ANTI-NUCLEOCAPSIDE IgG ANTIBODIES: A POTENTIAL MARKER FOR A MORE ACCURATE EPIDEMIOLOGICAL MONITORING OF SARS-COV-2 INFECTION

ABSTRACT

On March 11th, 2020, the World Health Organization (WHO) declared the pandemic status of CoronaVirus Disease-19 (COVID-19) caused by SARS-CoV-2. Viral nucleic acid detection using molecular testing is the gold standard to diagnose SARS-CoV-2 infection. Asymptomatic subjects or with mild symptoms may not be subjected to molecular diagnostic tests with important repercussions on epidemiological estimate. The overall evolution especially of post-pandemic dynamics, will be probably obtained by the detection of immune response. Humoral immune response against the nucleocapsid (N) protein is related to SARS-CoV-2 infection. The detection of these antibodies could discriminate cases with from cases without history of COVID-19 for a more accurate evaluation of population exposed to SARSCoV-2. In this retrospective study, we evaluated four subclasses of SARS-CoV-2 IgG (anti-S1, anti-S2, anti-RBD, anti-N) in n.200 blood samples (February-March 2022) of health workers of Azienda Sanitaria Provinciale (ASP) di Ragusa, already vaccinated against Covid-19 in the period February-March 2022. A statistically significant association between SARS-CoV-2 infection and seropositivity to anti-N IgG (p-value <0.0001) was found. In order to evaluate the SARS-CoV-2 anti-N antibodies titer trend, the cases with a positive history for COVID-19 were classified as follows cases with infection within three months and cases with infection after three months from serological test.No statistically association (p-value= 0.075) was found between seropositivity to anti-N IgG and SARS-CoV-2 infection within and after three months. We observed that approximately 30% of cases with a history for COVID-19 was seronegative for anti-N IgG within three months from infection.In post-pandemic period the evaluation of anti-N IgG in a time interval of less than three months could identify asymptomatic population exposed to SARS-CoV-2. Although our findings should be validated with a larger cohort, these results suggest that anti-N IgG might be used as a marker of early infection and assure a more accurate epidemiological estimate.