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

Leishmania (Viannia) braziliensis is associated with distinct clinical manifestations such as cutaneous, mucocutaneous, and disseminated leishmaniasis. One factor related to this clinical spectrum is the structure of parasite populations. This study investigates in vivo binomial BALB/c-L. (V.) braziliensis exploring the phenotypic variability of subpopulations (Thor03, Thor10 and Thor22) of Thor strain, which have previously been described as causing distinct pattern infection in vitro. In the third week after infection, differences were observed in the development curves of the lesions, with larger lesions in the Thor03 and Thor10. At this point, lymph nodes of mice infected with the Thor03 and Thor10 exhibited 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 those infected with the Thor strain, Thor03 and Thor22. In addition, no statistical differences in parasite load wer observed in the footpad in seventh week post inoculation. In contrast, the higher parasite load values were observed in the lymph nodes for Thor03, Thor10 and Thor22 subpopulations. The 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 paws and lymph nodes of these animals were unable to establish persistent lesions in subsequent experimental infection assays. Collectively, these findings highlight consistent differences of infectionevolution and host immune response modulation, during infection among the Thor03, Thor10 and Thor22 subpopulations , all derived from a single strain.