Which antibodies are produced against SARS-CoV-2 virus?

Our body produces different antibodies for different structural proteins (nucleocapsid, spike, membrane, envelope) after SARS-CoV-2 virus infections or vaccine administrations.
  • Anti-N antibodies that are produced against “NUCLEOCAPSID” proteins in virus content and Anti-S antibodies (in IgG, IgM, IgA structure) that are produced against “SPIKE” proteins which are located on external surface of the virus and enable the virus to enter into the cell can be found with current laboratory tests.
  • While high level of Anti-S prevents the virus from entering into the cell, Anti-N antibodies prevent the proliferation of the virus if the virus penetrates into the cell.
  • High Anti-N level implies that the individual possibly contacted the virus before the vaccination; however, it is not possible to prove it.
  • Antibody levels may vary depending on time of measurement, infection process and individual immune features.

What is neutralizing antibody?

Antibodies that have the function of ensuring viral inhibition are called “Neutralizing Antibodies”. Neutralizing antibodies produced against SARS-CoV-2 virus are dominantly produced against Spike (S) protein. The method used to evaluate the functions or effectiveness of these antibodies is known as “Plaque Reduction Neutralization Test” (PRNT). Requiring intensive workforce and cost, this test can be studied in specially equipped research laboratories. This is not a practical method to evaluate vaccination.

Which antibodies are produced after the administration of Covid-19 vaccine?

The people who are administered inactivated vaccine (for example Sinovac) against the Covid-19 produce antibodies (Anti-N and Anti-S) against both proteins just like they have contacted the virus; however, the people who are administered m-RNA (for example BioNtech) vaccine produce antibody only against Spike (S) protein (Anti-S) and those people do not have Nucleocapsid (N) antibodies.
Anti-N antibodies are generally produced during and after the infection rather than vaccine. It is observed that the Anti-N antibody response is usually low after the vaccination.

How much do the antibodies protect us?

No antibody level measured after the vaccination or infection can exactly show how much we are protected against the SARS-CoV-2. In addition to antibody production against the vaccine, cellular immune response is also critical for protection. There is no routine test to evaluate this.
Antibody test only shows whether our immune systems give antibody response to the vaccine or the virus or the extent of this response.

Which antibodies are detected at the laboratory of our hospital?

Three different antibody tests can be studied at our laboratories:
  1. Anti-SARS-CoV-2 Spike (S) IgG; to determine IgG antibodies produced against the spike protein of the virus,
  2. Anti-SARS-CoV-2 Spike (S) total; to determine total antibody response produced against the spike protein of the virus,
  3. Anti-SARS-CoV-2 Nucleocapsid (N) total; to determine total antibodies produced against Nucleocapsid protein of the virus.
According to data from producing company, the measured Anti-S (IgG) and Anti-S (total) antibodies have neutralizing features.

When can the antibody test be performed?

For the people who have history of SARS-CoV-2 viral infection, antibody levels can be tested in the 3 rd week after the onset of symptoms or later; for the people who have been administered the vaccine, in the 3 rd week after the second dose of vaccine or later.
For those who wonder if the immune response has developed or not after the vaccination, we work all these antibodies; however, we also frequently use “ Anti-SARS-CoV-2 Spike (S) Antibody” measurement to determine early antibody response.
Those who want to receive information in this manner or who want to make an appointment for test can apply to our laboratories.
We wish you healthy days…