Virulence and competitive ability in genetically diverse malaria infections
Virulence and competitive ability in genetically diverse malaria infections
复制标题
DOI：
10.1073/pnas.0500078102
复制
发表时间：
2005-05-24
影响因子：
11.1
通讯作者：
Read, AF
中科院分区：
文献类型：
--
作者：
de Roode, JC;Pansini, R;Read, AF
解释寄生虫的毒力是进化生物学面临的一个巨大挑战。直觉上，依赖宿主生存的寄生虫对宿主应该是良性的，但许多寄生虫会造成伤害。对此的一种解释是宿主内竞争有利于毒力，在遗传多样性感染中，毒性更强的菌株具有竞争优势。这一观点在理论上得到了很好的支持，但尚未得到经验的检验。在这里，我们提供的证据表明，宿主内竞争确实选择高寄生虫毒力。我们在实验室小鼠中研究了啮齿类疟疾夏氏疟原虫，这是一种寄生虫-宿主系统，可以很容易地监测毒力，并通过使用菌株特异性实时PCR定量竞争菌株。正如预测的那样，我们发现寄生虫的毒力和竞争能力之间有很强的关系，因此，更毒的菌株在混合菌株感染中具有竞争优势。在传播实验中，我们发现蚊子体内寄生虫种群的菌株组成与血液阶段寄生虫种群的组成直接相关。因此，宿主内竞争的结果决定了相对的传播成功。我们的研究结果表明，宿主内竞争是驱动毒力进化的一个主要因素，可以解释为什么许多寄生虫伤害他们的主机。
Explaining parasite virulence is a great challenge for evolutionary biology. Intuitively, parasites that depend on their hosts for their survival should be benign to their hosts, yet many parasites cause harm. One explanation for this is that within-host competition favors virulence, with more virulent strains having a competitive advantage in genetically diverse infections. This idea, which is well supported in theory, remains untested empirically. Here we provide evidence that within-host competition does indeed select for high parasite virulence. We examine the rodent malaria Plasmodium chabaudi in laboratory mice, a parasite-host system in which virulence can be easily monitored and competing strains quantified by using strain-specific real-time PCR. As predicted, we found a strong relationship between parasite virulence and competitive ability, so that more virulent strains have a competitive advantage in mixed-strain infections. In transmission experiments, we found that the strain composition of the parasite populations in mosquitoes was directly correlated with the composition of the bloodstage parasite population. Thus, the outcome of within-host competition determined relative transmission success. Our results imply that within-host competition is a major factor driving the evolution of virulence and can explain why many parasites harm their hosts.