Mutation Accumulation Is Determined By Replication Mode
Viral replication modes and mutation accumulation. a Stamping machine versus semi-conservative replication. As opposed to cells, which use only semi-conservative replication, viruses can adopt a variety of replication modes. In the stamping machine model, a single template strand is used to synthesize all progeny genomes within a given cell. However, this is not possible in practice because replication requires synthesis of complementary strands or anti-genomes . Under this model, the mutation frequency after one cell infection cycle will equal the mutation rate except if mutations occur during the first round of copying , in which case they will be present in all of the viral progeny. Under semi-conservative replication, multiple rounds of copying are required to produce enough progeny, thus allowing for the intra-cellular accumulation of mutations. b Relationship between lysis time and mutation accumulation. Longer cell infection cycles can allow for the production of more progeny viruses. Under semi-conservative replication, this will require more rounds of copying but, if replication follows the stamping machine model, the number of rounds of copying will not change . Hence under this model, a late-burst virus variant will undergo fewer total rounds of copying at the population scale than early-burst variants and will tend to accumulate fewer mutations
How Viruses Mutate And Create New Variants
As coronavirus variants circulate worldwide, a Tufts researcher explains the mechanisms of how viruses change and why its going to keep happening
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As the COVID-19 pandemic continues, new variants of the SARS-CoV-2 virus pop up, and some lead to increasing infections. The main new variantsnamed Alpha, Beta, and Delta and first identified in Britain, South Africa, and India, respectivelyhave properties that make them more successful in transmitting and replicating than the original virus.
Viruses are not technically living thingsthey invade living cells and hijack their machinery to get energy and replicate, and find ways to infect other living organisms and start the process over again.
How viruses mutate largely has to do with how they make copies of themselves and their genetic material, says , an associate professor of molecular biology and microbiology at the School of Medicine. Viruses can have genomes based on DNA or RNAunlike human genomes, which are made up of DNA, which then can create RNA.
Gaglia studies how viruses take control of infected cells and reprogram the cells machinery to reproduce themselves. Weve been working on a protein that the virus encodes that destroys the host RNA, blocking the cells from being able to express their own protein and blocking, among other things, antiviral response, she says.
What else affects mutations?
Viruses Naturally Change During Reproduction
A virus is life at its most simple, and essentially contains two main elements: a blueprint for reproduction , and proteins that let the virus enter cells, take over, and start replicating.
While only a few SARS-CoV-2 viruses are needed to cause an infection, replication of the virus in the lungs is explosive. Millions of virus particles are eventually produced, and some of these viruses are then exhaled to infect another host.
Importantly, the process of duplicating the virus RNA is imperfect. Eventually, errors will accumulate in the growing pool of viruses, causing what we refer to as virus variants.
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What Impact Do The New Variants Of The Covid
The COVID-19 vaccines that are currently in development or have been approved are expected to provide at least some protection against new virus variants because these vaccines elicit a broad immune response involving a range of antibodies and cells. Therefore, changes or mutations in the virus should not make vaccines completely ineffective. In the event that any of these vaccines prove to be less effective against one or more variants, it will be possible to change the composition of the vaccines to protect against these variants.
Data continues to be collected and analysed on new variants of the COVID-19 virus. WHO is working with researchers, health officials and scientists to understand how these variants affect the viruss behaviour, including their impact on the effectiveness of vaccines, if any. See WHOs Disease Outbreak News to get up-to-date information on the impact of COVID-19 virus variants on the effectiveness of the different vaccines. This is an area where the evidence remains preliminary and is developing quickly.
Mutations Vs Strains Vs Variants
The words “mutation,” “strain,” and “variant” are sometimes used interchangeably in headlines and news articles, but they pertain to three very different things.
A mutation is a single change in the virus’s genetic sequence . When a mutation simply changes the genome of a virus, it becomes a new variant. If those mutations make the variant more transmissible, less detectable by vaccines, and become more dominant within its population, then the variant qualifies as a strain.
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How Do Mutations Arise
Viruses smuggle their genetic information into a host cell in order to multiply. With every reproduction, there are small copying errors, and each of these errors also changes the genetic code of the virus. So it is constantly mutating, and that is quite normal.
Sometimes these mutations make the virus more effective, for example, by allowing it to elude immune reactions such as those brought about by vaccinations or prior illness. Sometimes they make the virus less effective, that is, weaken it. And often they have no effect at all.
In the evolution of virus mutations, the following applies: The strongest variant prevails. In the case of the coronavirus, this means that variants that are more infectious, for example, suppress the less dangerous forms of the virus.
What Is A Sars
When viruses are transmitted from one person to another, some of the new variants will be better at entering cells or duplicating themselves than others.
In these cases, the fitter variants are more likely to take over and become the main virus that replicates within a population.
