According to a new study published in Cell Host & Microbe, a vaccine against tuberculosis (TB) that has been around for about a century can offer protection against other infections as well.
Researchers from the University of Bonn and the Radboud University Medical Center, Nijmegen, in collaboration with counterparts from Australia and Denmark, have found that the BCG vaccine bolsters the immune system. BCG is an abbreviation for Bacillus Calmette-Guerin, the bacterium responsible for tuberculosis.
The BCG vaccine was first used medically in 1921. A hundred years after, it offers the only effective vaccination against the microbe causing TB.
Evidence suggests that the TB vaccine seems to enhance the immunity of patients. Scientists have only been unable to explain why this is the case before now.
People vaccinated with this biological preparation were found to have fewer infection issues. For instance, evidence from a West African country shows that newborns that were vaccinated died less often compared to those that were not.
This new study explains to an extent why the effects of vaccination may persist for years, reducing vulnerability to other infections.
There is what medical experts call “trained immunity.” This may be described as the immunological memory of the innate immune system. It enables improved innate immune response to different types of infections.
There is insufficient research to explain why trained immunity could be effective for years. Its efficacy remains long after the immune cells present in the blood when a vaccine was used have died off. Scientists wanted to learn more about this in the new research.
The team administered the BCG vaccine to 15 volunteers. It gave a placebo to five other subjects to enable assessment of vaccination effects.
Blood and bone marrow samples of these subjects were obtained three months after the vaccination. The researchers observed notable differences between persons in the two groups.
Immune cells in the blood of participants that got the vaccine produced considerably more cytokines. These inflammatory, intercellular messengers help to mediate and regulate immunity. They bolster the immune system.
Vaccination also promoted the activity of entirely different genes. These, in particular, included those involved in the production of cytokines.
Immune cells are of diverse types, but they all originate from the bone marrow. The hematopoietic stem cells, which give birth to all immune cells, come from the bone marrow.
Like other human cells, these cells contain in their nuclei numerous thousands of genes. These hereditary units may be compared to books containing instructions. Cells access these “books” for instructions whenever they want to produce a molecule.
However, it is not always possible or easy for cells to access the genes. The BCG vaccine changes the narrative in such cases when access is denied.
“We have found that after vaccination, certain genetic material becomes more accessible, which means that it can be read by the cells more frequently,” said Prof. Dr. Andreas Schlitzer, a Life and Medical Sciences (LIMES) researcher at the University of Bonn.
Vaccination makes genes accessible for many months or even years. This is helpful for the increased production of cytokines, leading to stronger immune systems.
Prof. Dr. Mihai G. Netea of Radboud University Medical Center, Nijmegen said their findings explain how long-term, improved immune response results from vaccination. It possibly explains the persistent training effect on immunity.
Possible COVID-19 use
Researchers are currently trying to develop vaccines to check the incidence of COVID-19 and other critical diseases among at-risk groups. This new study may contribute to that endeavor – the scientists are hopeful that BCG vaccination could prove helpful.
According to the team, the vaccine may not entirely keep the coronavirus at bay. But it could reduce the risk of severe infections, especially among health workers.
Another interesting finding in the study was that vaccination made cells more efficient in fighting pathogens. A molecule referred to as hepatic nuclear factor (HNF) causes the cells to release cytokines only when there is a real threat.
However, this is not a recommendation of the BCG vaccine for protection against other infections. The World Health Organization (WHO) has yet to approve it for that purpose.