66 results found
Gimeno-Molina B, Muller I, Kropf P, et al., 2022, The role of neutrophils in pregnancy, term and preterm labour, Life, Vol: 12, ISSN: 2075-1729
Neutrophils are surveillance cells, and the first to react and migrate to sites of inflammation and infection following a chemotactic gradient. Neutrophils play a key role in both sterile inflammation and infection, performing a wide variety of effector functions such as degranulation, phagocytosis, ROS production and release of neutrophil extracellular traps (NETs). Healthy term labour requires a sterile pro-inflammatory process, whereas one of the most common causes of spontaneous preterm birth is microbial driven. Peripheral neutrophilia has long been described during pregnancy, and evidence exists demonstrating neutrophils infiltrating the cervix, uterus and foetal membranes during both term and preterm deliveries. Their presence supports a role in tissue remodelling via their effector functions. In this review, we describe the effector functions of neutrophils. We summarise the evidence to support their role in healthy pregnancy and labour and describe their potential contribution to microbial driven preterm birth.
Takele Y, Adem E, Mulaw T, et al., 2022, Following successful anti-leishmanial treatment, neutrophil counts, CD10 expression and phagocytic capacity remain reduced in visceral leishmaniasis patients co-infected with HIV., PLoS Negl Trop Dis, Vol: 16
Visceral leishmaniasis (VL) patients co-infected with HIV (VL/HIV patients) experience frequent treatment failures, VL relapses, opportunistic infections, and higher mortality. Their immune system remains profoundly suppressed after clinical cure and they maintain higher parasite load. This is in contrast with patients with VL alone (VL patients). Since neutrophils play a critical role in the control of Leishmania replication and the regulation of immune responses, we tested the hypothesis that neutrophil activation status and effector functions are fully restored in VL, but not in VL/HIV patients. Our results show the neutrophil counts and all activation markers and effector functions tested in our study were reduced at the time of diagnosis in VL and VL/HIV patients as compared to controls. CD62L, CD63, arginase 1 expression levels and reactive oxygen species production were restored at the end of treatment in both groups. However, neutrophil counts, CD10 expression and phagocytosis remained significantly lower throughout follow-up in VL/HIV patients; suggesting that dysregulated neutrophils contribute to the impaired host defence against pathogens in VL/HIV patients.
Takele Y, Adem E, Franssen SU, et al., 2022, Impaired in vitro Interferon-gamma production in patients with visceral leishmaniasis is improved by inhibition of PD1/PDL-1 ligation, PLOS NEGLECTED TROPICAL DISEASES, Vol: 16, ISSN: 1935-2735
Molina B, Bayar E, Lee Y, et al., 2022, Cervicovaginal inflammation and neutrophil infiltration/activation in women at high-risk of prematurity, Publisher: WILEY, Pages: 54-54, ISSN: 1470-0328
Chan D, Bennett P, Lee YS, et al., 2022, Microbial-driven preterm labour involves crosstalk between the innate and adaptive immune response, Nature Communications, Vol: 13, ISSN: 2041-1723
There has been a surge in studies implicating a role of vaginal microbiota in spontaneous preterm birth (sPTB), but most are associative without mechanistic insight. Here we show a comprehensive approach to understand the causative factors of preterm birth, based on the integration of longitudinal vaginal microbiota and cervicovaginal fluid (CVF) immunophenotype data collected from 133 women at high-risk of sPTB. We show that vaginal depletion of Lactobacillus species and high bacterial diversity leads to increased mannose binding lectin (MBL), IgM, IgG, C3b, C5, IL-8, IL-6 and IL-1β and to increased risk of sPTB. Cervical shortening, which often precedes preterm birth, is associated with Lactobacillus iners and elevated levels of IgM, C3b, C5, C5a and IL-6. These data demonstrate a role for the complement system in microbial-driven sPTB and provide a scientific rationale for the development of live biotherapeutics and complement therapeutics to prevent sPTB.
