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Gain of function research explained

9 September 2021 by Vincent Racaniello

ferret

The term ‘gain of function’ is perhaps one of the most misunderstood in the scientific lexicon. I would like to explain what the phrase means from the perspective of a scientist who has done gain of function research for the past 40 years.

Gain of function (GoF) research gives an organism a new property or enhances an existing one. The organism can be a virus, bacterium, fungus, rodent, bird, fish or anything that can be experimentally manipulated (technically whales and elephants could be included in the definition but it would be very difficult to to GoF research on them).

Many have the impression that GoF research involves making an organism more deadly – for example, increasing the capacity of a virus to cause disease. That impression is incorrect. Certainly GoF research might lead to a more dangerous organism, but most of the time that is not the goal.

There are two broad approaches to GoF research. I’ll illustrate them with viruses but the principles could apply to any organism. In one approach, a virus is passaged in a host until a virus with different properties is obtained. An example is the adaptation of a strain of poliovirus – the type 2 Lansing strain – to replicate in mice and paralyze them. The Lansing strain does not infect mice, but an investigator passed the virus 99 times from mouse to mouse and ended up with a new strain that could now paralyze the mice. The new version of the virus had a new property – it could now infect mice. This experiment was GoF research.

Another way to do GoF research is to use recombinant DNA technology to engineer changes in the genome of the organism. In experiments done in my laboratory, we took a small piece of the genome of the mouse-adapted Lansing strain of poliovirus – coding for just eight amino acids – and spliced it into the genome of another poliovirus that is unable to infect mice. The recombinant virus from this experiment had a new property – the ability to infect mice. This experiment would also be classified as GoF.

An illustration of how GoF can be done on mice is our creation of transgenic mice susceptible to poliovirus. Mice cannot be infected with the virus because they do not produce the cell receptor for poliovirus. We introduced the human poliovirus receptor gene into the mouse germline, leading to mice that produce poliovirus receptor. After infection, these poliovirus receptor transgenic mice can be infected with poliovirus and develop paralysis. The mice have a new property – susceptibility to poliovirus infection. The mice are a product of a GoF experiment.

GoF research may have a myriad of useful outcomes. Do you want to make a different tasting beer? Modify an enzyme in the yeast used for fermentation. But in the past 30 years GoF research has received a bad name. The catalyst was a series of experiments on highly pathogenic avian H5N1 influenza viruses. These viruses rarely infect humans and do not transmit well among people. In experiments to understand what limited transmission, the virus was genetically modified and passaged among ferrets. The result was a virus that could transmit among ferrets by respiratory droplets. These GoF experiments were met with criticism, entirely unwarranted as the passaged viruses had lost their virulence for ferrets! Nevertheless since then a dark cloud has unjustifiably hung over all GoF research.

GoF research has been in the press again recently as a consequence of the COVID-19 pandemic. After the SARS-CoV pandemic of 2003, wildlife sampling efforts in China revealed many SARS-like coronaviruses in bats. To assess the potential of these viruses for infecting humans, their spike protein encoding genes were substituted into the SARS-like CoV WIV1. These recombinant viruses reproduced in human airway cells – no different from WIV1 – but at least one caused more severe disease in mice. Consequently these are GoF experiments. Some have suggested that such GoF work gave rise to SARS-CoV-2 in a lab, but this notion is impossible, as none of these viruses are close enough to be a precursor of the current pandemic virus.

The production of recombinant coronaviruses to assess pandemic potential was carried out in several laboratories, all funded by the NIH. Recently Dr. Anthony Fauci told Congress that the NIH did not fund GoF coronavirus research. The press has suggested that he lied, but the truth is that his definition of GoF research is that it only involves passaged of organisms in animals. This interpretation is not correct but being wrong does not mean you are lying.

I want readers to understand that the goals of GoF research are laudable, and only a small subset has the potential to harm humans. Consequently these experiments are highly regulated and carried out under high levels of biological containment. GoF is not a dirty word.

Filed Under: Basic virology Tagged With: avian influenza virus, coronavirus, COVID-19, ferret, gain of function research, GOF, pandemic, viral, virology, virus, viruses

TWiV 693: Vax to the future

16 December 2020 by Vincent Racaniello

On this episode, FDA EUA for Pfizer mRNA vaccine, efficacy of AstraZeneca ChAdOx1 COVID-19 vaccine, and an orally administered drug that blocks SARS-CoV-2 transmission in ferrets.

