Potencialização da atividade larvicida de proteínas tóxicas de Bacillus thuringiensis sobre Aedes aegypti pelo inibidor de proteases de sementes de Lonchocarpus sericeus (Poir) Kunth ex DC.

Abstract

Vector-borne diseases constitute a global public health problem. In Brazil, the primary vector of concern is Aedes aegypti, responsible for transmitting arboviruses such as dengue, Zika fever, and chikungunya. The main prevention method is combating the proliferation of the vector. To achieve this, synthetic chemical compounds are often used, which can cause environmental imbalances and lead to the emergence of resistant vector populations. Therefore, studies on bioinsecticides emerge as a sustainable alternative that may reduce the occurrence of resistant populations. Among the most researched bioinsecticides are bioactive compounds extracted from plants, such as protease inhibitors. Another class of bioactives are the Cry proteins from Bacillus thuringiensis, which cause changes in the organism by forming pores in the intestinal membrane of some insects, such as Ae. aegypti larvae. Thus, the objectives of this work focused on evaluating the enhancement of the larvicidal activity of Cry proteins from B. thuringiensis through synergism with protease inhibitors from Lonchocarpus sericeus (LsCTI). The inhibitor was obtained through trypsin affinity chromatography. The lethal concentration for 20% of the larvae (LC20) was determined by exposing Ae. aegypti larvae to different concentrations of Cry toxin. Synergistic assays were conducted with different concentrations of LsCTI, observing the larvicidal activity for each combination with the fixed LC20 concentration. The synergism of LsCTI with Cry proteins produced good results, with 80% mortality observed when combined with LC20 at concentrations as low as 12.5 μg/mL-1. Histological analysis revealed significant thinning of the larval midgut epithelium, indicating the effectiveness of the combination of the two compounds. The results show that the combination of LsCTI and Cry proteins is effective as a larvicide, suggesting potential use for controlling these vectors with reduced impact on non-target organisms.