使用古代DNA解开乙肝病毒进化

StephenW

使用古代DNA解开乙肝病毒进化
2021 年 10 月 7 日 |记者

纽约——由德国调查人员领导的一个国际团队将乙型肝炎病毒的进化追溯到 20,000 年前，发现了这种病毒在农业前人群中的证据。

“我们的数据表明，所有已知的 HBV 基因型都来自一种菌株，该菌株在这些人群出现分歧时感染了第一批美国人的祖先及其最亲近的欧亚亲属，”共同资深和共同通讯作者丹尼斯·库纳特 (Denise Kühnert)，隶属于该研究所的研究员。马克斯普朗克人类历史科学研究所传播、感染、多样化和进化小组及其考古遗传学部门在一份声明中说。

作者在周四发表在《科学》杂志上的一篇论文中解释说，尽管过去的研究将 HBV 的传播与人类迁移联系起来，导致世界不同地区出现了 9 种当代 HBV 基因型的不同集群，但有关其起源和早期传播的详细信息仍然存在未解决。

他们写道：“古老的 DNA 数据允许校准分子钟，所有已知 HBV 的最新共同祖先 (tMRCA) 的时间都可以追溯到 [大约 21,000 年前和大约 9,000 年前]。” “然而，这种病毒过去多样性的程度通常仍然未知，因为迄今为止仅重建了 19 个具有有限时间和地理分布的古老 HBV 基因组。”

研究人员使用 DNA 富集和测序，评估了 137 种与美洲原住民或欧亚裔遗骸相关的古老 HBV 分离株，可追溯到大约 400 至 10,500 年前。他们的系统发育分析表明，HBV 谱系有一个共同的祖先，可以追溯到 12,000 到 20,000 年前，HBV 感染可以追溯到欧洲和南美洲狩猎采集人群的全新世早期。

“许多人类病原体被认为是在引入农业后出现的，但 HBV 显然已经影响了史前狩猎采集人群，”共同资深和共同通讯作者、马克斯普朗克进化人类学研究所考古遗传学系主任约翰内斯克劳斯，在一份声明中说。

该团队指出，在古代美洲原住民中发现的一个谱系落入了一个与欧亚大陆谱系不同的进化枝，估计在 12,000 到 16,000 年前。该谱系似乎是 HBV 基因型的祖先，这些基因型已在当今美洲原住民人群中记录。

与此同时，在欧洲，中石器时代发现的病毒株在很大程度上被怀疑是由农业人口带来的 HBV 谱系所取代。研究人员报告说，尽管这种谱系在欧亚大陆西部存在了数千年，但它的突出地位最终也减弱了，留下了一种罕见的基因型，随着 HIV 的传播再次出现。

“[O]你的结果揭示了仅根据人类遗传和考古数据无法预料的模式，例如在公元前 2 千年末左右，欧亚西部 HBV 多样性几乎完全更新，”作者总结道。 “这些发现强调，古代病毒多样性的重建对于我们对人类历史的理解具有巨大的潜力。”

StephenW

Hepatitis B Virus Evolution Untangled Using Ancient DNA
Oct 07, 2021 | staff reporter

NEW YORK – An international team led by investigators in Germany has retraced hepatitis B virus evolution back to 20,000 years, uncovering evidence of the virus in pre-agricultural populations.

"Our data suggest that all known HBV genotypes descend from a strain that was infecting the ancestors of the First Americans and their closest Eurasian relatives around the time these populations diverged," co-senior and co-corresponding author Denise Kühnert, a researcher affiliated with the Max Planck Institute for the Science of Human History's transmission, infection, diversification, and evolution group and its archaeogenetics department, said in a statement.

Although past studies have linked the spread of HBV to human migrations, leading to distinct clusters of the nine contemporary HBV genotypes in different parts of the world, the authors explained in a paper published in Science on Thursday, details on its origin and early spread remain unresolved.

"Ancient DNA data permits molecular clock calibration, and the time to the most recent common ancestor (tMRCA) of all known HBV has been dated to between [around 21,000 years ago and around 9,000 years ago]," they wrote. "However, the extent of the past diversity of this virus remains generally unknown because only 19 ancient HBV genomes with a limited temporal and geographic distribution have been reconstructed to date."

Using DNA enrichment and sequencing, the researchers assessed 137 ancient HBV isolates associated with Native American or Eurasian remains going back some 400 to 10,500 years. Their phylogenetic analyses suggested HBV lineages share a common ancestor going back between 12,000 and 20,000 years, with HBV infections going back to the early Holocene period in hunter-gather populations in Europe and South America.

"Many human pathogens are thought to have emerged after the introduction of agriculture, but HBV was clearly already affecting prehistoric hunter-gatherer populations," co-senior and co-corresponding author Johannes Krause, director of the Max Planck Institute for Evolutionary Anthropology's archaeogenetics department, said in a statement.

The team noted that a lineage found in ancient Native Americans falls into a clade that diverged from lineages in Eurasia an estimated 12,000 to 16,000 years ago. That lineage appeared to be ancestral to the HBV genotypes that have been documented in individuals from Native American populations today.

In Europe, meanwhile, strains found during the Mesolithic period largely gave way to an HBV lineage suspected of being brought by farming populations. Though that lineage stuck around for thousands of years in western Eurasia, the investigators reported, its prominence eventually waned as well, leaving behind a rare genotype that cropped up again with the spread of HIV.

"[O]ur results reveal patterns that were not expected on the basis of human genetic and archaeological data alone, such as the near complete renewal of western Eurasian HBV diversity around the end of the 2nd millennium BCE," the authors concluded. "These findings highlight that the reconstruction of ancient viral diversity has great potential to contribute to our understanding of human history."