Enhancing the humoral and melanization responses of Aedes aegypti mosquito: a step towards the utilization of immune system against dengue fever
, Ahmed, A. M.; Al-Olayan, E. M. and Amoudy, M. A. . 2008
Great efforts are currently being done to utilize the immune system of mosquito vectors in the battle against the different mosquito-borne parasitic and viral diseases. Based on this control strategy, the current study has been conducted to induce and enhance the most effective immune responses, the humoral and melanization responses, in the dengue fever vector, Aedes aegypti against live bacteria and non-biological agents at 24h post-treatments. The humoral activity against Bacillus subtilis and Escherichia coli was investigated after thoracic injection of the same bacteria or the lipopolysaccharide (LPS) into mosquitoes using the inhibition zone assay. Melanization response was tested against the thoracic inoculated Sephadex® beads, positively charged CM A-25, negatively charged CM G-25 and neutral CM C-25, and inert glass beads. These immune responses were then enhanced via the oral administration of 0.3% thymoquinone (Thq), the main active ingredient of the black seeds, Nigella sativa, to mosquitoes. Data demonstrated that, on one hand mosquitoes exhibited strong humoral activity against the injected bacteria as well as against the well-known immune sensitive bacteria, Micrococcus luteus. Moreover, melanization response was strong against differently charged Sephadex® beads, but not against the inert glass beads. On the other hand, significant increases in the humoral anti-bacterial lyses activity and anti-beads melanization response (up to 6 folds in some cases) was clearly shown when mosquitoes were maintained on 0.3% Thq-glucose mixture (in 10% glucose). Therefore, these data may indicate that both humoral antimicrobial activity and melanization response could be enhanced to be more effective against disease-organisms transmitted by mosquitoes. Thus, this study suggests a possible immuno-control strategy in the battle against mosquito-born diseases which, in fact, will be tested against dengue viruses in the future studies.