Takele Y, Mulaw, Adem, et al., 2022, Immunological factors, but not clinical features, predict visceral leishmaniasis relapse in patients co-infected with HIV, Cell Reports Medicine, Vol: 3, ISSN: 2666-3791
Visceral leishmaniasis (VL) has emerged as a clinically important opportunistic infection in HIV patients, as VL/HIV co-infected patients suffer from frequent VL relapse. Here, we follow cohorts of VL patients with or without HIV in Ethiopia. By the end of the study 78.1% of VL/HIV, but none of the VL patients, experience VL relapse. Despite clinically defined cure, VL/HIV patients maintain higher parasite loads, lower BMI, hepatosplenomegaly and pancytopenia. We identify three immunological markers associated with VL relapse in VL/HIV patients: i) failure to restore antigen-specific production of IFNg, ii) persistently lower CD4+ T cell counts, and iii) higher expression of PD1 on CD4+ and CD8+ T cells. We show that these three markers, that can be measured in primary hospital settings in Ethiopia, combine well in predicting VL relapse. The use of our prediction model has the potential to improve disease management and patient care.
Chan D, Bennett PR, Lee YS, et al., 2021, Microbial-Driven Preterm Labour Involves Crosstalk between the Innate and Adaptive Immune Response., Publisher: SPRINGER HEIDELBERG, Pages: 108A-109A, ISSN: 1933-7191
Franssen SU, Takele Y, Adem E, et al., 2021, Diversity and within-host evolution of Leishmania donovani from visceral Leishmaniasis patients with and without HIV coinfection in northern Ethiopia., mBio, Vol: 12, Pages: 1-19, ISSN: 2150-7511
Visceral leishmaniasis (VL) is a fatal disease and a growing public health problem in East Africa, where Ethiopia has one of the highest VL burdens. The largest focus of VL in Ethiopia is driven by high prevalence in migrant agricultural workers and associated with a high rate of coinfection with HIV. This coinfection makes VL more difficult to treat successfully and is associated with a high rate of relapse, with VL/HIV patients frequently experiencing many relapses of VL before succumbing to this infection. We present genome-wide data on Leishmania donovani isolates from a longitudinal study of cohorts of VL and VL/HIV patients reporting to a single clinic in Ethiopia. Extensive clinical data allow us to investigate the influence of coinfection and relapse on the populations of parasites infecting these patients. We find that the same parasite population is responsible for both VL and VL/HIV infections and that, in most cases, disease relapse is caused by recrudescence of the population of parasites that caused primary VL. Complex, multiclonal infections are present in both primary and relapse cases, but the infrapopulation of parasites within a patient loses genetic diversity between primary disease presentation and subsequent relapses, presumably due to a population bottleneck induced by treatment. These data suggest that VL/HIV relapses are not caused by genetically distinct parasite infections or by reinfection. Treatment of VL does not lead to sterile cure, and in VL/HIV, the infecting parasites are able to reestablish after clinically successful treatment, leading to repeated relapse of VL. IMPORTANCE Visceral leishmaniasis (VL) is the second largest cause of deaths due to parasite infections and a growing problem in East Africa. In Ethiopia, it is particularly associated with migrant workers moving from regions of nonendemicity for seasonal agricultural work and is frequently found as a coinfection with HIV, which leads to frequent VL relapse following trea
Abera EA, Tajebe F, Getahun M, et al., 2019, Successful treatment of human visceral leishmaniasis restores antigen-specific IFN-gamma, but not IL-10 production, 17th International Congress of Immunology of the International-Union-of-Immunological-Societies (IUIS), Publisher: WILEY, Pages: 1186-1187, ISSN: 0014-2980
Thurairajah S, Alqurashi M, Chan D, et al., 2019, Characterisation of Peripheral Blood Neutrophil Phenotype and Effector Functions during Pregnancy, Labour and in Women at High Risk of Preterm Labour., 66th Annual Scientific Meeting of the Society-for-Reproductive-Investigation (SRI), Publisher: SAGE PUBLICATIONS INC, Pages: 123A-123A, ISSN: 1933-7191
Alqurashi M, Thurairajah S, Adan M, et al., 2019, Characterisation of Normal and Low Density Granulocytes in Pregnancy, Term Labour, and Women at High Risk of Preterm Labour., 66th Annual Scientific Meeting of the Society-for-Reproductive-Investigation (SRI), Publisher: SAGE PUBLICATIONS INC, Pages: 122A-123A, ISSN: 1933-7191
Tajebe F, Getahun M, Adem E, et al., 2017, Disease severity in patients with visceral leishmaniasis is not altered by co-infection with intestinal parasites, PLoS Neglected Tropical Diseases, Vol: 11, ISSN: 1935-2727
Visceral leishmaniasis (VL) is a neglected tropical disease that affects the poorest communities and can cause substantial morbidity and mortality. Visceral leishmaniasis is characterized by the presence of Leishmania parasites in the spleen, liver and bone marrow, hepatosplenomegaly, pancytopenia, prolonged fever, systemic inflammation and low body mass index (BMI). The factors impacting on the severity of VL are poorly characterized. Here we performed a cross-sectional study to assess whether co-infection of VL patients with intestinal parasites influences disease severity, assessed with clinical and haematological data, inflammation, cytokine profiles and BMI. Data from VL patients was similar to VL patients co-infected with intestinal parasites, suggesting that co-infection of VL patients with intestinal parasites does not alter disease severity.
