Food Webs in the Human Body: Linking Ecological Theory to Viral Dynamics

The dynamics of in-host infections are central to predicting the progression of natural infections and the effectiveness of drugs or vaccines, however, they are not well understood. Here, we apply food web theory to in-host disease networks of the human body that are structured similarly to food web models that treat both predation and competition simultaneously. We show that in-host trade-offs, an under-studied aspect of disease ecology, are fundamental to understanding the outcomes of competing viral strains under differential immune responses. Further, and importantly, our analysis shows that the outcome of competition between virulent and non-virulent strains can be highly contingent on the abiotic conditions prevailing in the human body. These results suggest the alarming idea that even subtle behavioral changes that alter the human body (e.g. weight gain, smoking) may switch the environmental conditions in a manner that suddenly allows a virulent strain to dominate and replace less virulent strains. These ecological results therefore cast new light on the control of disease in the human body, and highlight the importance of longitudinal empirical studies across host variation gradients, as well as, of studies focused on delineating life history trade-offs within hosts.

宿主内感染动态是预测自然感染进程以及药物或疫苗有效性的核心依据，但目前学界对其认知仍较为有限。我们将食物网理论（food web theory）应用于结构与同时兼顾捕食与竞争的食物网模型相似的人体宿主内疾病网络。研究表明，宿主内权衡——这一疾病生态学中尚未得到充分探索的研究方向——是解析差异化免疫应答下竞争病毒株结局的关键基础。更为重要的是，本分析显示，毒力毒株与弱毒毒株之间的竞争结局，在很大程度上取决于人体内部的非生物环境条件。上述研究结果提出了一个令人警醒的观点：即使是细微的行为改变（如体重增加、吸烟）也可能改变人体内部的环境条件，使得毒力毒株突然占据主导地位并取代弱毒毒株。因此，这些生态学研究结果为人体疾病防控提供了全新视角，同时凸显了两项研究的重要性：一是开展跨宿主变异梯度的纵向实证研究，二是聚焦于阐明宿主内生活史权衡的相关研究。