Vaccinated people have immunological imprint and unusual response to mRNA boosters against COVID-19 | vaccines | vaccine against Covid-19 | mRNA vaccines

People who took at least three doses of the original version of the COVID-19 mRNA vaccine had a strong immune imprint, a University of Washington (UW) study found.

Consequently, when vaccinated with the latest COVID-19 XBB.1.5 mRNA boosters, recipients produced little or no antibodies specific to the XBB.1.5 variant.

Immune imprinting occurs when previous infections or vaccinations leave such a strong immunological memory that the body continues to produce immune cells and antibodies targeting the previous immunological experience – even when exposed to a new variant or vaccine.

“[A impressão imunológica] it could be a problem if a person is unable to mount a useful immune response against a new variant,” Dr. Stanley Perlman, an immunologist and microbiologist at the University of Iowa, told The Epoch Times. He was not involved in the study.

Although this did not happen in this studymost antibodies produced after vaccination targeted the original COVID-19 variant and not XBB.1.5.

Surprising discoveries

“Printing is not a new concept, but the situation we are looking at appears to be quite unique,” ​​said David Veesler, who has a doctorate in structural biology, is professor and chair of the UW Department of Biochemistry, and a researcher at the Howard Hughes Medical Institute. , in a press release.

Immune imprinting is a well-recognized phenomenon that can occur with other infections and viruses.

New influenza infections distinct from previous variants may outperform influenza vaccinations and infections.

However, in the UW study, the immunological imprint persisted even among those infected with new Ômicron variants.

“It’s completely different from what we know about the flu virus,” Veesler said.

“Immune imprinting persists after multiple exposures to Ômicron spikes through vaccination and infection, including post-XBB.1.5 booster vaccination, which will need to be considered to guide future vaccination,” the authors wrote.

More than 20 people with a history of three or more Wuhan variant mRNA vaccines participated in the study. Most were infected with pre- and post-micron COVID-19 infections.

In addition to the original mRNA vaccines, most participants took the bivalent booster or the XBB.1.5 booster. At the time of the study, all participants had had four to seven injections.

The authors found that most antibodies produced after XBB.1.5 mRNA inoculation were better at neutralizing the original Wuhan COVID-19 variant.

The antibodies had the second highest neutralizing potency against the BA.2.86 Ômicron variant. Antibodies were the third most potent against XBB.1.5 in people who took the XBB.1.5 vaccine.

These antibodies were cross-reactive, meaning they could also bind to other variants, including the XBB.1.5 variants.

However, there were few or no antibodies specific for XBB.1.5.

Some people produced new immune cells that only recognized XBB.1.5. However, of the 12 participants evaluated, only five had immune cells that recognized XBB.1.5, but not the Wuhan variant.

“Most of the antibodies recovered by the updated vaccine boosters are cross-reactive and help block new variants, which is a good thing. However, could we do an even better job? The answer is probably yes,” Vessler said.

Two possible reasons

“There are two main hypotheses about what we are seeing,” Veesler said in the press release, “and I don’t know which of the two explains it yet.”

One hypothesis is that residents of Seattle, where most of the samples came from, were exposed to the virus so many times – mainly through vaccination but also infection – that they developed antibodies and immune memory cells preferable to the original virus.

“People in Seattle, myself included, have been very accommodating,” Veesler said. “We have been exposed many, many times over the last four years through vaccination and usually at least one infection. And it is very unusual to have so many exposures in such a short time – up to seven doses of vaccine in the cohort we analyzed.”

Another reason is that the mRNA vaccine creates a more robust immune imprinting effect than previously known vaccines. The authors cited another study who found that inoculation with killed COVID-19 viruses provided a reduced imprinting effect in humans.

“Inactivated vaccines induce a weaker immune response, so there is less opportunity for the response to be biased [para uma variante],” said Dr. Perlman.

“The mRNA vaccines may have been so good and triggered such strong immune responses that the impression may be stronger than what we are used to seeing with vaccines for other viruses, such as the flu virus,” Veesler said.

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