Parkinson's: the symptoms of a disease with 50% of patients still undiagnosed
13 April 2022
They discover how ovarian cancer defies immunotherapy and makes it one of the most difficult tumors to treat
13 April 2022
"The finding of when they are undetectable is not necessarily indicative of a reduction in immunity since the immune memory of T and B cells could generate long-term protection"
The antibodies against COVID-2 They become undetectable in serological tests, in 43,3% of patients, seven months after infection.
This is the main conclusion of a work that analyzed the evolution of IgG antibody levels in the population, within the framework of the national seroepidemiological study of SARS-CoV-2 (ENE-COVID).
IgG is the predominant class of immunoglobulin in the body and can be found in blood and other fluids.
It is an antibody that protects against bacterial and viral infections, and develops specifically several days after infection.
Most patients infected with SARS-CoV-2 develop IgG antibodies against different proteins of the virus such as the spike proteins (S) and nucleocapsid (N), and therefore can be used as antigens in clinical serology assays for the detection of antibodies.
However, as explained Mayte Perez Olmeda, head of the Serology Laboratory of the National Microbiology Center of the Carlos III Health Institute (ISCIII), researcher in the Infectious Diseases area of the CIBER (CIBERINFEC):
"Published data on how long the presence of antibodies against SARS-CoV-2 lasts after a natural infection is inconsistent, with research reporting a rapid decrease in IgG within 3 months after infection, to other works which show that IgG levels remain stable for 4 to 6 months",
The IgG antibody undetectable over the months
Within the framework of this new work, the ENE-COVID Study Group – in which members of the CIBER from the areas of Infectious Diseases and Epidemiology and Public Health and the ISCIII participate – took advantage of the possibilities of this large seroepidemiological project to analyze the Evolutionary trends in the detection of IgG against the N protein.
This is an immunoassay in the four rounds of the ENE-COVID study, developed over a period of seven months, between April and November 2020.
Well, of the 7.400 people who participated in the four rounds, a total of 2.595 (35,1%) were positive for IgG in at least one round.
"In 43,3% of patients who had tested positive in the first round, anti-nucleocapsid IgG became undetectable after seven months," he details. Jesús Oteo, scientific director of CIBERINFEC and one of the coordinators of this study.
Does the duration of antibodies depend on the severity of the disease?
According to the researcher, the reason for not detecting antibodies in such a high percentage of patients...
"It may be due to the fact that the majority of positive patients in our cohort were asymptomatic (about a third of the participants) or had mild infections, which would lead us to conclude that the IgG response is heterogeneous and is conditioned by the severity of the infection."
Undetected antibodies do not mean lack of immunity
The study confirms that a substantial percentage of patients infected by coronavirus You can have negative serological test results in the months after infection, which is why many people assume that they have not had the infection.
However, "this finding is not necessarily indicative of a reduction in immunity against SARS-CoV-2 since the immune memory associated with T and B cells could generate long-term protection, as occurs with other infectious diseases," underlines the director of the CIBERINFEC area.
Source: El Periódico de Aragón
