Cells In Cutaneous Leishmaniasis Research Articles

Opinion Article: NK Cells in Cutaneous Leishmaniasis: Protection or Damage?

Opinion Article: NK Cells in Cutaneous Leishmaniasis: Protection or Damage?

Programmed Cell Death Ligand (PD-L)-1 Contributes to the Regulation of CD4+ T Effector and Regulatory T Cells in Cutaneous Leishmaniasis.

Cutaneous Leishmaniasis (CL) affects up to one million people every year and treatments are costly and toxic. The regulation of the host immune response is complex and the knowledge of how CD4+ T cells are activated and maintained during Leishmania infection is still limited. Current therapies aim to target programmed cell death (PD)-1 and programmed cell death ligand (PD-L)-1 in order to boost T cell activity. However, the role of the PD-1/PD-L1 axis during Leishmania infection is still unclear. In this study, we found that patients with active and post-treatment CL displayed different subsets of CD4+PD-1+ T cells. Accordingly, L. major-infected mice upregulated PD-1 on activated CD4+ T effector cells and PD-L1 on resident macrophages and infiltrating monocytes at the site of infection. L. major-infected Pdl1−/− mice expressed lower levels of MHCII and higher levels of CD206 on macrophages and monocytes and, more importantly, the lack of PD-L1 contributed to a reduced frequency of CD4+Ly6Chi T effector cells and an increase of CD4+Foxp3+ regulatory T cells at the site of infection and in draining lymph nodes. Additionally, the lack of PD-L1 was associated with lower production of IL-27 by infiltrating monocytes and lower levels of the Th1 cytokines IFN-γ and TNF-α produced by CD4+ T effector cells. Pdl1−/− mice initially exhibited larger lesions despite having a similar parasite load. Our results describe for the first time how the interruption of the PD-1/PD-L1 axis influences the immune response against CL and suggests that this axis regulates the balance between CD4+Ly6Chi T effector cells and CD4+Foxp3+ regulatory T cells.

Granzyme B Inhibition by Tofacitinib Blocks the Pathology Induced by CD8 T Cells in Cutaneous Leishmaniasis

In cutaneous leishmaniasis, the immune response is not only protective but also mediates immunopathology. We previously found that cytolytic CD8 T cells promote inflammatory responses that are difficult to treat with conventional therapies that target the parasite. Therefore, we hypothesized that inhibiting CD8 T-cell cytotoxicity would reduce disease severity in patients. IL-15 is a potential target for such a treatment because it is highly expressed in human patients with cutaneous leishmaniasis lesions and promotes granzyme B‒dependent CD8 T-cell cytotoxicity. Here we tested whether tofacitinib, which inhibits IL-15 signaling by blocking Jak3, might decrease CD8-dependent pathology. We found that tofacitinib reduced the expression of granzyme B by CD8 T cells invitro and invivo systemic and topical treatment, with tofacitinib protecting mice from developing severe cutaneous leishmaniasis lesions. Importantly, tofacitinib treatment did not alter T helper type 1 responses or parasite control. Collectively, our results suggest that host-directed therapies do not need to be limited to autoimmune disorders and that topical tofacitinib application should be considered a strategy for the treatment of cutaneous leishmaniasis disease in combination with antiparasitic drugs.

Granzyme B Produced by Natural Killer Cells Enhances Inflammatory Response and Contributes to the Immunopathology of Cutaneous Leishmaniasis.

Skin lesions from patients infected with Leishmania braziliensis has been associated with inflammation induced by cytotoxic CD8+ T cells. In addition, CD8+ T cell-mediated cytotoxicity has not been linked to parasite killing. Meanwhile, the cytotoxic role played by natural killer (NK) cells in cutaneous leishmaniasis (CL) remains poorly understood. In this study, we observed higher frequencies of NK cells in the peripheral blood of CL patients compared with healthy subjects, and that NK cells expressed more interferon-γ, tumor necrosis factor (TNF), granzyme B, and perforin than CD8+ T cells. We also found that most of the cytotoxic activity in CL lesions was triggered by NK cells, and that the high levels of granzyme B produced in CL lesions was associated with larger lesion size. Furthermore, an in vitro blockade of granzyme B was observed to decrease TNF production. Our data, taken together, suggest an important role by NK cells in inducing inflammation in CL, thereby contributing to disease immunopathology.

