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From Cell Press:  New Insights on the D614G Strain of COVID: Will a New Mutated Strain Delay Vaccine Development?

Reporter: Stephen J. Williams, PhD

Two recent articles in Cell Press, both peer reviewed, discuss the emergence and potential dominance of a new mutated strain of COVID-19, in which the spike protein harbors a D614G mutation.

In the first article “Making Sense of Mutation: What D614G means for the COVID-19 pandemic Remains Unclear”[1] , authors Drs. Nathan Grubaugh, William Hanage, and Angela Rasmussen discuss the recent findings by Korber et al. 2020 [2] which describe the potential increases in infectivity and mortality of this new mutant compared to the parent strain of SARS-CoV2.  For completeness sake I will post this article as to not defer from their interpretations of this important paper by Korber and to offer some counter opinion to some articles which have surfaced this morning in the news.

Making sense of mutation: what D614G means for the COVID-19 pandemic remains unclear

 

Nathan D. Grubaugh1 *, William P. Hanage2 *, Angela L. Rasmussen3 * 1Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT 06510, USA 2Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, MA 02115, USA 3Center for Infection and Immunity, Columbia Mailman School of Public Health, New York, NY 10032, USA Correspondence: grubaughlab@gmail.com

 

Abstract: Korber et al. (2020) found that a SARS-CoV-2 variant in the spike protein, D614G, rapidly became dominant around the world. While clinical and in vitro data suggest that D614G changes the virus phenotype, the impact of the mutation on transmission, disease, and vaccine and therapeutic development are largely unknown.

Introduction: Following the emergence of SARS-CoV-2 in China in late 2019, and the rapid expansion of the COVID19 pandemic in 2020, questions about viral evolution have come tumbling after. Did SARS-CoV-2 evolve to become better adapted to humans? More infectious or transmissible? More deadly? Virus mutations can rise in frequency due to natural selection, random genetic drift, or features of recent epidemiology. As these forces can work in tandem, it’s often hard to differentiate when a virus mutation becomes common through fitness or by chance. It is even harder to determine if a single mutation will change the outcome of an infection, or a pandemic. The new study by Korber et al. (2020) sits at the heart of this debate. They present compelling data that an amino acid change in the virus’ spike protein, D614G, emerged early during the pandemic, and viruses containing G614 are now dominant in many places around the world. The crucial questions are whether this is the result of natural selection, and what it means for the COVID-19 pandemic. For viruses like SARS-CoV-2 transmission really is everything – if they don’t get into another host their lineage ends. Korber et al. (2020) hypothesized that the rapid spread of G614 was because it is more infectious than D614. In support of their hypothesis, the authors provided evidence that clinical samples from G614 infections have a higher levels of viral RNA, and produced higher titers in pseudoviruses from in vitro experiments; results that now seem to be corroborated by others [e.g. (Hu et al., 2020; Wagner et al., 2020)]. Still, these data do not prove that G614 is more infectious or transmissible than viruses containing D614. And because of that, many questions remain on the potential impacts, if any, that D614G has on the COVID-19 pandemic.

The authors note that this new G614 variant has become the predominant form over the whole world however in China the predominant form is still the D614 form.  As they state

“over the period that G614 became the global majority variant, the number of introductions from China where D614 was still dominant were declining, while those from Europe climbed. This alone might explain the apparent success of G614.”

Grubaugh et al. feel there is not enough evidence that infection with this new variant will lead to higher mortality.  Both Korber et al. and the Seattle study (Wagner et al) did not find that the higher viral load of this variant led to a difference in hospitalizations so apparently each variant might be equally as morbid.

In addition, Grubaugh et al. believe this variant would not have much affect on vaccine development as, even though the mutation lies within the spike protein, D614G is not in the receptor binding domain of the spike protein.  Korber suggest that there may be changes in glycosylation however these experiments will need to be performed.  In addition, antibodies from either D614 or G614 variant infected patients could cross neutralize.

