FUNDAMENTOS: A histopatologia e as respostas imunológicas do processo de cura da leishmaniose são ainda pouco estudadas. OBJETIVOS: Este estudo teve como objetivo avaliar os aspectos histopatológicos e imunológicos das lesões de pacientes com leishmaniose tegumentar, antes e após diferentes métodos terapêuticos. MÉTODOS: Foram estudados 23 indivíduos agrupados de acordo com os tratamentos: Glucantime, Glucantime + Leishvacin e Glucantime + Leishvacin associado com Bacilo Calmette-Guerin. Para a análise das alterações histopatológicas presentes na derme e epiderme, cortes histológicos foram corados com hematoxilina e eosina. Para avaliar a expressão de interferon (IFN)-γ, interleucina (IL) 12, IL-10 e IL-4 foi utilizada a técnica de imuno-histoquímica antes e após o tratamento. RESULTADOS: Antes do tratamento houve um intenso infiltrado de células mononucleares, após o tratamento, mesmo com um diagnóstico de cura clínica, apresentou-se ainda um moderado processo inflamatório. Na análise imuno-histoquímica, notamos uma diferença entre as citocinas, com expressão aumentada de citocinas IFN-γ e IL-12 em comparação com IL-10 e IL-4 tanto antes quanto depois do tratamento, e comparativamente, a diferença nesta expressão mostrou-se mais intensa antes do tratamento. No entanto, a expressão das citocinas analisadas por grupo de tratamento não mostraram diferenças estatisticamente significativas. CONCLUSÃO: Concluímos que uma cura clínica nem sempre coincide com a cura histopatológica, e que antes do tratamento há uma predominância de citocinas Th1. Para os tratamentos, não houve diferença na progressão da cura para todos os três tipos de tratamento, indicando a equivalência clínica dos tratamentos.

BACKGROUND: The histopathology and immune responses of the healing process of leishmaniasis are still poorly studied. OBJECTIVES: This study aimed to examine the histopathological and immunological aspects of lesions of patients with cutaneous leishmaniasis before and after different therapeutic methods. METHODS: We studied 23 individuals grouped according to the treatments: Glucantime, Glucantime + Leishvacin and Glucantime + Leishvacin associated with Bacillus Calmette-Guerin. For analysis of the histopathological changes present in the dermis and epidermis, histological sections were stained with hematoxylin and eosin. The samples were immunostained before and after treatment to analyze the expression of interferon (IFN)-γ, interleukin (IL) 12, IL-10 and IL-4. RESULTS: Before treatment the presence of intense infiltrates of mononuclear cells was noticed and after treatment, even with a diagnosis of clinical cure, the subjects still showed a moderate inflammatory process. In the immunohistochemical analyses, we noticed a difference between the cytokines, with increased expression of cytokines IFN-γ and IL-12 compared to IL 10 and IL-4, both before and after treatment and, comparatively, the difference in this expression was more intense before treatment. However, the cytokine expression analyzed by treatment group showed no statistically significant difference. CONCLUSION: We conclude that a clinical cure does not always coincide with the histopathological one, and that before treatment there is a predominance of Th1 cytokines. In terms of treatment type, there was no difference in the progression of healing for all the three types of treatment, indicating their clinical equivalence.

INTRODUÇÃO: Analisou-se a positividade da reação em cadeia da polimerase (PCR) na detecção de DNA de Leishmania em pacientes. MÉTODOS: DNA extraído foi submetido a L150/L152, 13Y/13Z e PCR seminested (snPCR). RESULTADOS: Resultados foram evidenciados por bandas de aproximadamente 120; 720 e 670pb para L150/L152, 13Y/13Z e snPCR, respectivamente. Positividades para L150/L152, 13Y/13Z e snPCR foram 76,9; 56,4 e 69,2 (p > 0,05), para suspeitos; e 93,7; 68,7 e 84,4 (p < 0,05) para confirmados, respectivamente. CONCLUSÕES: Resultados preliminares mostraram que os ensaios, principalmente L150/L152 e snPCR, podem detectar DNA de Leishmania e têm potencial para diagnóstico laboratorial das leishmanioses.