Taslimi Y, Sadeghipour P, Habibzadeh S, et al., 2017, A novel non-invasive diagnostic sampling technique for cutaneous leishmaniasis, PLoS Neglected Tropical Diseases, Vol: 11, ISSN: 1935-2727
Accurate diagnosis of cutaneous leishmaniasis (CL) is important for chemotherapy and epidemiological studies. Common approaches for Leishmania detection involve the invasive collection of specimens for direct identification of amastigotes by microscopy and the culturing of promastigotes from infected tissues. Although these techniques are highly specific, they require highly skilled health workers and have the inherent risks of all invasive procedures, such as pain and risk of bacterial and fungal super-infection. Therefore, it is essential to reduce discomfort, potential infection and scarring caused by invasive diagnostic approaches especially for children. In this report, we present a novel non-invasive method, that is painless, rapid and user-friendly, using sequential tape strips for sampling and isolation of DNA from the surface of active and healed skin lesions of CL patients. A total of 119 patients suspected of suffering from cutaneous leishmaniasis with different clinical manifestations were recruited and samples were collected both from their lesions and from uninfected areas. In addition, 15 fungal-infected lesions and 54 areas of healthy skin were examined. The duration of sampling is short (less than one minute) and species identification by PCR is highly specific and sensitive. The sequential tape stripping sampling method is a sensitive, non-invasive and cost-effective alternative to traditional diagnostic assays and it is suitable for field studies as well as for use in health care centers.
Mortazavi H, Sadeghipour P, Taslimi Y, et al., 2016, Comparing acute and chronic human cutaneous leishmaniasis caused by Leishmania major and Leishmania tropica focusing on arginase activity., Journal of the European Academy of Dermatology and Venereology, Vol: 30, Pages: 2118-2121, ISSN: 1468-3083
BACKGROUND: Cutaneous leishmaniasis (CL) in Iran is mainly caused by Leishmania major (L. major) and L. tropica. Arginase mediated L-arginine metabolism is an important issue in Leishmania parasite propagation. Arginase activity in human CL due to L. major and L. tropica have not been studied up to now. OBJECTIVES: We aimed to compare the clinical and laboratory aspects of acute and chronic CL, focussing on arginase activity. METHODS: In this case-control study, 30 patients with acute CL (duration ≤ 1 year), 13 patients with chronic CL (duration ≥ 2 year) and 11 healthy controls were recruited. Arginase activity was measured in skin biopsies of lesions, peripheral blood polymorphonuclear cells (PMNs), peripheral blood mononuclear cells (PBMCs) and plasma by standard methods. RESULTS: The median of arginase activity in the acute lesions was higher than in chronic samples and significantly higher than in healthy controls (P = 0.008). PMNs of both acute and chronic patients showed higher levels of arginase activity as compared to the levels in PBMCs and plasma. The median of arginase activity in the PMNs of patients with chronic CL was higher than that of patients with acute CL and significantly higher than that of the healthy controls (P = 0.010). CONCLUSION: The level of arginase activity in lesions of patients with acute and chronic CL was higher than the skin of healthy controls. The highest level of arginase activity was observed in PMNs from patients with chronic CL. This suggests that the high level of arginase activity in PMNs of patients with chronic CL may contribute to the chronicity.