Memory T cells in cutaneous leishmaniasis

Leishmania causes a spectrum of diseases that range from self-healing to fatal infections. Control of leishmania is dependent upon generating CD4+ Th1 cells that produce IFNγ, leading to macrophage activation and killing of the intracellular parasites. Following resolution of the disease, short-lived effector T cells, as well as long-lived central memory T cells and skin resident memory T cells, are retained and able to mediate immunity to a secondary infection. However, there is no vaccine for leishmaniasis, and the drugs used to treat the disease can be toxic and ineffective. While a live infection generates immunity, a successful vaccine will depend upon generating memory T cells that can be maintained without the continued presence of parasites. Since both central memory and skin resident memory T cells are long-lived, they may be the appropriate targets for a leishmaniasis vaccine.

CD8+ T cells in cutaneous leishmaniasis: the good, the bad, and the ugly.

CD8(+) T lymphocytes are components of the adaptive immune response and play an important role in protection against many viral and bacterial infections. However, their role in parasitic infections is less well understood. In leishmaniasis, a disease caused by intracellular protozoan parasites of the genus Leishmania, CD8(+) T cells have been shown to be protective. However, increasing evidence indicates that CD8(+) T cells may also exacerbate disease. In this review, we will describe the situations where CD8(+) T cells are either good or bad for the outcome of the infection and attempt to reconcile the dual role played by CD8(+) T cells in cutaneous leishmaniasis.

Analysis of localized immune responses reveals presence of Th17 and Treg cells in cutaneous leishmaniasis due to Leishmania tropica

PurposeThe interaction between the Leishmania parasite and the host cell involves complex, multifaceted processes. The disease severity in cutaneous leishmaniasis (CL) is largely dependent on the causative species. Most of the information on immune responses in human CL is available with respect to L. major infection and is lacking for L. tropica species. In this study, we employed cytokine/chemokine/receptor membrane cDNA array to capture comprehensive picture of immuno-determinants in localized human tissue during L. tropica infection. Expression of selected molecules was evaluated by real time PCR in dermal lesion tissues at pre- and post treatment stages. Plasma IL-17 level was estimated by sandwich ELISA.ResultsThe cDNA array analysis identified several immuno-determinants in tissue lesions of Indian CL including cytokines (IFN-γ, TNF-α, IL-1β, IL-10, IL-13), chemokines (IL-8, CCL2, CCL3, CCL4) and apoptotic molecules (Fas, TRAIL, IRF-1). Elevated mRNA levels of Th17 (IL-17, IL-23 and RORγt) and Treg (CD25, CTLA-4 and Foxp3) markers were observed in lesion tissues of CL patients compared to the control group, which subsided post treatment. Plasma IL-17 levels were found to be significantly higher in CL samples compared to controls.ConclusionsIn addition to defining comprehensive immunological responses inside lesion tissues of CL patients, our study demonstrated the presence of Th17 and Treg cells in CL caused by L. tropica.

The role of CD8+ T cells in cutaneous leishmaniasis caused by Leishmania braziliensis (40.9)

Abstract The leishmaniases are a group of diseases that affect millions of people worldwide. In the present study, we investigated the participation of CD8+ T cells during infection with L. braziliensis, the main etiolological agent of mucocutaneous leishmaniasis. Following inoculation of L. braziliensis into the ear dermis of BALB/c mice, we observed a high proportion of CD8+CD25+, at the time of lesion appearance, whereas CD8+CD69+ T cells were found at a greater proportion in the draining lymph nodes, at this same time point. Regarding cytokine production, a high percentage of CD8+IFN-g+ cells was detected as early as two weeks post infection, at the ear dermis. The same kinetics was observed for expression of CD107b. Interestingly, presence of IL-4+ and IL-10+ T cells was also detected during the course of infection in the ear dermis. Parasite load in β2-m deficient mice was smaller than in wild type (WT) mice. However, transfer of CD8+ cells obtained from L. braziliensis-primed mice induced the control of lesion development upon transfer to infected mice. These data indicate that CD8+ T cells may play a protective role in cutaneous leishmaniasis caused by L. braziliensis.

