Vaccines on Mucosal Immunity

Vaccine prevention of infections is one of the most effective ways to protect against the occurrence of diseases and their spread. At the same time, most modern vaccine preparations use either a weakened (inactivated) pathogen (bacterial or viral) or a modified toxin to form immune protection. During vaccination, the introduction of the antigen into the body is most often carried out by injecting the drug together with a set of additional substances with adjuvant or stabilizing features. Usually, the criterion for vaccine effectiveness is the level of immunoglobulins in the blood. This approach, with slight variations, is successfully used for vaccination in all developed countries of the world. However, recently an increasing number of researchers have been thinking about the feasibility of a modern vaccination system, paying attention to the possible health risks of those vaccinated due to the main vaccine preparation or additional vaccine components.

When pathogenic microorganisms enter through the respiratory tract or the digestive apparatus, the first barrier that determines the possibility of penetration of the pathogen into the body, and hence the onset of infectious disease, is the mucous layer. The immune system of the mucous membranes of the body plays a huge role in the development, maintenance and regulation of immune status and thus makes up an important component of the immune system. The immune system of the mucous membranes of different body systems closely interacts with each other. This relationship is especially close between the digestive and respiratory tracts (1). It is no coincidence that in recent years a significant number of vaccine developments involve vaccination by administering a vaccine preparation to the mucous membranes. It is essential that when using the mucosal vaccine, the mucosa in different parts of the body reacts as a whole (1). It should be noted, that there are already several successful vaccine preparations that use the non-injection route of vaccination. Currently, 5 mucosal vaccines (cholera, typhoid, polio, rotavirus, influenza) are registered, with the first four vaccines suggesting the oral route of administration. There are several reasons for choosing oral vaccines for mucosal immunization: 1. Ease of administration, which provides the possibility of self-vaccination, 2. Organization of the intestinal mucosa, which makes it possible to perceive foreign antigens through specific M cells, practically free from the mucus layer with a large number of compactly located specialized cells of the immune system (dendritic cells, T lymphocytes of various classes and B lymphocytes), which ensure the rapid formation of immune responses, 3. Lesser side effects, 4. Ease of production and low cost. A limitation to the creation of successful oral vaccines is based on the organization of the gastrointestinal tract, which involves the rapid destruction of pathogens or pathogenic factors (antigens) under the influence of gastric juice, bile and intestinal enzymes.

The problem of antigen delivery to intestinal M cells may be solved by using bacterial vectors of vaccine antigens – probiotic bacteria. Probiotic strains have been well studied for safety for the body, can remain viable after passing through the gastric barrier, improve inter-epithelial connections, and can also generate a number of surface structures that enhance the effectiveness of vaccination. Probiotics have been successfully used as vectors, the DNA of which has been successfully introduced with plasmid constructs that ensure the expression of antigens of pathogenic bacteria (1, 2, 3, 4). Another problem with mucosal vaccines is their relatively difficult assessment of efficacy because of usually small specific IgG response. However, the present pandemic infection of SARS-Cov-2 showed that IgG levels do not always correlate with protection against the virus. In summary,

The current Research Topic aims to update the scientific community on recent developments concerning mucosal immunity and protective vaccines for mucosal immunization. We welcome authors to submit original, review and mini-review articles focused on mucosal immunity and vaccines targeting mucosal immunity.

Information for the authors: All papers related to the subject of oral, nasal intestinal, or vaginal immunity and vaccines which are developing for mucosal immunization are eligible.

References:
1. Johansson EL, Wassén L, Holmgren J, Jertborn M, Rudin A. Nasal and vaginal vaccinations have differential effects on antibody responses in vaginal and cervical secretions in humans. Infect Immun. (2001) 69(12):7481-6.
2. Ma Y, Luo Y, Huang X, Song F, Liu G. Construction of Bifidobacterium infantis as a live oral vaccine that expresses antigens of the major fimbrial subunit (CfaB) and the B subunit of heat-labile enterotoxin (LTB) from enterotoxigenic Escherichia coli. Microbiology. (2012) 158(2):498-504.
3. de Azevedo M, Karczewski J, Lefévre F, Azevedo V, Miyoshi A, Wells JM, Langella P, Chatel JM. In vitro and in vivo characterization of DNA delivery using recombinant Lactococcus lactis expressing a mutated form of L. monocytogenes Internalin A. BMC Microbiol. (2012) 19;12:299.
4. Laiño J., Villena J., Zelaya H., Moyano R.O., Salva S., Alvarez S., Suvorov A. Nasal immunization with recombinant chimeric pneumococcal protein and cell wall from immunobiotic bacteria improve the resistance of infant mice to Streptococcus pneumoniae infection PLoS ONE. 2018. Т. 13. № 11. С. e0206661

Keywords: Vaccines, Mucosal immunity, Pathogens, Infectious agents

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