BACKGROUND Eosinophils are granulocytes that rapidly increase frequency in the bloodstream during helminthic infections and allergic responses. They are found in tissue infected by Leishmania during early disease, but their role during infection is not entirely understood. OBJECTIVES We aim to compare the disease due to Leishmania amazonensis in BALB/c and Δdbl-GATA1 mice, which lack eosinophils. METHODS BALB/c and Δdbl-GATA1 mice infected with L. amazonensis were observed for several weeks. The parasite load and dissemination pattern were assessed. FINDINGS The Δdbl-GATA1 mice developed an anticipated dissemination of L. amazonensis and a worsening disease. No differences were found in the lesion development or the parasite load in the footpad among Δdbl-GATA1 mice and BALB/c eight weeks after infection. However, nine weeks after infection, massive growth of metastatic lesions appeared in several parts of the skin in Δdbl-GATA1 mice, weeks earlier than BALB/c. We observed increased parasites in the bloodstream, probably an essential dissemination route. Thirteen weeks after infection, metastatic lesions were found in all Δdbl-GATA1 mice. MAIN CONCLUSION These results suggest a protective role of eosinophils in delaying the disease caused by L. amazonensis, although several limitations of this mice strain must be considered.

BACKGROUND Leishmania (Mundinia) enriettii is a species commonly found in the guinea pig, Cavia porcellus. Although it is a dermotropic species, there is still an uncertainty regarding its ability to visceralise during Leishmania life cycle. OBJECTIVE Here, we investigated the ability of L. enriettii (strain L88) to visceralise in lungs, trachea, spleen, and liver of C. porcellus, its natural vertebrate host. METHODS Animals were infected sub-cutaneously in the nose and followed for 12 weeks using histological (hematoxilin-eosin) and molecular tools (polymerase chain reaction-restriction fragment length polymorphism - PCR-RFLP). To isolate parasite from C. porcellus, animals were experimentally infected for viscera removal and PCR typing targeting hsp70 gene. FINDINGS Histological analysis revealed intense and diffuse inflammation with the presence of amastigotes in the trachea, lung, and spleen up to 12 weeks post-infection (PI). Molecular analysis of paraffin-embedded tissues detected parasite DNA in the trachea and spleen between the 4th and 8th weeks PI. At the 12th PI, no parasite DNA was detected in any of the organs. To confirm that the spleen could serve as a temporary site for L. enriettii, we performed additional in vivo experiments. During 6th week PI, the parasite was isolated from the spleen confirming previous histopathological and PCR observations. MAIN CONCLUSION Leishmania enriettii (strain L88) was able to visceralise in the trachea, lung, and spleen of C. porcellus.

O crescente uso das nanotecnologias nas terapias avançadas tem permitido a observação de reações adversas específicas relacionadas às nanoestruturas. A toxicidade de uma nova formulação lipossomal de antimoniato de meglumina após dose única foi avaliada em cães com leishmaniose visceral. Grupos de 12 animais receberam por via intravenosa uma dose única de antimoniato de meglumina lipossomal (grupo I [GI], 6,5 mg Sb/kg), lipossomas vazios (GII) ou solução salina isotônica (GIII). A avaliação de parâmetros hematológicos e bioquímicos não revelou alterações significativas quatro dias após a administração. Nenhum efeito indesejável foi registrado no GIII. No entanto, reações adversas foram observadas em 67,7% dos cães de ambos os grupos que receberam formulações lipossomais. Os efeitos colaterais iniciaram momentos após a administração em "bolus" e desapareceram no decurso dos primeiros 15 minutos após o tratamento. Prostração, sialorréia e defecação foram os sinais clínicos mais frequentes, registrados em 33,3% e 41,6% dos animais dos grupos GI e GII, respectivamente. Taquipnéia, midríase, miose, vômitos e cianose também foram registrados em ambos os grupos. As reações adversas observadas neste trabalho foram atribuídas à ativação do sistema complemento pelas vesículas lipídicas em fenômeno conhecido como Pseudoalergia Relacionada à Ativação do Complemento (PARAC). A influência das características físico-químicas da formulação lipossomal no desencadeamento de PARAC é abordada.

The increasing use of nanotechnologies in advanced therapies has allowed the observation of specific adverse reactions related to nanostructures. The toxicity of a novel liposome formulation of meglumine antimoniate in dogs with visceral leishmaniasis after single dose has been investigated. Groups of 12 animals received by the intravenous route a single dose of liposomal meglumine antimoniate (group I [GI], 6.5 mg Sb/kg), empty liposomes (GII) or isotonic saline (GIII). Evaluation of hematological and biochemical parameters showed no significant changes 4 days after administration. No undesired effects were registered in the GIII. However, adverse reactions were observed in 67.7% of dogs from both groups that received liposomal formulations. The side effects began moments after bolus administration and disappeared during the first 15 minutes after treatment. Prostation, sialorrhea and defecation were the most frequent clinical signs, registered in 33.3% and 41.6 % of animals from the groups GI and GII, respectively. Tachypnea, mydriasis, miosis, vomiting and cyanosis were also registered in both groups. The adverse reactions observed in this study were attributed to the activation of the complement system by lipid vesicles in a phenomenon known as Complement Activation-Related Pseudoallergy (CARPA). The influence of the physical-chemical characteristics of liposomal formulation in the triggering of CARPA is discussed.

