Cross-resistance is an immunological phenomenon that has been known to science for a long time. Cross-resistance is a consequence of some confusion by the immune system, which can recognize pathogens that are molecularly similar to each other. How does medicine use the phenomenon of cross-resistance, and how could it be related to COVID-19?

Contents:

    1. Cross-resistance - what is it?
    2. Cross-immunity - vaccinations
    3. Cross-resistance - mechanism of formation
    4. Cross-resistance - COVID-19
    5. Cross-resistance - possible negative effects

Cross-resistance - what is it?

Cross-resistance , otherwise heterologous, refers to the phenomenon in which the prior exposure of the immune system to one pathogen, e.g. a parasite, a virus bacterium, changes the body's response to another (heterologous) pathogen .

Cross-resistance is common among closely related species of pathogens, e.g. different species of mycobacteria. However, the phenomenon of cross-resistance may also occur between pathogens unrelated, e.g. bacteria, or belonging to completely different types of pathogens, such as bacteria and viruses.

Cross-immunity - vaccinations

Cross-resistance can play a role in enhancing the protective effect of vaccines. For example, the BCG (Bacillus Calmette-Guéri) vaccine against Mycobacterium tuberculosis may confer immunity against other mycobacteria, such as Mycobacterium leprae, which causes leprosy.

Interestingly, in the history of mankind, the first smallpox vaccine developed by Edward Jenner used not directly the smallpox virus, but the related vaccinia virus (vaccinia). This method of vaccination resulted in the person having a milder form of smallpox, but was later resistant to the lethal smallpox as a result of cross-immunity.

Studies have shown that people vaccinated with the vaccinia virus were less susceptible to other infectious diseases such as measles, scarlet fever, whooping cough and syphilis.

It is also worth noting that the aforementioned BCG vaccine against mycobacterium tuberculosis does not contain exactly the species of mycobacterium that causes disease in humans, but the species Mycobacterium boviscausing tuberculosis in cattle.

Research shows that cross resistance is not as predictable as it may seem. For example, with influenza viruses, cross-resistance may not occur because influenza viruses are genetically and antigenically very diverse. Hence, catching a cold caused by one strain of flu does not guarantee that we will not get sick from a cold caused by another strain. In this case, possibly the disease may be milder.

Cross-resistance - mechanism of formation

The phenomenon of cross-resistance results from the nature of our immune system, especially the acquired immune response, which includes B and T lymphocytes. immunological memory, i.e. the ability to specifically remember the pathogen, and more specifically its antigens (amino acid sequences). Later, re-exposure to the same pathogen is much faster and more effective.

How does the immune system remember a threat? It is possible thanks to the creation of special T-lymphocyte receptors (TCR) on the surface of T lymphocytes after contact with the pathogen. B lymphocytes, on the other hand, produce antigen-specific immune proteins - antibodies.

Specific T-cell receptors and antibodies are made through an extremely complex genetic process. In addition, recent studies show that other mechanisms, such as a non-specific immune response, which may be mediated by other immune cells - macrophages, may participate in cross-resistance.

Cross-resistance may be due to the similarity of some antigens to different pathogens. Then the T cells or antibodies can recognize them similarly to the pathogen they were formed for.

An example of cross-resistance between unrelated human viruses can be seen with Influenza A and Hepatitis C. The T cell response to the Hepat C virus NS31073-1081 antigen was found to be strongly cross-reactive to the NA231 antigen -239 influenza A virus.

Cross-resistance - COVID-19

Experts from infectious diseases, incl. The World He alth Organization indicates that there is no evidence to suggest that dogs or cats may be a source of SARS-CoV-2 infection and its transmission to humans.

Recently, there has been a reverse report in the media that owners of cats and dogs are actually less likely to contractCOVID-19 . Is it really so? Although it is theoretically possible, if only because of the phenomenon of cross resistance.

There are petsa reservoir of pathogens that are not dangerous to humans, but can stimulate cross-resistance. As it was described in the case of, for example, vaccinations with vaccinia virus and conferring cross-immunity to the smallpox virus.

Another example is distemper in dogs and measles in humans. However, this issue requires further observational studies on a large group of people and currently there is no scientific basis for this thesis.

Cross-resistance - possible negative effects

Cross-resistance can also have a negative side. It has been shown that viral or bacterial infections can induce the autoimmune process and the emergence of diseases such as multiple sclerosis and type 1 diabetes.

One of the potential mechanisms of this phenomenon is the so-called molecular mimicry, where the virus may possess amino acid sequences similar to those in our tissues. As a result of a similar reaction to cross-immunity, T lymphocytes and the antibodies of the body's own tissues, such as insulin-producing cells in the pancreas, are attacked.

About the authorKarolina Karabin, MD, PhD, molecular biologist, laboratory diagnostician, Cambridge Diagnostics Polska A biologist by profession, specializing in microbiology, and a laboratory diagnostician with over 10 years of experience in laboratory work. A graduate of the College of Molecular Medicine and a member of the Polish Society of Human Genetics. Head of research grants at the Laboratory of Molecular Diagnostics at the Department of Hematology, Oncology and Internal Diseases of the Medical University of Warsaw. She defended the title of doctor of medical sciences in the field of medical biology at the 1st Faculty of Medicine of the Medical University of Warsaw. Author of many scientific and popular science works in the field of laboratory diagnostics, molecular biology and nutrition. On a daily basis, as a specialist in the field of laboratory diagnostics, he runs the content department at Cambridge Diagnostics Polska and cooperates with a team of nutritionists at the CD Dietary Clinic. He shares his practical knowledge on diagnostics and diet therapy of diseases with specialists at conferences, training sessions, and in magazines and websites. She is particularly interested in the influence of modern lifestyle on molecular processes in the body.

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Category:

Immune system