Infection of Human Monocytes with Strains Induces a Downmodulated Response when Compared with Infection with .

Human infection with different species of leads to distinct clinical manifestations, ranging from relatively mild cutaneous ( braziliensis) to severe visceral () forms of leishmaniasis. Here, we asked whether infection of human monocytes by strains responsible for distinct clinical manifestations leads to early changes in immunological characteristics and ability of the host cells to control . We evaluated the expression of toll-like receptors and MHC class II molecules, cytokines, and control by human monocytes following short-term infection with (M2904), a reference strain of (BH46), and a wild strain of (wild). The induction of TLR2, TLR9, and HLA-DR were all lower in when compared with -infected cells. Moreover, -infected monocytes (both strains) produced lower TNF-alpha and a lower TNF-alpha/IL-10 ratio, resulting in a weaker inflammatory profile and a 100-fold less effective control of than cells infected with . Our results show that strains fail to induce a strong inflammatory response, less activation, and less control of from human monocytes, when compared with that induced by infection. This functional profile may help explain the distinct clinical course observed in patients infected with the different species.