There are still many unknowns to be resolved at this time in the midst of the COVID-19 pandemic. Recent data revealed in a new analysis of B cells and more than 1,000 different monoclonal antibodies from 8 coronavirus patients show that, contrary to previous hypotheses, the protective B cell responses to the SARS-CoV-2 spike protein remain stable and continue to evolve for a period of 5 months, a few months after the initial period of active viral replication.
Despite this, a large proportion of the neutralizing antibodies generated from these long-lived B cells have been unable to effectively recognize the different variants born after SARS-CoV-2 in the countries of Brazil and South Africa.
These results, from an academic-industry study, will in any case help in the design of future vaccines against coronavirus, with the aim of working to limit and slow down the evolution of the virus and thus stimulate better neutralizing antibody and B-lymphocyte responses against the emerging variants of SARS-CoV-2.
In the aforementioned study published in the Science Immunology journal, researchers at the University of Pittsburgh School of Pharmacy in the United States profiled the antibody and B-lymphocyte responses specific for the now known as spike protein in 8 covid patients with mild and severe symptomatology throughout five months.
In comparison with previous findings, the experts observed a significant decrease in the levels of neutralizing antibodies located in the blood over time; although the levels of spike protein-specific memory B lymphocytes did remain stable or even increased over the same period of time.
In addition, over the course of 120 days, monoclonal antibodies isolated from these B lymphocytes underwent an increase in somatic hypermutation, binding affinity and neutralizing potency, all of this as signs of persistent B cell activity. On the other hand, the researchers also observed some cross-neutralizing B-lymphocyte populations, although these comprised only a small fraction of the B-lymphocyte repertoire and were not prominent in the neutralizing response to the coronavirus itself.
As mentioned by the scientists in the study, a large proportion of the neutralizing antibody response only targeted epitopes (known as the portion of a macromolecule that is recognized by the immune system) conserved and shared between SARS-CoV-2 and SARS-CoV and did not effectively recognize the emerging SARS-CoV-2 variants from Brazil and South Africa that develop mutations at amino acid positions 417 and 484 of the spike protein.
The authors continue to investigate and study this situation, but so far, they suggest careful monitoring of circulating SARS-CoV-2 variants that look for multiple variability at these protein sites to finally determine how these mutations affect vaccine-induced immunity.
B lymphocytes are specialized cells of the immune system that play an important role in the humoral response, the main defense mechanism against pathogens that replicate outside the host cell (extracellular pathogens) such as Staphylococcus or Streptococcus bacteria.
The main function of B cells is the recognition of molecules unknown to the organism, called antigens, and the production of specific antibodies to neutralize them.
[This is a translation of the original article "Duro revés a la lucha contra el coronavirus: el último descubrimiento da miedo" published in espanadiario.net]