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Evidence of protective immunity to the pandemic coronavirus has surfaced following a recent outbreak of COVID-19 that inundated the crew of a fishing vessel.
The coronavirus, SARS-CoV-2, infected 104 of the 122 people on board, or about 85%, during a short trip. But looking through the data collected before and after the ship’s departure, the researchers noted that the 18 people spared the infection simply included the only three people on board who had potent pre-existing immune responses to SARS-CoV-2. Specifically, the three sailors were the only ones to have neutralizing antibodies against SARS-CoV-2, which are proteins that circulate in the blood and completely sink the infectious virus.
The numbers are small and the result is not final. Additionally, the study was published this month on a pre-print server, which means it was not published by a scientific journal or was not reviewed. by peers. Still, experts say the study was well-conducted and meaningful for collecting data that suggests powerful, pre-existing immune responses from a previous infection may indeed prevent someone from catching the virus again.
“Although this is a small study, it offers a remarkable, real human experience, at a time when we lack formal and categorical evidence that neutralizing antibodies truly offer protection against reinfection, as predicted by animal models. Danny Altmann, professor of immunology at Imperial College London, said in a statement.
Viral capture
For the study, researchers in Seattle, Wash., Were able to test 120 crew members of 122 people before they left. They looked for active infections by probing the genetic material of SARS-CoV-2 in the nose, and they looked for past infections by looking for antibodies that develop towards the end of an infection. All 120 were negative for SARS-CoV-2 in their noses. Six of them, however, had antibodies against the pandemic virus.
Upon closer examination of these six antibodies, only three had neutralizing antibodies, the researchers found. Although all antibodies suggest previous exposure to a virus, not all antibodies can neutralize viruses. And neutralizing antibodies are considered essential for protective immunity.
Researchers can’t say for sure what was going on with the three who had antibodies, but not neutralizing antibodies. Their best guess is that they just got false positive test results and didn’t really have antibodies to SARS-CoV-2. But it’s also possible that they had waning antibody responses, perhaps from a distant infection early in the infection, or a thriving antibody response during the early stages of an infection. Regardless, after the ship left and the COVID-19 outbreak broke, all three were infected with SARS-CoV-2.
Immunity inklings
When the ship returned after about 16 days at sea, with sick people on board, researchers retested all of the crew and followed them for up to 32 days. A total of 104 were infected, including one of two crew members they did not initially test.
As for the three with neutralizing antibodies, the 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 disembarkation. But, in a wrinkle of data, this person had very low positive tests seven days and 13 days after getting off the boat. The tests were not qualified as positive, based on predefined criteria. But it does suggest that residual viral material persisted in the person’s nose – something that has been observed in other studies.
Despite the study’s limitations and the data quarks, experts say this is well-made and useful information. Jonathan Ball, professor of molecular virology at the University of Nottingham, noted in a press release that although the study is small and leaves questions unanswered, it “gives us important insight into the type of immunity. which could protect against future infection ”.
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