic fibroblasts (HSF), also known as barrier cells, play an essential role in the immune function of spleen. A hypothesis holds that P. vivax—infected erythrocytes induce spleen structural remodeling to form barrier cells. Subsequently, these infected erythrocytes can selectively cytoadhere to these barrier cells to escape spleen clearance. In this work, we found that P. vivax surface-related antigen (PvSRA; PlasmoDB ID: PVX_084970), an exported protein on infected erythrocyte membrane, could bind with HSF. Considering the above hypothesis, we speculated that PvSRA might be involved in P. vivax immune evasion by changing HSF cell performance. To investigate this speculation, RNA sequencing, protein microarray, and bioinformatics analysis technologies were applied, and in vitro validations were further performed. The results showed that the recombinant PvSRA attracted HSF migration and interacted with HSF by targeting integrin β1 (ITGB1) along with changes in HSF cell performance, such as focal adhesion, extracellular matrix, actin cytoskeleton, and cell cycle. This study indicated that PvSRA might indeed participate in the immune evasion of P. vivax in the spleen by changing HSF function through PvSRA–ITGB1 axis.

Cellular Mechanisms of Liver Fibrosis

The liver is a central organ in the human body, coordinating several key metabolic roles. The structure of the liver which consists of the distinctive arrangement of hepatocytes, hepatic sinusoids, the hepatic artery, portal vein and the central vein, is critical for its function. Due to its unique position in the human body, the liver interacts with components of circulation targeted for the rest of the body and in the process, it is exposed to a vast array of external agents such as dietary metabolites and compounds absorbed through the intestine, including alcohol and drugs, as well as pathogens. Some of these agents may result in injury to the cellular components of liver leading to the activation of the natural wound healing response of the body or fibrogenesis. Long-term injury to liver cells and consistent activation of the fibrogenic response can lead to liver fibrosis such as that seen in chronic alcoholics or clinically obese individuals. Unidentified fibrosis can evolve into more severe consequences over a period of time such as cirrhosis and hepatocellular carcinoma. It is well recognized now that in addition to external agents, genetic predisposition also plays a role in the development of liver fibrosis. An improved understanding of the cellular pathways of fibrosis can illuminate our understanding of this process, and uncover potential therapeutic targets. Here we summarized recent aspects in the understanding of relevant pathways, cellular and molecular drivers of hepatic fibrosis and discuss how this knowledge impact the therapy of respective disease.

Leishmania infantum Enhances Migration of Macrophages via a Phosphoinositide 3-Kinase γ-Dependent Pathway

Leishmania infantum (L. infantum) and Leishmania major (L. major) are phylogenetically related protozoan parasites that cause different pathologies in humans (visceral and cutaneous infections, respectively). Here, we report on how these obligatory intracellular pathogens differentially affect the migration of macrophages. Resorting to gap closure assays of infected murine bone marrow derived macrophages, we observed that L. infantum enhances the mobility of these cells. This is not the case of L. major, whose impact on macrophage migration is null. Resorting to kinase inhibition assays, we witnessed that chemical inhibition of phosphoinositide 3-kinase-γ (PI3Kγ) critically impairs cell mobility in all experimental conditions. Importantly, the blockade of tyrosine kinases with dasatinib also slows down naı̈ve and L. major-parasitized cells but not macrophages exposed to L. infantum. The dasatinib-resistant phenotype of L. infantum-infected macrophages aligns with the hypothesis that this parasite invokes a tyrosine kinase-independent pathway to increase the PI3Kγ activity of macrophages and enhance migration.

SILAC-based quantitative proteomics reveals pleiotropic, phenotypic modulation in primary murine macrophages infected with the protozoan pathogen Leishmania donovani

Leishmaniases are major vector-borne tropical diseases responsible for great human morbidity and mortality, caused by protozoan, trypanosomatid parasites of the genus Leishmania. In the mammalian host, parasites survive and multiply within mononuclear phagocytes, especially macrophages. However, the underlying mechanisms by which Leishmania spp. affect their host are not fully understood. Herein, proteomic alterations of primary, bone marrow-derived BALB/c macrophages are documented after 72 h of infection with Leishmania donovani insect-stage promastigotes, applying a SILAC-based, quantitative proteomics approach. The protocol was optimised by combining strong anion exchange and gel electrophoresis fractionation that displayed similar depth of analysis (combined total of 6189 mouse proteins). Our analyses revealed 86 differentially modulated proteins (35 showing increased and 51 decreased abundance) in response to Leishmania donovani infection. The proteomics results were validated by analysing the abundance of selected proteins. Intracellular Leishmania donovani infection led to changes in various host cell biological processes, including primary metabolism and catabolic process, with a significant enrichment in lysosomal organisation. Overall, our analysis establishes the first proteome of bona fide primary macrophages infected ex vivo with Leishmania donovani, revealing new mechanisms acting at the host/pathogen interface. SIGNIFICANCE: Little is known on proteome changes that occur in primary macrophages after Leishmania donovani infection. This study describes a SILAC-based quantitative proteomics approach to characterise changes of bone marrow-derived macrophages infected with L. donovani promastigotes for 72 h. With the application of SILAC and the use of SAX and GEL fractionation methods, we have tested new routes for proteome quantification of primary macrophages. The protocols developed here can be applicable to other diseases and pathologies. Moreover, this study sheds important new light on the "proteomic reprogramming" of infected macrophages in response to L. donovani promastigotes that affects primary metabolism, cellular catabolic processes, and lysosomal/vacuole organisation. Thus, our study reveals key molecules and processes that act at the host/pathogen interface that may inform on new immuno- or chemotherapeutic interventions to combat leishmaniasis.

