The role of complement in the early phase of Leishmania (Leishmania) amazonensis infection in BALB/c mice

Complement-depleted and -non-depleted BALB/c mice were inoculated with Leishmania (Leishmania) amazonensis promastigotes into the hind footpad to study the role of the complement system in cutaneous leishmaniasis. Total serum complement activity was measured by hemolytic assay and C3 fragment deposit at the inoculation site was determined by direct immunofluorescence in the early period of infection, i.e., at 3, 24, 48 h and 7 days post-infection. The inflammatory reaction and the parasite burden were evaluated in the skin lesion at 7 and 30 days post-infection. Total serum complement activity decreased in the early phase of infection, from 3 to 24 h, in non-depleted mice compared to non-infected and non-depleted mice. C3 fragment deposit at the site of parasite inoculation was present throughout the period of infection in non-depleted mice. In contrast, no C3 fragment deposit was observed at the inoculation site in complement-depleted mice. Complement-depleted mice showed a significant decrease in the inflammatory response and a significant increase in the number of parasites (70.0 ± 5.3 vs 5.3 ± 1.5) at 7 days of infection (P < 0.05). A higher number of parasites were also present at 30 days of infection at the inoculation site of complement-depleted mice (78.5 ± 24.9 vs 6.3 ± 5.7). These experiments indicate that complement has an important role at the beginning of experimental cutaneous leishmaniasis caused by L. (L.) amazonensis by controlling the number of parasites in the lesion.

The role of natural killer cells in the early period of infection in murine cutaneous leishmaniasis

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

Comparative and sequential histopathology of plasmodium chabaudi-infected balb/c mice

1. Rodent experimental models have been useful to study severe malaria but few serial and controlled studies have been conducted. In the presente investigation, we describe the histopathology of lethal and non-lethal rodent malaria induced by Plasmodium berghei and P. chabaudi. P. berghei malaria shows a uniformly lethal course, while P. chabaudi malaria produces a non-lethal acute infection with recovery and periodical recurdescences. Sequential histopathological changes were also characterized in P. chabaudi malaria to determine the evolution of the lesions. 2. P. berghei-infected mice have a more severe organ involvement and lower blood regenerative changes than P. chabaudi-infected mice. Two patterns of organ involvement were observed by cimparing the two infections. The first is related to nonspecific parasitized red blood cell clearance by liver and spleen. The second is related to specific changes due to a specific parasite strain interaction with the host, such as those found in the lungs. 3. Sequential changes in P. chabaudi-infected mice were characterized by perihepatocytic reticulin fiber deposition during the recovery from infection, which faded in subsequent stages. Other organs had a similar regressive evolution, except splenic lymphoid tissue which underwent histological restoration or even hypertrophy after depletion in the acute stage. No brain or heart lesions were observed in either model during the acute and subsequent stages. 4. P. chabaudi infection, whose histopathology is described here for the first time, should be useful as a non-lethal experimental model to study the evolution of histological alterations in malaria

Comparative study of the biological behaviour in hamster of two isolates of Leishmania characterized respectively as L. major-like and L. donovani

Experimentos utilizando-se hamsters inoculados intraperitonealmente com 1 x 10**7 parasitas de 2 cepas, L. donovani (MHOM/BR/72/LD 46) e L. major-like (MCAN/BR/73/LD 70) isoladas no Novo Mundo foram realizados e estudados em grupos de 15,30,60 e 90 dias e infecçäo. A carga e a densidade parasitária mostraram progressivo aumento com a evoluçäo da infecçäo e foi maior nos grupos inoculados com L. donovani do que nos grupos inoculados com L. major-like. Os grupos inoculados com L. major-like mostraram densidade parasitária maior no baço que no fígado e foram semelhantes em ambos os órgäos nos grupos inoculados com L. donovani. A histopatologia mostrou intensa e difusa hiperplasia e hipertrofia do sistema reticuloendotelial com alto parasitismo nos grupos inoculados com L. donovani, enquanto foi encontrado envolvimento focal nestes órgäos nos grupos inoculados com L. major-like, formando nódulos de macrófagos discretamente parasitados. O comportamento biológico seria útil em estudos preliminares de identificaçäo de cepas de Leishmania em laboratórios regionais e na compreensäo da histopatologia das lesöes causadas por diferentes espécimes de leishmanias