Three crew members of a fishing boat in Seattle who were found to have antibodies capable of neutralizing the new coronavirus remained uninfected in an outbreak that swept through the ship, causing most people on board to sail, researchers reported.
The small real-world study, which has not been peer-reviewed, is one of the first in humans to suggest a link between neutralizing antibodies – those that stop the virus from stopping host cells – and protection against infection.
Researchers from the University of Washington and Fred Hutchinson Cancer Research Center in Seattle examined 120 of 122 people before they boarded in May, testing for both active virus and antibodies in the blood that would indicate a previous or persistent infection.
None of the crew tested positive for the virus, but six had some antibodies and of those, three had evidence of neutralizing antibodies.
More than two weeks after the boat sailed, it returned to shore with an infected crew member in need of hospital treatment.
Researchers then tested all crew over several weeks and found that 85 percent – 104 crew members – were infected.
However, none of the three with neutralizing antibodies tested positive, nor did they report any symptoms during the outbreak.
“Therefore, the presence of neutralizing antibodies from previous infection was significantly associated with protection against re-infection,” said the study’s authors.
– ‘Important insight’ –
Scientists have been unable to perform direct human tests to find out about the protection afforded by neutralizing antibodies, due to ethical concerns about potential seriousness and long-term consequences of the virus, the study’s authors said.
Danny Altmann, a professor of immunology at Imperial College London, said the new study, although small, was a “remarkable, real, human experiment at a time when we were short on hard line, formal, evidence that neutralizing antibodies really does protection against re-infection “- although this was predicted by animal testing.
“In short, it’s good news. Who knew immunology research on fishing boats could be so informative?” he added.
But research does not necessarily show that humans can not capture COVID-19 twice.
The three crew members who had weaker antibodies before sailing all tested positive on return – although researchers said their initial results could have been a false positive as a sign of early infection.
Commenting on the study, Jonathan Ball, a professor of molecular virology at the University of Nottingham, said it “suggests that individuals who have had prior exposure to viruses are susceptible to reinfection unless they have remarkable levels of neutralizing antibodies “.
Ball, who was not linked to the study, said that this “gives us an important insight into the type of immunity that can protect against future infection”, but it does not show whether exposure in the past can protect against severe infection in people who do not develop neutralizing antibodies.
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