Chlorella vulgaris lectin kills Aedes aegypti larvae

Abstract

Vector-borne diseases are considered public health concerns. As vaccines for some of these diseases are not available or still have serious restrictions, the vector control is an important strategy. Aedes aegypti mosquitoes can transmit dengue, yellow fever, chikungunya and Zika viruses. Chemical compounds are used to control A. aegypti populations which are usually toxic to non-target organisms, and thus the safety of their use is questionable. This work reports the purification and characterization of a lectin from Chlorella vulgaris microalgae (CvL) and its toxicity to the A. aegypti fourth instar larvae (L4). CvL was isolated (purification factor of 8.72; yield of 6.67) from the C. vulgaris aqueous extract (AE) with hemagglutinating activity of 185,130 titre mg−1. The characterization showed that CvL is a 17 kDa protein whose activity was inhibited various carbohydrates, resisted to heating up to 60 °C and was stable over a broad pH range. Additionally, CvL activity was strongly reduced by monovalent and divalent metal ions. AE and CvL were toxic to L4 and the concentrations that killed 50% of larvae after 24 h were 10.62% (v/v) and 164.24 μg mL−1, respectively. CvL inhibited the activity of trypsin-like enzymes from L4 gut and this effect, as well as the larvicidal activity, were abolished when the lectin was denatured by heating or when its carbohydrate-binding site was blocked by fructose or azocasein. These findings points the C. vulgaris biomass as a new source of a biomaterial with potential to control A. aegypti larvae by inhibition of trypsin-like enzymes representing a larvicidal mechanism.