Immunopathological characterization of human cutaneous leishmaniasis lesions caused by Leishmania (Viannia) spp. in Amazonian Brazil

Low expression of hypoxia-inducible factor-1α and differential expression of immune mediators during experimental infection with Leishmania (Viannia) spp

Leishmania (Viannia) species are the major agents of cutaneous leishmaniasis (CL) in the Americas. Ulcerative stigmatizing skin lesions generally characterize CL. The microenvironment during Leishmania infection is rich in inflammatory cells and molecules, which contrasts with low oxygen levels. The hypoxia-inducible factor (HIF)-1α activates several genes in response to hypoxia and inflammatory reactions, but its role in the CL course is poorly understood. We investigated the expression pattern of the genes HIF-1α, arginase, inducible NO synthase (iNOS), interferon (IFN)-γ, interleukin (IL)-12, and IL-10 in skin lesions and lymph nodes of golden hamsters infected with L. braziliensis, L. lainsoni, and L. naiffi. The animals were infected and followed for 105 days, with paw volume measurements and photos taken weekly. Euthanasia was performed at 0, 15, 56, and 105 days post-infection. The parasite load of paw and lymph node tissues were measured through absolute quantification at real-time PCR (qPCR), and reverse transcription qPCR (RT-qPCR) was applied to demonstrate the relative mRNA expression of the target genes. Among groups, animals infected with L. braziliensis had the highest parasite load in paws and lymph nodes. HIF-1α mRNA was down-regulated during chronic Leishmania (Viannia) infection but demonstrated less inhibition in hamsters infected with L. lainsoni and L. naiffi. Arginase was the most detectable gene in animals infected by L. braziliensis; IFN-γ and IL-10 genes were the most detectable in L. lainsoni and L. naiffi-infected animals. HIF-1α gene transcription seemed to be down-modulated byL. (Viannia)infection and was less inhibited by L. lainsoni and L. naiffi when compared toL. braziliensis. Animals with L. lainsoni and L. naiffi showed better control of the disease. Further studies are necessary to evaluate the mechanism influencing HIF-1α expression and its role on CL protection; such research could elucidate potential use of HIF-1α as a therapeutic target.

In Leishmania major, the Homolog of the Oncogene PES1 May Play a Critical Role in Parasite Infectivity

Leishmaniasis is a neglected tropical disease caused by Leishmania spp. The improvement of existing treatments and the discovery of new drugs remain ones of the major goals in control and eradication of this disease. From the parasite genome, we have identified the homologue of the human oncogene PES1 in Leishmania major (LmjPES). It has been demonstrated that PES1 is involved in several processes such as ribosome biogenesis, cell proliferation and genetic transcription. Our phylogenetic studies showed that LmjPES encodes a highly conserved protein containing three main domains: PES N-terminus (shared with proteins involved in ribosomal biogenesis), BRCT (found in proteins related to DNA repair processes) and MAEBL-type domain (C-terminus, related to erythrocyte invasion in apicomplexan). This gene showed its highest expression level in metacyclic promastigotes, the infective forms; by fluorescence microscopy assay, we demonstrated the nuclear localization of LmjPES protein. After generating mutant parasites overexpressing LmjPES, we observed that these clones displayed a dramatic increase in the ratio of cell infection within macrophages. Furthermore, BALB/c mice infected with these transgenic parasites exhibited higher footpad inflammation compared to those inoculated with non-overexpressing parasites.

Potential biomarkers of immune protection in human leishmaniasis

Leishmaniasis is a vector-borne neglected tropical disease endemic in over 100 countries around the world. Available control measures are not always successful, therapeutic options are limited, and there is no vaccine available against human leishmaniasis, although several candidate antigens have been evaluated over the last decades. Plenty of studies have aimed to evaluate the immune response development and a diverse range of host immune factors have been described to be associated with protection or disease progression in leishmaniasis; however, to date, no comprehensive biomarker(s) have been identified as surrogate marker of protection or exacerbation, and lack of enough information remains a barrier for vaccine development. Most of the current understanding of the role of different markers of immune response in leishmaniasis has been collected from experimental animal models. Although the data generated from the animal models are crucial, it might not always be extrapolated to humans. Here, we briefly review the events during Leishmania invasion of host cells and the immune responses induced against Leishmania in animal models and humans and their potential role as a biomarker of protection against human leishmaniasis.

In situ study of cellular immune response in human cutaneous lesions caused by Leishmania (Viannia) panamensis in Panama

AIMS

Leishmaniasis is considered a disease with multiple clinical/immunopathological characteristics, depending on the immunity of the host and the species of the parasite. In Panama, the most prevalent species that causes localized cutaneous leishmaniasis (LCL) is Leishmania (Viannia) panamensis, and its immune response is poorly studied. Therefore, we evaluated by immunohistochemistry, the in situ immune response during this infection.

METHODS AND RESULTS

Biopsies from Panamanian patients with LCL were collected and processed by histological techniques. Infection by L. (V.) panamensis was demonstrated by isolation in culture and molecular characterization by Hsp70-RFLP. The in situ immune response was assessed by immunohistochemistry. The immune response was characterized by predominance of T cells, mainly CD8 cells that showed positive correlation with IFN-γ and Granzyme B. CD4 cells presented positive correlation with both IFN-γ and IL-13, pointed by mixed cellular immune response. Regulatory response was characterized by FoxP3 cells, which showed positive correlation to IL-10 but not with TGF-β.

