Involvement of lipophorin in the immune response of Rhodnius prolixus (Hemiptera: Reduviidae): challenge with the plant-derived entomotoxin jaburetox

La Plata, Buenos Aires

Congreso; II Congress of the Latin American Society for Vector Ecology; 2022

Latin American Society for Vector Ecology

Lipophorin is the main lipoprotein circulating in insects. One of it its most thoroughly characterized function is the transport and transfer of lipids among target tissues. However, lipophorin also participates in insect immunity processes, changing the expression levels in response to pathogen challenges and neutralizing toxins in the hemolymph. On the other hand, ureases (urea amidohydrolases, E.C. 3.5.1.5.) are enzymes that catalyze the breakdown of urea in carbon dioxide and ammonia. In plants, besides generating bioavailable nitrogen, ureases fulfill a role in defense against phytophagous insects, thus exhibiting biotechnological potential for the rational control of pest species. Previous works in triatomines reported that the treatment with jaburetox, a recombinant peptide derived of the leguminous Canavalia ensiformis, induced toxic effects and the activation of the immune response. Even though the insecticidal effect of jaburetox was reported 15 years ago, several aspects of its mechanism of action are unknown. In this work, we employed the Chagas disease vector Rhodnius prolixus as a model to study the participation of lipophorin in the jaburetox-induced immune response. Analytical ultracentrifugation assays were conducted in order to assess lipophorin-jaburetox interaction in vitro. At 6 h after injection, lipophorin expression in the fat body, as well as its circulating levels in the hemolymph, were evaluated by biochemical, molecular and cellular approaches. The sedimentation rate obtained by analytical ultracentrifugation assays indicated a direct binding between lipophorin and jaburetox, reinforcing the implication of this mechanism of peptide detoxification in vivo. The results also show that, under our experimental conditions, treatment with jaburetox did not induce significant modifications neither in the expression of lipophorin in the fat body, nor in its circulating levels in the hemolymph. However, the injection of jaburetox impaired the association of lipophorin with the hemocytes, the main cells involved in insect immunity. Taken together, these findings support the involvement of lipophorin in the jaburetox-induced immune response of R. prolixus, providing valuable information to unravel the mechanisms of action of this toxin.