Toward a Novel Experimental Model of Infection To Study American Cutaneous Leishmaniasis Caused byLeishmania braziliensis

Abstract

Leishmania spp. cause a broad spectrum of diseases collectively known as leishmaniasis. Leishmania braziliensis is the main etiological agent of American cutaneous leishmaniasis (ACL) and mucocutaneous leishmaniasis. In the present study, we have developed an experimental model of infection that closely resembles ACL caused by L. braziliensis. In order to do so, BALB/c mice were infected in the ear dermis with 10 5 parasites and distinct aspects of the infection were evaluated. Following inoculation, parasite expansion in the ear dermis was accompanied by the development of an ulcerated dermal lesion which healed spontaneously, as seen by the presence of a scar. Histological analysis of infected ears showed the presence of a mixed inflammatory infiltrate consisting of both mononuclear and polymorphonuclear cells. In draining lymph nodes, parasite replication was detected throughout the infection. In vitro restimulation of draining lymph node cells followed by intracellular staining showed an up-regulation in the production of gamma interferon (IFN-␥) and in the frequency of IFN-␥-secreting CD4 ؉ and CD8 ؉ T cells. Reverse transcription-PCR of ears and draining lymph node cells showed the expression of CC chemokines. The dermal model of infection with L. braziliensis herein is able to reproduce aspects of the natural infection, such as the presence of an ulcerated lesion, parasite dissemination to lymphoid areas, and the development of a Th1-type immune response. These results indicate that this model shall be useful to address questions related to the concomitant immunity to reinfection and parasite persistence leading to mucocutaneous leishmaniasis.

Neutrophils and Macrophages Cooperate in Host Resistance againstLeishmania braziliensisInfection

“…1). 4 These results confirm our previous observations (14) and suggest that neutrophils are associated with lesion healing and pathogen control. Based on these results, we investigated whether transient neutrophil depletion altered the course of Lb infection in BALB/c mice.…”

“…Neutrophils have been shown to play an active role in the control of infections with specific and distinct pathogens such as Legionella (17), Toxoplasma (27), Mycobacterium (28), Entamoeba (29), Histoplasma (30), and Cryptosporidium (31). BALB/c mice infected in the ear dermis with L. braziliensis develop cutaneous lesions at the site of inoculation and histological analyses of infected ear sections have demonstrated a constant recruitment of neutrophils to the inoculation site (14). Since in this experimental model ear lesions heal spontaneously, we hypothesized that neutrophils exert a protective effect.…”

“…We have previously shown that BALB/c mice infected in the ear dermis with Lb develop cutaneous lesions at the site of inoculation (14). Histological analysis of ear sections demonstrated a constant recruitment of neutrophils to the inoculation site.…”

“…Lb (strain MHOM/BR/01/BA788) (14), L. amazonensis (strain MHOM/ BR/87/BA125) (15), L. major (MHOM/JL/80/Friedlin), and L. chagasi (MHOM/BR/00/BA262) promastigotes were grown in Schneider medium (Sigma-Aldrich) supplemented with 100 U/ml penicillin, 100 mg/ml streptomycin, and 10% heat-inactivated FCS (all from Invitrogen). Metacyclic Lb parasites were prepared as described in Spath and Beverley (16).…”

“…Upon inoculation of Lb promastigotes into the ear dermis of BALB/c mice, neutrophils can be detected throughout the duration of clinical disease (14). To determine the number of neutrophils to the site of Lb infection, ear sections were obtained at 2, 5, and 10 wk after parasite inoculation and were stained with H&E. These sections were compared with samples obtained from PBS-inoculated mice.…”