Cooper L A, Scott T W
Department of Entomology, University of Maryland, College Park, Maryland 20742, USA.
Genetics. 2001 Apr;157(4):1403-12. doi: 10.1093/genetics/157.4.1403.
Arthropod-borne viruses (arboviruses) cycle between hosts in two widely separated taxonomic groups, vertebrate amplifying hosts and invertebrate vectors, both of which may separately or in concert shape the course of arbovirus evolution. To elucidate the selective pressures associated with virus replication within each portion of this two-host life cycle, the effects of host type on the growth characteristics of the New World alphavirus, eastern equine encephalitis (EEE) virus, were investigated. Multiple lineages of an ancestral EEE virus stock were repeatedly transferred through either mosquito or avian cells or in alternating passages between these two cell types. When assayed in both cell types, derived single host lineages exhibited significant differences in infectivity, growth pattern, plaque morphology, and total virus yield, demonstrating that this virus is capable of host-specific evolution. Virus lineages grown in alternation between the two cell types expressed intermediate phenotypes consistent with dual adaptation to both cellular environments. Both insect-adapted and alternated lineages greatly increased in their ability to infect insect cells. These results indicate that different selective pressures exist for virus replication within each portion of the two-host life cycle, and that alternation of hosts selects for virus populations well adapted for replication in both host systems.
虫媒病毒在两个分类学上广泛分离的宿主群体之间循环，即脊椎动物扩增宿主和无脊椎动物媒介，这两者都可能单独或共同塑造虫媒病毒的进化过程。为了阐明与这种双宿主生命周期各部分内病毒复制相关的选择压力，研究了宿主类型对新大陆甲病毒——东部马脑炎（EEE）病毒生长特性的影响。祖先EEE病毒株的多个谱系通过蚊子或禽类细胞反复传代，或在这两种细胞类型之间交替传代。当在两种细胞类型中进行检测时，衍生的单宿主谱系在感染性、生长模式、蚀斑形态和总病毒产量方面表现出显著差异，表明这种病毒能够进行宿主特异性进化。在两种细胞类型之间交替生长的病毒谱系表现出与对两种细胞环境的双重适应一致的中间表型。适应昆虫的谱系和交替传代的谱系感染昆虫细胞的能力都大大增强。这些结果表明，在双宿主生命周期的每个部分内，病毒复制存在不同的选择压力，并且宿主交替选择了适合在两种宿主系统中复制的病毒群体。