INTRODUCTION: The study analyzed positivity of polymerase chain reaction (PCR) on detection of DNA from Leishmania in patients' samples. METHODS: Extracted DNA was submitted to L150/L152, 13Y/13Z, and seminested PCR (snPCR). RESULTS: Results were evidenced by bands of approximately 120, 720, and 670 bp for L150/L152, 13Y/13Z, and snPCR, respectively. L150/L152, 13Y/13Z, and snPCR positivity indexes were 76.9, 56.4, and 9.2 (p>0.05), respectively, for suspected and 93.7, 68.7, and 84.4 (p<0.05), respectively, for confirmed. CONCLUSIONS: Preliminary results showed that these assays, mainly L150/L152 and snPCR, can detect Leishmania DNA and carry potential on laboratory diagnosis of leishmaniasis.

For decades thimerosal has been used as a preservative in the candidate vaccine for cutaneous leishmaniasis, which was developed by Mayrink et al. The use of thimerosal in humans has been banned due to its mercury content. This study addresses the standardization of phenol as a new candidate vaccine preservative. We have found that the proteolytic activity was abolished when the test was conducted using the candidate vaccine added to merthiolate (MtVac) as well as to phenol (PhVac). The Montenegro's skin test conversion rates induced by MtVac and by PhVac was 68.06% and 85.9%, respectively, and these values were statistically significant (p < 0.05). The proliferative response of peripheral mononuclear blood cells shows that the stimulation index of mice immunized with both candidate vaccines was higher than the one in control animals (p < 0.05). The ability of the candidate vaccines to induce protection in C57BL/10 mice against a challenge with infective Leishmania amazonensis promastigotes was tested and the mice immunized with PhVac developed smaller lesions than the mice immunized with MtVac. Electrophoresis of phenol-preserved antigen revealed a number of proteins, which were better preserved in PhVac. These results do in fact encourage the use of phenol for preserving the immunogenic and biochemical properties of the candidate vaccine for cutaneous leishmaniasis.

O tratamento de primeira escolha para leishmaniose tegumentar americana é o antimonial pentavalente. Embora este tratamento seja na maioria das vezes efetivo e indicado, devem ser consideradas as desvantagens tais como efeitos colaterais, longa duração do tratamento e contra-indicação para cardiopatas, nefropatas, idosos, grávidas e outras condições. Com o advento da vacina antileishmaniose tegumentar americana para fins profiláticos e terapêuticos, associando-a ou não a outros fármacos, muitas pesquisas têm sido desenvolvidas, sendo a vacina a principal entre os atuais recursos no tratamento e prevenção da leishmaniose tegumentar americana. Em conclusão, a associação do antimônio com a vacina (imunoquimioterapia) apresentou o mesmo índice de cura em relação ao tratamento padrão (100%), e ainda reduziu o volume do sal em 17,9% e o tempo de cura significativamente, de 87 para 62 dias; conseqüentemente, reduzindo os efeitos colaterais.

The first choice of treatment for American cutaneous leishmaniasis is the pentavalent antimonial drug. Although it has been shown that this treatment is mostly effective and indicated, some disadvantages should be taken into account such as side effects, long term treatment inconveniences and counter-indication for patients suffering from cardiopathy, nephropathy; yet, aging, pregnancy and other conditions. With the advent of the vaccine anti-American cutaneous leishmaniasis as a prophylactic measure, studies on therapy using the vaccine associated or not with other drugs have been performed by many investigators and it is currently among the alternative treatments and prevention measures for American cutaneous leishmaniasis. In conclusion, the association between antimony and vaccine (immunochemotherapy) showed the same cure rate when compared with the standard treatment (100%) and it was also able to reduce the salt volume in 17.9% and treatment length from 87 to 62 days, decreasing side effects.

