病毒之間如何相互抑制_風聞

【來源龍騰網】

正文原創翻譯：

This winter’s “tripledemic” is one of several recent odd trends among respiratory virus infections. Viruses, it turns out, can block one another and take turns to dominate.

今年冬季的“三重流行病”是最近出現的呼吸道病毒感染異常趨勢之一。事實證明，病毒能夠相互抑制，交替佔據主流。

Three years into the pandemic, Covid-19 is still going strong, causing wave after wave as case numbers soar, subside, then ascend again. But this past autumn saw something new – or rather, something old: the return of the flu. Plus, respiratory syncytial virus (RSV) – a virus that makes few headlines in normal years – ignited in its own surge, creating a “tripledemic”.

大流行爆發三年後，新冠病毒仍在蔓延，隨着病例數量的攀升、下降、再攀升，引發了一波又一波疫情。但去年秋季出現了新病毒，更確切地説是老病毒：流感捲土重來。另外，呼吸道合胞病毒——平時很少成為頭條新聞——感染人數攀升，形成了“三重流行病”。

The surges in these old foes were particularly striking because flu and RSV all but disappeared during the first two winters of the pandemic. Even more surprising, one particular version of the flu may have gone extinct during the early Covid-19 pandemic. The World Health Organization’s surveillance programme has not definitively detected the B/Yamagata flu strain since March 2020.

這些老對手的病例激增尤為驚人，因為在大流行的頭兩年冬天，流感和呼吸道合胞病毒幾乎消失了。更驚人的是，有一種特殊的流感毒株可能在新冠大流行初期絕跡了。自2020年3月以來，世界衞生組織的監測計劃尚未明確發現乙型Yamagata系流感毒株。

“I don’t think anyone is going to stick their neck out and say it’s gone just yet,” says Richard Webby, a virologist at St Jude Children’s Research Hospital in Memphis. But, he adds, “we hope it got squeezed out.” Such an extinction would be a super rare event, Webby says.

“我想沒人敢冒險説它已經消失了”，孟菲斯聖猶達兒童研究醫院的病毒學家理查德·威比説道。但是，他補充道：“我們希望它被擠走了”。這種滅絕是極其罕見的事件，威比説道。

But then, the past few years have been highly unusual times for human-virus relations, and lockdowns and masks went a long way toward preventing flu and RSV from infiltrating human nostrils. Still, Webby thinks another factor may have kept them at bay while Covid-19 raged. It’s called viral interference, and it simply means that the presence of one virus can block another.

但在人類與病毒的關係方面，過去幾年是極不尋常的時期。封城和口罩對於預防流感和呼吸道合胞病毒滲入鼻孔有大有幫助。但威比認為在新冠病毒蔓延期間，另一個因素可能抑制了它們。這被稱為病毒干擾，是指一種病毒抑制另一種病毒。

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Viral interference can happen in individual cells in the laboratory, and in individual animals and people exposed to multiple viruses – but it can also play out across entire populations, if enough people get one virus for it to hinder the flourishing of others at scale. This results in waves of infections by individual viruses that take turns to dominate. “Looking back over the past couple of years, I’m pretty confident in saying that Covid can certainly block flu and RSV,” Webby says.

病毒干擾可發生在實驗室裏的單個細胞中，或者接觸多種病毒的單個動物和人的體內——但如果足夠多的人感染某種病毒，由它抑制其他病毒的大規模蔓延，那麼全體人口也會發生病毒干擾。“回顧過去幾年的情況，我確信新冠病毒肯定抑制了流感病毒和呼吸道合胞病毒”，威比説道。

It may be a while before we can be sure, but it looks likely that Covid-19 could block flu and RSV

我們可能暫時還不確定，但新冠病毒似乎能夠抑制流感和呼吸道合胞病毒。

It wouldn’t be the first time that scientists have observed such patterns. Back in 2009, for example, the virus to fear was swine flu, which had jumped from pigs to people in spring of that year. It looked poised to ramp up as autumn arrived – but suddenly, in some parts of Europe, it stagnated. The rhinovirus, responsible for the common cold and likely spread by children returning to school, took centre stage for a series of weeks before swine flu recaptured dominance. That flu strain then delayed the typical autumn rise of RSV by as much as two and a half months.

