What antibodies are specific for SARS-CoV-2 infection and what is their role in the body’s fight against

08.04.2021, 08:00

If you have been infected with the SARS-CoV-2 virus or know a colleague, friend, or family member who has been infected, it is important to understand how the body’s immune response to the virus is triggered. According to the explanations given by the doctors MedLife, an important component of this immune response is the production of anti-virus antibodies, respectively antibodies specifically targeted to the structural proteins of the virus. What are these antibodies? As a structure, they are immunoglobulins belonging to classes A, M, G, D, E, and as a target, they are directed on proteins N, M, E and S.

The coronavirus genome encodes 4 main structural proteins: protein N (nucleocapsid), which is basically the nucleus of the virus comprising viral RNA, protein M (membrane), protein E (viral envelope) and protein S (spike), the surface protein that gives the “crown” appearance due to the trimeric structure.

IgM and IgG antibodies appear after the body is exposed to coronavirus

To date, only three classes of antibodies are studied in the dynamics of the immune response generally induced by viruses: antibodies of type A, M and G. For coronaviruses and, especially for SARS-CoV-2, the role of antibodies of type IgA is little meaning. IgM and IgG antibodies have been studied since the onset of the pandemic and with the development of laboratory tests.

IgM – Imunoglobulina M is the type of antibody produced by the immune system immediately after infection. It is present in the first line of defense during viral infections, before the immune system produces IgG-type antibodies.

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IgG – Imunoglobulinele G are highly specific antibodies that are important for long-term immunity and immune memory.

It is now known that there is a significant difference in both the levels and the chronology of the appearance of these antibodies. If for most viruses, the first antibodies that appear are those of the IgM type, for SARS CoV-2 the situations in which the two classes of antibodies (IgM and IgG) appear and persist almost simultaneously are much more frequent.

What are anti-protein N (nucleocapsid) and anti-protein S (spike) antibodies?

Proteina N (nucleocapsida) is the protein that encapsulates the viral RNA and protects it from the host cell environment. In addition to its protective role, the N protein has the role of mediating the transcription of the viral genome, being essential in viral replication. This protein is strongly immunogenic, the antibodies directed against it being an important serological marker in highlighting the immune response to viral infection with SARS-CoV-2 virus.

Structure protein S (Spike) it is extremely complex. It has 2 subunits that make it possible to attach the virus to the cell, penetrate the virus into the cell and fuse it with the host cell. In other words, the structure of the Spike protein provides an important number of highly antigenic sites that determine neutralizing antibodies, respectively antibodies that prevent the virus from attaching and entering the host cell.

There are studies that have shown that anti-N antibodies can be detected earlier, but persist somewhat less than anti-S antibodies. Anti-S antibodies could neutralize the infectivity of the virus, especially by blocking the RBD (host cell binding) domain, which can give them the status of protective antibodies.

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Equally, there are frequent situations in which, despite evidence of SARS-CoV-2 infection, the body’s antibody response is not demonstrated by any commercially available test, ie there are people who “do not develop antibodies.”

The information provided by the presence of either antibody, either anti-N or anti-S, whether IgG or IgM class, is that there was SARS-CoV-2 infection, even if it was asymptomatic or there were common symptoms, overlooked at the time.

Tests that determine the presence of anti-protein N and anti-protein antibodies in the bloodI would

There are 3 types of MedLife labs tests for the detection of anti-SARS-CoV-2 antibodies.

  1. IgM anti-S antibody test – qualitative test, recommended for people who have been vaccinated and are not sure that they have suffered from COVID-19 disease.
  2. Anti-N IgG antibody test – a qualitative test, recommended for people who have not been vaccinated and are not sure that they have suffered from COVID-19 disease.
  3. IgG anti-S antibody test – quantitative test, recommended for people who have been vaccinated and are not sure that they have suffered from COVID-19 disease.

Test yourself in the nearest harvesting center MedLife and find out if your body has produced anti-SARS-CoV-2 antibodies.

The article is part of the campaign MedLife We are doing Romania well.

We have been with you for 26 years and we do not stop. Because today, more than ever, medicine means fighting through science and knowledge.

To meet our patients with a wide range of services and tests adapted to current needs, we have aligned ourselves with international standards and opened our own Real Time PCR laboratories to detect the SARS-CoV-2 virus. We have invested in the necessary infrastructure to assess whether the patient has gone through the disease and to test the post-infection or post-vaccination immune response.

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We are constantly adapting to the present and preparing for the future. We are doing Romania well.

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