A quantitative and morphometric study of mast cells in cutaneous leishmaniasis

Background Mast cells (MCs) are related with healing process in chronic inflammatory diseases, although in cutaneous leishmaniasis (CL) its importance is unknown. The aim of this study was to determine the correlation of MC with clinical findings in patients with the localized form of CL. Methods A cohort of 85 patients with CL was evaluated. MCs count was performed in pre-treatment biopsies and correlation with clinical findings and Leishmania species determined by PCR were performed. Results The MCs count in patients with CL caused by Leishmania (V.) braziliensis was 14.3 +/- 9.8 cells/mm(2), and 7.0 +/- 6.5 cells/mm(2) in patients with L. (L.) amazonensis (P < 0.05). The linear regression of MCs count with the age showed a tendency of cell number decreasing, according to ageing of the patient (r2 = 0.05; P < 0.05). The association of disease's duration and MCs count was positive (r2 = 0.11; P < 0.05). There was not any association of MCs count with number of lesions neither with Leishmania antigen expression. The MCs count was higher in patients with earlier healing after treatment (P < 0.05). Conclusion MC can be important in CL and related with healing lesion.

CD8 cytotoxic T cells in cutaneous leishmaniasis

CD8 T cells are essential in the defence against viruses, yet little is known of their participation in the host defence against parasites, such as Leishmania, which can cause a variety of clinical diseases, such as localized cutaneous, diffuse cutaneous, mucocutaneous and visceral leishmaniasis. Murine models of leishmaniasis suggest that CD8 T cells participate through IFN-gamma production, yet their cytotoxic capacity also plays an important role, as has been found in patients infected with various Leishmania strains, where CD8 T cell cytotoxicity and apoptosis of autologous Leishmania-infected macrophages correlate with cure. Yet the mechanisms underlying the CD8 T activation in patients with leishmaniasis remain an enigma. It is possible that dendritic cells activate CD8 T cells through mechanisms that include antigen cross-presentation. Here we summarize the recent findings of CD8 T cells in cutaneous leishmaniasis and discuss their significance in the control of the disease. Further knowledge in this field will undoubtedly improve the design of therapeutic and vaccine strategies.

The development of effector and memory T cells in cutaneous leishmaniasis: the implications for vaccine development.

Leishmania major infections induce the development of a CD4(+) T-helper 1 (Th1) response that not only controls the primary infection but also results in life-long immunity to reinfection. How that immunity is maintained is unknown, although because of the existence of infection-induced immunity, there has been an assumption that the development of a vaccine against leishmaniasis would be relatively easy. This has turned out not to be the case. One problem has been the finding that a large part of the immunity induced by a primary infection depends upon the presence of persistent parasites. Nevertheless, there are ample situations where immunologic memory persists without the continued presence of antigen, providing the prospect that a non-live vaccine for leishmaniasis can be developed. To do so will require an understanding of the events involved in the development of an effective protective T-cell response and, more importantly, an understanding of how to maintain that response. Here, we review work from our laboratory, describing how Th1 cells develop in L. major-infected mice, the nature of the memory T cells that provide protection to reinfection, and how that information may be utilized in the development of vaccines.

