Exploring the binomial BALB/c-Leishmania (Viannia) braziliensis model to assess the in vivo performance of Thor strain subpopulations.

Leishmania (Viannia) braziliensis is related to distinct clinical manifestations such as cutaneous, mucocutaneous, and disseminated leishmaniasis. One factor related to this clinical spectrum is the structure of parasite populations. This work assesses in vivo binomial BALB/c-L. (V.) braziliensis exploring the concept of phenotypic variability of subpopulations (Thor03, Thor10 and Thor22) of Thor strain, and previously described as causing distinct pattern infection in vitro. In the third week after infection, differences were observed in the development curve of the lesions, with larger sizes in the Thor03 and Thor10. In this point, lymph nodes of mice infected with the Thor03 and Thor10 showed lower IL-12 and TNF values compared to infection with the Thor strain and Thor22. The infection with the Thor10 showed highest values of the cytokine IL-10 compared to Thor strain, Thor03 and Thor22. In addition, no statistical differences in parasite load could be observed in the footpad in seventh week post inoculation. In contrast, the higher values for parasite load in the lymph nodes were obtained for Thor03, Thor10 and Thor22. Data obtained here show these subpopulations cause transient and non-severe footpad lesions with parasite persistence in draining lymph nodes, although some mice developed non-healing lesions. Parasites isolated from the paw and lymph nodes of these animals were not able to establish persistent lesions when used in subsequent experimental infection assays. Collectively, these findings point to consistent distinctions in the patterns of evolution of the infection and host immune response modulation, during infection among the Thor03, Thor10 and Thor22 subpopulations from a single strain.