Lymph node cell responsiveness in BALB/C mice infected with Leishmania mexicana

In the present study we measured the blastogenic response of lymph node cells from BALB/c mice infected with Leishmania mexicana throughout the course of infection. Results showed that infected mice displayed normal blastogenic responses in the lymph nodes until twenty weeks of infection. Thereafter, there was a gradual suppression. Comparison of the immunoresponsiveness in the spleen and lymph nodes, revealed normal responses in the lymph nodes several weeks after suppression in the spleen had occurred. Suppression of blastogenic responses in the lymph nodes was related to an adherent macrophage-like cell which actively suppressed normal proliferative responses to mitogens.

The retained capacity of Lutzomya longipalpis (Lutz & Neiva) to transmit Leishmania chagasi (Cunha & Chagas) after eight years (64 generations in a closed laboratory colony

A closed Lutzomyia longipalpis colony, from Ceará has been used to transmit Leishmania chagasi isolated from a fox in Pará state. The last time this colony was successfully used in similar transmission experiments was eight years (64 generations) ago indicating that this colony of Lu. longipalpis has fully maintained its vectorial capacity in spite of such a long period of maintainance in the laboratory.

Flagellates in the Malpighian tubules of laboratory-bred Lutzomyia longipalpis fed on a hamster experimentally infected with Leishmania mexicana amazonensis

As a preparatory stage for a study aiming at identifying the species and subspecies of local Leishmania in naturally infected sandflies through immunoradiometric assay with monoclonal antibodies, we tried to obtain experimental infections of phlebotomines with well characterized stocks of parasites, in order to test the effectiveness of the method.

Observations on the sandfly (Diptera: Psychodidae) fauna of Além Paraíba state of Minas Gerais, Brazil, and the isolation of a parasite of the Leishmania braziliensis complex from Psychodopygus hirsuta hirsuta

Dissection of 765 sandflies captured in Além Paraíba (the type locality of Leishmania braziliensis) resulted in the isolation, from Psychodopygus hirsuta hirsuta, of a parasite of the Le. braziliensis complex.

Activación de celulas supresoras de la respuesta de hipersensibilidad tardía en ratones BALB/c infectados o vacunados con Leishmania mexicana pifanoi

Los ratones BALB/c inmunizados SC con promastigotes no viables de Leishmania mexicana pifanoi, desarrollaron respuestas de hipersensibilidad tardia (RHT) contra el parásito. En contraposición, los ratones BALB/c infectados crónicamente con L.m. pifanoi y aquellos inmunizados IV con una dosis supraóptima de parásitos muertos, mostraron inhibición de la RHT. La supresión de la RHT en los animales infectados, estuvo precedida por un estado transitorio de inmunidad celular, manifestado durante la fase inicial del desarrollo de las lesiones (4-12 semanas). La inhibición de la RHT observada en los animales infectados o inmunizados con dosis supraóptimas, fue causada por un mecanismo activo, transferible a receptores singénicos a través de las células esplénicas de los donantes suprimidos. La población de células supresoras fue no adherente a "nylon", sensible al tratamiento con un suero anti-timocitos de ratón y C', y de acción específica sobre la RHT contra antígenos leishmánicos. Se propone que la ocurrencia de células T supresoras de la RHT en los animales infectados crónicamente o inmunizados con dosis supraóptimas, es causada por el exceso de carga antigénica. Esta última, en el caso de los animales infectados, secundaria a una falla primaria en el control inmunológico de la población parasitaria.

Lutzomyia gasparviannai Martins, Godoy & Silva, 1962, probable vector of Leishmania mexicana ssp. in Viana municipality, Espírito Santo State, Brazil

Dos flebótomos atraídos pelo Proechimys iheringi numa área onde esse roedor foi achado naturalmente infectado por Leishmania mexicana ssp., 98,1% foram Lutzomyia gasparviannai, o que sugere que essa espécie não antropofílica seja o transmissor entre os roedores mas não habitualmente ao homem.