A quantitative study of epidermal Langerhans cells in cutaneous leishmaniasis caused by Leishmania tropica

The purpose of this study was to characterize the number and distribution of epidermal Langerhans cells in different clinical forms of dry-type cutaneous leishmaniasis (CL). Sixteen cases of dry-type cutaneous leishmaniasis caused by Leishmania tropica were studied. These cases were classified clinically as five cases of acute leishmaniasis with indurated papules, nodules and plaques with central crust formation and duration < 2 years, six cases of lupoid leishmaniasis with characteristic papules around previous scars of cutaneous leishmaniasis with duration > 2 years, and five cases of chronic nonlupoid type with nonhealing lesions of duration > 2 years. Paraffin-embedded blocks were stained with hematoxylin and eosin (H&E) and stained immunohistochemically for CD1a. The number of Langerhans cells per millimeter length of epidermis was increased in acute cases compared to chronic and lupoid cases. Lesions of acute leishmaniasis contain the greatest amounts of antigen for presentation, so Langerhans cells increase in number and in trafficking to present antigens derived from Leishman bodies to the cellular immune system. In chronic leishmaniasis, the Langerhans cell population is reduced, perhaps because of exhaustion of the source of Langerhans cells, or because of reduced response to modified antigen.

Immune effector mechanism in parasitic infections

In this article is a summary of our recent findings on the role of nitric oxide (NO) as an effector mechanism against the intracellular parasite, Leishmania major. NO is produced in large amounts in murine macrophages following activation by IFN γ synthesized by Th1 cells. NO production is inhibited by IL-4, a product of Th2 cells. A set of stable cell surface markers has now been identified. ST2L and IL-18R are selectively expressed on Th2 and Th1 cells respectively. Antibody against ST2L can down-regulate Th2 cells in the highly susceptible BALB/c mice leading to control of otherwise fatal L. major infection. These results show directly the critical role of the balance between Th1 and Th2 cells in cutaneous leishmaniasis.

Leishmania Major Infection in Major Histocompatibility Complex Class II-Deficient Mice: CD8 + T Cells Do not Mediate a Protective Immune Response

In order to evaluate the role of CD8 + T cells in cutaneous leishmaniasis, major histocompatibility complex (MHC) class II-deficient mice of C57BL/6 background lacking functional CD4 + T cells were infected with Leishmania major. In contrast to C57BL/6 wild-type mice which are resistant to infection with L. major, these mice developed severe skin lesions that did not heal. In comparison to susceptible BALB/c mice, however, lesion development in MHC class II-deficient mice was very much retarded, even though the increase in the parasite load in lymphoid organs was only slightly delayed. Lymph node cells from L. major-infected MHC class II-deficient mice produced very low levels of interferon-γ upon stimulation with L. major antigen, whereas the response to the mitogen concanavalin A was not impaired. Interestingly, they did not release lymphokines associated with disease exacerbation (interleukin 4 and interleukin 10) either, suggesting that the delayed lesion development is caused by the lack of disease-promoting CD4 + cells rather than by the presence of protective CD8 + cells. The lack of L. major-reactive immunoglobulins in the serum of infected MHC class II-deficient mice indicates that B cells also cannot respond to parasite antigens in the absence of MHC class II-mediated helper signals. The data demonstrate that MHC class II-deficient mice are unable to restrict the spreading of L. major, although they contain highly increased proportions of CD8 + T cells. Thus, MHC class II-restricted immune responses, most likely mediated by functional CD4 + T cells, are essential for the control of primary infections with L. major.

Differential expression of chemokines in patients with localized and diffuse cutaneous American leishmaniasis.

The abundance of macrophages in localized cutaneous leishmaniasis (LCL) and diffuse cutaneous leishmaniasis (DCL) lesions and differences in the composition of T cell subsets indicate involvement of cell-specific chemotaxis processes. The expression of macrophage chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1 alpha and -1 beta, RANTES (regulated on activation, normal T cell expressed and secreted), I-309, and interleukin-8 were investigated in lesions of patients with LCL or DCL. In LCL, high levels of MCP-1 and moderate levels of MIP-1 alpha were detected. In DCL, MCP-1 expression was significantly lower and MIP-1 alpha expression was predominant. All other chemokines investigated were minimally expressed or absent. These findings suggest that MCP-1 and MIP-alpha are responsible for the recruitment of macrophages and T cells in cutaneous leishmaniasis. The results show that self-healing LCL is associated with higher levels of MCP-1, which may stimulate macrophage microbicidal mechanisms, and nonhealing DCL is associated with higher levels of MIP-alpha.