Comparative proteomics and immunoreactivity of Lonomia venomous caterpillars identify hemolins as predominant toxins

The hemotoxic venom from Lonomia caterpillars is known to cause severe human envenomation in Latin America. The cases have mainly been associated with Lonomia obliqua and Lonomia achelous, which produce venoms with opposing activity on the coagulation pathway. However, other species have recently been reported to cause human envenoming. Our research sought to characterize the bristle extract proteomes of two Lonomia species related to accidents in Colombia, L. casanarensis and L. orientoandensis, and to determine the immunoreactivity of an anti-L. casanarensis serum against these two species. Bristle extracts were digested and prepared for shot-gun proteomics. Clustering and principal component analysis (PCA) based on protein relative abundance were performed, and toxin abundance was compared between species. The immunoreactivity of an anti-L. casanarensis serum was evaluated by immunoprecipitation and western blotting. Although predicted non-toxic proteins were abundant in the proteomes of Lonomia extracts, possible toxins represented a significant proportion of the extract: 38.36% in L. casanarensis and 33.11% in L. orientoandensis. Both venoms contained toxin groups previously reported in other venomous animals, including proteins similar to L. obliqua procoagulant factors Losac and Lopap. Significant differences in the relative abundance of proteins were detected in the bristle extracts of L. casanarensis and L. orientoandensis for lipocalins, serine peptidases, and phospholipases A₂. The anti-L. casanarensis serum showed cross-reactivity with the L. orientoandensis extract. Our data suggests that polyclonal antibodies mainly recognize proteins similar to the hemolin Losac and those belonging to the hexamerin family. This study is the first to characterize the proteome and immunoreactivity of bristle extracts from two medically important Lonomia species, L. casanarensis and L. orientoandensis. Our results reveal variation in bristle extract composition within the genus, which has possible implications for the efficacy of available antivenoms and the development of alternative interventions.