Yizengaw E, Getahun M, Tajebe F, et al., 2016, Visceral leishmaniasis patients display altered composition and maturity of neutrophils as well as impaired neutrophil effector functions, Frontiers in Immunology, Vol: 7, ISSN: 1664-3224
Immunologically, active visceral leishmaniasis (VL) is characterised by profound immunosuppression, severe systemic inflammatoryresponses and an impaired capacity to control parasite replication. Neutrophils are highly versatile cells, which play a crucial rolein the induction as well as the resolution of inflammation, the control of pathogen replication and the regulation of immuneresponses. Neutrophil functions have been investigated in human cutaneous leishmaniasis, however, their role in human visceralleishmaniasis is poorly understood.In the present study we evaluated the activation status and effector functions of neutrophils in patients with active VL and aftersuccessful anti-leishmanial treatment. Our results show that neutrophils are highly activated and have degranulated; high levels ofarginase, myeloperoxidase and elastase, all contained in neutrophils’ granules, were found in the plasma of VL patients. Inaddition, we show that a large proportion of these cells are immature. We also analysed effector functions of neutrophils that areessential for pathogen clearance and show that neutrophils have an impaired capacity to release neutrophil extracellular traps,produce reactive oxygen species and phagocytose bacterial particles, but not Leishmania parasites.Our results suggest that impaired effector functions, increased activation and immaturity of neutrophils play a key role in thepathogenesis of VL.
Takele Y, Adem E, Getahun M, et al., 2016, Malnutrition in Healthy Individuals Results in Increased Mixed Cytokine Profiles, Altered Neutrophil Subsets and Function, PLOS One, Vol: 11, ISSN: 1932-6203
Malnutrition is commonly associated with increased infectious disease susceptibility and severity. Whereas malnutrition might enhance the incidence of disease as well as its severity, active infection can in turn exacerbate malnutrition. Therefore, in a malnourished individual suffering from a severe infection, it is not possible to determine the contribution of the pre-existing malnutrition and/or the infection itself to increased disease severity. In the current study we focussed on two groups of malnourished, but otherwise healthy individuals: moderately malnourished (BMI: 18.4-16.5) and severely malnourished (BMI <16.5) and compared several immune parameters with those of individuals with a normal BMI (≥18.5). Our results show a similar haematological profile in all three groups, as well as a similar ratio of CD4+ and CD8+ T cells. We found significant correlations between low BMI and increased levels of T helper (Th) 1 (Interferon (IFN)-γ, (interleukin (IL)-2, IL-12), Th2 (IL-4, IL-5, IL-13), as well as IL-10, IL-33 and tumor necrosis factor-α, but not IL-8 or C reactive protein. The activities of arginase, an enzyme associated with immunosuppression, were similar in plasma, peripheral blood mononuclear cells (PBMC) and neutrophils from all groups and no differences in the expression levels of CD3ζ, a marker of T cell activation, were observed in CD4+ and CD8+T cells. Furthermore, whereas the capacity of neutrophils from the malnourished groups to phagocytose particles was not impaired, their capacity to produce reactive oxygen species was impaired. Finally we evaluated the frequency of a subpopulation of low-density neutrophils and show that they are significantly increased in the malnourished individuals. These differences were more pronounced in the severely malnourished group. In summary, our results show that even in the absence of apparent infections, healthy malnourished individuals display dysfunctional immune responses that might
Adem E, Tajebe F, Getahun M, et al., 2016, Successful treatment of human visceral leishmaniasis restores antigen-specific IFN-γ, but not IL-10 production, PLOS Neglected Tropical Diseases, Vol: 10, Pages: e0004468-e0004468, ISSN: 1935-2735
One of the key immunological characteristics of active visceral leishmaniasis (VL) is a profound immunosuppression and impaired production of Interferon-γ (IFN-γ). However, recent studies from Bihar in India showed using a whole blood assay, that whole blood cells have maintained the capacity to produce IFN-γ. Here we tested the hypothesis that a population of low-density granulocytes (LDG) might contribute to T cell responses hyporesponsiveness via the release of arginase. Our results show that this population is affected by the anticoagulant used to collect blood: the frequency of LDGs is significantly lower when the blood is collected with heparin as compared to EDTA; however, the anticoagulant does not impact on the levels of arginase released. Next, we assessed the capacity of whole blood cells from patients with active VL to produce IFN-γ and IL-10 in response to antigen-specific and polyclonal activation. Our results show that whole blood cells produce low or levels below detection limit of IFN-γ and IL-10, however, after successful treatment of VL patients, these cells gradually regain their capacity to produce IFN-γ, but not IL-10, in response to activation. These results suggest that in contrast to VL patients from Bihar, India, whole blood cells from VL patients from Gondar, Ethiopia, have lost their ability to produce IFN-γ during active VL and that active disease is not associated with sustained levels of IL-10 production following stimulation.
