Maintenance of neutralizing antibodies over ten months in convalescent SARS‐CoV‐2 afflicted patients

Sonnleitner, Sissy Therese; Prelog, Martina; Jansen, Bianca; Rodgarkia‐Dara, Chantal; Gietl, Sarah; Schönegger, Carmen Maria; Koblmüller, Stephan; Sturmbauer, Christian; Posch, Wilfried; Almanzar, Giovanni; Jury, Hanna; Loney, Tom; Tichy, Alexander; Nowotny, Norbert; Walder, Gernot

Knowledge of the level and duration of protective immunity against SARS‐CoV‐2 after primary infection is of crucial importance for preventive approaches. Currently, there is a lack of evidence on the persistence of specific antibodies. We investigated the generation and maintenance of neutralizing antibodies of convalescent SARS‐CoV‐2‐afflicted patients over a ten‐month period post‐primary infection using an immunofluorescence assay, a commercial chemiluminescent immunoassay and an in‐house enzyme‐linked neutralization assay. We present the successful application of an improved version of the plaque‐reduction neutralization assay which can be analysed optometrically to simplify data interpretation. Based on the results of the enzyme‐linked neutralization assay, neutralizing antibodies were maintained in 77.4% of convalescent individuals without relevant decay over ten months. Furthermore, a positive correlation between severity of infection and antibody titre was observed. In conclusion, SARS‐CoV‐2‐afflicted individuals have been proven to be able to develop and maintain neutralizing antibodies over a period of ten months after primary infection. Findings suggest long‐lasting presumably protective humoral immune responses after wild‐type infection.