Noden Bruce H, Vaughan Jefferson A, Pumpuni Charles B, Beier John C
Department of Biomedical Science, School of Health and Applied Sciences, Polytechnic of Namibia, Windhoek, Namibia.
Parasitol Int. 2011 Dec;60(4):440-6. doi: 10.1016/j.parint.2011.07.007. Epub 2011 Jul 13.
The mosquito midgut is a site of complex interactions between the mosquito, the malaria parasite and the resident bacterial flora. In laboratory experiments, we observed significant enhancement of Plasmodium falciparum oocyst production when Anopheles gambiae (Diptera: Culicidae) mosquitoes were membrane-fed on infected blood containing gametocytes from in vitro cultures mixed with sera from rabbits immunized with A. gambiae midguts. To identify specific mechanisms, we evaluated whether the immune sera was interfering with the usual limiting activity of gram-negative bacteria in An. gambiae midguts. Enhancement of P. falciparum infection rates occurred at some stage between the ookinete and oocyst stage and was associated with greater numbers of oocysts in mosquitoes fed on immune sera. The same immune sera did not affect the sporogonic development of P. yoelii, a rodent malaria parasite. Not only did antibodies in the immune sera recognize several types of midgut-derived gram-negative bacteria (Pseudomonas spp. and Cedecea spp.), but gentamicin provided in the sugar meal 3 days before an infectious P. falciparum blood meal mixed with immune sera eliminated the enhancing effect. These results suggest that gram-negative bacteria, which normally impair P. falciparum development between the ookinete and oocyst stage, were altered by specific anti-bacterial antibodies produced by immunizing rabbits with non-antibiotic-treated midgut lysates. Because of the differences in developmental kinetics between human and rodent malaria species, the anti-bacterial antibodies had no effect on P. yoelii because their ookinetes leave the midgut much earlier than P. falciparum and so are not influenced as strongly by resident midgut bacteria. While this study highlights the complex interactions occurring between the parasite, mosquito, and midgut microbiota, the ultimate goal is to determine the influence of midgut microbiota on Plasmodium development in anopheline midguts in malaria endemic settings.
蚊子的中肠是蚊子、疟原虫和常驻细菌群落之间复杂相互作用的场所。在实验室实验中，我们观察到，当用含有来自体外培养物的配子体的感染血液与用冈比亚按蚊中肠免疫的兔子血清混合后，通过膜饲法喂养冈比亚按蚊（双翅目：蚊科）蚊子时，恶性疟原虫卵囊产量显著增加。为了确定具体机制，我们评估了免疫血清是否干扰了冈比亚按蚊中肠中革兰氏阴性菌通常的限制活性。恶性疟原虫感染率的提高发生在动合子和卵囊阶段之间的某个阶段，并且与以免疫血清为食的蚊子中更多数量的卵囊有关。相同的免疫血清对啮齿动物疟原虫约氏疟原虫的孢子生殖发育没有影响。免疫血清中的抗体不仅识别几种类型的源自中肠的革兰氏阴性菌（假单胞菌属和西地西菌属），而且在与免疫血清混合的感染性恶性疟原虫血餐之前3天在糖餐中提供的庆大霉素消除了增强作用。这些结果表明，通常会损害动合子和卵囊阶段之间恶性疟原虫发育的革兰氏阴性菌，被用未用抗生素处理的中肠裂解物免疫兔子产生的特异性抗菌抗体改变了。由于人类和啮齿动物疟原虫物种在发育动力学上的差异，抗菌抗体对约氏疟原虫没有影响，因为它们的动合子比恶性疟原虫更早离开中肠，因此受常驻中肠细菌的影响较小。虽然这项研究突出了寄生虫、蚊子和中肠微生物群之间发生的复杂相互作用，但最终目标是确定中肠微生物群对疟疾流行地区按蚊中肠内疟原虫发育的影响。