Jarvis JN, Meintjes G, Bicanic T, et al., 2015, Cerebrospinal fluid cytokine profiles predict risk of early mortality and immune reconstitution inflammatory syndrome in HIV-associated cryptococcal meningitis, Plos Pathogens, Vol: 11, ISSN: 1553-7374
Understanding the host immune response during cryptococcal meningitis (CM) is of criticalimportance for the development of immunomodulatory therapies. We profiled the cerebrospinalfluid (CSF) immune-response in ninety patients with HIV-associated CM, and examinedassociations between immune phenotype and clinical outcome. CSF cytokine,chemokine, and macrophage activation marker concentrations were assayed at diseasepresentation, and associations between these parameters and microbiological and clinicaloutcomes were examined using principal component analysis (PCA). PCA demonstrated aco-correlated CSF cytokine and chemokine response consisting primarily of Th1, Th2, andTh17-type cytokines. The presence of this CSF cytokine response was associated with evidenceof increased macrophage activation, more rapid clearance of Cryptococci from CSF,and survival at 2 weeks. The key components of this protective immune-response were interleukin(IL)-6 and interferon-γ, IL-4, IL-10 and IL-17 levels also made a modest positivecontribution to the PC1 score. A second component of co-correlated chemokines was identifiedby PCA, consisting primarily of monocyte chemotactic protein-1 (MCP-1) and macrophageinflammatory protein-1α (MIP-1α). High CSF chemokine concentrations wereassociated with low peripheral CD4 cell counts and CSF lymphocyte counts and were predictiveof immune reconstitution inflammatory syndrome (IRIS). In conclusion CSF cytokineand chemokine profiles predict risk of early mortality and IRIS in HIV-associated CM. Wespeculate that the presence of even minimal Cryptococcus-specific Th1-type CD4+ T-cellresponses lead to increased recruitment of circulating lymphocytes and monocytes into the central nervous system (CNS), more effective activation of CNS macrophages and microglialcells, and faster organism clearance; while high CNS chemokine levels may predisposeto over recruitment or inappropriate recruitment of immune cells to the CNS and IRISfollowing peri
Kapp K, Pruefer S, Michel CS, et al., 2014, Granulocyte functions are independent of arginine availability, JOURNAL OF LEUKOCYTE BIOLOGY, Vol: 96, Pages: 1047-1053, ISSN: 0741-5400
Rath M, Mueller I, Kropf P, et al., 2014, Metabolism via arginase or nitric oxide synthase: two competing arginine pathways in macrophages, Frontiers in Immunology, Vol: 5, ISSN: 1664-3224
Macrophages play a major role in the immune system, both as antimicrobial effector cellsand as immunoregulatory cells, which induce, suppress or modulate adaptive immuneresponses. These key aspects of macrophage biology are fundamentally driven by thephenotype of macrophage arginine metabolism that is prevalent in an evolving or ongoingimmune response. M1 macrophages express the enzyme nitric oxide synthase, whichmetabolizes arginine to nitric oxide (NO) and citrulline. NO can be metabolized to furtherdownstream reactive nitrogen species, while citrulline might be reused for efficient NOsynthesis via the citrulline–NO cycle. M2 macrophages are characterized by expression ofthe enzyme arginase, which hydrolyzes arginine to ornithine and urea. The arginase pathwaylimits arginine availability for NO synthesis and ornithine itself can further feed into theimportant downstream pathways of polyamine and proline syntheses, which are importantfor cellular proliferation and tissue repair. M1 versus M2 polarization leads to opposing outcomesof inflammatory reactions, but depending on the context, M1 and M2 macrophagescan be both pro- and anti-inflammatory. Notably, M1/M2 macrophage polarization can bedriven by microbial infection or innate danger signals without any influence of adaptiveimmune cells, secondarily driving the T helper (Th)1/Th2 polarization of the evolving adaptiveimmune response. Since both arginine metabolic pathways cross-inhibit each other onthe level of the respective arginine break-down products andTh1 andTh2 lymphocytes candrive or amplify macrophage M1/M2 dichotomy via cytokine activation, this forms the basisof a self-sustaining M1/M2 polarization of the whole immune response. Understanding thearginine metabolism of M1/M2 macrophage phenotypes is therefore central to find newpossibilities to manipulate immune responses in infection, autoimmune diseases, chronicinflammatory conditions, and cancer.