Over the course of the pandemic, this has occurred several times. The original SARS-CoV-2 virus that emerged from Wuhan in 2019 was later replaced by a variant called D614G, followed by the Alpha variant and now, the Delta variant.
Every time someone gets infected with SARS-CoV-2, there is a chance the virus could generate a more fit variant, which could then spread to others.
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Needless To Say These Solutions Are On Top Of The Current Hand Washing And Physical Distance Methods
Image credits: michaelmina_lab
In short, Mina explained how mutations are a likely possibilitywe already see it happening in the UKso we cant rely on this one very niche set of vaccines to keep the virus at bay. It hasnt mutated to an extent that would cause alarm, but why risk it?
So, Mina proposes first diversifying the vaccines to include a more varied set of proteins for our immunity to be aware of and killed-virus vaccines , among other variants.
Second, considering that the new variants have not yet escaped immunity but seem more transmissible, it is important to consider how current vaccine development could be sped up.
Lastly, theres a need to scale up frequent accessible rapid testing for at-home, office, and school use. This should help slow the spread and would not be hindered by mutations.
Image credits: michaelmina_lab
This is, of course, on top of the now-common precautions of wearing masks, keeping up to hygiene standards, and staying at home.
The tweet thread led to many people responding. For the most part, people were debating and asking questionsin fact, you can go and read through the response that Mina gave in the thread here.
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Could A New Covid
Ray says that widespread infection with the delta variant has resulted in an increased number of cases in children, including uncommon severe infections and deaths.
There is no convincing evidence that any of the variants have special propensity to infect or cause disease in children. We need to be vigilant in monitoring such shifts, but we can only speculate at this point, he says.
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Read More About The Spread Of Covid
Omicron is the latest COVID variant of concern to be identified by the World Health Organization .
“It’s interesting because it carries more mutations than the other variants of concern we’ve seen so far,” Dr Juno said.
When scientists first looked at Omicron’s genetic sequence, they found more than 50 mutations, 32 of which are on the all-important spike protein.
Of particular concern is the fact that several of Omicron’s mutations have been seen in other variants and are associated with increased transmissibility and the ability to evade immune protection.
“It’s the same basic virus, the same genetic structure, and it’s got mostly the same sequence,”Eddie Holmes, a leading viral evolution expert at the University of Sydney, told the Health Report.
“But the spike protein the protein that sits on the surface of the virus that interacts with host cells, the one that we use our vaccines to work against that’s very, very different.
“It’s a reconfiguration of what we had before.”
Of the more than 30 mutations found on the spike protein, 10 are located in the “receptor-binding domain” the part that interacts with the body’s ACE-2 receptors and mediates the virus’s entry into our cells.
” is certainly novel in that respect,” Professor Holmes said.
“The really key question is how well the vaccines will prevent infection and more importantly, disease.”
So Where Did Omicron Come From
The recent reports of a new variant of concern, Omicron, has raised global alarm bells.
Discovered by the impressive virus sequencing efforts of South African scientists, Omicron contains an incredible 32 changes in the spike protein alone. This includes mutations that can increase transmission and evade immunity.
So there is a risk that Omicron may spread rapidly and reduce the effectiveness of current vaccines.
Read more:The hunt for coronavirus variants: how the new one was found and what we know so far
With low overall vaccination coverage in southern Africa , some have suggested global inequities in the supply of COVID vaccines may be responsible for the emergence of Omicron.
However, the extensive mutations in Omicron are also consistent with the virus changing over an extended time, as it replicated in a person with a compromised immune system.
Such highly mutated variants have been documentedin the past but have generally not spread widely.
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Can Vaccination Promote Mutations At All
Theoretically, however, there is the possibility that vaccinations exert an immunological pressure on the virus, says Georg Behrens. “Then it tries to escape this pressure through such a mutation,” he said.
That is because the virus is currently encountering populations that are only partially vaccinated. As a result, some people have an immune response, while others still offer the possibility of becoming infected. “That’s what the virus loves,” said Behrens. “And this can lead to other mutations. This is how the virus trains itself, basically.”
In summary: In very rare cases, vaccinations can cause mutations to arise and theoretically promote their spread, but it is much more likely that dangerous mutations are created where a virus can spread quickly and unhindered.
This article was translated from German.
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The Return Of The Revenge Of Predictions Of Global Disaster By Geert Vanden Bossche
What is Geert Vanden Bossche up to these days? What is he claiming now? Whats led to all the social media chatter about his latest claims, examples of which include:
Juan Morales
I cant help but note right here why Bret Weinstein, promoter of the unproven anti-helminthic drug ivermectin that he is, loves Geert Vanden Bossches message. Right in the very first summary paragraph of his blog post, Vanden Bossche advocates for, in addition to calling an immediate halt to the mass vaccination program for COVID-19, replacing it by widespread use of antiviral chemoprophylactics while dedicating massive public health resources to scaling early multidrug treaments of Covid-19 disease.You can also see why antivaxxers love the message, which is yet another variant of the favorite antivaccine trope that it is the vaccinated who spread disease, not the unvaccinated.
