Antibodies block SARS-CoV-2 infection in fishing crew

When an outbreak of COVID-19 swept through their fishing vessel, crew members who had significant levels of antibodies against the virus that causes COVID-19 were protected against re-infection. This finding was reported this week by researchers from the University of Washington School of Medicine and Fred Hutchinson Cancer Research Center.

The findings suggest that candidate vaccines designed to generate similar antibodies, called neutralizing antibodies, may be able to prevent infection in people. A number of potential vaccines are in various trial stages. Currently, the only proof such vaccines can protect against the virus, SARS-CoV-2, come from studies in animals.

“Our results provide the first direct evidence that anti-SARS-CoV-2 neutralizing antibodies are protective against SARS-CoV-2 infection in humans,” the researchers wrote.

The study paper is available on MedRxiv, a website where researchers can post pre-publication versions of their studies for discussion. Such posts, called pre-prints, have not yet undergone peer review nor been published in a scientific journal.

The lead author of the paper was Amin Additia, a research scientist in the lab of Dr. Alex Greninger, an assistant professor of laboratory mediine and pathology at the UW School of Medicine who led the research project. Katharine Crawford and Adam Dingens from the Fred Hutchinson Cancer Research Center’s laboratory of Jesse Bloom, an affiliate associate professor in the UW Department of Genome Sciences, performed the anti-spike antibody and neutralization assays. The spike of the coronavirus contains its infectivity machinery that allows it to fuse with and enter human cells, and anti-spike antibodies interfere with this virus protein mechanism.

In the study, researchers investigated an outbreak aboard a fishing vessel that sailed from Seattle in May.  Prior to departure, the ship’s crew of 122 men and women were tested to see if they were infected with the virus. They also had blood drawn to see if they had antibodies to the virus from a prior infection. None were found to be currently infected, but three had significant levels of anti-SARS-CoV-2 antibodies indicating they had previously been infected.

Importantly, these three crew members had types of antibodies that have been shown to be able to neutralize the virus and prevent infection in animals. Such antibodies target proteins the virus uses to attach to and invade human cells, the SARS-CoV-2 spike protein.

Three other crew members initially tested positive for antibodies against one protein, the nucleocapsid protein, of SARS-CoV-2, but subsequent analysis of their blood samples found low anti-spike antibody activity. All three became infected during the shipboard outbreak.

Despite the pre-departure screening, COVID-19 broke out while the vessel was at sea. The outbreak forced the ship to return to port. As part of an outbreak investigation, all 122 people who had been on board the ship were again tested for the virus. Almost all had their blood drawn to test for antibodies.

The study paper is available on MedRxiv, a website where researchers can post pre-publication versions of their studies for discussion. Such posts, called pre-prints, have not yet undergone peer review nor been published in a scientific journal.

The lead author of the paper was Amin Additia, a research scientist in the lab of Dr. Alex Greninger, an assistant professor of laboratory mediine and pathology at the UW School of Medicine who led the research project. Katharine Crawford and Adam Dingens from the Fred Hutchinson Cancer Research Center’s laboratory of Jesse Bloom, an affiliate associate professor in the UW Department of Genome Sciences, performed the anti-spike antibody and neutralization assays. The spike of the coronavirus contains its infectivity machinery that allows it to fuse with and enter human cells, and anti-spike antibodies interfere with this virus protein mechanism.

These tests revealed that 104 of the 122 crew members had become infected during the outbreak. This was a high attack rate of more than 85%. However, none of the three crew members who had neutralizing antibodies before the ship went to sea showed signs of reinfection nor had they experienced any symptoms. The fact that none of the three with neutralizing antibodies got infected, while 103 of the 117 without antibodies did,  indicated having the antibodies was significantly associated with protection.

“We’re homing in on the immunological responses we need to prevent SARS-CoV-2 infection. We can’t wait to get this virus behind us,” said Greninger.

The title of the MedRxiv preprint title is, “Neutralizing antibodies correlate with protection from SARS-CoV-2 in humans during a fishery vessel outbreak with high attack rate.”

This research was supported by the Deparment of Laboratory Medicine and Pathology and grants from the National Institute of Allergy and Infectious Disease (R01AI141707, F30AI149928) and the Howard Hughes Medical Institute.

– Written by Michael McCarthy

For details about UW Medicine, please visit http://uwmedicine.org/about.