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The vaccine against the causative agent of typhoid fever helped immune cells attack other pathogens
Ekaterina Kharybina, N+1
Some vaccines lead to nonspecific activation of the immune response. A research team from Liverpool studied the immune system's response to the management of a live weakened typhoid vaccine Ty21a. It turned out that Ty21a changes the expression of immune cell genes and affects their activity in response to other antigens, that is, it helps to fight other pathogens. An article by Pennington et al. The nonspecific effects of oral vaccination with live-attenuated Salmonella Typhi strain Ty21a is published in Science Advances.
According to the readiness of the body to fight foreign objects, innate and acquired immunity are distinguished. The first one has the ability to effectively attack a dangerous biomaterial that enters the body for the first time. It is realized by phagocytes, granulocytes and some lymphocytes. Acquired immunity works quickly only when the object re-enters the body. T- and B-lymphocytes are responsible for it.
Vaccines are used to train the body's immune cells before encountering a real infection. For example, for the prevention of measles, rubella, polio, tuberculosis, weakened live strains of these microorganisms are injected into people. Immune cells remember them and when they re-enter an already active strain, they recognize and kill it faster. Recently, it has been shown that vaccines against tuberculosis (BCG, Calmet-Guerin Bacillus), measles and oral polio vaccine increase the effectiveness of the immune system as a whole, reducing the overall mortality in the case of infectious diseases.
A group of scientists from the University of Liverpool and the Liverpool School of Tropical Medicine, led by Melita Gordon, demonstrated the nonspecific effect of the oral Ty21a vaccine against the Salmonella typhi strain that causes typhoid fever. They analyzed monocyte receptors in volunteers two weeks, three and six months after vaccination. It turned out that after three months, the genes of some receptors are more actively expressed, for example, TLR-4 and TLR-5. Since monocytes circulate in the blood for about a day, the researchers concluded that there is an epigenetic change in the regulation of the genes of the precursor of these cells.
Two variants of the vaccine's effect on the immune system. Above: traditional formation of specific memory of adaptive immunity cells. At the bottom: strengthening of the nonspecific activity of innate immunity cells by the vaccine, aimed at destroying various pathogens.
Figure from the press release of the University of Liverpool Typhoid vaccine may protect against other infections – VM.
The scientists also cultured in vitro T- and B-lymphocytes, monocytes of the control and vaccinated Ty21a groups and evaluated their activity after stimulation with different antigens. For example, monocytes of vaccinated volunteers secreted more interferon-γ, and B-lymphocytes secreted more interleukin 4 in response to the Candida albicans fungus antigen. The authors noted that in comparison with other vaccines leading to similar effects, Ty21a is safer and cheaper. And thanks to its stimulating nonspecific effect on immunity, it can be included in vaccination programs.
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