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Chickens immunized with the spike protein of the pandemic coronavirus raise antibodies against it which are found in their eggs.
Charles River Avian
By Jon Cohen
ScienceCOVID-19 reports are supported by the Pulitzer Center and the Heising-Simons Foundation.
As the world waits for a widely available, safe and effective COVID-19 vaccine, scientists are becoming increasingly creative in their search for other ways to protect people from the disease. Now, a clinical trial has started in Australia to find out whether nasal drops containing anti-SARS-CoV-2 chicken antibodies can offer temporary protection.
The Stanford University team sponsoring the unusual Phase I study hopes the antibodies can protect people at increased risk of infection for several hours. If the idea comes to fruition – and there isn’t animal data yet to show it can work – people might sniff nasal drops before getting on an airplane, working in a crowded space, going into a college dorm or joining a family. “There is a huge opportunity,” says Daria Mochly-Rosen, Stanford protein chemist leading the project.
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Other protective nasal sprays are in development, but Stanford’s approach is exceptionally low-tech, relying on antibodies collected from egg yolks of chickens immunized with Spike, the surface protein of SARS-CoV. -2. The trial will assess the safety of these antibodies given intranasally and how long they persist in the nose. The research team also plans to test whether the antibody-laden nasal drops protect hamsters deliberately exposed to the coronavirus.
“The concept, in principle, sort of makes sense,” says Michael Diamond, an infectious disease clinician at Washington University St. Louis School of Medicine who is developing a nasally administered vaccine against COVID-19 . “But there are a few issues to consider. One is how long chicken antibodies will last before they break down, he says, and the other is whether humans will develop an immune response against them.
Mochly-Rosen is confident the antibodies will pass these tests, but says, “The proof is in the pudding” – the placebo-controlled safety trial currently underway in 48 people in Australia.
The project is part of SPARK, a Mochly-Rosen nonprofit organization launched in 2006 to help academics conduct proof of concept studies that could translate biomedical research ideas into medicines. Antibodies made in the laboratory for human drugs are expensive to develop and then to manufacture, typically relying on large numbers of cells grown in bioreactors. To make the chicken antibodies, on the other hand, the researchers inject the spike protein into the breasts of the chickens. Birds develop a vigorous immune response, which includes laying eggs containing antibodies against the coronavirus protein. Researchers collect the antibodies – a distinctive variety of chicken called immunoglobulin Y (IgY) – from the yolks and formulate the nasal drops. The team thinks a dose of the egg derivative could cost just $ 1.
The idea came from a director of Spark in Australia, Michael Wallach of the Sydney University of Technology, who made vaccines to protect chickens from disease and tested chicken antibodies in an influenza model of mouse. And there are precedents: Clinical trials are testing whether IgY gargle solutions can protect patients with cystic fibrosis from respiratory tract infection by Pseudomonas aeruginosa, while others are testing an IgY mouthwash to prevent dental plaque caused by Streptococcus mutans and a food supplement to treat Helicobacter pylori.
Mochly-Rosen argues that the antibody’s natural breakdown – the so-called half-life – in the nose is not what will limit the length of time it could protect a person. “It’s not the half-life of the drug that matters,” she says. “This is how quickly the nose releases the material that is introduced to it.” She notes that humans swallow more than a liter of mucus each day, which is washed away by cilia lining the nasal cavity. And she adds that large studies have not found anti-IgY antibodies in humans, even in chicken farmers who have antibodies to pig and rabbit proteins. (Diamond says this doesn’t apply to a nasal drip of IgY. “Normally we don’t sniff our chickens,” he says.)
In addition to the human trial, Mochly-Rosen and colleagues are evaluating anti-IgY responses in rats. She says a “challenge” study in hamsters, in which scientists gave them nasal drops and then tried to infect rodents and cause disease, was blocked because these animals remain rare.
Other researchers are considering nasal protections against COVID-19. A team led by scientists at Columbia University Medical Center showed in a preprint published on November 5 that they could protect ferrets from SARS-CoV-2 with a nasal spray containing a lipopeptide that binds to the peak and prevents the viruses to fuse with cells. Another group designed around 35,000 mimics of the angiotensin-2 converting enzyme, the main receptor the virus clings to, selected the strongest lure and then showed that when administered as a spray nasal, it protected hamsters from infection.
If the Australian trial establishes safety, reveals no obvious side effects, and finds no significant response against the chicken antibody, SPARK hopes to initiate an efficacy trial in the United States. “The number of patients with COVID-19 in Australia is zero, so we have to come back here,” says Mochly-Rosen, who has already started discussing such a study with the U.S. Food and Drug Administration.
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