Corware K, Yardley V, Mack C, et al., 2014, Protein energy malnutrition increases arginase activity in monocytes and macrophages, Nutrition & Metabolism, Vol: 11, ISSN: 1743-7075
Background: Protein energy malnutrition is commonly associated with immune dysfunctions and is a major factorin susceptibility to infectious diseases.Methods: In this study, we evaluated the impact of protein energy malnutrition on the capacity of monocytes andmacrophages to upregulate arginase, an enzyme associated with immunosuppression and increased pathogenreplication.Results: Our results show that monocytes and macrophages are significantly increased in the bone marrow andblood of mice fed on a protein low diet. No alteration in the capacity of bone marrow derived macrophagesisolated from malnourished mice to phagocytose particles, to produce the microbicidal molecule nitric oxide andto kill intracellular Leishmania parasites was detected. However, macrophages and monocytes from malnourished miceexpress significantly more arginase both in vitro and in vivo. Using an experimental model of visceral leishmaniasis, weshow that following protein energy malnutrition, the increased parasite burden measured in the spleen of these micecoincided with increased arginase activity and that macrophages provide a more permissive environment for parasitegrowth.Conclusions: Taken together, these results identify a novel mechanism in protein energy malnutrition that mightcontributes to increased susceptibility to infectious diseases by upregulating arginase activity in myeloid cells.
Ssemaganda A, Kindinger L, Bergin P, et al., 2014, Characterization of neutrophil subsets in healthy human pregnancies, PLOS One, Vol: 9, ISSN: 1932-6203
We have previously shown that in successful pregnancies increased arginase activity is a mechanism that contributes to the suppression of the maternal immune system. We identified the main type of arginase-expressing cells as a population of activated low-density granulocytes (LDGs) in peripheral blood mononuclear cells and in term placentae. In the present study, we analyzed the phenotype of LDGs and compared it to the phenotype of normal density granulocytes (NDGs) in maternal peripheral blood, placental biopsies and cord blood. Our data reveal that only LDGs but no NDGs could be detected in placental biopsies. Phenotypically, NDGs and LDGs from both maternal and cord blood expressed different levels of maturation, activation and degranulation markers. NDGs from the maternal and cord blood were phenotypically similar, while maternal, cord and placental LDGs showed different expression levels of CD66b. LDGs present in cord blood expressed higher levels of arginase compared to maternal and placental LDGs. In summary, our results show that in maternal and cord blood, two phenotypically different populations of neutrophils can be identified, whereas in term placentae, only activated neutrophils are present.
Conceicao-Silva F, Morgado FN, Fernandes Pimentel MI, et al., 2013, Two women presenting worsening cutaneous ulcers during pregnancy: diagnosis, immune response, and follow-up, PLOS Neglected Tropical Diseases, Vol: 7, ISSN: 1935-2735
Glass DG, McAlinden N, Kropf P, et al., 2013, Optical tweezers: manipulating and quantifying immune cell interactions to understand the importance of L-arginine on T-cell function, Annual Congress of the British-Society-for-Immunology, Publisher: WILEY-BLACKWELL, Pages: 139-139, ISSN: 0019-2805
Cloke T, Munder M, Bergin P, et al., 2013, Phenotypic Alteration of Neutrophils in the Blood of HIV Seropositive Patients, PLOS ONE, Vol: 8, ISSN: 1932-6203
Kapp K, Pruefer S, Habermeier A, et al., 2013, GRANULOCYTE FUNCTION IS NOT IMPAIRED BY ARGININE DEFICIENCY, Publisher: FERRATA STORTI FOUNDATION, Pages: 423-423, ISSN: 0390-6078
Munder M, Engelhardt M, Knies D, et al., 2013, Cytotoxicity of tumor antigen specific human T cells is unimpaired by arginine depletion, PLOS One, Vol: 8, ISSN: 1932-6203
Tumor-growth is often associated with the expansion of myeloid derived suppressor cells that lead to local or systemic arginine depletion via the enzyme arginase. It is generally assumed that this arginine deficiency induces a global shut-down of T cell activation with ensuing tumor immune escape. While the impact of arginine depletion on polyclonal T cell proliferation and cytokine secretion is well documented, its influence on chemotaxis, cytotoxicity and antigen specific activation of human T cells has not been demonstrated so far. We show here that chemotaxis and early calcium signaling of human T cells are unimpaired in the absence of arginine. We then analyzed CD8+ T cell activation in a tumor peptide as well as a viral peptide antigen specific system: (i) CD8+ T cells with specificity against the MART-1aa26–35*A27L tumor antigen expanded with in vitro generated dendritic cells, and (ii) clonal CMV pp65aa495–503 specific T cells and T cells retrovirally transduced with a CMV pp65aa495–503 specific T cell receptor were analyzed. Our data demonstrate that human CD8+ T cell antigen specific cytotoxicity and perforin secretion are completely preserved in the absence of arginine, while antigen specific proliferation as well as IFN-γ and granzyme B secretion are severely compromised. These novel results highlight the complexity of antigen specific T cell activation and demonstrate that human T cells can preserve important activation-induced effector functions in the context of arginine deficiency.
