Over years of studying antibody responses against the flu in the Wilson lab at the University of Chicago, researchers kept coming up with a strange finding: antibodies that seemed to bind not only to the flu virus, but to every virus the lab could throw at them. Since antibodies are usually highly specific to individual pathogens, in order to maximize their targeted protective response, this pattern was extremely unusual.
Until finally, they realized: The antibodies weren’t responding to the viruses, but rather to something in the biological material in which the viruses had been grown. In every case, the virus had been propagated in chicken eggs — more specifically, in a part of the egg called the allantois. The findings were published on June 15 in mBio.
“Growing vaccines in eggs is the old school way of doing things because it’s cheap and you can grow a lot of virus in eggs,” said first author Jenna Guthmiller, PhD, a postdoctoral fellow at UChicago. “Now we’re finding that these antibodies bind to this glycan – a sugar molecule – found in eggs, which means that people who are getting vaccinated are producing an antibody response against this egg component that’s not related to the virus at all.”
The fact that vaccines grown in eggs can lead to this off-target antibody response is unexpected, but the implications aren’t yet known. It could mean that the immune system diverts resources away from developing protective antiviral antibodies to produce these egg sugar antibodies instead, which could have implications for vaccine effectiveness.
clinicalnews.org/2021/07/01...
mBio. Study Paper: