Immunosuppression has been reported to occur during active visceral leishmaniasis and some factors such as the cytokine profile may be involved in this process. In the mouse model of cutaneous leishmaniasis using Leishmania (Leishmania) major, the Th1 response is related to protection while the Th2 response is related to disease progression. However, in hamsters, which are considered to be an excellent model for the study of visceral leishmaniasis, this dichotomy is not observed. Using outbred 45- to 60-day-old (140 to 150 g) male hamsters infected intraperitoneally with 2 x 10(7) L. (L.) chagasi amastigotes, we evaluated the immune response of spleen cells and the production of cytokines. We used 3 to 7 hamsters per group evaluated. We detected a preserved response to concanavalin A measured by index of proliferation during all periods of infection studied, while a proliferative response to Leishmania antigen was detected only at 48 and 72 h post-infection. Messenger RNA from cytokines type 1 (IL-2, TNF-α, IFN-γ) and type 2 (IL-4, IL-10 and TGF-β) detected by reverse transcriptase polymerase chain reaction and produced by spleen cells showed no qualitative difference between control non-infected hamsters and infected hamsters during any period of infection evaluated. Cytokines were measured by the DNA band intensity on agarose gel using the Image Lab 1D L340 software with no differences observed. In conclusion, the present results showed an antigen-dependent immunosuppression in hamsters with active visceral leishmaniasis that was not related to the cytokine profile.

Abnormal surface expression of HLA-DR by leukocytes is associated with a poor prognosis in critical care patients. Critical care patients often receive total parenteral nutrition with lipid emulsion (LE). In this study we evaluated the influence of fish oil LE (FO) on human monocyte/macrophage (Mφ) expression of surface HLA-DR under distinct activation states. Mononuclear leukocytes from the peripheral blood of healthy volunteers (n=18) were cultured for 24 hours without LE (control) or with 3 different concentrations (0.1, 0.25, and 0.5%) of the follow LE: a) pure FO b) FO in association (1:1-v/v) with LE composed of 50% medium-chain trygliceride and 50% soybean oil (MCTSO), and c) pure MCTSO. The leukocytes were also submitted to different cell activation states, as determinate by addition time: no INF-γ addition, 18 hours before, or at the time of LE addition. HLA-DR expression on Mφ surface was evaluated by flow cytometry using specific monoclonal antibodies. In relation to controls (for 0.1%, 0.25%, and 0.5%: 100) FO decreased the expression of HLA-DR when added alone [in simultaneously-activated Mφ, for 0.1%: 70 (59 ± 73); for 0.25%: 51 (48 ± 56); and for 0.5%: 52.5 (50 ± 58)] or in association with MCTSO [in simultaneously-activated Mφ, for 0.1%: 50.5 (47 ± 61); for 25%: 49 (45 ± 52); and for 0.5%: 51 (44 ± 54) and in previously-activated Mf, for 1.0%: 63 (44 ± 88); for 0.25%: 70 (41 ± 88); and for 0.5%: 59.5 (39 ± 79)] in culture medium (Friedman p < 0.05). In relation to controls (for 0.1%, 0.25%, and 0.5%: 100), FO did not influence the expression of these molecules on non-activated Mφ [for 0.1%: 87.5 (75±93); for 0.25%: 111 (98 ± 118); and for 0.5%: 101.5 (84 ± 113)]. Results show that parenteral FO modulates the expression of HLA-DR on human Mφ surface accordingly to leukocyte activation state. Further clinical studies evaluating the ideal moment of fish oil LE infusion to modulate leukocyte functions may contribute to a better understanding of its immune modulatory properties.

La expresión anómala del HLA-DR sobre la superficie de los leucocitos se asocia con un pronóstico sombrío en pacientes críticos. A menudo, estos pacientes reciben nutrición parenteral total con una emulsión lipídica (EL). En este estudio, evaluamos la influencia de una EL de aceite de pescado (AP) en la expresión del HLA-DR en la superficie de monocitos/macrófagos humanos (MΦ) bajo diferentes estados de activación. Se cultivaron leucocitos mononucleares de sangre periférica de voluntarios sanos (n = 18) durante 24 horas sin la EL (control) o con 3 concentraciones distintas (0,1, 0,25 y 0,5%) de la siguiente EL: a) AP puro b) AP en asociación con EL (1:1 v/v) compuesta de 50% de triglicéridos de cadena media y 50% de aceite de soja (TCMAS), y c) TCMAS puro. También sometimos a los leucocitos a diferentes estados de activación celular, determinado por INF-γ tiempo de adición: no INF-γ adición 18 horas antes, o en el momento de añadir la EL. La expresión del HLA-DR sobre la superficie de los MΦ se evaluó mediante citometría de flujo utilizando anticuerpos monoclonales específicos. En relación con los controles (para 0,1%, 0,25% y 0,5%: 100) el AP disminuyó la expresión de HLA-DR cuando se añadía solo [en MΦ activados simultáneamente, para 0,1%: 70 (59 ± 73); para 0,25%: 51 (48 ± 56); y para 0,5%: 52.5 (50 ± 58)] o en asociación con TCMAS [en MΦ activados simultáneamente para 0,1%: 50,5 (47 ± 61); para 0,25%:(45 ± 52); y para 0,5%: 51 (44 ± 54) y en MΦ previamente activados para 0,1%: 63 (44 ± 88); para 0,25%: 70 (41 ± 88); y para 0,5%: 59,5 (39 ± 79)] en el medio de cultivo (Friedman p < 0,05). Con respecto a los controles, (para 0,1%, 0,25% y 0,5%: 100), el AP no influyó en la expresión de estas moléculas en MΦ no activados [para 0,1%: 87,5 (75 ± 93); para 0,25%: 111 (98 ± 118); y para 0,5%: 101,5 (84 ± 113)]. Los resultados muestran que el AP parenteral modula la expresión del HLA-DR sobre la superficie de los MΦ humanos en función del estado de activación leucocitaria. Estudios clínicos adicionales que evalúen el momento idóneo de añadir la infusión de EL con aceite de pescado para modular las funciones leucocitarias podrían contribuir a entender mejor sus propiedades inmunomoduladoras.

Abnormal surface expression of HLA-DR by leukocytes is associated with a poor prognosis in critical care patients. Critical care patients often receive total parenteral nutrition with lipid emulsion (LE). In this study we evaluated the influence of fish oil LE (FO) on human monocyte/macrophage (Mphi) expression of surface HLA-DR under distinct activation states. Mononuclear leukocytes from the peripheral blood of healthy volunteers (n = 18) were cultured for 24 hours without LE (control) or with 3 different concentrations (0.1, 0.25, and 0.5%) of the follow LE: a) pure FO b) FO in association (1:1 - v/v) with LE composed of 50% mediumchain trygliceride and 50% soybean oil (MCTSO), and c) pure MCTSO. The leukocytes were also submitted to different cell activation states, as determinate by INF-γ addition time: no INF-γ addition, 18 hours before, or at the time of LE addition. HLA-DR expression on Mphi surface was evaluated by flow cytometry using specific monoclonal antibodies. In relation to controls (for 0.1%, 0.25%, and 0.5%: 100) FO decreased the expression of HLA-DR when added alone [in simultaneously-activated Mphi, for 0.1%: 70 (59 ± 73); for 0.25%: 51 (48 ± 56); and for 0.5%: 52.5 (50 ± 58)] or in association with MCTSO [in simultaneously-activated Mphi, for 0.1%: 50.5 (47 ± 61); for 25%: 49 (45 ± 52); and for 0.5%: 51 (44 ± 54) and in previously-activated Mphi, for 1.0%: 63 (44 ± 88); for 0.25%: 70 (41 ± 88); and for 0.5%: 59.5 (39 ± 79)] in culture medium (Friedman p < 0.05). In relation to controls (for 0.1%, 0.25%, and 0.5%: 100), FO did not influence the expression of these molecules on non-activated Mphi [for 0.1%: 87.5 (75 ± 93); for 0.25%: 111 (98 ± 118); and for 0.5%: 101.5 (84 ± 113)]. Results show that parenteral FO modulates the expression of HLA-DR on human Mphi surface accordingly to leukocyte activation state. Further clinical studies evaluating the ideal moment of fish oil LE infusion to modulate leukocyte functions may contribute to a better understanding of its immune modulatory properties.

La expresión anormal del HLA-DR en la superficie de los leucocitos se asocia con un pronóstico peor en los enfermos críticos. Estos enfermos a menudo reciben nutrición parenteral total con una emulsión lipídica (EL.) En este estudio evaluamos la influencia de la EL de aceite de pescado (AP) sobre la expresión del HLA-DR de superficie por los monocitos /macrófagos humanos (Mfi) en distintos estados de activación. Se cultivaron leucocitos mononucleares de sangre periférica de voluntarios sanos (n = 18) durante 24 horas sin EL (control) o con tres concentraciones diferentes (0,1, 0,25 y 0,5%) de la siguiente EL: a) AP puro b) AP en asociación (1:1 en v/v) con la EL compuesta de un 50% de triglicéridos de cadena media y 50% de aceite de soja (TCMAS), y c) TCMAS puro. Se sometió a los leucocitos a tres estados de activación diferentes, como venía determinado por el tiempo de adición de INF-γ: sin añadir INF-γ, 18 horas antes o en el momento de añadir la EL. La expresión de HLA-DR en la superficie de los Mfi se evaluó mediante citometría de flujo empleando anticuerpos monoclonales específicos. En relación con los controles (para 0,1%, 0,25% y 0,5%: 100) el AP disminuyó la expresión de HLA-DR cuando se añadía solo {en Mfi activados de forma simultánea, para 0,1%: 70 (59 ± 73); para 0,25%: 51 (48 ± 56) y para 0,5%: 52,5 (50 ± 58)} o en asociación con TCMAS [en Mfi activados de forma simultánea, para 0,1%: 50,5 (47 ± 61); para 25%: 49 (45 ± 52); y para 0,5%: 51 (44 ± 54) y en Mfiactivados previamente, para 1,0%: 63 (44 ± 88); para 0,25%: 70 (41 ± 88); y para 0,5%: 59,5 (39 ± 79)] en medio de cultivo (Friedman p < 0,05.) En relación con los controles (para 0,1%, 0,25% y 0,5%: 100), el AP no influyó en la expresión de estas moléculas en los Mfino activados [para 0,1%: 87,5 (75 ± Ó93); para 0,25%: 111 (98 ± 118); y para 0,5%: 101,5 (84 ± 113)}. Los resultados muestran que el AP parenteral modula la expresión del HLA-DR sobre la superficie de los Mfihumanos en función del estado de activación de los leucocitos. Estudios clínicos adicionales que evalúen el momento ideal de la infusión de la EL con aceite de pescado para modular las funciones leucocitarias podrían contribuir a un mejor conocimiento de sus propiedades inmunomoduladoras.

Renal involvement in visceral leishmaniasis (VL) is very frequent but the pathogenesis of this nephropathy is poorly understood. In previous studies using dogs with VL we have detected new immunopathological elements in the glomeruli such as T cells and adhesion molecules. Although Leishmania (Leishmania) chagasi-infected dogs and hamsters are considered to be good models for VL, their use is limited for immunopathologic studies. The use of isogenic mouse strains susceptible to L. (L.) chagasi infection was an alternative but, on the other hand, the renal lesions of these animals have not yet been characterized. Thus, our purpose in the present study was to characterize mice infected with L. (L.) chagasi as a suitable model to study VL nephropathy. Kidney samples were obtained from control mice (N = 12) and from BALB/c mice (N = 24) injected intraperitoneally with 20 million L. (L.) chagasi amastigotes 7, 15, and 30 days after injection and processed for histopathological studies and detection of IgG deposits. Glomerular hypercellularity was clearly visible and, upon Mason's trichrome and periodic acid methenamine silver staining, a pattern suggestive of mesangial proliferative glomerulonephritis was observed in mice with VL. Time-dependent IgG deposits were also seen in infected mice. We consider L. (L.) chagasi-infected mice to be a suitable model for studies of the immunopathogenesis of glomerular lesions in VL.