How to master the host immune system? Leishmania parasites have the solutions!

Infection by protozoan parasites of the genus Leishmania results in the development of leishmaniasis, an increasingly prevalent group of diseases affecting over 12 million people worldwide. Leishmaniasis can have very different outcomes ranging from cutaneous lesions, mucosal lesions to visceralization depending on the species of the infecting parasite and on the immune response developed by the host. As an obligate intracellular parasite, residing within macrophages, Leishmania evolved in strict contact with the host immune system, developing different mechanisms to evade or modulate the immune response. Various types of immune responses are observed during different Leishmania spp. infections, resulting in parasite clearance but also contributing to the pathogenesis, thus increasing the complexity of the course of the disease. Interestingly, depending on the type of leishmaniasis developed, opposite treatment strategies, which either boost or inhibit the inflammatory response, have shown efficacy. In this review, we summarize the contribution of different immune cell types to the development of the anti-leishmanial immune response and the parasite strategies to evade and modulate host immunity. Further, we discuss the involvement of co-infecting pathogens in the determination of the outcome of leishmaniasis and on the effectiveness of treatment and the implication of the immune response for treatment and vaccine development.

Leishmania infection inhibits macrophage motility by altering F-actin dynamics and the expression of adhesion complex proteins

Leishmania is an intracellular protozoan parasite that causes a broad spectrum of clinical manifestations, ranging from self-healing skin lesions to fatal visceralizing disease. As the host cells of choice for all species of Leishmania, macrophages are critical for the establishment of infections. How macrophages contribute to parasite homing to specific tissues and how parasites modulate macrophage function are still poorly understood. In this study, we show that Leishmania amazonensis infection inhibits macrophage roaming motility. The reduction in macrophage speed is not dependent on particle load or on factors released by infected macrophages. L. amazonensis-infected macrophages also show reduced directional migration in response to the chemokine MCP-1. We found that infected macrophages have lower levels of total paxillin, phosphorylated paxillin, and phosphorylated focal adhesion kinase when compared to noninfected macrophages, indicating abnormalities in the formation of signaling adhesion complexes that regulate motility. Analysis of the dynamics of actin polymerization at peripheral sites also revealed a markedly enhanced F-actin turnover frequency in L. amazonensis-infected macrophages. Thus, Leishmania infection inhibits macrophage motility by altering actin dynamics and impairing the expression of proteins that function in plasma membrane-extracellular matrix interactions.

The modulation of MiR-155 and MiR-23a manipulates Klebsiella pneumoniae Adhesion on Human pulmonary Epithelial cells via Integrin α5β1 Signaling

Micro-RNAs (miRNAs) critically regulate several host defense mechanisms, but their roles in the bacteria-epithelium interplay remain unclear. Our results displayed that the expression of miR-155 and miR-23a were down-regulated in K. pneumoniae-infected pulmonary epithelial cells. The elevated bacterial adhesion on A549 cells followed the enhancement of the cellular levels of these two miRNAs. Meanwhile, a mechanistic study demonstrated that miR-155 promoted integrin α5β1 function and resulted in the increased actin polymerization. Moreover, a non-histone nuclear protein, high mobility group nucleosomal-binding domain 2 (HMGN2) served as the potential target of miR-155 and miR-23a to regulate the integrin α5β1 expression and K. pneumoniae adhesion. Furthermore, the expression of a known integrin transcription suppressor-Nuclear Factor-I (NFI) was also repressed by miR-155, which paralleled with its chromatin location in the promoter regions of integrin α5 and β1. These results uncover novel links between miRNAs and integrin function to regulate bacterial adhesion, indicating a potential mechanism of host cell autonomous immune response to K. pneumoniae infection.

The site of the bite: Leishmania interaction with macrophages, neutrophils and the extracellular matrix in the dermis

Leishmania spp., the causative agents of leishmaniasis, are intracellular parasites, transmitted to humans via the bite of their sand fly vectors. Once inoculated, the promastigotes are exposed to the dermis, which is composed of extracellular matrix (ECM), growth factors and its resident cells. Promastigote forms are phagocytosed by macrophages recruited to the site of the sand fly bite, either directly or after interaction with neutrophils. Since Leishmania is an intracellular parasite, its interaction with the host ECM has been neglected as well as the immediate steps after the sand fly bite. However, promastigotes must overcome the obstacles presented by the dermis ECM in order to establish the infection. Thus, the study of the interaction between Leishmania promastigotes and ECM components as well as the earliest stages of infection are important steps to understand the establishment of the disease, and could contribute in the future to new drug developments towards leishmaniasis.