Host Cell Signalling and Leishmania Mechanisms of Evasion

Leishmania parasites are able to secure their survival and propagation within their host by altering signalling pathways involved in the ability of macrophages to kill pathogens or to engage adaptive immune system. An important step in this immune evasion process is the activation of host protein tyrosine phosphatase SHP-1 by Leishmania. SHP-1 has been shown to directly inactivate JAK2 and Erk1/2 and to play a role in the negative regulation of several transcription factors involved in macrophage activation. These signalling alterations contribute to the inactivation of critical macrophage functions (e.g., Nitric oxide, IL-12, and TNF-α). Additionally, to interfere with IFN-γ receptor signalling, Leishmania also alters several LPS-mediated responses. Recent findings from our laboratory revealed a pivotal role for SHP-1 in the inhibition of TLR-induced macrophage activation through binding to and inactivating IL-1-receptor-associated kinase 1 (IRAK-1). Furthermore, we identified the binding site as an evolutionarily conserved ITIM-like motif, which we named kinase tyrosine-based inhibitory motif (KTIM). Collectively, a better understanding of the evasion mechanisms utilized by Leishmania parasite could help to develop more efficient antileishmanial therapies in the near future

Leishmania-Induced IRAK-1 Inactivation Is Mediated by SHP-1 Interacting with an Evolutionarily Conserved KTIM Motif

Parasites of the Leishmania genus can rapidly alter several macrophage (MØ) signalling pathways in order to tame down the innate immune response and inflammation, therefore favouring their survival and propagation within their mammalian host. Having recently reported that Leishmania and bacterial LPS generate a significantly stronger inflammatory response in animals and phagocytes functionally deficient for the Src homology 2 domain-containing protein tyrosine phosphatase (SHP-1), we hypothesized that Leishmania could exploit SHP-1 to inactivate key kinases involved in Toll-like receptor (TLR) signalling and innate immunity such as IL-1 receptor-associated kinase 1 (IRAK-1). Here we show that upon infection, SHP-1 rapidly binds to IRAK-1, completely inactivating its intrinsic kinase activity and any further LPS-mediated activation as well as MØ functions. We also demonstrate that the SHP-1/IRAK-1 interaction occurs via an evolutionarily conserved ITIM-like motif found in the kinase domain of IRAK-1, which we named KTIM (Kinase Tyrosyl-based Inhibitory Motif). This regulatory motif appeared in early vertebrates and is not found in any other IRAK family member. Our study additionally reveals that several other kinases (e.g. Erk1/2, IKKα/β) involved in downstream TLR signalling also bear KTIMs in their kinase domains and interact with SHP-1. We thus provide the first demonstration that a pathogen can exploit a host protein tyrosine phosphatase, namely SHP-1, to directly inactivate IRAK-1 through a generally conserved KTIM motif

Alteration of macrophage signalling and functions by the protozoan parasite «Leishmania»

