Characterization of Regulatory T Cells in Patients Infected by Leishmania Infantum.

High IL-10 levels are pivotal to parasite survival in visceral leishmaniasis (VL). Antigenic stimuli induce IL-10 expression and release of adenosine by CD39/CD73. Due their intrinsic ability to express IL-10 and produce adenosine from extracellular ATP, we evaluated the IL-10, CD39, and CD73 expression by Regulatory T cells (Treg) correlated with VL pathology. Using flow cytometry, Treg cells was analyzed in peripheral blood samples from VL patients (in the presence and absence of Leishmania infantum soluble antigen (SLA)) and healthy individuals (negative endemic control-NEC group), without any treatment. Additionally, IL-10 levels in leukocytes culture supernatant were measured in all groups by ELISA assay. VL patients presented more Treg frequency than NEC group, independently of stimulation. ELISA results demonstrated that SLA induced higher IL-10 expression in the VL group. However, the NEC group had a higher Treg IL-10+ compared to the VL group without stimulation and SLA restored the IL-10 in Treg. Additionally, an increase in Treg CD73+ in the VL group independently of stimuli compared to that in the NEC group was observed. We suggest that Treg are not the main source of IL-10, while the CD73 pathway may be an attempt to modulate the exacerbation of immune response in VL disease.

A glucuronoxylan-specific xylanase from a new Paenibacillus favisporus strain isolated from tropical soil of Brazil.

A new xylanolytic strain, Paenibacillus favisporus CC02-N2, was isolated from sugarcane plantation fields in Brazil. The strain had a xylan-degrading system with multiple enzymes, one of which, xylanase Xyn30A, was identified and characterized. The enzyme is a single-domain xylanase belonging to family 30 of the glycosyl hydrolases (GH30). Xyn30A shows high activity on glucuronoxylans, with a Vmax of 267.2 U mg⁻¹, a Km of 4.0 mg/ml, and a kcat of 13,333 min⁻¹ on beechwood xylan, but it does not hydrolyze arabinoxylans. The three-dimensional structure of Xyn30A consists of a common (ß/α)8 barrel linked to a side-chain-associated ß-structure, similar to previously characterized GH30 xylanases. The hydrolysis products from glucuronoxylan were methylglucuronic-acid-substituted xylooligomers (acidic xylooligosaccharides). The enzyme bound to insoluble xylan but not to crystalline cellulose. Our results suggest a specific role for Xyn30A in xylan biodegradation in natural habitats. The enzyme is a good candidate for the production of tailored xylooligosaccharides for use in the food industry and in the biotechnological transformation of biomass.