Role of antigen-presenting cells in non-ulcerated skin lesions caused by Leishmania (Leishmania) infantum chagasi.

In Central America, infection by Leishmania (Leishmania) infantum chagasi causes visceral leishmaniasis and non-ulcerated cutaneous leishmaniasis (NUCL). This work aimed to evaluate the participation of subpopulations of antigen-presenting cells in skin lesions of patients affected by NUCL through double-staining immunohistochemistry using cellular and intracellular markers. Twenty-three skin biopsies from patients affected by NUCL were used. Histological sections stained by HE were used for histopathological study. Immunohistochemical studies were performed using primary antibodies against Langerhans cells, dermal dendritic cells, T lymphocytes, and the cytokines IL-12, IFN-γ, TNF-α, iNOS, and IL-10. The histopathological lesions were characterized by an inflammatory infiltrate, predominantly lymphohistiocytic, of variable intensity, with a diffuse arrangement associated with epithelioid granulomas and discreet parasitism. Double-staining immunohistochemistry showed higher participation of dendritic cells producing the proinflammatory cytokine IL-12 in relation to the other evaluated cytokines. Activation of the cellular immune response was marked by a higher density of CD8 Tc1-lymphocytes followed by CD4 Th1-lymphocytes producing mainly IFN-γ. The data obtained in the present study suggest that antigen-presenting cells play an important role in the in situ immune response through the production of proinflammatory cytokines, directing the cellular immune response preferentially to the Th1 and Tc1 types in NUCL caused by L. (L.) infantum chagasi.

Leishmania (L.) infantum chagasi isolated from skin lesions of patients affected by non-ulcerated cutaneous leishmaniasis lead to visceral lesion in hamsters.

In Central America, Leishmania (L.) infantum chagasi infection causes visceral leishmaniasis (VL) and non-ulcerated cutaneous leishmaniasis (NUCL). The aim of the present study was to evaluate the course of an experimental infection in hamsters caused by L. (L.) infantum chagasi isolated from patients affected by NUCL compared with a strain isolated from a patient with VL. Stationary phase parasites in culture were inoculated through subcutaneous and intraperitoneal routes in hamsters. Following the post-infection times, a histopathological study, parasite load and cytokine determination in skin from the cutaneous inoculation site and viscera were performed. Animals subcutaneously infected with the different strains did not develop macroscopic lesions at the inoculation site, and the histopathological changes in the dermis were very slight. Regarding the histopathological study of the viscera, we observed the portal mononuclear inflammatory infiltrate, the presence of nodules in the hepatic parenchyma and the proliferation of macrophages in the spleen, which increased over the infection course. Overall, the parasite load in the liver and spleen and in the total IgG titres in the sera of infected hamster showed an increase with the time of infection, regardless of the route of inoculation. Regarding cellular immunity, we did not observe an increase or decrease in pro- and anti-inflammatory cytokines compared to the healthy control, except for IL-10, which was evident in the infected animals. The data showed that strains isolated from NUCL cause visceral lesions in the hamsters regardless of the route of inoculation, and they were similar to parasites isolated from VL humans.

Macrophage Polarization in the Skin Lesion Caused by Neotropical Species of Leishmania sp.

Macrophages play important roles in the innate and acquired immune responses against Leishmania parasites. Depending on the subset and activation status, macrophages may eliminate intracellular parasites; however, these host cells also can offer a safe environment for Leishmania replication. In this sense, the fate of the parasite may be influenced by the phenotype of the infected macrophage, linked to the subtype of classically activated (M1) or alternatively activated (M2) macrophages. In the present study, M1 and M2 macrophage subsets were analyzed by double-staining immunohistochemistry in skin biopsies from patients with American cutaneous leishmaniasis (ACL) caused by L. (L.) amazonensis, L. (V.) braziliensis, L. (V.) panamensis ,and L. (L.) infantum chagasi. High number of M1 macrophages was detected in nonulcerated cutaneous leishmaniasis (NUCL) caused by L. (L.) infantum chagasi (M1 = 112 ± 12, M2 = 43 ± 12 cells/mm2). On the other side, high density of M2 macrophages was observed in the skin lesions of patients with anergic diffuse cutaneous leishmaniasis (ADCL) (M1 = 195 ± 25, M2 = 616 ± 114), followed by cases of localized cutaneous leishmaniasis (LCL) caused by L. (L.) amazonensis (M1 = 97 ± 24, M2 = 219 ± 29), L. (V.) panamensis (M1 = 71 ± 14, M2 = 164 ± 14), and L. (V.) braziliensis (M1 = 50 ± 13, M2 = 53 ± 10); however, low density of M2 macrophages was observed in NUCL. The data presented herein show the polarization of macrophages in skin lesions caused by different Leishmania species that may be related with the outcome of the disease.