科學家已經不是第一次觀察到這種現象了。例如2009年春天，豬流感傳染給人類而引起恐慌，看上去勢必會在秋季爆發，但突然在歐洲部分地區停止了傳播。引起感冒並可能由兒童傳播的鼻病毒重返校園，連續幾周佔據主流後，豬流感才再次佔據主流。這種流感毒株將通常在秋天爆發的呼吸道合胞病毒延緩了兩個半月。

Running interference

連續干擾

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There are a number of ways that interference can happen in the body. One occurs when two viruses use the same molecule to gain entry into host cells. If virus A gets there first, and grabs on to all those molecular doorknobs, then virus B will have no opportunity to enter.

人體內會發生多種干擾方式。一種是當兩種病毒利用同一分子進入宿主細胞時，如果病毒A捷足先登，霸佔了所有的分子門把手，病毒B就沒機會進入了。

Another kind of interference might happen if two viruses compete for the same resources inside the cell, such as the machinery to make new viral proteins or the means to escape that cell to infect others. “Think of it as a race between two viruses,” Webby says.

當兩種病毒競爭細胞內的同一資源時可能發生干擾，例如製造新病毒蛋白的機制，或者逃逸後感染其他細胞的手段。“可以看成兩種病毒的競爭”，威比説道。

But the best-understood method of interference concerns a defensive molecule called interferon that’s made by cells of all animals with backbones (and possibly some invertebrates too). Indeed, viral interference is the reason interferon got its name to begin with. When a cell senses a virus, any virus, it starts making interferon. And that, in turn, activates a slew of defensive genes. Some of the products of those genes work inside the cell or at its boundaries, where they prevent additional viruses from entering and block viruses already present from replicating or exiting the cell.

但是，最為人所知的干擾方式是所有的脊椎動物（可能還有某些無脊椎動物）的細胞分泌一種名為干擾素的防禦分子。事實上，干擾素正是因為病毒干擾而得名，細胞在感知到病毒時開始分泌干擾素，而干擾素會激活大量的防禦基因。這些基因的某些產物在細胞內部或邊緣發揮作用，阻止更多的病毒進入細胞，並抑制細胞內現有病毒的複製或逃逸。

Cells secrete interferon into their surroundings, warning other cells to put up their guard. The result of all this: If a second virus then comes along, cells have their defences already activated, and they may be able to shut it out.

細胞向周圍分泌干擾素，警告其他細胞築起防線。結果是這樣的：如果第二種病毒入侵，此時細胞已經激活防禦機制，有可能將它們拒之門外。

This “beware” message can spread throughout the body. So, in theory, getting a respiratory virus such as the rhinovirus could activate defences in, say, the gut, protecting the same person from an entirely different virus, such as norovirus. But the situation will vary depending on the viruses involved, the amount of interferon produced, and other factors. “Most of the viruses themselves have ways to neutralise the interferon system,” says Ganes Sen, a virologist at the Cleveland Clinic in Ohio, who wrote about the interactions between interferon and viruses for the Annual Review of Virology in 2015. “It’s a tug of war.”

“警報”信息可傳遍整個身體。所以從理論上，感染一種呼吸道病毒（例如鼻病毒）能激活內臟的防禦機制，防止這個人感染另一種截然不同的病毒，例如諾如病毒。但具體情況取決於病毒的種類、分泌干擾素的多少以及其他因素。“大多數病毒有辦法破壞干擾素系統”，俄亥俄州克利夫蘭醫學中心的病毒學家加內·森説道。2015年，他曾在《病毒學年鑑》上發表過關於干擾素與病毒之間相互作用的文章。“這是一場拉鋸戰”。

Scientists study that back-and-forth in animals and other systems in the laboratory. For example, Ellen Foxman, an immunologist at Yale School of Medicine, investigates viral interactions in lab-grown tissues made from real human airway cells. In one experiment, she studied swine flu and a typical representative of the rhinovirus family. When Foxman and her co-authors Anchi Wu, Valia Mihaylova and Marie Landry infected the human tissue first with the rhinovirus, and then with swine flu, interferon prevented the flu from getting a foothold. In similar studies, Foxman found that rhinovirus infection also interfered with subsequent Sars-CoV-2 infection (the virus that causes Covid-19).

科學家們在實驗室裏反覆研究了動物和其他系統內的相互作用。例如，耶魯醫學院的免疫學家埃倫·福克斯曼研究了實驗室培育的組織中發生的病毒相互作用，該組織是利用真實的人類支氣管細胞培育而成。她在一次試驗中研究了豬流感和一種典型的鼻病毒，福克斯曼與她的合著者吳安琪、瓦利亞·米哈洛娃、瑪利·蘭德里先讓人類組織感染了鼻病毒，然後感染豬流感，結果干擾素阻止了豬流感站穩腳跟。在類似的研究中，福克斯曼發現感染鼻病毒也會干擾隨後感染的SARS-CoV-2病毒（導致2019冠狀病毒病）。

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While some viruses can block others, it is still possible to get two viruses at once

雖然某些病毒能抑制其他病毒，但仍有可能同時受到兩種病毒的感染。

It’s not always reliable to extrapolate from tissues in the laboratory to people or populations, but Foxman thinks the studies reflect biological truth. “It’s probable that if you get a rhinovirus infection, that’s going to make you relatively resistant to another virus for some period of time,” she says. Foxman speculates that the protective effect probably lasts days or weeks.

根據實驗室裏的組織去推斷人或人羣未必可靠，但福克斯曼認為這些研究反映出一個生物真相。“如果你感染了鼻病毒，它可能使你在一段時期內相對免疫另一種病毒”，她説道。福克斯曼推測，這種保護效應可能持續數天或數週。

But don’t go counting on a cold granting you temporary immunity from other viruses. Interference isn’t guaranteed. It’s certainly possible to catch more than one virus at the same time. And interferon isn’t always beneficial, either – sometimes, it can make people more susceptible to infection, not less. A well-known example is that the flu makes people more susceptible to a secondary bacterial infection.

但是，不要指望感冒讓你暫時免疫其他病毒。干擾未必發生，同時感染一種以上病毒是有可能的。干擾素並不總是有益的，有時使人更容易感染病毒。眾所周知的例子是，流感使人更容易感染第二種病毒。

In the ongoing pandemic, it’s still hard to say how much of a role, if any, interference played in shutting down RSV and flu in populations around the globe. During the first Covid wave in 2020, Foxman thinks that not enough people had Covid for it to be interfering with other viruses on a grand scale. (RSV underwent an unusual summer peak in 2021 as people eased up on masking and other precautions.)

在持續不斷的大流行中，尚不確定干擾在阻斷全球人口感染呼吸道合胞病毒和流感中起了多大作用（如果起作用的話）。福克斯曼認為，在2020爆發的第一波新冠疫情中，感染新冠病毒的人數不足以大規模干擾其他病毒（2021年夏季出現了異常的呼吸道合胞病毒感染高峯，因為人們放鬆了佩戴口罩和其他預防措施）。

But by the second Covid winter, in 2021-22, Webby thinks he sees population-level evidence for interference. Influenza was starting to pick up in the fall, he says, but then the omicron variant of Covid burst onto the scene. Flu rates fell – even though people were back at work and school and traveling for the holidays. The coronavirus had a big advantage that season, he says, because many people still lacked immunity to it. It doesn’t mean Covid will always edge out influenza in the future.

但是，在2021-22年爆發的第二波冬季新冠疫情中，威比認為自己發現了干擾在起效的羣體證據。流感在秋天進入高峯期，他説道，但後來奧密克戎毒株突然爆發。流感發病率下降，儘管人們恢復了工作、學習、假日旅行。新冠病毒在那個季節有很大優勢，他説道，因為許多人仍然對它缺少免疫力。這並不意味着新冠病毒在將來總能戰勝流感。

In the third Covid winter now underway in the Northern Hemisphere, conditions are different yet again. Many people now have immunity to Covid, from a recent bout or from vaccination, but fewer have experienced RSV or flu in recent memory. That set the scene for flu and RSV to stage a massive dual comeback, hitting early and hard.

現在北半球已進入第三波冬季新冠疫情，情況又有所不同。許多人從最近的感染或疫苗接種中對新冠病毒產生了免疫力，但在近期感染呼吸道合胞病毒或流感的人比較少，這給流感和呼吸道合胞病毒的大規模捲土重來創造了條件，它們會提前洶湧來襲。

Any potential interference during the present tripledemic winter will become more obvious once epidemiologists can look back on the season and see if each virus took its turn. Already, there are indicators that the fall surges of RSV and flu might have peaked, while Covid is on the upswing after the winter holidays. But there are still several cold months to come, providing ample opportunity for any of the trio to rise again.

如果流行病學家回顧這個季節，看看每一種病毒是否交替出現，那麼當下冬天“三重流行病”疫情中出現的任何潛在干擾都會更加明顯。有跡象表明，秋天激增的呼吸道合胞病毒和流感可能已達到高峯，而新冠病毒在寒假過後呈現上升趨勢。但接下來還有幾個寒冷的月份，“三重流行病”中的每一種病毒都有充足的機會捲土重來。