Diferentes fases da infecção por Schistosoma mansoni afetam a susceptibilidade de macrófagos derivados de medula óssea a Leishmania (Leishmania) amazonensis in vitro

Abstract

Schistosomiasis and leishmaniasis are classified as neglected tropical diseases and affect mostly tropical, low-income populations that lack access to proper health care. As a further matter, both diseases have their pathogenesis directly linked to the host’s immune response. Schistosoma mansoni, the etiologic agent of schistosomiasis in Brazil, elicits three different immune response types during its life cycle: the pre-postural phase is characterized by a Th-1 immune response, while acute and chronic phases are predominantly marked by a Th-2 and a regulatory response, respectively. On its turn, American tegumentary leishmaniasis (ATL) corresponds to a spectrum of diseases, ranging from localized, self-healing ulcers to multiple, disfiguring lesions. A strong Th-1 response is associated with Leishmania sp. control, but leads to extensive tissue damage. Au contraire, Th-2 and regulatory responses, while limiting Th-1-driven damage, favour the parasite’s intracellular growth. L. (Leishmania) amazonensis is one of several Leishmania species that cause ATL, and its endemic regions overlap with S. mansoni transmission areas. Some works have addressed S. mansoni and Leishmania sp. coinfection and have shown enhanced cell susceptibility, preeminence of a regulatory immune response and worse response to treatment. However, no study up until now has investigated the consequences of each phase of schistosomiasis in the intracellular parasitism of L. (L.) amazonensis in macrophages. BALB/c mice uninfected or after 3, 8 and 12 weeks of S. mansoni infection were euthanized in order to recover bone marrow cells, which were cultured in the presence of L929 conditioned medium to induce macrophage differentiation. Macrophages were then plated on round coverslips in 24-well plates and infected with L. (L.) amazonensis stationary phase promastigotes, 10 promastigotes per cell. Replicas from each experimental group were kept uninfected. Coverslips were fixed and stained at 48 and 72 hours post-infection. Culture supernatants were collected with 24, 48 and 72 hours post-infection. Although the percentage of infected macrophages showed no difference between groups, macrophages recovered form animals with acute schistosomiasis had an increased number of intracellular amastigotes, accompanied by lower nitric oxide production. No differences were found in arginase activity and IL-10 levels. During pre-postural infection, macrophages showed higher concentrations of TGF-β and CCL5 in culture supernatant, while acute infection lead only to higher TGF-β levels. Chronic infection had increased TGF-β and CXCL2 concentrations, while its CCL5 levels were lower than the control group. These results clearly show that all S. mansoni infection phases differently influence macrophage maturation and how these cells respond to L. (L.) amazonensis infection in vitro. Long-term effects on ATL may also happen due to divergent cell recruitment and activation by infected macrophages. Together, these results further show the importance of studies revolving around S. mansoni and L. (L.) amazonensis coinfection, for the mechanisms involved in this process are yet to be better understood.