Influence of and on the Humoral Immunity of .

Chagas disease is a human infectious disease caused by and can be transmitted by triatomine vectors, such as . One limiting factor for development is the composition of the bacterial gut microbiota in the triatomine. Herein, we analyzed the humoral immune responses of nymphs treated with antibiotics and subsequently recolonized with either or . The treatment with antibiotics reduced the bacterial load in the digestive tract, and the recolonization with each bacterium was successfully detected seven days after treatment. The antibiotic-treated insects, recolonized with , presented reduced antibacterial activity against and phenoloxidase activity in hemolymph, and lower nitric oxide synthase (NOS) and higher defensin C gene (DefC) gene expression in the fat body. These insects also presented a higher expression of DefC, lower prolixicin (Prol), and lower NOS levels in the anterior midgut. However, the antibiotic-treated insects recolonized with had increased antibacterial activity against and lower activity against , higher phenoloxidase activity in hemolymph, and lower NOS expression in the fat body. In the anterior midgut, these insects presented higher , defensin A (DefA) and DefC expression, and lower Prol expression. The immune modulation by these two bacteria was observed not only in the midgut, but also systemically in the fat body, and may be crucial for the development and transmission of the parasites and .