Covert infections as a mechanism for long-term persistence of baculoviruses
Covert infections as a mechanism for long-term persistence of baculoviruses
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DOI：
10.1046/j.1461-0248.2003.00459.x
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发表时间：
2003-06-01
期刊：
影响因子：
8.8
通讯作者：
Hails, RS
中科院分区：
文献类型：
--
作者：
Burden, JP;Nixon, CP;Hails, RS
病原体在野生种群中的流行程度通常通过宿主中明显症状的出现来估计，这通常被用作病原体对宿主动态影响的唯一衡量标准。然而，分子方法的发展提高了我们检测无症状感染的灵敏度。杆状病毒是昆虫病原体，与许多微寄生虫一样，通常仅在其宿主达到爆发密度时发现，此时发生动物流行病。传统观点认为，杆状病毒的长期存在依赖于它们在外部环境中以闭塞体的形式存活。这些是包埋病毒颗粒的蛋白质基质，并提供一定程度的紫外线照射保护。然而，甘蓝夜蛾也被证明具有持续的、非致死性杆状病毒感染（M. brassicae核多角体病毒），这可能代表另一种假定的持久性机制。在这里，我们提出的证据表明，这种隐蔽的感染也存在，并经常在自然种群的蛾。持续性感染通过暴露于另一种杆状病毒而被触发进入致命的公开状态，随后在采样的人群中将两种密切相关但不同的杆状病毒鉴定为持续性感染。这些结果有广泛的影响，我们了解宿主病原体相互作用的领域，在使用病原体作为生物控制剂，并在毒力的演变。
The prevalence of pathogens in wild populations has often been estimated by the appearance of overt symptoms in the host, and this is typically used as the sole gauge of the impact of the pathogen on host dynamics. However, the development of molecular methods has increased the sensitivity with which we can detect asymptomatic infections. Baculoviruses are insect pathogens that, like many microparasites, are usually only found when their hosts reach outbreak densities, when a disease epizootic occurs. Conventional wisdom is that the long-term persistence of baculoviruses relies on their survival in the external environment in the form of occlusion bodies. These are proteinaceous matrices in which the virus particles are embedded, and which provide a degree of protection from UV irradiation. However, Mamestra brassicae has also been shown to harbour a persistent, non-lethal baculovirus infection (M. brassicae nucleopolyhedrovirus) in laboratory culture, which may represent another putative persistence mechanism. Here, we present evidence that such covert infections are also present and frequent in natural populations of the moth. The persistent infections were triggered into the lethal overt state by exposure to another baculovirus, and two closely related but different baculoviruses were subsequently identified as persistent infections within the populations sampled. These results have broad-ranging implications for our understanding of host pathogen interactions in the field, in the use of pathogens as biocontrol agents, and in the evolution of virulence.