Dogs are the main domestic reservoirs of L. (L.) chagasi. Once in the vertebrate host, the parasite may cause visceral leishmaniasis, which can also be transmitted to humans. Infected symptomatic dogs show disorganization in the white pulp in spleen tissue and a reduction in T lymphocytes in peripheral blood. To investigate whether apoptosis is involved in white pulp disorganization and diminished T cell counts in peripheral blood, apoptotic T cells from the spleen and peripheral blood of dogs naturally infected with L. (L.) chagasi and presenting clinical manifestations were quantified and compared with healthy dogs. Thirteen symptomatic adult dogs infected by L. (L.) chagasi and six healthy dogs from a nonendemic area (controls) were included in the study. Samples from spleen and peripheral blood were used to quantify apoptosis in CD3 lymphocytes by flow cytometry using Anexin V and Multicaspase kits; the results were compared using the Mann Whitney test. The percentage of total T cells was lower in Leishmania infected dogs compared to healthy controls (P<0.05). Apoptosis levels in T cells from PBMC and spleen were higher in infected dogs than in controls (P<0.05). The least squares method test was used to determine the effect between the degree of structural organization of spleen white pulp and the percentage of apoptosis in the spleen. A significant effect on the level of white pulp morphological disorganization and percentage of apoptosis in spleen T cells was observed (F=20.45; P=0.0014). These data suggest that apoptosis is an important for the immunopathogenesis of canine visceral leishmaniasis.

The aim of this study was to evaluate the most frequent lesions in the bone marrow of dogs naturally infected by Leishmania (Leishmania) chagasi. Thirty-three dogs sacrificed at the Zoonosis Control Center of Araçatuba, a municipality endemic for visceral leishmaniasis (VL), were used. The animals were classified as asymptomatic, oligosymptomatic, and symptomatic groups. At the necropsy, bone marrow samples were collected from the femur, fixed, processed, and stained with hematoxylin and eosin. The lesion intensity was classified as mild, moderate, or severe. The parasite load was determined using immunohistochemistry. The most important lesions consisted of multifocal to diffuse granulomas, megakaryocytic dysplasia, and medullary aplasia. There were no statistical differences between the three clinical groups regarding parasite load and lesion intensity. Asymptomatic dogs also presented high parasitism in the bone marrow as dogs with clinical signs of VL. It was concluded that, regardless of clinical group, the bone marrow is a site for multiplication of Leishmania chagasi. Possibly, the bone marrow dysplasia may arise from the presence of many parasitized and activated macrophages in this organ. Consequently, it affects the profile of hematopoietic cells in the bone marrow and systemic circulation.

BackgroundThe antibody Ki-67 is a reliable and easy tool to accurately assess the growth fraction of neoplasms in humans and animals, and it has been used to predict the clinical outcome. Therefore, the aim of the present study was to investigate the immunohistochemical expression pattern of Ki-67 in normal and neoplastic perianal glands of dogs to evaluate the possible use of this proliferation marker as an ancillary method of perianal tumor diagnosis. We studied 42 cases of perianal gland neoplasms including adenomas (n = 15), epitheliomas (n = 15), and carcinomas (n = 12). As controls, 13 tissue samples from normal perianal glands were used. A Ki-67 index was established by a computer-assisted image analysis and compared with manual counting.ResultsOut of the 42 cases of perianal gland neoplasms, 34 were from males and eight from females. Recurrence was reported in 14 cases, being higher (8/12) in carcinomas. Immunostaining for Ki-67 revealed that the carcinomas showed a higher proliferation rate (9.87%) compared to groups of epitheliomas (2.66%) and adenomas (0.36%). For adenomas and epitheliomas of the perianal glands the computer-assisted counting and the manual counting gave similar results; however, only the computer-assisted image analysis was efficient to predict the perianal gland carcinoma recurrence.ConclusionSince there were significant differences in the number of Ki-67-positive nuclei, this marker proved to be effective in helping the classification of perianal gland neoplasms and to refine the diagnosis criteria, especially in those samples with high variation in morphology/area. Also, higher Ki-67 index is related to recurrence in cases of perianal gland carcinomas. Further, the computer-assisted image analysis proved to be a fast and reliable method to assess the Ki-67 index in perianal gland neoplasms.

Visceral leishmaniasis is a multisystemic zoonotic disease that can manifest with several symptoms, including neurological disorders. To investigate the pathogenesis of brain alterations occurring during visceral leishmaniasis infection, the expression of the cytokines IL-1β, IL-6, IL-10, IL-12p40, IFN-γ, TGF-β and TNF-α and their correlations with peripheral parasite load were evaluated in the brains of dogs naturally infected with Leishmania infantum. IL-1β, IFN-γ and TNF-α were noticeably up-regulated, and IL-10, TGF-β and IL-12p40 were down-regulated in the brains of infected dogs. Expression levels did not correlate with parasite load suggestive that the brain alterations are due to the host's immune response regardless of the phase of the disease. These data indicate the presence of a pro-inflammatory status in the nervous milieu of dogs with visceral leishmaniasis especially because IL-1β and TNF-α are considered key factors for the initiation, maintenance and persistence of inflammation.