 

Conclusions: While there has already been much breathless commentary on what this mutation means for the COVID19 pandemic, the global expansion of G614 whether through natural selection or chance means that this variant now is the pandemic. As a result its properties matter. It is clear from the in vitro and clinical data that G614 has a distinct phenotype, but whether this is the result of bonafide adaptation to human ACE2, whether it increases transmissibility, or will have a notable effect, is not clear. The work by Korber et al. (2020) provides an early base for more extensive epidemiological, in vivo experimental, and diverse clinical investigations to fill in the many critical gaps in how D614G impacts the pandemic.

The link to the Korber Cell paper is here: https://www.cell.com/cell/fulltext/S0092-8674(20)30820-5

Tracking changes in SARS-CoV-2 Spike: evidence that D614G increases infectivity of the COVID-19 virus

DOI: https://doi.org/10.1016/j.cell.2020.06.043

Keypoints

  • The consistent increase of G614 at regional levels may indicate a fitness advantage

 

  • G614 is associated with lower RT PCR Ct’s, suggestive of higher viral loads in patients

 

  • The G614 variant grows to higher titers as pseudotyped virions

Summary

A SARS-CoV-2 variant carrying the Spike protein amino acid change D614G has become the most prevalent form in the global pandemic. Dynamic tracking of variant frequencies revealed a recurrent pattern of G614 increase at multiple geographic levels: national, regional and municipal. The shift occurred even in local epidemics where the original D614 form was well established prior to the introduction of the G614 variant. The consistency of this pattern was highly statistically significant, suggesting that the G614 variant may have a fitness advantage. We found that the G614 variant grows to higher titer as pseudotyped virions. In infected individuals G614 is associated with lower RT-PCR cycle thresholds, suggestive of higher upper respiratory tract viral loads, although not with increased disease severity. These findings illuminate changes important for a mechanistic understanding of the virus, and support continuing surveillance of Spike mutations to aid in the development of immunological interventions.

 

References

  1. Grubaugh, N.D., Hanage, W.P., Rasmussen, A.L., Making sense of mutation: what D614G means for the COVID-19 pandemic remains unclear, Cell (2020), doi: https:// doi.org/10.1016/j.cell.2020.06.040.
  2. Korber, B., Fischer, W.M., Gnanakaran, S., Yoon, H., Theiler, J., Abfalterer, W., Hengartner, N., Giorgi, E.E., Bhattacharya, T., Foley, B., et al. (2020). Tracking changes in SARS-CoV-2 Spike: evidence that D614G increases infectivity of the COVID-19 virus. Cell 182.
  3. Endo, A., Centre for the Mathematical Modelling of Infectious Diseases COVID-19 Working Group, Abbott, S., Kucharski, A.J., and Funk, S. (2020). Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China. Wellcome Open Res 5, 67.
  4. Hu, J., He, C.-L., Gao, Q.-Z., Zhang, G.-J., Cao, X.-X., Long, Q.-X., Deng, H.-J., Huang, L.-Y., Chen, J., Wang, K., et al. (2020). The D614G mutation of SARS-CoV-2 spike protein enhances viral infectivity and decreases neutralization sensitivity to individual convalescent sera. bioRxiv 2020.06.20.161323.
  5. Wagner, C., Roychoudhury, P., Hadfield, J., Hodcroft, E.B., Lee, J., Moncla, L.H., Müller, N.F., Behrens, C., Huang, M.-L., Mathias, P., et al. (2020). Comparing viral load and clinical outcomes in Washington State across D614G mutation in spike protein of SARS-CoV-2. Https://github.com/blab/ncov-D614G.

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UPDATED 12/05/2020

 

 

 

 

 

 

In the future, George Church believes, almost everything will be better because of genetics. If you have a medical problem, your doctor will be able to customize a treatment based on your specific DNA pattern. When you fill up your car, you won’t be draining the world’s dwindling supply of crude oil, because the fuel will come from microbes that have been genetically altered to produce biofuel. When you visit the zoo, you’ll be able to take your children to the woolly mammoth or passenger pigeon exhibits, because these animals will no longer be extinct. You’ll be able to do these things, that is, if the future turns out the way Church envisions it—and he’s doing everything he can to see that it does.

