Reuling Isaie J, Stone Will J R, van de Vegte-Bolmer Marga, van Gemert Geert-Jan, Siebelink-Stoter Rianne, Graumans Wouter, Lanke Kjerstin, Bousema Teun, Sauerwein Robert W
Department of Medical Microbiology, Radboud University Medical Center, Geert Grooteplein 28, Microbiology 268, 6500 HB, Nijmegen, The Netherlands.
Malar J. 2017 Aug 5;16(1):315. doi: 10.1186/s12936-017-1959-9.
Mosquito-feeding assays are important tools to guide the development and support the evaluation of transmission-blocking interventions. These functional bioassays measure the sporogonic development of gametocytes in blood-fed mosquitoes. Measuring the infectivity of low gametocyte densities has become increasingly important in malaria elimination scenarios. This will pose challenges to the sensitivity and throughput of existing mosquito-feeding assay protocols. Here, different gametocyte concentration methods of blood samples were explored to optimize conditions for detection of positive mosquito infections.
Mature gametocytes of Plasmodium falciparum were diluted into whole blood samples of malaria-naïve volunteers. Standard centrifugation, Percoll gradient, magnetic cell sorting (MACS) enrichment were compared using starting blood volumes larger than the control (direct) feed.
MACS gametocyte enrichment resulted in the highest infection intensity with statistically significant increases in mean oocyst density in 2 of 3 experiments (p = 0.0003; p ≤ 0.0001; p = 0.2348). The Percoll gradient and standard centrifugation procedures resulted in variable infectivity. A significant increase in the proportion of infected mosquitoes and oocyst density was found when larger volumes of gametocyte-infected blood were used with the MACS procedure.
The current study demonstrates that concentration methods of P. falciparum gametocyte-infected whole blood samples can enhance transmission in mosquito-feeding assays. Gametocyte purification by MACS was the most efficient method, allowing the assessment of gametocyte infectivity in low-density gametocyte infections, as can be expected in natural or experimental conditions.
蚊虫叮咬试验是指导传播阻断干预措施的开发和支持其评估的重要工具。这些功能性生物测定法可测量吸食血液的蚊虫中配子体的孢子生殖发育情况。在疟疾消除场景中，测量低配子体密度的感染性变得越来越重要。这将对现有蚊虫叮咬试验方案的灵敏度和通量构成挑战。在此，探索了血液样本的不同配子体浓缩方法，以优化检测阳性蚊虫感染的条件。
将恶性疟原虫的成熟配子体稀释到未感染疟疾的志愿者的全血样本中。使用比对照（直接）喂食更大的起始血量，比较标准离心、Percoll梯度离心、磁性细胞分选（MACS）富集法。
MACS配子体富集导致感染强度最高，在3个实验中的2个实验中平均卵囊密度有统计学显著增加（p = 0.0003；p≤0.0001；p = 0.2348）。Percoll梯度离心和标准离心程序导致感染性各不相同。当使用更大体积的经MACS程序处理的配子体感染血液时，发现感染蚊虫的比例和卵囊密度显著增加。
当前研究表明，恶性疟原虫配子体感染的全血样本的浓缩方法可增强蚊虫叮咬试验中的传播。通过MACS进行配子体纯化是最有效的方法，能够评估低密度配子体感染中的配子体感染性，这在自然或实验条件下都是可以预期的。