Parasites of the genus Leishmania are able to secure their survival and propagation within their host by altering key signalling pathways involved in the ability of macrophages (MØs) to directly kill pathogens or to activate cells of the adaptive immune system. One important step in this immune evasion process is the Leishmania-induced activation of host protein tyrosine phosphatase SHP-1. SHP-1 has been shown to directly inactivate JAK2 and Erk1/2, and to play a role in the negative regulation of several transcription factors involved in MØ activation such as: NF-B, STAT-1α, and AP-1. These signalling alterations contribute to the inactivation of critical MØ functions such as the production of IFN-γ-induced nitric oxide (NO), a free radical associated with parasite killing and clearance. In addition to interfering with IFN-γ receptor signalling, Leishmania is able to alter several LPS-mediated responses (e.g. IL-12, TNF-α, NO production) through mechanisms not yet fully understood. A main goal of this study was to better understand the mechanisms used by the parasite to block Toll-like receptor (TLR)-mediated functions. Experiments performed revealed a pivotal role for SHP-1 in the inhibition of TLR-induced MØ activation through binding to and inactivating IL-1 receptor-associated kinase 1 (IRAK-1). We identified the binding site as an evolutionarily conserved ITIM-like motif, which we named kinase tyrosine-based inhibitory motif (KTIM). Further experiments and sequence analysis revealed that several cytosolic kinases other than IRAK-1 possess potential KTIMs, suggesting it could represent a regulatory mechanism widely used by kinases. The final experimental section aimed to explore the differential ability of the two different stages of Leishmania, promastigotes and amastigotes, to alter MØ signalling and function. In conclusion, this work uncovers a new mechanism whereby Leishmania is ableLes parasites du genre Leishmania assurent leur survie et leur propagation par l'altération de voies de signalisation impliquées dans la capacité des macrophages (MØs) à détruire directement les pathogènes ou à activer les cellules du système immunitaire acquis. Une étape critique de ce mécanisme d'inactivation est l'activation par Leishmania de la protéine phosphatase SHP-1 de la cellule hôte. Il a été démontré que la protéine SHP-1 peut inactiver directement JAK2 ainsi que Erk1/2 et joue un rôle dans la régulation négative de plusieurs facteurs de transcription, tels que NF-κB, STAT-1α et AP-1, impliqués dans l'activation des MØs. L'altération de ces voies de signalisation contribue à l'inactivation de fonctions critiques des MØs telle que la production d'oxyde nitrique (NO) induite par l'IFN-γ, un radical-libre impliqué dans l'anéantissement du parasite. En plus d'inhiber les fonctions engendrées par l'IFN-γ, Leishmania est capable d'inhiber de nombreuses fonctions induites par le LPS, incluant la production d'IL-12, de TNF-α et de NO, et cela par des mécanismes encore peu compris. Le but principal de cette étude était de mieux comprendre les stratégies employées par le parasite afin d'inhiber les fonctions induites par les Toll-like receptors (TLRs). Nos résultats révèlent le rôle critique de SHP-1 dans l'inhibition de l'activation des MØs induite par les TLRs, par l'interaction et l'inactivation de la kinase 1 associée au récepteur IL-1 (IRAK-1). Nous avons également identifié le site de liaison qui semble être un motif conservé lors de l'évolution ressemblant à un ITIM, que nous avons nommé motif de kinase à base de tyrosine inhibiteur (KTIM). Des expériences supplémentaires et l'analyse de séquences ont révélées que plusieurs autres kinases cytosoliques autres qu'IRAK-1 possèdent un motif potentiel KTIMs, suggérant que le KTIM pourrait

The place of dining in Frank Lloyd Wright\u27s houses

Part one of this research examines Wright\u27s speech with respect to the notion of a cosmic container, the art of the potter and its implications for the architect. Part two discusses the place of dining in Wright\u27s projects in view of the preceding analysis. The dining area is considered indexical of Wright\u27s sentience towards an archetypal mode of uniting family and fellowship like an ancient mannerbund. It is discovered that the dining table, locus of a desiring gaze meant to unite, is in Wright\u27s houses an important magnet for the organization of the interior in the relations between the parts and the whole. It is also discovered that the setting for the shared meal is a marker for the boundary between the house and the surrounding landscape; it is that which joins both literally and transcendentally by reference to the archetypal relation of nourishment between two bodies, mother and child

The place of dining in Frank Lloyd Wright\u27s houses

Part one of this research examines Wright\u27s speech with respect to the notion of a cosmic container, the art of the potter and its implications for the architect. Part two discusses the place of dining in Wright\u27s projects in view of the preceding analysis. The dining area is considered indexical of Wright\u27s sentience towards an archetypal mode of uniting family and fellowship like an ancient mannerbund. It is discovered that the dining table, locus of a desiring gaze meant to unite, is in Wright\u27s houses an important magnet for the organization of the interior in the relations between the parts and the whole. It is also discovered that the setting for the shared meal is a marker for the boundary between the house and the surrounding landscape; it is that which joins both literally and transcendentally by reference to the archetypal relation of nourishment between two bodies, mother and child

Patterns and trends of hepatitis C virus infection in Jordan: an observational study

