A lab at the center of a longstanding controversy about dangerous virus research has engineered heartier influenza viruses that could streamline vaccine production. The researchers contend that their findings may help bring future pandemics under control faster—but the study also demonstrates the risk of curtailing so-called gain-of-function (GOF) studies, in which viruses are made more transmissible or more pathogenic, the researchers argue.
The U.S. government suspended funding of GOF studies last year and ordered a review of their risks and benefits. The current work, by Yoshihiro Kawaoka's group at the University of Wisconsin, Madison, was performed before that happened; it's not clear whether its funding would have been stopped.
The team set out to address a perennial problem in the production of influenza vaccines. To keep up with the ever-mutating flu virus, researchers each year create new vaccines tailormade to combat the strains they expect to dominate. Every year, it's a scramble to produce the vaccines in time for the flu season.
The viruses used to make vaccines typically contain a "backbone" of six genes that remains the same, plus two variable genes that code for proteins that stud the viral surface. These surface proteins are critical for infection and transmission, but when used in the vaccine, they teach the body how to make antibodies that can thwart the disease. Every year, vaccinemakers build viruses that have the standard backbone plus the surface proteins currently in circulation.
Most companies then grow these viruses in eggs, but more recently, some have started using mammalian cells—like those from dog or monkey kidneys—as a growth medium. The viruses are killed and purified to make the vaccine.
In the new study, Kawaoka's team randomly mutated the genes in the backbone of the virus to create a large library of variants and then tested them with a wide variety of different surface proteins. As the investigators explain online today in Nature Communications, they found a novel backbone that dramatically increased the yield of the viruses, both in eggs and mammalian cells—in some cases more than 200-fold. The researchers did extensive studies to unravel the molecular mechanisms that led to the improved replication, but they came up with more hints than clear-cut answers.
The new backbone could help streamline annual vaccine production, which could be especially relevant during a pandemic, notes Kawaoka’s group, when the sudden emergence of novel strains forces companies to rapidly make millions of doses of a new vaccine. When a novel H1N1 strain emerged in 2009, for instance, most vaccine doses didn't arrive until after the ensuing pandemic had hit its peak.
The study "tackles a question that is of great pragmatic importance for vaccines,” says virologist Gary Nabel in Cambridge, Massachusetts, who is the chief scientific officer at Sanofi, which makes influenza vaccines. “If you can't make enough vaccine at an acceptable cost, it won't be available to many who need it. The Kawaoka paper takes a logical and systematic approach to achieve this goal.”
Kawaoka’s group conducted its study in part with funding from the U.S. National Institute of Allergy and Infectious Diseases (NIAID). Last October, the U.S. government paused funding of all GOF experiments with influenza that could be “reasonably anticipated” to increase transmissibility or pathogenicity, and asked researchers to halt ongoing work. Kawaoka, who had completed his study at that time, says the policy would have brought the research to a halt because the team was specifically looking for viruses that reproduced faster. “I don’t think people who are seriously concerned about [GOF studies] are concerned about this type of work,” he says. “The net was cast too wide.”
But NIAID Director Anthony Fauci says “it is very likely” that Kawaoka's group would have been granted an exemption and continued to receive funding because the study specifically aims to improve vaccines against influenza. “In the past, we have granted exemptions for similar studies,” Fauci says. He notes that the new study is especially relevant because it worked in mammalian cells, which ultimately are a better way to grow the virus than eggs: It’s a faster production system and avoids mutations that occur when the virus adapts to chicken eggs, which can compromise vaccine effectiveness.
Kawaoka stresses that the experiment did not create dangerous viruses or give out clues about how to engineer them. Flu viruses with the new backbone only marginally increased the severity of disease in mice, the team found. And even if they were more dangerous than common flu strains, it would not make any difference because manufacturers kill the virus as part of the vaccine production process, notes the group. Kawaoka also says he doubts that anyone could glean information from their paper that could help construct more deadly human influenza viruses. “We have no idea whether these mutations would make other influenza viruses more pathogenic or transmissible,” he says.
The National Science Advisory Board for Biosecurity (NSABB), which advises the U.S. government on GOF research policies, is awaiting a risk/benefit analysis being done by Gryphon Scientific. As part of this assessment, the Infectious Diseases Society of America on 10 August submitted recommendations urging NSABB to narrow its definition of GOF research so that "low risk studies" such as Kawaoka's can proceed.
Former NSABB member Arturo Casadevall, an immunologist at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, describes Kawaoka’s new work as “tremendously important” and says it should give the policymakers pause. “Moratoriums and pauses are blunt instruments,” Casadevall wrote in an email. “I worry that even if exclusions are made for certain experiments so that they continue, the GOF controversy combined with its pauses/moratoriums has already created an environment where scientists may be discouraged from experimental work that is clearly in the public interest. I hope that the NSABB takes notice of this paper as an example of the potential value of these experiments.”