CONCLUSIONS

L. (V.) panamensis infection triggers a mixed cellular immune response, characterized by the presence of pro-inflammatory, anti-inflammatory and regulatory elements in the skin lesion of Panamanian patients. These data contribute to a better understanding of the immunopathogenesis of Leishmania Viannia infection in Panama.

Tissue Damage in Human Cutaneous Leishmaniasis: Correlations Between Inflammatory Cells and Molecule Expression

Cutaneous leishmaniasis (CL) is caused by the bite of the infected sand fly, which inoculates parasites of Leishmania spp and triggers an immune response. An exacerbated cutaneous inflammatory response is crucial for controlling parasite burden but can also promote tissue damage. This study aimed to characterize the populations of natural killer (NK), CD57⁺, CD4⁺, and CD8⁺ T cells, CD20⁺ B cells, as well as CD68⁺ macrophages, in biopsies of ulcerated CL lesions, and quantify the production of perforin⁺, grazyme B⁺, interleukin 1 beta (IL-1β⁺) and Tumor Necrosis Factor (TNF-α⁺ cells). We then correlated these parameters with necrosis, inflammation and the number of amastigotes. CD4⁺ T cells were positively correlated to the extent of inflammation, B cells and IL-1β⁺ were associated with the extent of necrosis, CD68⁺ macrophages and perforin were correlated with the number of amastigotes, and CD57⁺ NK cells was correlated to CD68⁺ macrophages and amastigotes. In sum, the finding suggests that the production of cytotoxic granules and cytokines by inflammatory cells contributes to tissue damage in CL lesions.

Histopathological features of skin lesions in patients affected by non-ulcerated or atypical cutaneous leishmaniasis in Honduras, Central America

In Honduras visceral leishmaniasis and non-ulcerated or atypical cutaneous leishmaniasis (NUCL) are caused by the species Leishmania (L.) infantum chagasi. NUCL is the most common clinical form in the southern regions of the country, mainly affecting the young. In view of the lack of knowledge about the pathogenesis of the disease pattern caused by L. (L) infantum chagasi in individuals affected by NUCL, the aim of the present study was to describe in detail the histopathological features of the skin lesion caused by the parasite. Biopsies from human NUCL lesions with a positive parasitological diagnosis were collected and processed using standard histological techniques. Paraffin sections stained by haematoxylin and eosin were used to examine the histopathological alterations seen in the skin. The lesions varied between 3 and 5 mm, and the majority of the patients (60%) had a single lesion. Lesions were more frequently seen in females (65%), with an average age of 33.4 years. Microscopically, the skin lesions were characterized by mononuclear inflammatory infiltrate in the dermis composed of lymphocytes, macrophages and a few plasma cells. The intensity of the infiltration varied from discrete to intense. In both cases, the parasitic infection was discrete. Granulomas were present in 60% of cases and were associated with intense inflammation. The data revealed by the histopathological alterations in the skin of individuals affected by NUCL suggest activation of a cellular immune response that potentially controls parasite spreading.

Combination of flow cytometry and qPCR to study the immune response of american cutaneous leishmaniasis patients

American Cutaneous leishmaniasis (ACL) is a public health problem. The immunological response is mainly dependent on T cell cytokine responses and might influence disease presentation, susceptibility and development. The understanding of the host immune response role in the control and in the pathology of leishmaniasis is relevant and has implications on diagnosis, follow-up and vaccine development. In this study, the differences in the immune response and T cell profile of patients before treatment was investigated through flow cytometry and real time PCR in peripheral blood mononuclear cells after different antigenic stimulations. Among the main findings are the significant presence of TNF and IFN-γ gene expression after 24 h of in vitro stimulation, and 48 h later the presence of CD4⁺ T and CD8⁺ T cells producing IL-10 and IL-4. This may be due to the differences in cytokine release over time and the presence of cells other than lymphocytes influencing the mRNA transcript detection. Evaluation of the immune response of individuals with leishmaniasis or other diseases should associate different technologies and times points for a clear and more reliable assessment of the immune response. This would help in the design of vaccine strategies/immunotherapies.

Histopathological characteristics of cutaneous lesions caused by Leishmania Viannia panamensis in Panama

Cutaneous leishmaniasis (CL) is an endemic disease in the Republic of Panama, caused by Leishmania (Viannia) parasites, whose most common clinical manifestation is the presence of ulcerated lesions on the skin. These lesions usually present a chronic inflammatory reaction, sometimes granulomatous, with the presence of lymphocytes, plasma cells and macrophages. This study describes the histopathological characteristics found in the skin lesions of patients with CL caused by Leishmania (V.) panamensis in Panama. We analyzed 49 skin biopsy samples from patients with clinical suspicion of CL, by molecular tests (PCR for subgenus Viannia and HSP-70) and by Hematoxylin-Eosin staining. Samples were characterized at the species level by PCR-HSP-70/RFLP. From the 49 samples studied, 46 (94%) were positive by PCR and were characterized as Leishmania (V.) panamensis. Of these, 48% were positive by Hematoxylin-Eosin staining with alterations being observed both, in the epidermis (85%) and in the dermis (100%) of skin biopsies. The inflammatory infiltrate was characterized according to histopathological patterns: lymphohistiocytic (50%), lymphoplasmacytic (61%) and granulomatous (46%) infiltration, being the combination of these patterns frequently found. The predominant histopathological characteristics observed in CL lesions caused by L. (V.) panamensis in Panama were: an intense inflammatory reaction in the dermis with a combination of lymphohistiocytic, lymphoplasmacytic and granulomatous presentation patterns and the presence of ulcers, acanthosis, exocytosis and spongiosis in the epidermis.