A Dual Effect for the Black Seed Oil on the Malaria Vector Anopheles gambiae: Enhances Immunity and Reduces the Concomitant Reproductive Cost
, Ahmed, A. M. . 2007
Great efforts are currently being done to utilize the immune system of mosquito vector in the battle against malaria. However, this strategy still facing some limiting factors mainly the reproductive cost, the price of immune induction. This study has been introduced to show that inducing non-costly immune responses in the African malaria vector, Anopheles gambiae, is possible via the oral administration of black seed oil (BSO), a natural botanical extract from Nigella sativa, to mosquitoes. The humoral anti-Micrococcus luteus activity, induced by LPS injection, and melanization, against inoculated Sephadex® beads, were studied here (at 18 h post-treatment). The humoral anti-bacterial activity was measured using inhibition zone assay. The degrees of melanization response against negatively charged CM C-25 and neutral CM G-25 Sephadex® beads were monitored under the microscope. Reproductive cost was monitored in terms of percentages of follicular apoptosis and resorption at 18 and 24 h post-treatment respectively. Data of this study demonstrate that, mosquitoes maintained on 0.3% BSO-glucose mixture (in 10% glucose) showed, on one hand, significant increases in the humoral anti-bacterial activity or melanization response when injected with LPS or inoculated with beads respectively. Moreover, these tow responses were more pronounced in blood fed mosquitoes. On the other hand, significant declines in the % of follicular apoptosis and resorption were reported in the ovaries of the same immunized mosquitoes. In addition, BSO showed no toxic effect on ookinetes development, both in vivo and in vitro, or on the viability of mosquito cells in vitro. Therefore, these data may indicate that the non-toxic BSO may have a dual effect as it enhanced immunity and reduced the concomitant impact on the reproductive fitness. Thus, this study suggests BSO as a candidate in support of the immuno-control strategy in the battle against malaria.
