Researchers have identified a potent cocktail of antibodies that may help doctors to treat Covid-19 infections and protect those at risk from falling ill with the disease.
The antibodies were originally collected from patients who were hospitalised with severe Covid-19, but they would be manufactured at scale by pharmaceutical firms and transfused into the blood to fight the virus or prevent it from taking hold.
Scientists at Columbia University in New York screened antibodies from 40 Covid-19 patients and identified 61 types from five individuals that effectively wiped out coronavirus. Among them were nine that displayed “exquisite potency” for neutralising the pathogen.
Tests on cells showed that the antibodies killed off the virus, while experiments with hamsters revealed that an infusion of one of the more potent antibodies protected the animals from disease. “It shut off infectious virus completely in the lung tissue of the hamsters we treated,” said David Ho, a professor of medicine at Columbia who led the research.
“We specifically isolated very potent antibodies that can be mass produced and then administered,” Ho said. “We would assume that these could be used to prevent or treat Sars-Cov-2. We ‘d be looking to treat early in the course of infection, particularly those at risk of developing severe disease such as the elderly and those with underlying illness.”
He added: “In terms of prevention, these could certainly substitute for vaccines, and again we’d be looking at the most vulnerable, for example, nursing home residents.”
While major efforts are under way to develop vaccines for coronavirus, there is still uncertainty over how effective a vaccine will be and how long any protection it confers will last. Immune responses tend to be weaker in older people, so even if vaccines become available in the coming year, infusions of synthetic antibodies that protect for months at a time would still be valuable.
Antibodies are one of the body’s main lines of defence against viral infections. When a virus invades cells and multiplies, the immune system learns to recognise the intruder and churns out antibodies to deactivate the microbe. The antibodies attack from different angles, latching on to the proteins from which the virus is made.
Pharmaceutical companies already manufacture synthetic antibodies in bulk, purifying them from cells that are grown in large fermenters. Estimates suggest that a dose of antibodies might cost $50 (£39) to produce, Ho said.
Work is under way to test all of the antibodies in animals, but the researchers hope to synthesise enough to launch a phase I safety trial in humans in October. If the trial finds the transfusions are safe, trials for efficacy could start early next year, Ho said. The antibodies can be engineered so that they persist in the blood for three to six months.
Writing in the journal, Nature, the scientists describe how most of the antibodies bind to the club-like “spike” proteins that cover the surface of the virus. These create the corona from which the virus takes its name. Some of the most potent antibodies defeated the virus by latching on to the spike protein in such a way that it could no longer invade human cells.
Transfusions of antibody-containing blood plasma from recovered Covid-19 patients suggest they can help patients when given before the virus causes catastrophic damage. But the synthetic cocktails Ho envisages are expected to be more effective because they can be designed to contain high levels of the most potent antibodies.
The mix of antibodies is so diverse that the researchers believe it will be hard for mutated variants of the virus to evade them. “Using a cocktail of different antibodies that are directed to different sites in spike will help prevent the virus from becoming resistant to the treatment,” Ho said.