Killer Bee Molecules: Antimicrobial Peptides as Effector Molecules to Target Sporogonic Stages of Plasmodium

A new generation of strategies is evolving that aim to block malaria transmission by employing genetically modified vectors or mosquito pathogens or symbionts that express anti-parasite molecules. Whilst transgenic technologies have advanced rapidly, there is still a paucity of effector molecules with potent anti-malaria activity whose expression does not cause detrimental effects on mosquito fitness. Our objective was to examine a wide range of antimicrobial peptides (AMPs) for their toxic effects on Plasmodium and anopheline mosquitoes. Specifically targeting early sporogonic stages, we initially screened AMPs for toxicity against a mosquito cell line and P. berghei ookinetes. Promising candidate AMPs were fed to mosquitoes to monitor adverse fitness effects, and their efficacy in blocking rodent malaria infection in Anopheles stephensi was assessed. This was followed by tests to determine their activity against P. falciparum in An. gambiae, initially using laboratory cultures to infect mosquitoes, then culminating in preliminary assays in the field using gametocytes and mosquitoes collected from the same area in Mali, West Africa. From a range of 33 molecules, six AMPs able to block Plasmodium development were identified: Anoplin, Duramycin, Mastoparan X, Melittin, TP10 and Vida3. With the exception of Anoplin and Mastoparan X, these AMPs were also toxic to an An. gambiae cell line at a concentration of 25 µM. However, when tested in mosquito blood feeds, they did not reduce mosquito longevity or egg production at concentrations of 50 µM. Peptides effective against cultured ookinetes were less effective when tested in vivo and differences in efficacy against P. berghei and P. falciparum were seen. From the range of molecules tested, the majority of effective AMPs were derived from bee/wasp venoms.

新一代阻断疟疾传播的策略正逐步演化，这类策略通过搭载表达抗寄生虫分子的基因修饰传播媒介、蚊虫病原体或共生菌来实现防控目标。尽管转基因技术发展迅猛，但目前仍缺乏兼具强效抗疟活性、且其表达不会对蚊虫适合度造成不利影响的效应分子。
本研究旨在评估多款抗菌肽（antimicrobial peptides, AMPs）对疟原虫及按蚊的毒性作用。本研究靶向疟原虫早期孢子增殖阶段，首先筛选了多款抗菌肽对蚊虫细胞系及伯氏疟原虫（Plasmodium berghei）动合子的毒性。
研究人员将筛选获得的潜在候选抗菌肽饲喂蚊虫，以监测其对蚊虫适合度的不利影响，并评估其阻断斯氏按蚊（Anopheles stephensi）体内啮齿类疟疾感染的效果。
后续本研究又开展了抗菌肽对冈比亚按蚊（An. gambiae）体内恶性疟原虫（Plasmodium falciparum）活性的检测：首先利用实验室培养的疟原虫感染蚊虫，最终通过野外初步试验完成验证，试验所用的配子体及蚊虫均采自西非马里的同一区域。
本次研究共测试了33款分子，最终筛选出6种可阻断疟原虫发育的抗菌肽：阿诺平（Anoplin）、杜拉霉素（Duramycin）、肥大细胞脱颗粒肽X（Mastoparan X）、蜂毒素（Melittin）、TP10以及Vida3。
在25 μM浓度下，除阿诺平与肥大细胞脱颗粒肽X外，其余候选抗菌肽均对冈比亚按蚊细胞系具有毒性。
但在50 μM浓度下开展蚊虫吸血饲喂试验时，这些抗菌肽并未降低蚊虫的寿命或产卵量。
对体外培养的动合子有效的抗菌肽，在活体试验中的防控效果往往更差，且不同抗菌肽对伯氏疟原虫与恶性疟原虫的防控效果存在差异。
本次测试的有效抗菌肽中，绝大多数均源自蜂类（蜜蜂/胡蜂）的毒液。