Evidence and implications of pre-existing humoral cross-reactive immunity to SARS-CoV-2

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged throughout the world. Building knowledge around Covid-19 is crucial to devise facts based approaches to respond efficiently against this pandemic. Aim: We aimed to investigate pre-existing humoral cross-reactive immunity to SARS-CoV-2. Method: We have tested the reactivity against SARS-CoV-2 nucleocapsid (N) antigen of sera collected from healthy healthcare volunteers in 2014. We assessed immunoglobulins reactive against SARS-CoV-2 N-antigen using a well-validated serological platform; Elecsys assay. Results: Sera from 32 subjects (out of 135 [23.7%]) were reactive to SARS-CoV-2 N-antigen, suggesting the presence of anti-SARS-CoV-2 N-antigen antibodies. Conclusion: Although the clinical relevance of the observed reactivity can only be speculated and needs to be investigated, the implication of this finding for coronavirus disease 2019 seroepidemiological survey and vaccines' clinical trials is critical.