Department of Biochemistry and Molecular Biology, The Huck Center for Malaria Research, Pennsylvania State University, University Park, Pennsylvania, USA.
mSphere. 2022 Jun 29;7(3):e0010622. doi: 10.1128/msphere.00106-22. Epub 2022 May 19.
Some antimalarial drugs that have lost clinical usefulness have been repurposed for experimental applications. One example is sulfadiazine, an analog of -aminobenzoic acid (pABA), which inhibits the parasite's folate synthesis pathway to block DNA synthesis. Sulfadiazine treatment of mice infected with Plasmodium yoelii and P. berghei is routinely used to enrich for gametocytes by killing asexual blood-stage parasites, but it is not well known if there are downstream effects on transmission. To determine if there was a significant effect of sulfadiazine exposure upon transmission, we transmitted Plasmodium yoelii (17XNL strain) parasites to Anopheles stephensi mosquitoes and evaluated the prevalence and intensity of infection under different sulfadiazine treatment conditions. We observed that there was a reduction in both the number of mosquitoes that became infected and in the intensity of infection if parasites were exposed to sulfadiazine in the mouse host or mosquito vector. Sulfadiazine treatment could be marginally overcome if mosquitoes were provided fresh pABA. In contrast, we determined that gametocytes exposed to sulfadiazine could develop into morphologically mature ookinetes , thus sulfadiazine exposure in the host may be reversible if the drug is washed out and the parasites are supplemented with pABA in the culture media. Overall, this indicates that sulfadiazine dampens host-to-vector transmission and that this inhibition can only be partially overcome by exposure to fresh pABA and . Because gametocytes are of great interest for developing transmission-blocking interventions, we recommend the use of less disruptive approaches for gametocyte enrichment. In this work, we have uncovered a substantial problem with how many studies of the sexual stages of rodent malaria parasites are conducted. Briefly, the isolation of sexual blood-stage parasites, or gametocytes, is essential to study pretransmission and transmission-stage biology of malaria. A routine method for the isolation of this specific stage in rodent-infectious malaria models is drug treatment with sulfadiazine, an antifolate that selectively kills actively replicating asexual blood-stage parasites but not gametocytes. Thus, researchers use this as a convenient way to produce highly enriched gametocyte samples. However, in this work, we describe how this standard drug selection with sulfadiazine not only kills asexual blood-stage parasites but also substantially impacts host-to-vector transmission.
一些失去临床应用价值的抗疟药物已被重新用于实验应用。磺胺嘧啶就是一个例子，它是对氨基苯甲酸（pABA）的类似物，可抑制寄生虫的叶酸合成途径，阻断 DNA 合成。用磺胺嘧啶治疗感染约氏疟原虫和伯氏疟原虫的小鼠，通过杀死无性血期寄生虫来常规富集配子体，但尚不清楚这是否对传播有下游影响。为了确定磺胺嘧啶暴露是否对传播有显著影响，我们将约氏疟原虫（17XNL 株）寄生虫传播给按蚊，并在不同磺胺嘧啶处理条件下评估感染的流行率和强度。我们观察到，如果寄生虫在小鼠宿主或蚊子载体中暴露于磺胺嘧啶，感染蚊子的数量和感染强度都会降低。如果蚊子提供新鲜的 pABA，磺胺嘧啶的治疗效果可能会略有改善。相比之下，我们发现暴露于磺胺嘧啶的配子体可以发育成形态成熟的卵囊，因此，如果药物被冲洗掉并且寄生虫在培养基中补充 pABA，宿主中的磺胺嘧啶暴露可能是可逆的。总的来说，这表明磺胺嘧啶抑制了宿主到媒介的传播，而这种抑制作用只能通过暴露于新鲜的 pABA 和 来部分克服。由于配子体对于开发阻断传播的干预措施非常重要，因此我们建议使用干扰较小的方法来富集配子体。在这项工作中，我们揭示了一个严重的问题，即许多关于啮齿动物疟原虫有性阶段的研究都是如何进行的。简而言之，分离有性血期寄生虫，即配子体，对于研究疟疾的前传播和传播阶段生物学至关重要。在啮齿动物感染性疟疾模型中，分离这种特定阶段的常规方法是用磺胺嘧啶进行药物治疗，磺胺嘧啶是一种抗叶酸药物，可选择性杀死活跃复制的无性血期寄生虫，但不杀死配子体。因此，研究人员将其作为一种方便的方法来产生高度富集的配子体样本。然而，在这项工作中，我们描述了磺胺嘧啶这种标准药物选择不仅杀死了无性血期寄生虫，而且还对宿主到媒介的传播产生了重大影响。
