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WASHINGTON: Scientists have discovered antibodies in the blood of recovered Covid-19 patients that provide powerful protection against SARS-CoV-2, the coronavirus that causes the disease, when tested in animals and human cell cultures.
Injections of such antibodies could, in principle, be given to patients in the early stage of Covid-19 to reduce the level of virus and protect against severe disease, according to the researchers from the Scripps Research Institute in the US.
These antibodies may also be used to provide temporary, vaccine-like protection against SARS-CoV-2 infection for healthcare workers, elderly people, and others who respond poorly to traditional vaccines or are suspected of a recent exposure to the coronavirus, they said.
The research, published on Monday in the journal Science, offers a paradigm of swift reaction to an emergent and deadly viral pandemic.
It sets the stage for clinical trials and additional tests of the antibodies, which are now being produced as potential treatments and preventives for Covid-19, the researchers said.
"The discovery of these very potent antibodies represents an extremely rapid response to a totally new pathogen," said Dennis Burton from the Scripps Research Institute.
"It has been a tremendous collaborative effort, and we're now focused on making large quantities of these promising antibodies for clinical trials," said Thomas Rogers, an adjunct assistant professor at Scripps Research, and assistant professor of Medicine at University of California, San Diego.
Developing a treatment or vaccine for severe Covid-19 is currently the world's top public health priority, the researchers said.
One approach to new viral threats is to identify, in the blood of recovering patients, antibodies that neutralise the virus's ability to infect cells, they said.
These antibodies, the researchers said, can then be mass-produced, using biotechnology methods, as a treatment that blocks severe disease and as a vaccine-like preventive that circulates in the blood for several weeks to protect against infection.
This approach already has been demonstrated successfully against Ebola virus and the pneumonia-causing respiratory syncytial virus, commonly known as RSV, they said.
The researchers took blood samples from patients who had recovered from mild-to-severe Covid-19.
They developed test cells that express ACE2, the receptor that SARS-CoV-2 uses to get into human cells.
In a set of initial experiments, the team tested whether antibody-containing blood from the patients could bind to the virus and strongly block it from infecting the test cells.
The scientists were able to isolate more than 1,000 distinct antibody-producing immune cells, called B cells, each of which produced a distinct anti-SARS-CoV-2 antibody.
The team obtained the antibody gene sequences from these B cells so that they could produce the antibodies in the laboratory.
By screening these antibodies individually, the team identified several that, even in tiny quantities, could block the virus in test cells, and one that could also protect hamsters against heavy viral exposure.