The serologic assay is an important tool in the diagnosis of leishmaniasis. One of the most commonly used tests is enzyme-linked immunosorbent assay (ELISA). Since total Leishmania promastigotes are used as antigen in the routine assay, false-positive reactions are frequent due to cross-reaction with sera from other diseases, mainly Chagas' disease. Therefore, an antigen that determines less cross-reactivity has been pursued for the serodiagnosis of leishmaniasis. In the present study we analyzed the use of recombinant Leishmania infantum heat shock protein (Hsp) 83 in ELISA for the serodiagnosis of cutaneous (N = 12) and mucocutaneous leishmaniasis (N = 14) and we observed the presence of anti-L. infantum Hsp 83 antibodies in all samples as well as anti-Leishmania total antigen antibodies. When cross-reactivity was tested, chronic Chagas' disease patients (N = 10) did not show any reactivity. Therefore, we consider this L. infantum Hsp 83 to be a good antigen for routine use for serodiagnosis of tegumentary leishmaniasis.

Leishmaniasis is a disease caused by protozoa of the genus Leishmania, and visceral leishmaniasis is a form in which the inner organs are affected. Since knowledge about immunity in experimental visceral leishmaniasis is poor, we present here a review on immunity and immunosuppression in experimental visceral leishmaniasis in mouse and hamster models. We show the complexity of the mechanisms involved and differences when compared with the cutaneous form of leishmaniasis. Resistance in visceral leishmaniasis involves both CD4+ and CD8+ T cells, and interleukin (IL)-2, interferon (IFN)- gamma, and IL-12, the latter in a mechanism independent of IFN- gamma and linked to transforming growth factor (TGF)-ß production. Susceptibility involves IL-10 but not IL-4, and B cells. In immune animals, upon re-infection, the elements involved in resistance are different, i.e., CD8+ T cells and IL-2. Since one of the immunopathological consequences of active visceral leishmaniasis in humans is suppression of T-cell responses, many studies have been conducted using experimental models. Immunosuppression is mainly Leishmania antigen specific, and T cells, Th2 cells and adherent antigen-presenting cells have been shown to be involved. Interactions of the co-stimulatory molecule family B7-CTLA-4 leading to increased level of TGF-ß as well as apoptosis of CD4+ T cells and inhibition of macrophage apoptosis by Leishmania infection are other components participating in immunosuppression. A better understanding of this complex immune response and the mechanisms of immunosuppression in experimental visceral leishmaniasis will contribute to the study of human disease and to vaccine development.

Several organs are affected in visceral leishmaniasis, not only those rich in mononuclear phagocytes. Hypergammaglobulinemia occurs during visceral leishmaniasis; anti-Leishmania antibodies are not primarily important for protection but might be involved in the pathogenesis of tissue lesions. The glomerulonephritis occurring in visceral leishmaniasis has been attributed to immune complex deposition but in other organs the mechanism has not been studied. In the current study we demonstrated the presence of IgG in the lung and liver of hamsters with visceral leishmaniasis. Hamsters were injected intraperitoneally with 2 x 10(7) amastigotes of Leishmania (Leishmania) chagasi and the presence of IgG in the liver and lung was evaluated at 7, 15, 30, 45, 80 and 102 days postinfection (PI) by immunohistochemistry. The parasite burden in the spleen and liver increased progressively during infection. We observed a deposit of IgG from day 7 PI that increased progressively until it reached highest intensity around 30 and 45 days PI, declining at later times. The IgG deposits outlined the sinusoids. In the lung a deposit of IgG was observed in the capillary walls that was moderate at day 7 PI, but the intensity increased remarkably at day 30 PI and declined at later times of infection. No significant C3 deposits were observed in the lung or in the liver. We conclude that IgG may participate in the pathogenesis of the inflammatory process of the lung and liver occurring in experimental visceral leishmaniasis and we discuss an alternative mechanism other than immune complex deposition.

Renal involvement in visceral leishmaniasis (VL) is very frequent. The renal lesions of humans and dogs are similar but their pathogenesis has not been clearly elucidated. There is growing evidence that the cellular immune response is involved in the pathogenesis of immunologically mediated glomerulonephritis. Since T cells could participate in the pathogenesis of nephropathy, in the present study we investigated the possible involvement of CD4+ and CD8+ T cells in the nephropathy of canine VL. Six dogs naturally infected with Leishmania (Leishmania) chagasi from the endemic area in the Northeast of Brazil, the town of Teresina in the State of Piauí, were studied. An expressive inflammatory infiltrate of CD4+ T cells both in glomeruli and in interstitium was present in 4 animals and absent in 2. CD8+ T cells were detected only in one animal. CD4+ T cells alone were observed in 3 animals; when CD8+ T cells were present CD4+ T cells were also present. CD4+ T cells were observed in cases of focal segmental glomerulosclerosis, diffuse membranoproliferative glomerulonephritis, diffuse mesangial proliferative glomerulonephritis and crescentic glomerulonephritis. CD8+ T cells were present only in a case of crescentic glomerulonephritis. Leishmania antigen was detected in glomeruli and in interstitial inflammatory infiltrate in 4 animals and immunoglobulins were observed in 4 dogs. In this study we observed that T cells, in addition to immunoglobulins, are present in the renal lesion of canine VL. Further studies are in progress addressing the immunopathogenic mechanisms involving the participation of immunoglobulins and T cells in canine VL nephropathy.