Abebe T, Takele Y, Weldegebreal T, et al., 2013, Arginase activity - a marker of disease status in patients with visceral leishmaniasis in Ethiopia, PLOS Neglected Tropical Diseases, Vol: 7, ISSN: 1935-2735
The underlying mechanisms resulting in the profound immune suppression characteristic of human visceral leishmaniasis (VL) are not fully understood.Here, we tested the hypothesis that arginase, an enzyme associated with immunosuppression, is higher in patients with VL and contributes to impaired T cell responses. We recruited patients with VL before and after treatment and healthy controls and measured the arginase metabolism in the blood of these individuals. Our results show that arginase activity is significantly higher in the blood of patients with active VL as compared to controls. These high levels of arginase decline considerably once the patients are successfully treated. We identified the phenotype of arginase-expressing cells among PBMCs as neutrophils and show that their frequency was increased in PBMCs of patients before treatment; this coincides with reduced levels of L-arginine in the plasma and decreased expression levels of CD3ζ in T cells.
Takele Y, Abebe T, Weldegebreal T, et al., 2013, Arginase activity in the blood of patients with visceral leishmaniasis and HIV infection, PLOS Neglected Tropical Diseases, Vol: 7, ISSN: 1935-2735
BackgroundVisceral leishmaniasis is a parasitic disease associated with high mortality. The most important foci of visceral leishmaniasis in Ethiopia are in the Northwest and are predominantly associated with high rates of HIV co-infection. Co-infection of visceral leishmaniasis patients with HIV results in higher mortality, treatment failure and relapse. We have previously shown that arginase, an enzyme associated with immunosuppression, was increased in patients with visceral leishmaniasis and in HIV seropositive patients; further our results showed that high arginase activity is a marker of disease severity. Here, we tested the hypothesis that increased arginase activities associated with visceral leishmaniasis and HIV infections synergize in patients co-infected with both pathogens.Methodology/Principal FindingsWe recruited a cohort of patients with visceral leishmaniasis and a cohort of patients with visceral leishmaniasis and HIV infection from Gondar, Northwest Ethiopia, and recorded and compared their clinical data. Further, we measured the levels of arginase activity in the blood of these patients and identified the phenotype of arginase-expressing cells. Our results show that CD4+ T cell counts were significantly lower and the parasite load in the spleen was significantly higher in co-infected patients. Moreover, our results demonstrate that arginase activity was significantly higher in peripheral blood mononuclear cells and plasma of co-infected patients. Finally, we identified the cells-expressing arginase in the PBMCs as low-density granulocytes.ConclusionOur results suggest that increased arginase might contribute to the poor disease outcome characteristic of patients with visceral leishmaniasis and HIV co-infection.
Cloke T, Munder M, Taylor G, et al., 2012, Characterization of a novel population of low-density granulocytes associated with disease severity in HIV-1 infection, PLOS One, Vol: 7, ISSN: 1932-6203
The mechanisms resulting in progressive immune dysfunction during the chronic phase of HIV infection are not fully understood. We have previously shown that arginase, an enzyme with potent immunosuppressive properties, is increased in HIV seropositive (HIV+) patients with low CD4+ T cell counts. Here we show that the cells expressing arginase in peripheral blood mononuclear cells of HIV+ patients are low-density granulocytes (LDGs) and that whereas these cells have a similar morphology to normal-density granulocyte, they are phenotypically different. Importantly, our results reveal that increased frequencies of LDGs correlate with disease severity in HIV+ patients.
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