Hosts: Vincent Racaniello, Dickson Despommier, Alan Dove, Rich Condit, and Brianne Barker

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Show notes at microbe.tv/twiv

Filed Under: This Week in Virology Tagged With: antiviral drug, ChAdOx1, coronavirus, COVID-19, EIDD-2801, ferret, MK-4482, mRNA vaccine, nucleoside analog, pandemic, Pfizer, SARS-CoV-2, vaccine, viral, virology, virus, virus transmission, viruses

An antiviral compound that blocks SARS-CoV-2 transmission in ferrets

11 December 2020 by Vincent Racaniello

COVID-19 vaccine candidates are garnering all the news these days, which is appropriate as they are our key to ending this pandemic. Earlier in this outbreak antiviral drugs received a good deal of attention, but they have proven less useful in curtailing infection. Less discussed are the many antiviral drug candidates that are in testing, including one that appears to be effective in a ferret model of infection.

MK-4482 is an orally available pro-drug of the nucleoside analog N4-hydroxycytidine (NHC) (pictured above). The latter is a nucleoside analogue which is incorporated into RNA by the viral RNA-dependent RNA polymerase. Once incorporated into RNA, NHC is recognized as either C or U by the RNA polymerase. As a consequence, many mutations are introduced into the viral genome, causing lethal mutagenesis and inhibition of infectivity. NHC has been previously shown to have broad-spectrum anti-RNA virus activity and blocks transmission of influenza virus in a guinea pig model of infection.

When ferrets are inoculated intransally with SARS-CoV-2, the virus reproduces efficiently in the upper and lower respiratory tract. Infectious virus is detectable in nasal wash up to 7 days post-infection. The animals lose weight but do not succumb to disease. Oral administration of MK-4482 at 12 or 36 hours after infection, followed by treatment twice daily for 3.5 days, leads to complete clearance of infectious virus 24 – 36 hours later, demonstrating oral efficacy of therapeutic administration of the drug in ferrets.

To assess whether MK-4482 can impact transmission of SARS-CoV-2, animals were inoculated intranasally with virus and then co-housed with naive animals 30 hours later for 3 days. In experiments with untreated animals, all co-housed ferrets became infected. In contrast, when ferrets were treated with MK-4482 12 hours after infection, they did not transmit infection to co-housed animals, demonstrating that NHC can block transmission when given 12 hours after infection.

These results are promising and justify studies of the efficacy of MK-4482 in humans. The drug has already passed phase I safety trials which revealed that the drug reaches concentrations in the blood that exceed the antiviral level needed for inhibition of SARS-CoV-2 in cell culture. Consequently efficacy trials in humans appear to be warranted.

My one main concern with this study is that the drug was only administered to ferrets 12 and 36 hours after infection. It would be important to know how long after infection the drug can be administered and still limit infection and transmission. If, like the influenza antivirals Tamiflu and Relenza, the drug must be administered 24-48 hours after infection to have an effect on disease outcome, the usefulness might be limited.

With COVID-19 vaccines advancing in many countries, does it still make sense to pursue clinical development of antiviral compounds? The answer is yes. Antiviral drugs might be used to stop outbreaks and prevent transmission. For example, if an outbreak is detected in a nursing home, all occupants could be treated to prevent spread of infection. Indeed, if compounds such as MK-4482 had been available in December 2019, it might have been possible to impede the spread of SARS-CoV-2 before it left China.

Filed Under: Basic virology, Information Tagged With: antiviral drug, coronavirus, COVID-19, EIDD-2801, ferret, MK-4482, N4-hydroxycytidine, NHC, pandemic, SARS-CoV-2, viral, virology, virus, viruses

Avian influenza virus transmission experiments proceed, as they should

4 April 2019 by Vincent Racaniello

ferretThe decision by the US government to allow the resumption of experiments on aerosol transmission of avian influenza viruses has once again raised the hackles of some individuals who feel that the work is too risky. I disagree with their view on this work.

Science reports that ‘Controversial lab studies that modify bird flu viruses in ways that could make them more risky to humans will soon resume after being on hold for more than 4 years’. Denise Grady of the New York Times wrote that “Research that could make flu viruses more dangerous” are set to resume. Note that the experiments done in the Kawaoka and Fouchier laboratories that allow aersol transmission of avian H5N1 viruses among ferrets discussed here previously actually made the viruses much less pathogenic. This fact is ignored in all the discourse about the work. [Read more…] about Avian influenza virus transmission experiments proceed, as they should

Filed Under: Basic virology, Commentary Tagged With: aerosol transmission, avian influenza, ferret, fouchier, gain of function, H5N1, influenza, kawaoka, viral, virology, virus, viruses

TWiV 396: Influenza viruses with Peter Palese

3 July 2016 by Vincent Racaniello

TWiVVincent speaks with Peter Palese about his illustrious career in virology, from early work on neuraminidases to universal influenza virus vaccines, on episode #396 of the science show This Week in Virology.

You can find TWiV #396 at microbe.tv/twiv, or listen below.

