Macrophage Polarisation During Leishmania (Viannia) braziliensis Infection in Mice

Leishmania (Viannia) braziliensis causes cutaneous and mucocutaneous leishmaniasis. Macrophages are host cells for parasite replication and act as effector cells against the parasite. The two main macrophage phenotypes (M1 and M2) and their polarisation states have been implicated in Leishmania infection despite scarce data on L. (V.) braziliensis. In this study, we investigated the temporal and spatial distribution and predominance of M1 and M2 macrophages during L. (V.) braziliensis infection in Balb/c mice. Animals were infected with L. (V.) braziliensis promastigotes and were monitored for 25 weeks. Histopathological evaluation of footpad lesions, regional lymph nodes, and spleen; cellularity; and macrophage population quantification of M1, and M2 macrophages by flow cytometry were performed in different tissues. The results showed that after infection with either strain of L. (V.) braziliensis the lesions were small and non-ulcerated. The dissemination of parasites to tissues reinforced the characteristic visualisation of dermotropicL. (V.) braziliensis. The proportion of M2 macrophages in different tissues was significantly higher than that of M1 macrophages. Overall, the results reported here confirm that Leishmania an intracellular parasite, promotes and influences macrophage phenotype polarisation in different tissues over time, and researchers testing therapies based on macrophage phenotype regulation should consider this evidence.