O objetivo deste trabalho foi estudar as alterações histopatológicas e a detecção do parasito nos olhos de cães naturalmente infectados por Leishmania chagasi. Utilizaram-se os olhos de 25 cães com exame parasitológico e sorológico positivo para Leishmania chagasi. Os animais foram submetidos à semiotécnica oftálmica rotineira. Fragmentos do globo ocular foram coletados e destinados à imunoistoquímica e histopatologia. Entre as estruturas avaliadas, a conjuntiva da terceira pálpebra foi a que mais demonstrou imunomarcação da Leishmania chagasi. Na avaliação histopatológica, foi observado predominantemente infiltrado inflamatório mononuclear, variando de discreto a intenso nas diversas estruturas oculares. Congestão vascular e perivasculite também foram observadas. As alterações histopatológicas do bulbo do olho em cães com leishmaniose visceral podem estar relacionadas à presença do anticorpo.

The objective of the present study was to investigate the histopathological alterations and detection of parasites that occur in the eyes of dogs naturally infected with Leishmania chagasi. The eyes of 25 dogs with a positive parasitological and serological exam for L. chagasi were submitted to routine ophthalmic examination. Fragments were obtained from the eyeball and were analyzed by immunohistochemistry and histopathology. Among the structures studied, the conjunctiva of the third eyelid was the tissue most frequently stained for L. chagasi. Histopathological analysis revealed a predominantly mononuclear inflammatory infiltrate whose intensity ranged from discrete to intense in the various ocular structures. Vascular congestion and perivasculitis were also observed. The histopathological alterations that occur in the eyeball of dogs with visceral leishmaniasis might be related to the presence of antibodies.

Neste trabalho, estudamos a infecção experimental de camundongos Suíços/NIH com Leishmania major em comparação com camundongos isogênicos C57BL/6 e BALB/c que são resistentes e suceptíveis a esta infecção, respectivamente. Camundongos Suiços mostraram lesões que se curaram espontaneamente e se restringiram ao local de inoculação. Células linfóides derivadas destes animais desenvolveram uma resposta do tipo Th1, caracterizada pela produção de níveis altos de IFN-<FONT FACE="Symbol">g</font> e níveis baixos de IL-4. Com o objetivo de estudar a importância da microbiota no desenvolvimento da leishmaniose cutânea neste modelo, camundongos Suiços sem germes foram infectados na pata com promastigotas de L. major, convencionalizados após 3 semanas de infecção e as lesões comparadas com as observadas em camundongos convencionais. Os camundongos convencionalizados apresentaram lesões significativamente maiores do que as observadas nos camundongos convencionais. A análise histopatológica das lesões de todos os animais convencionalizados mostrou abcessos de tamanhos e formas variáveis e a presença de numerosos macrófagos parasitados. Nas lesões dos camundongos convencionais não houve a formação de abscessos e foram observados poucos macrófagos parasitados. Entretanto, células de ambos os grupos experimentais desenvolveram uma resposta similar do tipo Th1, caracterizada pela produção de altos níveis de IFN-<FONT FACE="Symbol">g</font> e baixos níveis de IL-4. Neste trabalho, demonstramos que os camundongos Suíços/NIH são resistentes à infecção por L. major, com o desenvolvimento de um fenótipo do tipo Th1 e que a ausência da microbiota no início da infecção influencia significativamente o tamanho da lesão e no processo inflamatório nestes animais.

Infection of Swiss/NIH mice with Leishmania major was compared with infection in isogenic resistant C57BL/6 and susceptible BALB/c mice. Swiss/NIH mice showed self-controlled lesions in the injected foot pad. The production of high levels of interferon-<FONT FACE="Symbol">g</font> (IFN-<FONT FACE="Symbol">g</font>) and low levels of interleukin-4 (IL-4) by cells from these animals suggests that they mount a Th1-type immune response. The importance of the indigenous microbiota on the development of murine leishmaniasis was investigated by infecting germfree Swiss/NIH in the hind footpad with L. major and conventionalizing after 3 weeks of infection. Lesions from conventionalized Swiss/NIH mice were significantly larger than conventional mice. Histopathological analysis of lesions from conventionalized animals showed abscesses of variable shapes and sizes and high numbers of parasitized macrophages. In the lesions from conventional mice, besides the absence of abscess formation, parasites were rarely observed. On the other hand, cells from conventional and conventionalized mice produced similar Th1-type response characterized by high levels of IFN-<FONT FACE="Symbol">g</font> and low levels of IL-4. In this study, we demonstrated that Swiss/NIH mice are resistant to L. major infection and that the absence of the normal microbiota at the beginning of infection significantly influenced the lesion size and the inflammatory response at the site of infection.

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.