新冠病毒到底哪裡來的?從哪裡開始的?全球口水滿天飛,中、美兩國互相指控吵翻天。但來自美國、英國及澳洲的科學家發現,新冠病毒不可能是人為製造出來的,它是從自然界產生,甚至早在10多年前就已經存在在人群裡傳播,靠著不斷突變,終致找到威力最強大的模式爆發。
曾領導完成龐大的人類基因組計畫,被稱為「史上最有影響力的美國國衛院院長之一」、美國國家衛生研究院院長柯林斯(Francis Collins)發表在「國家衛生研究院院長部落格」(NIH Director's Blog),標題為《基因體研究顯示2019冠狀病毒病起源於自然界》(Genomic Study Points to Natural Origin of COVID-19)的文章,援引NIH國際研究小組對比多種冠狀病毒基因體(genome)資料得出結論:新冠病毒(SARS-CoV-2)是從自然界產生。
柯林斯在專文中盛讚新近加州斯克里普斯研究所(Scripps Research Institute)安德森(Kristian Andersen)、杜蘭大學醫學院(Tulane University School of Medicine)蓋瑞(Robert Garry)等人發表在《自然醫學(Nature Medicine)》期刊的研究結果:新冠病毒特徵是棘突蛋白(spike protein)及一些獨特的變異性,讓病毒能夠結合人體細胞的「血管收縮素轉化酶2」(ACE2),而且結合能力強大,遠超出電腦模型推估,原因則很可能是天擇(natural selection),而非實驗室產物。
新冠病毒功能特異,是自然演化結果
這份研究從新冠病毒(SARS-CoV-2)的基因組序列和病毒結構進行分析,以了解病毒的起源和演化;並與其它冠狀病毒做比較。
https://directorsblog.nih.gov/20 ... origin-of-covid-19/
No matter where you go online these days, there’s bound to be discussion of coronavirus disease 2019 (COVID-19). Some folks are even making outrageous claims that the new coronavirus causing the pandemic was engineered in a lab and deliberately released to make people sick. A new study debunks such claims by providing scientific evidence that this novel coronavirus arose naturally.
The reassuring findings are the result of genomic analyses conducted by an international research team, partly supported by NIH. In their study in the journal Nature Medicine, Kristian Andersen, Scripps Research Institute, La Jolla, CA; Robert Garry, Tulane University School of Medicine, New Orleans; and their colleagues used sophisticated bioinformatic tools to compare publicly available genomic data from several coronaviruses, including the new one that causes COVID-19.
The researchers began by homing in on the parts of the coronavirus genomes that encode the spike proteins that give this family of viruses their distinctive crown-like appearance. (By the way, “corona” is Latin for “crown.”) All coronaviruses rely on spike proteins to infect other cells. But, over time, each coronavirus has fashioned these proteins a little differently, and the evolutionary clues about these modifications are spelled out in their genomes.
The genomic data of the new coronavirus responsible for COVID-19 show that its spike protein contains some unique adaptations. One of these adaptations provides special ability of this coronavirus to bind to a specific protein on human cells called angiotensin converting enzyme (ACE2). A related coronavirus that causes severe acute respiratory syndrome (SARS) in humans also seeks out ACE2.
Existing computer models predicted that the new coronavirus would not bind to ACE2 as well as the SARS virus. However, to their surprise, the researchers found that the spike protein of the new coronavirus actually bound far better than computer predictions, likely because of natural selection on ACE2 that enabled the virus to take advantage of a previously unidentified alternate binding site. Researchers said this provides strong evidence that that new virus was not the product of purposeful manipulation in a lab. In fact, any bioengineer trying to design a coronavirus that threatened human health probably would never have chosen this particular conformation for a spike protein.
The researchers went on to analyze genomic data related to the overall molecular structure, or backbone, of the new coronavirus. Their analysis showed that the backbone of the new coronavirus’s genome most closely resembles that of a bat coronavirus discovered after the COVID-19 pandemic began. However, the region that binds ACE2 resembles a novel virus found in pangolins, a strange-looking animal sometimes called a scaly anteater. This provides additional evidence that the coronavirus that causes COVID-19 almost certainly originated in nature. If the new coronavirus had been manufactured in a lab, scientists most likely would have used the backbones of coronaviruses already known to cause serious diseases in humans.
So, what is the natural origin of the novel coronavirus responsible for the COVID-19 pandemic? The researchers don’t yet have a precise answer. But they do offer two possible scenarios.
In the first scenario, as the new coronavirus evolved in its natural hosts, possibly bats or pangolins, its spike proteins mutated to bind to molecules similar in structure to the human ACE2 protein, thereby enabling it to infect human cells. This scenario seems to fit other recent outbreaks of coronavirus-caused disease in humans, such as SARS, which arose from cat-like civets; and Middle East respiratory syndrome (MERS), which arose from camels.
The second scenario is that the new coronavirus crossed from animals into humans before it became capable of causing human disease. Then, as a result of gradual evolutionary changes over years or perhaps decades, the virus eventually gained the ability to spread from human-to-human and cause serious, often life-threatening disease.
Either way, this study leaves little room to refute a natural origin for COVID-19. And that’s a good thing because it helps us keep focused on what really matters: observing good hygiene, practicing social distancing, and supporting the efforts of all the dedicated health-care professionals and researchers who are working so hard to address this major public health challenge.
Finally, next time you come across something about COVID-19 online that disturbs or puzzles you, I suggest going to FEMA’s new Coronavirus Rumor Control web site. It may not have all the answers to your questions, but it’s definitely a step in the right direction in helping to distinguish rumors from facts.作者: hsuamwang 時間: 2020-4-2 01:57 PM