O comportamento e hábitos alimentares de algumas espécies da flebotomíneos têm sido útil na compreensão da epidemiologia das leishmanioses. No município de Porteirinha (MG), foram realizadas capturas mensais sistematizadas utilizando-se 28 armadilhas luminosas tipo CDC, durante o período de janeiro a dezembro de 2002. Foram capturadas 14 espécies de flebotomíneos, totalizando 1.408 exemplares. De acordo com o ambiente, os resultados obtidos mostraram que o peridomicílio apresentou a maior (53,3%) porcentagem dos espécimens encontrados na região, embora parte (46,7%) da fauna também tenha sido encontrada no intradomicílio. O repasto sanguíneo de 38 fêmeas de Lutzomyia longipalpis, provenientes do campo, foi identificado através da reação de precipitina. Os resultados indicam que Lutzomyia longipalpis foi a espécie predominante (65,1%), mostrando-se oportunista, podendo sugar uma ampla variedade de vertebrados.

Studies on the behavioral and feeding habits of some species of phlebotominae sand flies have contributed to the comprehension of the epidemiology of leishmaniasis. In the present work, systematic captures were performed monthly in the municipality of Porteirinha (MG) using 28 light traps (CDC) from January to December 2002. Fourteen different species of phlebotomine were captured in a total of 1,408 specimens. The highest percentage of individuals (53.3%) was collected in the peridomicile against 46.7% in the intradomicile. Lutzomyia longipalpis was the predominant species in that region. The blood feeding of 38 females of this species from the field was analyzed by precipitin reaction. The results indicated that Lutzomyia longipalpis is an opportunist (65.1%) species that feeds on a wide variety of vertebrates in nature.

The performances of ELISA assays with different antigen preparations, such as Leishmania amazonensis or L. chagasi lysates and the recombinant antigens rK-39 and rK-26, were compared using sera or eluates from dried blood collected on filter paper to detect anti-Leishmania antibodies in dogs from a visceral leishmaniasis-endemic area in Brazil. Of 115 IFAT-reactive dogs at 1:40 titre, 106 (92.2%) were positive in parasitological exams (skin and/or spleen). These animals were compared to healthy animals (n = 25), negative for IFAT at a titre of 1:40 and parasitological exams. The sensitivities of crude and recombinant antigens were similar and remarkably high for both sera and eluates (97-100%). Specificity was higher than 96% for sera and eluates for different antigens, except for L. chagasi antigen using eluates (88%). Concordance values among the tests were higher either for sera or eluates (J = 0.95-1.00). High concordances were observed between sera and eluates tested with different antigens (kappa = 0.93-0.97). Crude and recombinant antigens identified different clinical phases of canine leishmaniasis. These results show that eluates could be used in canine surveys to identify L. chagasi infection. Recombinant antigens added little when compared to crude antigen in identifying positive dogs. Cross-reactivity with other diseases whose distribution often overlaps VL-endemic areas is a limitation of crude antigen use however.

Proteínas imunogênicas da vacina polivalente de promastigotas mortas de leishmanias (Leishvacin®) produzida pela Biobrás Bioquímica do Brasil, Montes Claros, Minas Gerais, Brasil foram identificadas e purificadas por eletroforese em gel de poliacrilamida e eletroeluição. Camundongos C57BL/10 foram vacinados com proteínas de pesos moleculares estimados em 42, 46, 63, 66, 73, 87, 97 e 160kDa em três doses de 30µg de cada proteína combinada com 250µg de Corynebacteriumparvum em intervalos de 15 dias e desafiados com uma infecção desafio de 10(5) promastigotas infectantes de Leishmania (Leishmania) amazonensis na base da cauda. Foram avaliadas a habilidade dessas proteínas em induzir resposta imune e proteção dos animais vacinados após a infecção desafio. Nenhuma diferença estatística foi observada nos níveis de IFN-g nos grupos vacinados em comparação ao grupo controle. Proteção de 28,57; 42,86; 57,14; 42,86; 42,86, 57,14; 42,86; 57,14% foi demonstrado para cada proteína.