UPDATED 12/05/2020

George Church backs a startup solution to the massive gene therapy manufacturing bottleneck

Source: https://endpts.com/george-church-backs-a-startup-solution-to-the-massive-gene-therapy-manufacturing-bottleneck/
Jason Mast: Associate Editor
George Church and his graduate students have spent the last decade seeding startups on the razor’s edge between biology and science fiction: gene therapy to prevent aging, CRISPRed pigs that can be used to harvest organs for transplant, and home kits to test your poop for healthy or unhealthy bacteria. (OK, maybe they’re not all on that razor’s edge.)

But now a new spinout from the Department of Genetics’ second floor is tackling a far humbler problem — one that major company after major company has stumbled over as they tried to get cures for rare diseases and other gene therapies into the clinic and past regulators: How the hell do you build these?

CEO Lex Vovner of 64x Bio

 

 

 

“There’s a lot happening for new therapies but not enough attention around this problem,” Lex Rovner, who was a post-doc at Church’s lab from 2015 to 2018, told Endpoints News. “And if we don’t figure out how to fix this, many of these therapies won’t even reach patients.”

This week, with Church and a couple other prominent scientists as co-founders, Rovner launched 64x Bio to tackle one key part of the manufacturing bottleneck. They won’t be looking to retrofit plants or build gene therapy factories, as Big Pharma and big biotech are now spending billions to do. Instead, with $4.5 million in seed cash, they will try to engineer the individual cells that churn out a critical component of the therapies.

George Church
The goal is to build cells that are fine-tuned to do nothing but spit out the viral vectors that researchers and drug developers use to shuttle gene therapies into the body. Different vectors have different demands; 64x Bio will look to make efficient cellular factories for each.

“While a few general ways to increase vector production may exist, each unique vector serotype and payload poses a specific challenge,” Church said in an emailed statement. “Our platform enables us to fine tune custom solutions for these distinct combinations that are particularly hard to overcome.”

Before joining Church’s lab, Rovner did her graduate work at Yale, where she studied how to engineer bacteria to produce new kinds of protein for drugs or other purposes. And after leaving Church’s lab in 2018, she initially set out to build a manufacturing startup with a broad focus.

Yet as she spoke with hundreds of biotech executives on LinkedIn and in coffee shops around Cambridge, the same issue kept popping up: They liked their gene therapy technology in the lab but they didn’t know how to scale it up.

“Everyone kept saying the same thing,” Rovner said. “We basically realized there’s this huge problem.”

The issue would soon make headlines in industry publications: bluebird delaying the launch of Zynteglo, Novartis delaying the launch of Zolgensma in the EU, Axovant delaying the start of their Parkinson’s trial.

Part of the problem, Rovner said, is that gene therapies are delivered on viral vectors. You can build these vectors in mammalian cell lines by feeding them a small circular strand of DNA called a plasmid. The problem is that mammalian cells have, over billions of years, evolved tools and defenses precisely to avoid making viruses. (Lest the mammal they live in die of infection).

There are genetic mutations that can turn off some of the internal defenses and unleash a cell’s ability to produce virus, but they’re rare and hard to find. Other platforms, Rovner said, try to find these mutations by using CRISPR to knock out genes in different cells and then screening each of them individually, a process that can require hundreds of thousands of different 100-well plates, with each well containing a different group of mutant cells.

“It’s just not practical, and so these platforms never find the cells,” Rovner said.

64x Bio will try to find them by building a library of millions of mutant mammalian cells and then using a molecular “barcoding” technique to screen those cells in a single pool. The technique, Rovner said, lets them trace how much vector any given cell produces, allowing researchers to quickly identify super-producing cells and their mutations.

