Fishing boat outbreak may offer virus immunity insight: study

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Three crew of a Seattle fishing boat who were found to have antibodies able to neutralise the new coronavirus remained uninfected in an outbreak that swept through the ship, sickening most people on board, researchers have reported.

 

The small real-world study, which has not been peer-reviewed, is among the first in humans to suggest a link between neutralising antibodies—those that stop the virus latching onto host cells—and protection from infection.

 

Researchers from the University of Washington and Fred Hutchinson Cancer Research Center in Seattle screened 120 of 122 people before they boarded the fishing vessel in May, testing both for active virus and for antibodies in the blood that would indicate a previous or ongoing infection.

 

None of the crew tested positive for the virus, but six had some antibodies and of those, three had evidence of neutralising antibodies.

 

More than two weeks after the boat set sail, it returned to shore with an infected crew member who needed hospital treatment.

 

Researchers then tested all the crew over several weeks and found that 85 percent—104 crew members—were infected.

 

But none of the three with neutralising antibodies tested positive, nor did they report any symptoms during the outbreak.

 

"Therefore, the presence of neutralising antibodies from prior infection was significantly associated with protection against re-infection," the authors of the study said.

 

'Important insight'

 

Scientists have not been able to run direct human tests to find out about the protection conferred by neutralising antibodies, because of ethical concerns over potential severity and long term impacts of the virus, the study authors said.

 

Danny Altmann, a professor of immunology at Imperial College London, said the new study, though small, was a "remarkable, real-life, human experiment at a time when we've been short of hard-line, formal, proof that neutralising antibodies genuinely offer protection from re-infection"—although that had been predicted by animal testing.

 

"In short, it's good news. Who knew immunology research on fishing boats could be so informative?" he added.

 

But the research does not necessarily show people cannot catch COVID-19 twice.

 

The three crew who had weaker antibodies before setting sail all tested positive on return—although researchers said their initial results could have been a false positive or sign of early infection.

 

In a commentary on the study, Jonathan Ball, a professor of molecular virology at University of Nottingham, said it "suggests that individuals who have had a prior exposure to virus are susceptible to reinfection unless they have appreciable levels of neutralising antibodies".

 

Ball, who was not linked to the research, said this "gives us an important insight into the type of immunity that might protect from future infection", but it does not show whether or not past exposure can protect against severe infection in people who do not develop neutralising antibodies.

 

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[Karlston]

Hint of COVID-19 immunity: 3 sailors with antibodies spared in outbreak at sea

The study is small and tricky to interpret, but it offers inklings of COVID-19 immunity.

Enlarge / Fishing vessels in Seattle.

Getty | Art Seitz

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Hints of protective immunity against the pandemic coronavirus have surfaced in the wake of a recent COVID-19 outbreak that flooded the crew of a fishing vessel.

 

The coronavirus, SARS-CoV-2, infected 104 of the 122 people on board, about 85 percent, during a short voyage. But trawling through data collected before and after the ship set sail, researchers noted that the 18 spared from infection just happened to include the only three people on board that had potent, pre-existing immune responses against SARS-CoV-2. Specifically, the three sailors were the only ones found to have SARS-CoV-2 neutralizing antibodies, which are proteins that circulate in the blood and completely sink the infectious virus.

 

The numbers are small and the finding is not definitive. Additionally, the study appeared this month on a pre-print server, meaning it has not been published by a scientific journal or gone through peer review. Still, experts say the study was well done and significant for netting data that hint that potent, pre-existing immune responses from a past infection can indeed protect someone from catching the virus again.

 

“While this is a small study, it offers a remarkable, real-life, human experiment at a time when we’ve been short of hardline, formal, proof that neutralizing antibodies genuinely offer protection from re-infection, as predicted by animal models,” Danny Altmann, a professor of immunology at Imperial College London, said in a media statement.

Viral catch

For the study, researchers in Seattle, Washington were able to test 120 members of the 122-person crew before they set sail. They looked for active infections by probing for SARS-CoV-2 genetic material in noses, and they looked for past infections by probing for antibodies that develop toward the end of an infection. All 120 were negative for SARS-CoV-2 in their nose. Six, however, had antibodies against the pandemic virus.

 

On further examination of those six with antibodies, only three had neutralizing antibodies, the researchers found. Though all antibodies suggest past exposure to a virus, not all antibodies can neutralize viruses. And neutralizing antibodies are considered critical for protective immunity.

 

The researchers can’t say for sure what was going on with the three who had some antibodies, but not neutralizing antibodies. Their best guess is that they simply had false positive test results and didn’t truly have antibodies against SARS-CoV-2. But it’s also possible that they had waning antibody responses, perhaps from a distant infection at the beginning of the infection, or a burgeoning antibody response during the early stages of an infection. Regardless, after the ship set sail and the COVID-19 outbreak struck, all three were infected with SARS-CoV-2.

Immunity inklings

When the ship returned after about 16 days at sea, with sick aboard, the researchers re-tested all the crew members and followed them for up to 32 days. A total of 104 were infected, including one of the two crew members they didn’t initially test.

 

As for the three with neutralizing antibodies, initial tests for SARS-CoV-2 genetic material in their noses were all negative. Two of the three tested negative at three different times—from the day they got off the boat to 18 days later. The third crew member tested negative after three and ten days of disembarking. But, in a data wrinkle, this person had very weakly positive tests seven days and 13 days after getting off the boat. The tests didn’t qualify as positive, based on preset criteria. But it does suggest some remnant viral material was lingering in the person’s nose—which has been seen in other studies.

 

Despite the limitations of the study and quirks of the data, experts say it's well done and helpful information. Jonathan Ball, professor of molecular virology at the University of Nottingham, noted in a media statement that although the study was small and leaves questions lingering, it “gives us important insight into the type of immunity that might protect from future infection.”

 

 

Hint of COVID-19 immunity: 3 sailors with antibodies spared in outbreak at sea