Cadar Dániel, Schmidt-Chanasit Jonas, Tappe Dennis
WHO Collaborating Centre for Arbovirus and Haemorrhagic Fever Reference and Research, Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany.
Faculty of Mathematics, Informatics and Natural Sciences, Universität Hamburg, 20148 Hamburg, Germany.
Microorganisms. 2021 May 25;9(6):1141. doi: 10.3390/microorganisms9061141.
(VSBV-1) is an emerging zoonotic pathogen discovered in several exotic squirrel species and associated with fatal human encephalitis. The dynamics of VSBV-1 spread and evolution in its presumed natural hosts are unknown. Here, we present the phylogeny, micro-evolution, cross-species transmission and spread of VSBV-1 at a temporal and spatial resolution within the limits of animal husbandry. The results showed that VSBV-1 can be classified into six distinct groups and that the most recent common ancestor of the known German strains emerged at least 20 years ago. We here demonstrate that the genetic diversity of the VSBV-1 groups is shaped primarily by in situ evolution and most of the amino acid changes are deleterious polymorphisms removed by purifying selection. Evidence of adaptive evolution has been found in the G and L genes which might have an influence on transmission fitness. Furthermore, there was also evidence for some form of adaptive changes in the glycoprotein which suggests that many sites might be subjected to positive pressure evolving under episodic directional selection, indicating past occurrence of positive selection. Host switching events were detected as dominant evolutionary mechanisms driving the virus-host associations. Virus spread by animal trade followed by subsequent local micro-evolution in zoos and holdings is responsible for diversifying strains. Time-resolved phylogeny indicated that Prevost's squirrels might be the original squirrel species carrying and seeding the virus in Germany. This study provides the first insight into the ecology and micro-evolutionary dynamics of this novel viral pathogen in the captive exotic squirrel population under artificial ecological conditions (zoos and animal husbandry) and co-housing of different squirrel species.
VSBV-1是在几种外来松鼠物种中发现的一种新出现的人畜共患病原体，与人类致命性脑炎有关。VSBV-1在其假定的自然宿主中的传播和进化动态尚不清楚。在此，我们在畜牧范围内以时间和空间分辨率展示了VSBV-1的系统发育、微观进化、跨物种传播和扩散。结果表明，VSBV-1可分为六个不同的组，已知德国毒株的最近共同祖先至少出现在20年前。我们在此证明，VSBV-1各群体的遗传多样性主要由原地进化塑造，大多数氨基酸变化是通过纯化选择去除的有害多态性。在G和L基因中发现了适应性进化的证据，这可能对传播适应性有影响。此外，在糖蛋白中也有某种形式的适应性变化的证据，这表明许多位点可能受到间歇性定向选择下的正选择压力，表明过去发生过正选择。宿主转换事件被检测为驱动病毒-宿主关联关系的主要进化机制。病毒通过动物贸易传播，随后在动物园和养殖场进行局部微观进化，导致毒株多样化。时间分辨系统发育表明，赤腹松鼠可能是德国携带和传播该病毒的原始松鼠物种。本研究首次深入了解了这种新型病毒病原体在人工生态条件（动物园和畜牧业）下圈养外来松鼠种群以及不同松鼠物种混养情况下的生态学和微观进化动态。