The technology was developed partially in-house but draws from IP at Harvard and the Wyss Institute. Harvard’s Pam Silver and Wyss’s Jeffrey Way are co-founders.

The company is now based in SoMa in San Francisco. With the seed cash from Fifty Years, Refactor and First Round Capital, Rovner is recruiting and looking to raise a Series A soon. They’re in talks with pharma and biotech partners, while they try to validate the first preclinical and clinical applications.

Gene therapy is one focus, but Rovner said the platform works for anything that involves viral vector, including vaccines and oncolytic viruses. You just have to find the right mutation.

“It’s the rare cell you’re looking for,” she said.

AUTHOR
Jason Mast
Associate Editor
jason@endpointsnews.com
@JasonMMast
Jason Mas

 

In 2005 he launched the Personal Genome Project, with the goal of sequencing and sharing the DNA of 100,000 volunteers. With an open-source database of that size, he believes, researchers everywhere will be able to meaningfully pursue the critical task of correlating genetic patterns with physical traits, illnesses, and exposure to environmental factors to find new cures for diseases and to gain basic insights into what makes each of us the way we are. Church, tagged as subject hu43860C, was first in line for testing. Since then, more than 13,000 people in the U.S., Canada, and the U.K. have volunteered to join him, helping to establish what he playfully calls the Facebook of DNA.

 

Church has made a career of defying the impossible. Propelled by the dizzying speed of technological advancement since then, the Personal Genome Project is just one of Church’s many attempts to overcome obstacles standing between him and the future.

 

“It’s not for everyone,” he says. “But I see a trend here. Openness has changed since many of us were young. People didn’t use to talk about sexuality or cancer in polite society. This is the Facebook generation.” If individuals were told which diseases or medical conditions they were genetically predisposed to, they could adjust their behavior accordingly, he reasoned. Although universal testing still isn’t practical today, the cost of sequencing an individual genome has dropped dramatically in recent years, from about $7 million in 2007 to as little as $1,000 today.

 

“It’s all too easy to dismiss the future,” he says. “People confuse what’s impossible today with what’s impossible tomorrow.”, especially through the emerging discipline of “synthetic” biology. The basic idea behind synthetic biology, he explained, was that natural organisms could be reprogrammed to do things they wouldn’t normally do, things that might be useful to people. In pursuit of this, researchers had learned not only how to read the genetic code of organisms but also how to write new code and insert it into organisms. Besides making plastic, microbes altered in this way had produced carpet fibers, treated wastewater, generated electricity, manufactured jet fuel, created hemoglobin, and fabricated new drugs. But this was only the tip of the iceberg, Church wrote. The same technique could also be used on people.

 

“Every cell in our body, whether it’s a bacterial cell or a human cell, has a genome,” he says. “You can extract that genome—it’s kind of like a linear tape—and you can read it by a variety of methods. Similarly, like a string of letters that you can read, you can also change it. You can write, you can edit it, and then you can put it back in the cell.”

 

This April, the Broad Institute, where Church holds a faculty appointment, was awarded a patent for a new method of genome editing called CRISPR (clustered regularly interspersed short palindromic repeats), which Church says is one of the most effective tools ever developed for synthetic biology. By studying the way that certain bacteria defend themselves against viruses, researchers figured out how to precisely cut DNA at any location on the genome and insert new material there to alter its function. Last month, researchers at MIT announced they had used CRISPR to cure mice of a rare liver disease that also afflicts humans. At the same time, researchers at Virginia Tech said they were experimenting on plants with CRISPR to control salt tolerance, improve crop yield, and create resistance to pathogens.

 

The possibilities for CRISPR technology seem almost limitless, Church says. If researchers have stored a genetic sequence in a computer, they can order a robot to produce a piece of DNA from the data. That piece can then be put into a cell to change the genome. Church believes that CRISPR is so promising that last year he co-founded a genome-editing company, Editas, to develop drugs for currently incurable diseases.

Source: news.nationalgeographic.com

See on Scoop.itCardiovascular and vascular imaging

 

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