MicroRNA-155 Deficiency Exacerbates Trypanosoma cruzi Infection

Chagas disease, caused by the intracellular protozoan parasite , is a public health problem affecting 6 to 8 million people, mainly in Latin America. The role of microRNAs in the pathogenesis of Chagas disease has not been well described. Here, we investigate the role of microRNA-155 (miR-155), a proinflammatory host innate immune regulator responsible for T helper type 1 and type 17 (Th1 and Th17) development and macrophage responses during infection. For this, we compared the survival and parasite growth and distribution in miR-155 and wild-type (WT) C57BL/6 mice. The lack of miR-155 caused robust parasite infection and diminished survival of infected mice, while WT mice were resistant to infection. Immunological analysis of infected mice indicated that, in the absence of miR-155, there was decreased interferon gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α) production. In addition, we found that there was a significant reduction of CD8-positive (CD8 ) T cells, natural killer (NK) cells, and NK-T cells and increased accumulation of neutrophils and inflammatory monocytes in miR-155 mice. Collectively, these data indicate that miR-155 is an important immune regulatory molecule critical for the control of infection.