Immunogenic proteins from nonliving promastigote polyvalent Leishmania vaccine against American tegumentary leishmaniasis (Leishvacin®), produced by Biobrás (Biochemistry of Brazil ), Montes Claros, State of Minas Gerais, Brazil, were identified and purified by polyacrylamide electrophoresis gel and electroelution. C57BL/10 mice were vaccinated with proteins with estimated molecular weights of 42, 46, 63, 66, 73, 87, 97, and 160kDa in three doses of 30µg of each protein at 15-day intervals combined with 250µg of Corynebacterium parvum followed by a challenge infection with 10(5) infective promastigotes from Leishmania (Leishmania) amazonensis. The ability of these proteins to induce immune response and protection was analyzed. No statistical difference was observed in the level of IFN-g induced by proteins in vaccinated groups in comparison with control groups. Six months after challenge infection, protection levels of 28.57; 42.86; 57.14; 42.86; 42.86, 57.14; 42.86 and 57.14% were demonstrated for each purified protein.

Neste estudo, descrevemos etapas iniciais de padronização de uma nova metodologia para detecção de anticorpos antipromastigotas vivas de Leishmania (Viannia) braziliensis, pela citometria de fluxo e a análise de sua aplicabilidade para estudos clínicos. Foram avaliados 39 indivíduos com sorologia convencional (RIFI) positiva para leishmaniose, classificados quanto à ausência/presença de lesão (L- e L+). Os resultados foram expressos sob a forma de percentual de parasitas fluorescentes positivos (PPFP). A análise dos dados, na diluição 1:1.024, permitiu distinguir 95% dos pacientes L+ como um grupo de alta reatividade (PPFP>50%) e 72% dos indivíduos L- como um grupo de baixa reatividade (PPFP<50%). A análise dos títulos da reação de imunofluorescência indireta não demonstrou nenhuma relação com a ausência/presença de lesão. Em conjunto, nossos dados sugerem a aplicabilidade da citometria de fluxo na identificação dos casos de infecção ativa, o que não tem sido possível através das reações sorológicas convencionais.

In the current study we described initial standardization steps of a new methodology to detect anti-live Leishmania (Viannia) braziliensis promastigote antibodies by flow cytometry, followed by analysis of its applicability to clinical studies. We have studied 39 individuals with positive conventional serology to leishmaniasis, classified according to the absence/presence of cutaneous lesions (L- and L+). The results were expressed as percentage of positive fluorescent parasites (PPFP). Data analysis at dilution of 1:1,024, allowed the distinction of 95% of L+ patients as a group of high reactivity (PPFP>50%) and 72% of L- individuals as a group of low reactivity (PPFP<50%). The analysis of immunofluorescence assay titers did not show any relationship with the absence/presence of lesion. Together, our data support the applicability of flow cytometry to identify cases of active infection, which has not been possible through conventional serological reactions.

Estudos anteriores revelaram que uma vacina preparada com promastigotas mortas de cinco cepas de Leishmania pode induzir uma imunidade protetora para a leishmaniose tegumentar americana no homem e em modelos experimentais. Um dos problemas do uso desta vacina é a complexidade de sua composição e a necessidade de se incorporar diferentes cepas de Leishmania. Por esta razão, extratos antigênicos de cada uma das cinco cepas constituintes da vacina foram preparados e usados individualmente em estudos imunológicos com camundongos C57BL/10. A Leishvacin® e a vacina monovalente PH8 induziram os maiores níveis de Interferon-g (IFN-gama) detectado no sobrenadante de células esplênicas dos animais vacinados. Cada grupo imunizado com vacinas monovalentes desenvolveram uma imunidade protetora seis meses após a infecção desafio com promastigotas de Leishmania (Leishmania) amazonensis e nenhuma diferença estatística foi observada entre os grupos vacinados. Pode-se concluir que vacinas compostas por cepas isoladas de Leishmania protegem camundongos C57BL/10 contra, pelo menos, da infecção por L. (L.) amazonensis.