Background: Hepatitis C virus (HCV) infection levels in Jordan remain uncertain. No HCV national population-based survey has ever been conducted in the country. To meet the World Health Organization’s target of reducing HCV incidence to ≤5 per 100,000 people per year by 2030, it is essential to determine the infection levels, identify affected individuals and populations, and provide appropriate treatment using direct-acting antivirals to individuals carrying the virus. Methods: The study utilized the HCV testing database of 28,798 attendees of Biolab Diagnostic Laboratories in Jordan, covering the period from January 19, 2010, to May 26, 2023. Cross-sectional and cohort study analyses were conducted, including estimating HCV antibody (Ab) prevalence, examining associations with HCV Ab positivity, determining the HCV viremic rate, and estimating HCV incidence rate using a retrospective cohort study design. Results: A total of 27,591 individuals, with a median age of 31.3 and 52.9% being females, underwent HCV Ab testing, while 1,450 individuals, with a median age of 42.2 and 32.8% being females, underwent HCV RNA PCR testing. The study sample HCV Ab prevalence was 4.0% (95% CI: 3.7–4.2%). After applying probability weights, the weighted HCV Ab prevalence was 5.8% (95% CI: 4.6–7.3%). Age was strongly associated with HCV Ab positivity, particularly among individuals aged 50 years or older, who had 10-fold higher odds of being HCV Ab positive compared to those aged 10–19 years. Males had 2.41-fold higher odds of testing positive for HCV Ab compared to females. The HCV viremic rate was 54.1% (95% CI: 43.0–65.0%). The cumulative incidence of HCV infection, after 5 years of follow-up, was estimated to be 0.41% (95% CI: 0.17–0.99%). The HCV incidence rate was calculated at 1.19 per 1,000 person-years (95% CI, 0.50–2.87). Conclusion: Prevalence and incidence of HCV infection were substantial, estimated at ~5% and 1 per 1,000 person-years, respectively, and highlighting the presence of core groups actively engaged in the virus’ acquisition and transmission. The high observed viremic rate indicates the need for expanding HCV treatment efforts to effectively control HCV transmission in Jordan. Utilizing quality diagnostic laboratories and innovative testing strategies is key to identifying infection carriers and facilitating linkage to treatment and care.The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This publication was made possible by NPRP grant number 12S-0216-190094 from the Qatar National Research Fund (a member of Qatar Foundation; https://www.qnrf.org ). The statements made herein are solely the responsibility of the authors. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors alone are responsible for the views expressed in this publication and they do not necessarily represent the views, decisions, or policies of Biolab Diagnostic Laboratories.Scopu

Comparative Study of the Ability of Leishmania mexicana Promastigotes and Amastigotes To Alter Macrophage Signaling and Functions▿

Leishmania alternates between two morphologically different stages, promastigotes and amastigotes. While the majority of reports focused on how the promastigote form can alter macrophage (Mφ) signaling and function, fewer reports investigated signaling alterations mediated by amastigotes, and there is a lack of comparative studies. In this study, we performed a comparison between the ability of both forms of the parasite to alter Mφ signaling and functions. Here, we show that both promastigotes and amastigotes were able to rapidly activate host protein tyrosine phosphatases (PTPs), importantly the Src homology 2 domain-containing PTP (SHP-1). However, we found that PTP-1B is specifically activated by promastigote but not amastigote infection and that lmcpb−/− promastigotes were no longer able to activate PTP-1B. We also show a similarity in the way promastigotes and amastigotes inactivate the transcription factors (TFs) STAT-1α and AP-1, but we show differences in the modulation of NF-κB, with promastigotes cleaving the p65 subunit, generating a smaller p35 subunit, and amastigotes fully degrading the p65 subunit with no p35 production. Importantly, we show that the cysteine proteinase LmCPb plays a key role in the alteration of NF-κB, STAT-1α, and AP-1 by promastigote and amastigote infections, ultimately leading to the inability of these TFs to translocate to the nucleus in response to gamma interferon (IFN-γ) stimulation and thus contributing to the ability of both parasite forms to effectively block IFN-γ-mediated nitric oxide (NO) production in Mφs

Molecular characterization of patients with chronic hepatitis C virus infection in Jordan: implications on response to direct-acting antiviral therapy

Objectives: To investigate the molecular characteristics of Hepatitis C Virus (HCV) detected in patients with chronic HCV infection in Jordan. Methods: The study included 48 Jordanian treatment-naïve patients with active chronic HCV recruited from seven governorates. HCV genotype and the resistance-associated substitutions (RAS) profile were investigated by next-generation sequencing of the NS5B, NS5A, and NS3 regions of HCV. Results: “Unusual genotype 4 subtypes” were detected in four (8.3%) patients (4n-n = 1, 4o-n = 2, 4v-n = 1); one patient (2.1%) was co-infected by genotypes 1b+4a. Overall prevalence of NS5A RASs was 38.3% (3% cutoff); genotype 4a showed the highest NS5A RAS prevalence (n = 11, 55.0%). Overall prevalence of NS3 RASs was 21.8% (7/32), all genotype 1a-infected patients. Conclusions: We report, for the first time in Jordanian patients with chronic HCV infection, the detection of unusual genotype 4 subtypes 4n, 4o, and 4v. Baseline RASs in NS5A are frequent, with complex RASs patterns in some of the unusual subtypes. Our data support the need for sequencing surveillance programs in sub-Saharan Africa, Asia, and the Middle East and North African region to monitor response to treatment in these subtypes and to facilitate the World Health Organization's 2030 elimination strategy