Interleukin- 2 production during murine infection by Leishmania mexicana amazonensis

Highly susceptible BALB/c mice, resistant C57B1/6 and their F1 progeny (BDF1) were infected subcutaneously in the foot pad with Leishmania mexicana amazonenesis. At various times after infection, spleen or draining popliteal lymph node cells were assayed for their capacity to generate Interleukin-2 (I1-2) by Concanavalin A (ConA) stimulation. In both BALB/c and C57B1/6 strains there was a transient increase in their capacity to produce I1-2, from the 3rd to the 10th week post-infection. Return to pre-infection levels ocurred between 13th to 16th week post-infection in all three strains. BALB/c mice always produced higher titers of 11-2 than C57B1/6, but such differences were statistically significant only at 3 and 10 weeks post-infection. BDF1 mice had titers similar to those observed in BALB/c mice. I1-2 production by ConA-stimulated lymph node cells was lower as compared to the spleen, but with a similar pattern among the three mice strains. Our data show that susceptibility to infection by l. mexicana amazonenesis is not associated with deficient ConA-stimulated I1-2 production.

Infecção experimental de Lutzomyia whitmani em cães infectados com Leishmania braziliensis braziliensis

Lutzomyia (N.) whitmani foi infectada em lesões leishmanióticas de três de nove cães parasitados por Leishmania braziliensis braziliensis . Os índices de infecção desses flebotomíneos foram 8,3% (1/12), 7,1% (1/14) e 1,8% (3,160), respectivamente. Por outro lado, 180 Lu. whitmani que se alimentaram em áreas não-ulceradas em um dos cães foram negativos, após dissecação. É discutida a potencialidade de Lu. whitmani como vector de L.B. braziliensis na região endêmica de Três Braços, Bahia, Brasil.

Experimental infection of Lutzomyia longipalpis fed on a patient with cutaneous leishmaniasis due to Leishmania mexicana amazonensis

The authors were able to infect phlebotomine sandflies on a human case of American Cutaneous Leishmaniasis by feeding females of Lutzomyia longipalpis on a patient with a lesion due to Leishmania mexicana amazonensis.

The susceptibility of wild caught sand flies to infection by a subspecies of Leishmania mexicana isolated from proechimys iheringi denigratus (Rodentia, echimyidae)

Several species of wild caught sand flies were collected in the same site where a subspecies of leishmania mexicana was isolated from the rodent Proechimys iheringi denigratus. The absence of natural infection in these sand flies permitted us to test, with relative assurance, the susceptibility of wild caught females to infection by this parasite. the success obtained in these experimental infections suggest that one or more of the sand fly species encountered in high numbers in the same site where the infected rodents were captured may be the vector(s) of this subspecies of l. mexicana.

Infecção natural de Equus asinus por Leishmania braziliensis braziliensis - Bahia, Brasil

Em Corte de Pedra, Valença, Bahia, foi encontrado um jumento (Equus asinus), com infecção natural por Leishmania braziliensis braziliensis. O parasito foi isolado de uma lesão localizada na cicatriz da castração e identificado através de anticorpos monoclonais.

Active cutaneous leishmaniasis in Brazil, induced by Leishmania donovani chagasi

L.d. chagasi was isolated from active cutaneous leishmaniasis in both human and canine infections in an endemic area in Rio de Janeiro, Brazil. Both isolates were identified by molecular and immunological characterization of the parasite using three different methods: electrophoretic mobility of isoenzymes; restriction endonuclease fragment analysis of kDNA and serodeme analysis using monoclonal antibodies. This seems to be the first well documented case in the New World of a "viscerotropic" Leishmania inducing a case of cutaneous leishmaniasis. This observation emphasizes that the diagnosis of the etiologic agent of human or canine visceral leishmaniasis based solely upon clinical and epidemiological critwria may lead to erroneous conclusions.

Leishmaniasis in Bolivia: II. The involvement of Psychodopygus yucumensis and Psychodopygus llanosmartinsi in the selvatic transmission cycle of Leishmania braziliensis braziliensis in a lowland subandean region

An epidemiological survey of the vectors of cutaneous leishmaniasis ("espúndia" type) was caried out in the Alto Beni region of Bolivia, an area of Andean foothills at the Eastern limit of the Amazonian lowlands. The climate is typical wet tropical (15ºS latitude). Anthropophilic phlebotomine sandfly species were sampled at 20 sites, all forested. The importance of species from the Psychodopygus group, already suspected as a vector in the transmission of Leishmania from the braziliensis complex, was confirmed by: 1) the aggressiveness and diversity of the species encountered (83% of catches, nine species), 2) the discovery of a new anthropophilic species, P. yucumensis and 3) the isolation of a strain of Leishmania braziliensis braziliensis indistinguishable from human strains from the same area, from two species, P. llanosmartinsi and P. yucumensis.