As a structure, antibodies are immunoglobulins belonging to classes A, M, G, D, E and as a target, they are directed to proteins N, M, E and S.
The coronavirus genome encodes 4 main structural proteins: protein N (nucleocapsid), which is practically the core of the virus containing viral RNA, protein M (membrane), protein E (viral envelope) and protein S (spike), a surface protein that gives the appearance of the “crown” due to the tripartite structure.
Antibodies specific for SARS-CoV-2 virus infection: IgM and IgG
So far, Only three classes of antibodies are studied in the dynamics of the immune response It is generally caused by viruses: antibodies type A, M and C. According to MedLife experts, for coronaviruses and, especially for SARS-CoV-2, the role of IgA antibodies is poorly understood. IgM and IgG antibodies have been studied since the onset of the pandemic and with the development of laboratory tests:
- IgM Immunoglobulin 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.
- IgG Immunoglobulins 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 time of onset of these antibodies. If for most viruses the first antibodies to appear are those of the IgM type, for SARS CoV-2 the conditions in which the two classes of antibodies (IgM and IgG) appear and remain almost simultaneously are much more common.
What are antibodies against N proteins (nucleocapsid) and anti-S proteins (spike)?
Protein N (nucleocapsid) is pthe protein that encapsulates viral RNA and protects it from the host cell environment. In addition to its protective role, N protein has the role of mediating the transcription of the viral genome, which is essential for virus replication. This protein is highly immunogenic, the antibodies directed against it are an important serological marker in the labeling of the immune response to viral infection with SARS-CoV-2 virus.
The structure of protein S (Spike) is extremely complex. He’s got two subunits that enable the virus to attach to the cell, penetrate the virus into the cell, and fuse with the host cell. In other words, the structure of the Spike protein provides a significant number of highly antigenic sites that identify neutralizing antibodies, antibodies respectively that prevent the virus from adhering and entering the host cell.
Similarly, there are common conditions in which, despite evidence of SARS-CoV-2 infection, the body’s antibody response is not demonstrated by any commercially available people who “do not develop antibodies”.
The information provided by the presence of either antibody, anti-N, anti-S, IgG or IgM class is that there was a SARS-CoV-2 infection, even if it was asymptomatic or there were common symptoms, which were overlooked over time.
How can the presence of antibodies against N proteins and S proteins be detected in the blood?
- Try the IgM anti-S anticorpi – a quality test, recommended for people who have been vaccinated and are not sure they have suffered from COVID-19 disease.
- Try the anti-N IgG anticropi – a qualitative test, recommended for people who have not been vaccinated and are not certain to have COVID-19 disease.
- Try IgG anti-S antibody – a quantitative test, recommended for people who have been vaccinated and are not certain to have COVID-19.
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