Leishmania (Leishmania) Amazonensis Promastigotes With Distinct Virulence Profile and Their Extracellular Vesicles Differently Modulate the Macrophage Functions

Leishmania spp. is the aetiologic agent of leishmaniasis, a disease endemic in several developing countries. The parasite expresses and secretes several virulence factors that subvert macrophage function and immune response. Extracellular vesicles (EVs) can carry molecules of the parasites that show immunomodulatory effects on macrophage activation and disease progression. In the present work, we detected a significantly higher expression of lpg3 and gp63 genes in Leishmania amazonensis promastigotes recovered after successive experimental infections (IVD-P) compared to those cultured for a long period (LT-P). In addition, we observed a significantly higher percentage of infection and internalized parasites in groups of macrophages infected with IVD-P. Macrophages previously treated with EVs from LT-P showed higher percentages of infection and production of inflammatory cytokines after challenge with the parasite compared to untreated ones. However, macrophages infected with parasites and treated with EVs did not reduce the parasite load. In addition, no synergistic effects were observed in infected macrophages treated with EVs and reference drugs. In conclusion, parasites cultured for a long period in vitro and recovered from animals’ infection differently affect the macrophage response. Furthermore, EVs produced by these parasites affected macrophage response in the early infection of these cells.