Viruses exhibit a diverse array of strategies for infecting host cells and for virion release after replication. Cell exit strategies generally involve either budding from the cell membrane or killing the host cell. The conditions under which either is at a selective advantage is a key question in the evolutionary theory of viruses, with the outcome having potentially important impacts on the course of infection and pathogenicity. Although a plethora of external factors will influence the fitness of either strategy; here, we focus just on the effects of the physical properties of the system. We develop theoretical approaches to assess the effects of the time delays between initial infection and virion release. We show that the length of the delay before apoptosis is an important trait in virus evolutionary dynamics. Our results show that for a fixed time to apoptosis, intermediate delays lead to virus fitness that is lower than short times to apoptosis — leading to an apoptotic strategy — and long times to apoptosis — leading to a budding strategy at the between-cell level. At fitness minima, selection is expected to be disruptive and the potential for adaptive radiation in virus strategies is feasible. Hence, the physical properties of the system are sufficient to explain the existence of both budding and virus-induced apoptosis. The fitness functions presented here provide a formal basis for further work focusing on the evolutionary implications of trade-offs between time delays, intracellular replication and resulting mutation rates.

中文翻译：

---

病毒的进化动力学：病毒粒子释放策略、时间延迟和适应度最小值

病毒表现出多种感染宿主细胞和复制后释放病毒粒子的策略。细胞退出策略通常涉及从细胞膜出芽或杀死宿主细胞。任一者处于选择优势的条件是病毒进化理论中的一个关键问题，其结果对感染过程和致病性具有潜在的重要影响。尽管大量外部因素会影响任一策略的适用性；在这里，我们只关注系统物理属性的影响。我们开发了理论方法来评估初始感染和病毒粒子释放之间的时间延迟的影响。我们发现细胞凋亡前的延迟时间是病毒进化动力学的一个重要特征。我们的结果表明，对于固定的细胞凋亡时间，中间延迟导致病毒适应度低于短时间的细胞凋亡（导致细胞凋亡策略）和长的细胞凋亡时间（导致细胞间水平的出芽策略）。在适应度最低时，选择预计会具有破坏性，并且病毒策略中适应性辐射的潜力是可行的。因此，该系统的物理特性足以解释出芽和病毒诱导的细胞凋亡的存在。这里提出的适应度函数为进一步的工作提供了正式的基础，重点是时间延迟、细胞内复制和由此产生的突变率之间权衡的进化影响。