Marius Strioga, PhD in Biomedical Sciences from the National Cancer Institute, answered these questions for the Delphi portal and explained why, even after being diagnosed with a coronavirus, immunity may not develop and would threaten to infect the one again.
– What is the difference between naturally formed immunity and post-vaccination?
– In the case of COVID-19, this is still not well known. We know in principle that the immune response after a natural infection may differ from that induced by the vaccine. In some cases, vaccine-induced immunity is superior, in others, after natural infection.
As with COVID-19, it’s hard to say. When we use a vaccine, we give a specific dose of a specific antigen. Vaccination aims to induce both cellular and humoral immunity, as well as the formation of both T lymphocytes and antibodies.
As the natural immune response develops, as we can see, antibody titers are lower in some and higher in others. Others who are sick have no antibodies. Of course, it all depends on the individual characteristics of the immune system.
Also, it all depends a lot on the amount of virus that enters the body when an immune response occurs naturally. If, for example, there are fewer viral particles (virions), it is possible that a non-specific immune response: macrophages, dendritic cells and, in part, neutrophils will destroy it, confront this virus and simply not access the components. of the specific immune response.
There are also certain hierarchical levels in the immune system: the ascending chain is a nonspecific immune response that recognizes everything that is strange and potentially harmful to the body, without differentiating what is too threatening and has specific components: lymphocytes, antibodies very accurate and precise. targeting an already specific pathogen.
© DELFI / Robert Narmontas
To obtain a specific immune response, this threat must first be addressed by the components of the nonspecific immune response, the ascending chain. They are versatile, but everything comes at a price. Because they universally recognize what is alien, their effectiveness and sensitivity in destroying this threat is less. When you acknowledge everything, it obviously has no potential to deliberately destroy you. If the virus has entered a small number and these primary components have been able to destroy it, its competence and capacity were sufficient, then this information can no longer be communicated to the exact special armies, for example, of T lymphocytes, of B lymphocytes, from which antibodies will be made.
Therefore, in people who suffer from a mild and likely asymptomatic form with low levels of the virus, a specific immune response may not occur. If they were subsequently infected with a sufficiently high dose of the virus, they would be as if they were re-infected because there is no immune memory.
When we use vaccines, we seem to avoid this, as the dose is calculated, which we believe should elicit an immune response, stronger or weaker, here is another question: it depends on age, comorbidities, etc. . But this is already a standardized dose of antigens (not a virus, but a gene encoding a particular protein).
Therefore, the chances of a vaccinated immune response in all vaccinated people are apparently much higher, because here we know what and how much we apply.
In the case of a natural infection, it depends on the amount of virus that has entered: in some cases it may be too little to trigger a specific immune response, in other cases the immune system may react too violently, in this case we have the called cytokine storm. But they are usually expressions of one or another imbalance of the immune system.
Panevėžys doctors are vaccinated against the coronavirus vaccine
© JP / Rimvydas Ančerevičius
– Why do people get COVID-19 again?
– Getting sick again when, for example, you have had a serious form, you have become infected again and you get sick again, perhaps only one of these cases in the world is normally described.
But the resulting immune response may protect against the disease, but not prevent infection and the spread of the virus. Therefore, it may be the case that a coronavirus infection, say symptomatic, has produced an immune response, but after a while the virus is detected again.
It may be detected because the immune system protects us from disease. But again, there are different components of the immune system: those that protect against disease and those that prevent infection.
If there are no class A or insufficient sterilizing immunoglobulin antibodies that protect against infection, the possibility of infection persists even though you are ill and have developed immune system components that primarily protect against the disease: immunoglobulin G class antibodies , T lymphocytes. After all, these components are only included in the fight when the virus begins to “act”, that is, it begins to infect epithelial cells in the nasopharynx, the airways for a while, multiply in them. and when it is already attempted to provoke the disease it is destroyed.
While this is happening, one person will be infected for a while and will infect other people. Then, of course, we will detect the virus. Nothing surprising here. Because there are both vaccines and natural infections, when the immune response that develops prevents the disease, but does not provide protection against the possibility of infection and spread of the virus for some time, of course, shorter than in the absence of a immune response to this pathogen. And if we do a smear right now and look for a virus, we will find it.
Another thing is that the virus can persist. Although the immune response has already developed and developed, it cannot actively reproduce, but it can persist for a while. For example, this is the case with the measles virus. It is known that after measles, when the rash ends and does not become infected after 4 days, the measles virus remains in the cells of the body’s immune system for up to half a year.
The same can happen with coronavirus, so that after a few months of illness, there would still be such a chronic and silent tune. Apparently, it starts to multiply, infecting some other cells, but the immune system suddenly silences it and can quietly persist for a while longer.
When you re-detect coronavirus after an illness, the immune response you have developed may not protect against the infection and you may become infected for a while but not get sick. It may remain in a state called latent and secretive, still live in the nasopharynx, but not hurt and no longer be distributed.
To determine which variant there is, it is necessary to scan the genome of the virus during the first infection and do the same during the second infection, and then compare whether it is the same virus or another.
– Could this latent state also explain the persistence of symptoms in some people after COVID-19, such as fatigue, lack of strength?
– Wow. These symptoms of fatigue and persistence may be due to damage to the organs caused by the virus when the infection was active or to a strong immune response that developed at that time to destroy the virus.
Of course, it cannot be ruled out that the virus may persist, as even the measles virus is known to cause a relatively serious condition called subacute sclerosing panencephalitis, which develops subacute brain inflammation. It is a complication of measles infection due to the persistence and survival of the virus despite the immune response. There is a theoretical possibility that this is the case with coronavirus, but it needs to be proven.
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