The present study aimed to estimate the cell response and parasite load in the popliteal lymph nodes of dogs with visceral leishmaniasis (VL), comparing these findings with the clinical staging of the disease. From the necropsy, 33 dogs were classified as symptomatic (S), asymptomatic (A), or oligosymptomatic (O). Cytology and histopathology were used to determine any presence of microscopic lesions and immunohistochemistry, for parasite load. Dog hyperimmune serum was used as the primary antibody. The inflammatory infiltrate in lymph nodes consisted of macrophages and plasmocytes. The granulomas invaded the trabecular and sinusoid regions and sometimes compressed the lymphocytes of the cortical region (atrophy) and medullary cord cells. Parasite load intensity was unrelated to the density of the macrophages infiltrating the lymph node. Significant differences in parasite load (P < 0.05) were observed between the three groups of infected dogs. Follicular hyperplasia of the cortical region occurred among A and O, while follicular atrophy predominated among S. The parasite load was the greatest among S, followed by O. It can be concluded that, regardless of clinical condition, the most evident cell response consisted of macrophages and plasmocytes. Lymphoid atrophy was observed among animals with intense granulomatous reaction and high parasite load, such as among the symptomatic dogs (P < 0.05). Likewise, the oligosymptomatic dogs also presented high density of parasites in the lymph nodes. Thus, we can confirm that dogs with clinical manifestations of VL have an immune system that is less effective for controlling infection by Leishmania chagasi, thereby favoring parasite multiplication.

In dogs, there is an association of chronic visceral leishmaniasis with neurological symptoms, and very few publications have investigated whether these neurological manifestations correlate with specific alterations in brain. A total of 42 mixed-breed adult dogs were selected from the Veterinary Hospital of UNESP-Araçatuba and the Control Zoonosis Center in Araçatuba, São Paulo State, Brazil, which is an endemic area for visceral leishmaniasis. Animals presenting positive ELISA and/or positive parasitological diagnosis of Leishmania were enrolled in the group of infected dogs (n=32). Animals with negative ELISA results and parasitological tests for Leishmania, including a negative immunofluorescence test for toxoplasmosis and neosporosis, were included as the control group (n=10). Brain samples were collected, stored in 10% buffered formalin and subjected to routine histological procedures, following by staining with haematoxylin-eosin (HE) and immunohistochemical examination for T and B lymphocytes and phagocytic cells. Cerebrospinal fluid was collected to determine the anti-Leishmania antibody titers. Histological examination of HE stains demonstrated intense inflammatory infiltrate, primarily in the choroid plexus, which was composed of mononuclear cells with no detectable parasites. Immunohistochemistry revealed that CD3(+) T lymphocytes were the major components of the inflammatory infiltrate at the choroid plexus and in the brain. Infected dogs had more CD3(+) T cells than uninfected animals (P=0.0002). Cerebrospinal fluid from infected dogs contained high titers of anti-Leishmania antibodies in comparison with control animals (P<0.0001), which suggests a compromise of the blood-cerebrospinal fluid barrier. Leukocyte entry into the brain suggests the participation of these cells in the pathogenesis of neurological disorders during the advanced stages of leishmaniasis and confirms that the choroid plexus is an important structure for T cell influx.

Visceral leishmaniasis is a multisystemic zoonotic disease that can manifest with several symptoms, including neurological disorders. Because glial cells are extensively associated with the immune response within the brain, we evaluated the morphology of astrocytes and microglia of dogs naturally infected with Leishmania chagasi. We used immunohistochemical and lectin-histochemical techniques for morphological analyses and we also examined the glial correlation with lymphocyte infiltration of the brain and with the presence of anti-Leishmania antibodies within the cerebrospinal fluid of the dogs. Although we did not detect a shared morphological pattern in the astrocytes or microglia in the brain tissue, these cells were more intensely labelled in infected dogs than in the control group. The density of microglia was increased in the ependymal/subependymal area, thus demonstrating a strong correlation with the presence of T lymphocytes and with cerebrospinal fluid antibody titres. Thus, our results indicate a pro-inflammatory state in the brains of dogs naturally infected with L. chagasi and strongly suggest that microglia and astrocytes are involved in the pathogenesis of the neurological disorders of visceral leishmaniasis in dogs.

Visceral leishmaniasis is an important parasitic disease that affects humans and animals. The response against the protozoan involves the interaction of both innate and adaptive branches of the immune system, and an important immune sensor is represented by the toll-like receptor (TLR) family. Here, we investigated the pattern of TLR-2, TLR-4 and TLR-9 gene expression in different compartments (brain, choroid plexus, spleen and lymph node) of dogs naturally infected with Leishmania infantum. Gene expression of the TLRs varied according to the compartment evaluated. In the brain, there was only an upregulation of TLR-2, whereas in the choroid plexus, TLR-2 and TLR-9 were both upregulated. Further, the peripheral lymphoid organs (spleen and lymph nodes) showed increased TLR-2 and TLR-4 expression. This study provides the first insight about TLR expression in the central nervous system of infected dogs, and gives additional evidence of the compartmentalization of the immune response during visceral leishmaniasis.