Periodic Evaluation of Anti-SARS-CoV-2 Antibody Levels and Determination of Surrogate Virus Neutralization in Healthcare Workers with COVID-19

Abstract

Since its first detection in Wuhan, China, in December 2019, coronavirus disease-2019 (COVID-19) has turned into a pandemic, causing high rate of death and economic losses worldwide. Severe acut respiratory syndrome coronavirus-2 (SARS-CoV-2) is a zoonotic, positive-polar RNA virus and initiates an immune response that targets proteins involved in viral infection and replication and includes the production of neutralizing antibodies. Antibodies remain detectable in the plasma for months, binding to virus antigens quickly and strongly and they block infiltration and replication. The detection of total antibody and virus neutralization provides clues about the severity of the disease and the risk of reinfection, as well as being used in epidemiological studies such as virus exposure and determination of infection rate in the population. In this study, it was aimed to determine the disappearance time of total antibodies from the plasma by periodically monitoring the healthcare workers who have been documented as symptomatically or asymptomatically infected with COVID-19 and also to predict the risk of re-infection and the need for vaccination by measuring surrogate virus neutralization. After 30-45 days from the diagnosis of COVID-19 disease (in the acute period), in the 3rd, 6th and 9th months peripheral blood samples were taken from 123 healthcare professionals working in different areas of our hospital in terms of transmission risk and total antibody levels were measured against the SARS-CoV-2 N antigen and surrogate virus neutralization by serological methods. After the first reverse transcriptase polymerase chain reaction (RT-PCR) positivity, SARS-CoV-2-specific anti-nucleocapsid total antibody concentrations were reached to a peak value between 30-45 days (80.37 COI + 37.26) and persisted as positive in most of the participants (111/123, 90.2%) up to six months. Higher peak anti-nucleocapsid antibody titers were associated with longer detection of the antibody (r=0.745, p<0.02). The higher antibody titers were also found to be associated with increased age, more symptomatic disease, higher risk of recurrent virus exposure and lower RT-PCR Ct values and the time for these antibodies to disappear from the blood was also longer (p<0.02). Surrogate virus neutralization were over 70% in 97.8% (90/92) of the participants in the acute period of infection. The SARS-CoV-2 anti-nucleocapsid total antibody level is dynamic and disappears from the plasma within months, this period is shorter in young people, those with asymptomatic patients, those with lower antibody titer and low frequency of virus exposure and also the neutralization of the virus is much more lower. Monitoring of the antibody levels will guide about the immune response against SARS-CoV-2 and these results will give information about re-infection.