Data from: A nutrient mediates intraspecific competition between rodent malaria parasites in vivo

Hosts are often infected with multiple strains of a single parasite species. Within-host competition between parasite strains can be intense and has implications for the evolution of traits that impact patient health, such as drug resistance and virulence. Yet the mechanistic basis of within-host competition is poorly understood. Here, we demonstrate that a parasite nutrient, para-aminobenzoic acid (pABA), mediates competition between a drug resistant and drug susceptible strain of the malaria parasite, Plasmodium chabaudi. We further show that increasing pABA supply to hosts infected with the resistant strain worsens disease and changes the relationship between parasite burden and pathology. Our experiments demonstrate that, even when there is profound top-down regulation (immunity), bottom-up regulation of pathogen populations can occur and that its importance may vary during an infection. The identification of resources that can be experimentally controlled opens up the opportunity to manipulate competitive interactions between parasites, and hence, their evolution.

宿主常可被同一寄生虫物种的多个毒株共同感染。寄生虫毒株间的宿主体内竞争往往极为激烈，且会对影响宿主健康的性状演化产生重要影响，例如抗药性与毒力。然而，目前学界对宿主体内竞争的机制基础仍缺乏深入认知。本研究证实，一种寄生虫源性营养物质——对氨基苯甲酸（para-aminobenzoic acid，pABA）可介导查氏疟原虫（Plasmodium chabaudi）抗药株与敏感株之间的竞争。我们进一步发现，向感染了抗药株的宿主提升pABA供给量，会加重疾病严重程度，并改变寄生虫载量与病理损伤之间的关联。本实验结果表明，即便存在显著的自上而下调控（宿主免疫），病原体种群仍可发生自下而上调控，且该调控的重要性可能随感染进程发生动态变化。可通过实验操控的营养资源的鉴定，为我们调控寄生虫间的竞争互作乃至其演化进程提供了全新的可行路径。