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Filed Under: This Week in Virology Tagged With: aerosol transmission, ferret, Flu, gain of function, H5N1, influenza, influenza virus, neuraminidase, relenza, swine flu, tamiflu, universal vaccine, vaccine, viral, virology, virus, viruses

Moving beyond metagenomics to find the next pandemic virus

14 March 2016 by Vincent Racaniello

I was asked to write a commentary for the Proceedings of the National Academy of Sciences to accompany an article entitled SARS-like WIV1-CoV poised for human emergence. I’d like to explain why I wrote it and why I spent the last five paragraphs railing against regulating gain-of-function experiments.

Towards the end of 2014 the US government announced a pause of gain-of-function research involving research on influenza virus, SARS virus, and MERS virus that “may be reasonably anticipated to confer attributes to influenza, MERS, or SARS viruses such that the virus would have enhanced pathogenicity and/or transmissibility in mammals via the respiratory route.”

From the start I have opposed the gain-of-function pause. It’s a bad idea fostered by individuals who continue to believe, among other things, that influenza H5N1 virus adapted to transmit by aerosol among ferrets can also infect humans by the same route. Instead of stopping important research, a debate on the merits and risks of gain-of-function experiments should have been conducted while experiments were allowed to proceed.

Towards the end of last year a paper was published a paper on the potential of SARS-virus-like bat coronaviruses to cause human disease. The paper reawakened the debate on the risks and benefits of engineering viruses. Opponents of gain-of-function research began to make incorrect statements about this work. Richard Ebright said that ‘The only impact of this work is the creation, in a lab, of a new, non-natural risk”. Simon Wain-Hobson wrote that a novel virus was created that “grows remarkably well” in human cells; “if the virus escaped, nobody could predict the trajectory”. I have written extensively about why these are other similar statements ignore the value of the work. In my opinion these critics either did not read the paper, or if they did, did not understand it.

Several months later I was asked to write the commentary on a second paper examining the potential of SARS like viruses in bats to cause human disease. I agreed to write it because the science is excellent, the conclusions are important, and it would provide me with another venue for criticizing the gain-of-function pause.

In the PNAS paper, Menachery et al. describe a platform comprising metagenomics data, synthetic virology, transgenic mouse models, and monoclonal antibody therapy to assess the ability of SARS-CoV–like viruses to infect human cells and cause disease in mouse models. The results indicate that a bat SARS-like virus, WIV1-CoV, can infect human cells but is attenuated in mice. Additional changes in the WIV1-CoV genome are likely required to increase the pathogenesis of the virus for mice. The same experimental approaches could be used to examine the potential to infect humans of other animal viruses identified by metagenomics surveys. Unfortunately my commentary is behind a paywall, so for those who cannot read it, I’d like to quote from my final paragraphs on the gain-of-function issue:

The current government pause on these gain-of-function experiments was brought about in part by several vocal critics who feel that the risks of this work outweigh potential benefits. On multiple occasions these individuals have indicated that some of the SARS-CoV work discussed in the Menachery et al. article is of no merit. … These findings provide clear experimental paths for developing monoclonal antibodies and vaccines that could be used should another CoV begin to infect humans. The critics of gain-of-function experiments frequently cite apocalyptic scenarios involving the release of altered viruses and subsequent catastrophic effects on humans. Such statements represent personal opinions that are simply meant to scare the public and push us toward unneeded regulation. Virologists have been manipulating viruses for years—this author was the first to produce, 35 y ago, an infectious DNA clone of an animal virus—and no altered virus has gone on to cause an epidemic in humans. Although there have been recent lapses in high-containment biological facilities, none have resulted in harm, and work has gone on for years in many other facilities without incident. I understand that none of these arguments tell us what will happen in the future, but these are the data that we have to calculate risk, and it appears to be very low. As shown by Menacherry et al. in PNAS, the benefits are considerable.

A major goal of life science research is to improve human health, and prohibiting experiments because they may have some risk is contrary to this goal. Being overly cautious is not without its own risks, as we may not develop the advances needed to not only identify future pandemic viruses and develop methods to prevent and control disease, but to develop a basic understand- ing of pathogenesis that guides prevention. These are just some of the beneficial outcomes that we can predict. There are many examples of how science has progressed in areas that were never anticipated, the so-called serendipity of science. Examples abound, including the discovery of restriction enzymes that helped fuel the biotechnology revolution, and the development of the powerful CRISPR/Cas9 gene-editing technology from its obscure origins as a bacterial defense system.

Banning certain types of potentially risky experiments is short sighted and impedes the potential of science to improve human health. Rather than banning experiments, such as those described by Menachery et al., measures should be put in place to allow their safe conduct. In this way science’s full benefits for society can be realized, unfettered by artificial boundaries.

Filed Under: Basic virology, Commentary, Information Tagged With: aerosol transmission, benefits, coronavirus, ferret, gain of function, H5N1, influenza, MERS, metagenomics, moratorium, pathogenicity, pause, risks, SARS, viral, virology, virus, viruses

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