What is immune imprinting and how does it work?

Jan. 31, 2023

Why in News?

Variant-specific or bivalent boosters have been made available in nations in the hope that they may offer superior protection against coronavirus infection compared to the initial vaccination.
However, numerous studies have revealed that immune imprinting, a mechanism in human bodies, may be rendering these new boosters much less effective than anticipated.

What’s in Today’s Article?

What is Immune Imprinting?

Immune imprinting is a tendency of the body to repeat its immune response based on the first variant it encountered (through infection or vaccination) when it comes across a newer or slightly different variant of the same pathogen.
The phenomenon was first observed in 1947 (then called the "original antigenic sin"), when scientists noted that people who previously had flu, and were then vaccinated against the current circulating strain, produced antibodies against the first strain they had encountered.
Over the years, scientists have realised that imprinting acts as a database for the immune system, helping it put up a better response to repeat infections.

How does Immune Imprinting Works?

After the human body is exposed to a virus for the first time, it produces memory B cells that circulate in the bloodstream and quickly produce antibodies whenever the same strain of the virus infects again.
When a similar (not identical) variant of the virus is encountered by the body, the immune system, rather than generating new B cells, activates memory B cells.
This, in turn, produces antibodies that bind to features found in both the old and new strains, known as cross-reactive antibodies.
Although these cross-reactive antibodies do offer some protection against the new strain, they aren’t as effective as the ones produced by the B cells when the body first came across the original virus.

What are the Findings of the Recent Study?

To carry out the experiment, some participants in the research were given a booster (fourth shot) of the original vaccine while others received a booster of the new bivalent vaccine.
The bivalent COVID-19 vaccines include -
- A component of the original virus strain to provide broad protection against COVID-19 and
- A component of the omicron variant to provide better protection against COVID-19 caused by the omicron variant.
It was found that across all coronavirus strains tested, bivalent boosters did not produce a noticeably greater antibody response capable of neutralising the virus than did boosting with the initial monovalent (mRNA) vaccinations.
The study suggested immune imprinting might be posing a hurdle in the success of the bivalent or variant-specific vaccines. However, that doesn’t mean people shouldn’t get the bivalent booster.
But now there is a need to come up with a vaccine that can overcome imprinting and stop the transmission of the virus.

How to Circumvent Immune Imprinting?

Several ongoing studies are now looking for a solution to imprinting.
Some scientists have suggested that nasal vaccines may be more effective than injection-based ones at preventing infections.
Even if the mucous membranes have some remnants of previous exposure, they think they would provide stronger protection.
Additionally, scientists are examining if giving annual intervals between coronavirus vaccinations could lessen the issue of imprinting.
The development of pan-sarbecovirus vaccines, which will provide protection against all COVID-causing variations, is another area of intense research. However, it would take time for those initiatives to mature.