Antigenic extracts from five Leishmania stocks were used to vaccinate C57BL/10 mice. The Leishvacin® and PH8 monovalent vaccine yielded the highest IFN-gamma levels in the supernatants of spleen cell culture from vaccinated animals. Each single strain immunized group showed evidence of protective immunity six months after the challenge with promastigotes of Leishmania (Leishmania) amazonensis. No differences were detected between the vaccinated groups. It can be concluded that vaccines composed of single Leishmania stocks can provide protection to C57BL/10 mice against L. (L.) amazonensis infection.

A indução de imunidade no homem contra a leishmaniose cutânea tem sido estudada por vários pesquisadores usando uma grande variedade de preparações antigênicas, como: promastigotas vivas ou atenuadas, extratos de promastigotas, antígenos parcialmente purificados e proteínas puras. Neste trabalho foram isoladas 11 proteínas de L. (L.) amazonensis com pesos moleculares variando de 13.5 a 97 kDa por eletroforese em gel de poliacrilamida e por eletroeluição. Estas proteínas foram combinadas em diferentes preparações vacinais com gp63 e BCG. As vacinas foram avaliadas in vitro quanto à capacidade de estimular linfócitos de pessoas vacinadas com Leishvacin<FONT FACE="Symbol">â</font> a produzirem IFN-<FONT FACE="Symbol">g</font> e a estimularem a proliferação de linfócitos de camundongos vacinados. Assim, camundongos C57BL/10 foram vacinados em intervalos de 15 dias com três doses de cada vacina contendo 30 <FONT FACE="Symbol">m</font>g de cada proteína. 100 <FONT FACE="Symbol">m</font>g de BCG foram usados somente na primeira dose. Sete dias após a última dose os animais receberam a primeira infecção desafiado com 105 promastigotas infectantes e um segundo desafio foi administrado 143 dias após, com o mesmo número de parasitas. Sessenta dias após o segundo desafio, proteções de 42,86% foram obtidas com as vacinas constituídas de gp63+46+22kDa, gp63+13.5+25+42kDa, gp63+46+42kDa, gp63+66kDa e gp63+97kDa; 57,14% de proteção foi obtido com a vacina gp63+46+97kDa, gp63+46+97+13.5kDa, gp63+46+33kDa, e 71,43% com a vacina constituída de gp63 mais todas as proteínas. Em contraste, a vacina gp63+46+33kDa não induziu proteção nos camundongos vacinados, indicando que possivelmente a proteína de 40kDa induziu a uma atividade imunossupressora da resposta imunoprotetora. Estes resultados sugerem que uma futura vacina contra a leishmaniose cutânea deverá conter, excluindo-se a proteína de 40kDa, um coquetel de proteínas imunogênicas indutoras de proteção de camundongos contra a leishmaniose cutânea.

In the past few years, induction of protective immunity to cutaneous leishmaniasis has been attempted by many researchers using a variety of antigenic preparations, such as living promastigotes or promastigote extracts, partially purified, or defined proteins. In this study, eleven proteins from Leishmania (Leishmania) amazonensis (LLa) with estimated molecular mass ranging from 97 to 13.5kDa were isolated by polyacrylamide gel electrophoresis and electro-elution. The proteins were associated as vaccine in different preparations with gp63 and BCG (Bacilli Calmette-Guérin). The antigenicity of these vaccines was measured by their ability to induce the production of IFN-<FONT FACE="Symbol">g</font> by lymphocyte from subjects vaccinated with Leishvacin<FONT FACE="Symbol">â</font> . The immunogenicity was evaluated in vaccinated mice. C57BL/10 mice were vaccinated with three doses of each vaccine consisting of 30 <FONT FACE="Symbol">m</font>g of each protein at 15 days interval. One hundred <FONT FACE="Symbol">m</font>g of live BCG was only used in the first dose. Seven days after the last dose, they received a first challenge infection with 105 infective promastigotes and four months later, a second challenge was done. Two months after the second challenge, 42.86% of protection was obtained in the group of mice vaccinated with association of proteins of gp63+46+22kDa, gp63+13.5+25+42kDa, gp63+46+42kDa, gp63+66kDa, and gp63+97kDa; 57.14% of protection was demonstrated with gp63+46+97+13.5kDa, gp63+46+97kDa, gp63+46+33kDa, and 71.43% protection for gp63 plus all proteins. The vaccine of gp63+46+40kDa that did not protect the mice, despite the good specific stimulation of lymphocytes (LSI = 7.60) and 10.77UI/ml of IFN-<FONT FACE="Symbol">g</font> production. When crude extract of L. (L.) amazonensis was used with BCG a 57.14% of protection was found after the first challenge and 28.57% after the second, the same result was observed for gp63. The data obtained with the vaccines can suggest that the future vaccine probably have to contain, except the 40kDa, a cocktail of proteins that would protect mice against cutaneous leishmaniasis.

An atypical case of acquired immunodeficiency syndrome-associated mucocutaneous lesions due to Leishmania braziliensis is described. Many vacuolated macrophages laden with amastigote forms of the parasite were found in the lesions. Leishmanin skin test and serology for leishmaniasis were both negative. The patient was resistant to therapy with conventional drugs (antimonial and amphotericin B). Interestingly, remission of lesions was achieved after an alternative combined therapy of antimonial associated with immunotherapy (whole promastigote antigens). Peripheral blood mononuclear cells were separated and stimulated in vitro with Leishmania antigens to test the lymphoproliferative responses (LPR). Before the combined immunochemotherapy, the LPR to leishmanial antigens was negligible (stimulation index - SI=1.4). After the first course of combined therapy it became positive (SI=4.17). The antigen responding cells were predominantly T-cells (47.5%) most of them with CD8+ phenotype (33%). Very low CD4+ cells (2.2%) percentages were detected. The increased T-cell responsiveness to leishmanial antigens after combined therapy was accompanied by interferon-g (IFN-g) production as observed in the cell culture supernatants. In this patient, healing of the leishmaniasis lesions was associated with the induction of a specific T-cell immune response, characterized by the production of IFN-g and the predominance of the CD8+ phenotype among the Leishmania-reactive T-cells.

A resposta imune induzida por uma proteína recombinante de Leishmania (Leishmania) amazonensis de 33 kD (Larp33) foi avaliada em linfócitos de indivíduos vacinados com a Leishvacin® e em camundongos através de vacinação. Larp33 foi expressa em Escherichia coli após clonagem de um fragmento genômico de L. (L.) amazonensis de 2,2 kb no vetor pDS56-6His. Larp33 foi reconhecida por anticorpos IgG presentes no soro de indivíduos vacinados com Leishvacin® e induziu proliferação em linfócitos desses indivíduos em níveis comparáveis ao antígeno total de Leishmania. A análise por imunoblot indicou que Larp33 corresponde a uma proteína de aproximadamente 40 kD expressa em promastigotas de L. (L.) amazonensis e L. (Viannia) braziliensis. Hibridização com sonda de DNA correspondente a parte do fragmento clonado, também demonstrou que o gene codificador desta proteína é expresso em promastigotas destas duas espécies. Larp33 em associação com BCG (Bacille Calmette-Guerin) foi capaz de induzir 75% de proteção em camundongos C75BL/10 e BALB/c, suceptíveis à infecção por L. (L.) amazonensis. Linfócitos dos camundongos protegidos produziram IL-2 e IFN-<FONT FACE="Symbol">g</font> em resposta a Larp33. Nossos resultados indicam que Larp33 é imunogênica para linfócitos de indivíduos vacinados com Leishvacin ® e protetora para camundongos contra a infecção por L. (L.) amazonensis

