Will there be no universal vaccine?
Why it is not possible to create a universal flu vaccine: a new explanation has been found
Polina Gershberg, Naked Science
The imperfection of our immune system leads to the fact that the body is helpless before new strains of the influenza pathogen.
Distrust of influenza vaccination, in addition to the usual "arguments" of anti–vaccinators, is also fueled by the fact that it is impossible to get vaccinated against influenza once in many years - unlike many other diseases. The annual nature of this procedure generates both distrust of the effectiveness of the vaccine and various conspiracy theories about the conspiracy of pharmaceutical companies with officials and "killers in white coats".
The need to meet each new flu season with a fresh vaccination in reality is explained by the abundance of strains of this virus and its variability. The flu virus is constantly evolving, so last year's immune response may not work this year.
In a new article published in Cell, scientists from Rockefeller University show why it is now impossible to just take and create a "general–purpose vaccine" for all types of flu at once - and how this may change in the future. According to the work, one of the problems is the way in which the immune system reacts to a virus or a vaccine against it. The immune system does not retain the "memory" of previous versions of the virus, but develops its response to each new strain from scratch, using fresh immune cells.
"If we can figure out how to help the immune system build on what it has already learned, we could develop more effective vaccines for rapidly developing viruses such as influenza, or HIV, or hepatitis C," explains author Gabriel D. Victor.
The team investigated how the immune cells of model animals (mice) reacted to the first and repeated exposure to the flu vaccine. In particular, they tracked the behavior of B cells. These are white blood cells that secrete antibodies – proteins that attack viruses or mark them for attack by other specialized cells. In case of infection or vaccination, B cells are sent to the so-called germinal or germinal centers in the lymph nodes. This is the place where they acquire or change the specialization necessary to target a specific enemy by switching classes of antibodies.
"The germ center is like a training camp," Viktor gives an example. "They get in there very bad and come out of there very good, releasing better antibodies that bind more closely to their targets." These trained B cells become the cellular memory of the immune system and can secrete antibodies that attach to one part of the virus.
The return of more "experienced" B-lymphocytes to the germ centers would make it possible to obtain immune cells of a wider spectrum of action (figure from the article in Cell).
Ideally, these B cells return to the germ centers the next time the body encounters a virus or vaccine, and produce even more complex antibodies to better target a slightly different version of the virus, eventually becoming able to produce broadly neutralizing antibodies from which no modification of the virus can escape. And this is what researchers need to create a universal vaccine.
In the case of infection with the influenza virus or vaccination against it, this does not happen. Scientists genetically labeled the germ centers of mice with fluorescent tags during the first vaccination to see the migration of B cells that visited there when the vaccine was re-administered. It turned out that more than 90% of the B cells that came to the germ centers were unlabeled for the second time - that is, untrained beginners. Genetic analysis also showed that these cells did not undergo the mutation that B cells of the germinal center usually experience, that is, it also confirmed that they were there for the first time.
Why the "training camp veterans" did not return, despite the fact that many of them are able to communicate with the virus, and why the return for the second time is reserved only for a few selected B-cells are the most important questions.
If scientists in subsequent studies find the same results for humans as for mice, and if an answer is found, then perhaps they will find a way to bypass these "bottlenecks" and find long-lasting and effective recipes for vaccines against influenza viruses and other viruses that are completely immune to vaccination today, such as HIV.
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