I cant help but cite Andrew Wakefield again regarding measles, just to remind you how similar this argument is to Wakefields:
So Vanden Bossche issues a dire warning:
As noted by Alexis Madrigal, founder of the COVID Tracking Project:
Madrigal also notes that there is a lot of randomness to where the worst outbreaks occur during pandemics, and this one is no different:
Vanden Bossche seems to sense that this is a weakness in his argument, which appears to be why he pivots to the Lambda variant:
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Why This Years Flu Vaccine May Not Work For You
Flu viruses do this all the time. The mutations are called drift and vaccines, formulated months in advance, often don’t protect well against drifted viruses although they may provide a little of what’s called cross protection.
“We are recommending strongly still that people who havent been vaccinated get vaccinated. Every year vaccine is the best way to protect yourself against the flu,” the CDC’s flu expert Dr. Joe Bresee told NBC News.
Though reduced, this cross-protection might reduce the likelihood of severe outcomes such as hospitalization and death, CDC said in a health advisory to doctors. And the vaccine still protects against half the circulating H3N2,as well as H1N1 flu and the B strains.
“Cross-protection might reduce the likelihood of severe outcomes such as hospitalization and death.”
So CDC sticks with its advice that everyone six months and older should get a flu vaccine every year.
But because even vaccinated people may be more vulnerable than usual, CDC is reminding doctors they can and should use two antiviral drugs to treat flu and in some cases to prevent it. Theyre called Tamiflu and Relenza, and giving them to people within a day or two of infection can keep them out of the hospital and reduce how long theyre sick.
For people in nursing homes and other institutions where flu is a big danger, doctors should think about using the drugs to prevent infection, CDC said.
Last season, it was H1N1 flu that affected the most people.
How Can We Prevent Future New Variants Of The Covid
Stopping the spread at the source remains key. Current measures to reduce transmission including frequent hand washing, wearing a mask, physical distancing, good ventilation and avoiding crowded places or closed settings continue to work against new variants by reducing the amount of viral transmission and therefore also reducing opportunities for the virus to mutate.
Scaling up vaccine manufacturing and rolling out vaccines as quickly and widely as possible will also be critical ways of protecting people before they are exposed to the virus and the risk of new variants. Priority should be given to vaccinating high-risk groups everywhere to maximize global protection against new variants and minimize the risk of transmission. Moreover, ensuring equitable access to COVID-19 vaccines is more critical than ever to address the evolving pandemic. As more people get vaccinated, we expect virus circulation to decrease, which will then lead to fewer mutations.
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Global Vaccine Coverage Benefits Us All
Expanding global vaccine coverage by increasing supplies, ensuring equitable distribution, and combating hesitancy and misinformation remains critical.
High global vaccine coverage will limit overall viral evolution, protect immunocompromised people and lessen chances highly mutated viruses can spread, all of which can directly or indirectly lower the risks of new variants emerging.
With the global community now highly interconnected, countries will struggle to keep their citizens safe in the face of pandemic threats without embracing a framework for greater international cooperation and coordination.
The Effects Of Virus Variants On Covid
This article is part of a series of explainers on vaccine development and distribution. Learn more about vaccines from how they work and how theyre made to ensuring safety and equitable access in WHOs Vaccines Explained series.
All viruses including SARS-CoV-2, the virus that causes COVID-19 evolve over time. When a virus replicates or makes copies of itself, it sometimes changes a little bit, which is normal for a virus. These changes are called mutations. A virus with one or more new mutations is referred to as a variant of the original virus.
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But These Measurements Are Complex
However, there are few reasons why this isnt necessarily the case. A key thing to consider is the timing of viral load measurement. Viral load is usually only measured at a single point in time in most people often shortly after symptoms appear, when the infection is in full swing. But if the virus is cleared much more quickly in vaccinated people, this would be missed by most reports. The window of time when a vaccinated person is infectious and the amount of viral replication going on in their body could be much lower than anticipated.
Another reason why viral replication may apparently be similar in both vaccinated and unvaccinated people is the way that peak viral load is typically measured. Its most often determined by quantitative PCR , which measures how many copies of the viruss genetic material are present, not the number of actual infectious viral particles.
Whether there are infectious copies of the virus in someone can only be accurately assessed by extracting the virus, adding it to cells in a lab and seeing if more viral particles are created. Studies have shown that detecting the viruss genetic material doesnt always mean infectious virus is present.
Indeed, a recent Swiss preprint suggests that measuring viral load by qPCR at a single time point doesnt tell the whole story. This study measured the amount of virus in samples from 384 infected people for five consecutive days after their symptoms started.