August 19, 2020
Not all antibodies are alike
Fascinating report in The Seattle Times about an outbreak of COVID-19 on a fishing boat out of Seattle. The owners had worked with the virology lab at UW and Fred Hutchinson Cancer Research to screen 120 out of 122 employees just prior to departure. Luckily, they also tested for antibodies to look for prior exposure. Out of 120, 6 had positive levels of antibodies that bind to the viral capsule, indicating prior exposure. Only 3 of the 6 also had positive levels of neutralizing antibodies which keep the spike protein from attaching to human cells. Everyone tested negative for the virus at the time of departure.
However, as we know, a negative test for the virus one day can become positive the next day, since it takes a few days after exposure for the infection to show up. Within 18 days the boat returned to port due to a crew member being sick. That was just the beginning. By the end of the outbreak, 104 out of 122 had been infected, as confirmed by SARS-CoV-2 PCR testing. That’s 85% of the crew. The 3 with neutralizing antibodies did not get sick or show signs of reinfection. The other 3 crew members with the capsule antibodies did get infected. Researchers thinks this implies false positives, but it is not clear yet..
The protection the neutralizing antibodies afforded is good news. These are small numbers but add to the optimism of finding an effective vaccine that develops the neutralizing antibodies. This also supports the concerns cited in this article that the capsule antibody test may show prior exposure, but is not helpful in confirming immunity. A positive test may be a false positive from a prior coronavirus (common cold) infection, as well. Hence, some of the confusion over antibody testing and results.
I am impressed that the company worked with the researchers and they were able to get such good data and test results, as well as follow up of the crew. The information gained is valuable, but once again, points to the need for rapid testing to catch infections early. They had done everything that was available to prevent this scenario. And confirms to me that I do not want to be in close quarters with anyone not in my own pod.
Wash your hands, cover your nose, and keep safe six. Avoid closed spaces.
And finally, my caveat is that this is my experience and my opinions, which are subject to change as more information is available, and not related to the organization I work for. Thanks for reading.
https://www.seattletimes.com/seattle-news/health/seattle-fishing-boat-outbreak-suggests-antibodies-protect-against-coronavirus-infection/
https://www.medrxiv.org/content/10.1101/2020.08.13.20173161v1.full.pdf
https://www.sciencedaily.com/releases/2020/08/200814163313.htm