In the search for Leishmania recombinant antigens that can be used as a vaccine against American Cutaneous Leishmaniasis, we identified a Leishmania (Leishmania) amazonensis recombinant protein of 33 kD (Larp33) which is recognized by antibodies and peripheral blood leukocytes (PBL) from subjects vaccinated with Leishvacin ®, Larp33 was expressed in Escherichia coli after cloning of a 2,2 kb Sau3A digested genomic fragment of L. (L.) amazonensis into the pDS56-6 His vector. Immunoblotting analysis indicated that Larp33 corresponds to an approximately 40-kD native protein expressed in promastigotes of L.(L.) amazonensis and L. (Viannia) braziliensis. Northern blots of total RNA also demonstrated that the gene coding for this protein is expressed in promastigotes of the major lineages of Leishmania causing American Cutaneous Leishmaniasis. Larp33 induced partial protection in susceptible mouse strains (BALB/c and C57BL/10) against L. (L.) amazonensis after vaccination using Bacille Calmette-Guerin (BCG) as adjuvant. In vitro stimulation of splenocytes from BALB/c protected mice with Larp33 elicited the secretion of IL-2 and IFN-<FONT FACE="Symbol">g</font>, suggesting that a Th1 cell-mediated protective response is associated with the resistance observed in these mice. As revealed by its immunogenic and antigenic properties, this novel recombinant antigen is a suitable candidate to compose a vaccine against cutaneous leishmaniasis

Os objetivos deste trabalho visaram uma análise comparativa das alterações histopatológicas e da expressão de CR3 e CR4 no fígado e baço de cães natural e experimentalmente infectados com L. chagasi. As lesões histopatológicas fundamentais observadas principalmente nos cães naturalmente infectados foram: os granulomas epitelióides hepáticos, a hiperplasia e a hipertrofia das células de Kupffer, dos folículos de Malpighi e das células mononucleadas da polpa vermelha do baço. Os cortes de fígado e baço corados pela técnica de imunocitoquímica mostraram a presença dos antígenos CD11b,c\CD18 nos animais controles e infectados, sem diferenças qualitativas e quantitativas no fígado. Entretanto, no baço dos cães natural e experimentalmente infectados a expressão de CD 18 (subunidade beta2 da molécula comum aos leucócitos) foi sempre aumentada. Em leishmaniose a resposta imune celular é considerada a mais importante na resolução da doença. A expressão de CD11 b,c\CD 18 pelos macrófagos deve representar um papel central na resposta celular. Estes resultados indicam que tanto na leishmaniose visceral canina experimental ou natural existe uma diferença na ativação de CD 18, o qual deve exercer uma importante função na resposta imunológica na infecção por Leishmania chagasi.

The objective of this study was to compare the histopathological changes and expression of CR3 and CR4 in the liver and spleen of dogs naturally and experimentally infected with L. chagasi. The basic histopathological lesions observed mainly in naturally infected dogs were: epithelioid hepatic granulomas, hyperplasia and hypertrophy of Kupffer cells, Malpigui follicles and mononucleated cells of the red pulp of the spleen. Sections from the liver and spleen by immunocytochemistry technique showed the presence of CD11b,c\CD 18 antigens in the control and infected animals and no qualitative or quantitative differences in the liver. Nevertheless, CD18 was always increased in the spleen of naturally and experimentally infected dogs. These results indicate that there is a difference in the activaton of CD 18 in both experimental and natural cases of canine visceral leishmaniasis that should play an important role in the immunological response to Leishmania chagasi infection.