In order to study the role of natural killer (NK) cells during the early period of Leishmania infection, BALB/c mice were selectively and permanently depleted of NK cells by injection with 90Sr and subsequently infected with Leishmania (Leishmania) amazonensis (HSJD-1 strain). 90Sr is known to selectively deplete NK cells, leaving an intact T- and B-cell compartment and preserving the ability to produce both interferon alpha and IL-2. This method of depletion has advantages when compared with depletion using anti-NK cell monoclonal antibodies because the effect is permanent and neither activates complement nor provokes massive cell death. In the present study, after one month of treatment with 90Sr, the depletion of NK cells was shown by a more than ten-fold reduction in the cytotoxic activity of these cells: 2 x 106 spleen cells from NK-depleted animals were required to reach the same specific lysis of target cells effected by 0.15 x 106 spleen cells from normal control animals. The histopathology of the skin lesion at 7 days after Leishmania infection showed more parasites in the NK cell-depleted group. This observation further strengthens a direct role of NK cells during the early period of Leishmania infection.

Estudamos a susceptibilidade à Leishmania (Viannia) panamensis em linhagens de camundongos BALB/c, DBA/2J, CBA/HJ e C57BL/6. Os camundongos da linhagem C57BL/6 eram resistentes, apresentando lesões autolimitantes na pata. Os das linhagens BALB/c e DBA/2J eram suscetíveis, apresentando edema na pata, evidente aos 20 dias pós-infecção que progrediu para uma lesão tipo tumoral nas fases tardias. Os animais da linhagem CBA/HJ apresentaram resistência intermediária. Em contraste a outros modelos de leishmaniose cutânea murina, a lesão nos camundongos infectados pela L. (V.) panamensis mostrou ser restrita ao local de inoculação na pele. Estudamos também o desenvolvimento de resposta celular e anticorpos anti-Leishmania nas linhagens BALB/c c C57BL/6. A resposta proliferativa de células do linfonodo a antígenos de L. (V.) panamensis foi bifásica em ambas as linhagens. Uma resposta inicial foi observada com 20 dias de infecção, seguida por uma fase refratária entre 40 e 80 dias e uma segunda resposta ao redor do quarto mês de infecção. A resposta nesta segunda fase estava mais alta na linhagem C57BL/6 do que na BALB/c. Por outro lado, os camundongos BALB/c apresentaram níveis de anticorpo anti-Leishmania muito mais elevados que os da linhagem C57BL/6. O modelo e a correlação das variáveis imunológicas com o curso da infecção são discutidos.

We studied the susceptibility to Leishmania (Viannia) panamensis in strains of mice. The C57BL/6 strain was resistant and showed self-controlled lesion at the injected foot pad. The BALB/c and DBA/2J strains were susceptible and showed a foot swelling that started day 20 post-infection and progressed to a tumour-like lesion in later period of observation. The CBA/HJ strain was found to be of intermediary resistance. In contrast to other known cutaneous leishmaniasis in mice, the lesion in L. (V.) panamensis-infected mice was restricted to the inoculation site in the skin. In addition, we studied the development of cellular response and antibodies against Leishmania antigen in BALB/c and C57BL/6 strains. The proliferative response of lymph node cells against L. (V.) panamensis antigen was biphasic in both strains. An initial response was seen on day 20, followed by a refractory period between 40 and 80 days and a second response around fourth month post-infection. The response in the latter period was higher in C57BL/6 strain than in BALB/c strain. BALB/c strain presented much higher anti-Leishmania antibody level than C57BL/6 strain. The model and the correlation of immunological variables and the course of the infection are discussed.