EFFECTS OF THE PEPTIDE JABURETOX ON THE IMMUNE SYSTEM OF RHODNIUS PROLIXUS.

LOPES, F.C.; COSTE GRAHL, M.V.; FRUTTERO, L.L.; PERIN, A.P.A.; STANISÇUASKI, F.

Porto Alegre

Congreso; Toxi-latin. Modern toxicology for health and prevention.; 2018

Comisión organizadora Toxi-latin http://toxilatin2018.com/organizacao/

INTRODUCTION: Ureases from plants were characterized as moonlighting proteins, presenting fungitoxitoxic and entomotoxic effects, independent of their enzymatic functions. Based in one of these ureases our group developed a recombinant peptide called Jaburetox (Jbtx), which display several effects on insects. Previous data demonstrated that Jbtx activates the immune system in the Chagas disease vector Rhodnius prolixus. The insect immune response comprises cellular and humoral mechanisms, including phagocytosis, encapsulation, melanization, anti-microbial protein synthesis and activation of the pro-phenoloxidase cascade (pro-PO). The PO enzymes trigger the pathogens' encapsulation in the hemolymph and produce quinones that are toxic to microorganisms. It has been demonstrated that mammalian defense cells release extracellular nucleic acids (NEAs) to protect the system against pathogens. However, there are little information about NEAs and their mechanism of action in insects. OBJECTIVES: To investigate the immune response triggered by the interaction toxin-NEAs in the insect R. prolixus. MATERIALS AND METHODS: For the immune responses assay, R. prolixus nymphs were subjected to different treatments, via injection (control, Jbtx, NEAs, NEAs plus Jbtx). After 6 and 18 hours after treatment the responses were evaluated. The cellular response was evaluated by the number of free and aggregated cells using a hemocytometer. The humoral response was estimated by PO activity and quantified spectrophotometrically. For the immunocompetence assay, the insects were injected with Jbtx plus NEAs, and 5 hours later the same insects received another injection of Staphylococcus aureus. Then, the hemolymph was collected and the number of colony forming units were assessed by the drop-plate method. RESULTS AND DISCUSSION: Our results demonstrated that the Jbtx treatment, at 6 and 18 h, and also the NEAs treatment, at 6 h, stimulated the cellular and humoral responses. The immunocompetence assay demonstrated that the pre-treatment with Jbtx rendered the insects more susceptible to the pathogen infection. The NEAs acted in a protective way. These data corroborate with the literature, which demonstrated that NEAs increases the survival rate of the insects infected with pathogens. CONCLUSION: Our results suggest that both Jbtx and NEAs activate the insect immune system but have contrasting effects on the insect defense against pathogens infections.FINANCIAL SUPPORT: CAPES.