A recent study conducted in a cohort of healthcare workers showed that the levels of IgG antibodies against SARS-CoV-2 Spike protein remained stable, or even increased, seven months after the infection.
The result of the study is published in the journal ‘Nature Communications’ which also supported the idea that pre-existing antibodies against common cold coronaviruses could provide safety against COVID-19. This study was coordinated by the Barcelona Institute for Global Health (ISGlobal), an institution supported by the “la Caixa” Foundation, in collaboration with the Hospital Clinic of Barcelona.
It is critical to better understand the dynamics and duration of immunity to SARS-CoV-2 as well as the possible role of pre-existing antibodies against the coronaviruses that cause common colds, in order to predict the pandemic’s evolution and develop effective strategies.
Hence, keeping this goal in mind, the team led by ISGlobal researcher Carlota Dobano followed a unit of healthcare workers at the Hospital Clinic (SEROCOV study) from the beginning of the pandemic, in order to assess the levels of antibodies against different SARS-CoV-2 antigens over time.
Dobano said, “This is the first study that evaluates antibodies to such a large panel of SARS-CoV-2 antibodies over 7 months.”
The blood samples from 578 participants have been analysed by the team of researchers, taken at four different time points between March and October 2020. For the research, they used the Luminex technology to measure, in the same sample the level and type of IgA, IgM or IgG antibodies to 6 different SARS-CoV-2 antigens as well as the presence of antibodies against the four coronaviruses that cause common colds in humans.
Gemma Moncunill, senior co-author of the study said, “Rather surprisingly, we even saw an increase of IgG anti-Spike antibodies in 75 per cent of the participants from month five onwards, without any evidence of re-exposure to the virus.”
However, in the cohort, no reinfections were observed. The results regarding antibodies against human cold coronaviruses (HCoV), suggest that they could confer cross-safety against coronavirus infection or disease. People who were infected by SARS-CoV-2 had lower levels of HCoV antibodies. Moreover, asymptomatic individuals had higher levels of anti-HCoV IgG and IgA than those with symptomatic infections.
“Although cross-protection by pre-existing immunity to common cold coronaviruses remains to be confirmed, this could help explain the big differences in susceptibility to the disease within the population,” concluded Dobano.
In collaboration with researchers at the University of Barcelona, they also analysed the neutralising activity of antibodies and the funding for the study was conducted from the European innovation network EIT Health. However, the findings further showed that the majority of infections among healthcare workers occurred during the first pandemic wave (the percentage of participants with SARS-CoV-2 antibodies increased only slightly between March and October — from 13.5 per cent to 16.4 per cent).
With the exception of IgM and IgG antibodies against the nucleocapsid (N), the rest of IgG antibodies (including those with neutralising activity) remained stable over time, confirming results from other recent studies.