Trypanosoma cruzi is a flagellate protozoan pathogen that causes Chagas disease. Currently there is no preventive treatment and the efficiency of the two drugs available is limited to the acute phase. Therefore, there is an unmet need for innovative tools to block transmission in endemic areas. In this study, we engineered a novel recombinant molecule able to adhere to the T. cruzi surface, termed scFv-10D8, that consists of a single-chain variable fragment (scFv) derived from mAb-10D8 that targets gp35/50. The synthetic gene encoding scFv-10D8 was cloned and fused to a 6×His tag and expressed in a prokaryotic expression system. Total periplasmic or 6xHis tag affinity-purified fractions of scFv-10D8 retained the capacity to bind to gp35/50, as shown by Western blot analyses. Pre-incubation of metacyclic trypomastigotes with scFv-10D8 showed a remarkable reduction in cell invasion capacity. Our results suggest that scFv-10D8 can be used in a paratransgenic approach to target parasites in insect vectors, avoiding dissemination of infective forms. Such advances in the development of this functional molecule will surely prompt the improvement of alternative strategies to control Chagas disease by targeting mammalian host stages.

Background: Some studies indicated that body mass index (BMI) is inversely proportional to serum testosterone concentrations in men. Purposes: This study aimed to analyze the effects of aging and obesity on total testosterone (TT), free testosterone (FT), bioavailable testosterone (BT), luteinizing hormone (LH), and sex hormone-binding globulin (SHBG) levels. Methods: A cross-sectional study was performed to assess the clinical and laboratory profiles of 701 patients treated at a private urology clinic in Ponta Grossa, Brazil, from January 2016 to December 2018. Results: Patients’ age ranged from 16 to 88 years (mean, 56.9 ± 13.62 years). Age did not significantly influence serum TT concentrations, except compared to patients aged >70 years. However, changes were observed in FT and BT (p < 0.05). The mean SHBG increased with age (p < 0.05). A tendency toward LH elevation was observed in older patients, but it was not statistically significant. An inverse proportional relationship between TT, FT, and BT and the testosterone deficiency rate (TT < 300 ng/dL) was observed within BMI groups (p < 0.05). The testosterone deficiency rate was 21.5% in individuals with normal BMI, 29% in overweight individuals, and 37% in obese individuals. Conclusions: Aging affected the testosterone concentrations in men and became increasingly evident using FT and BT instead of TT. SHBG increased with age. Obesity was associated with a decrease in TT, FT, and BT but also increased the rate of hypogonadism.