Titers of antibodies the receptor-binding domain (RBD) of ancestral SARS-CoV-2 are predictive for levels of neutralizing antibodies to multiple variants (preprint)

Diagnostic assays currently used to monitor the efficacy of COVID-19 vaccines measure levels of antibodies to the receptor-binding domain of ancestral SARS-CoV-2 (RBDwt). However, the predictive value for protection against new variants of concern (VOCs) has not been firmly established. Here, we used bead-based arrays and flow cytometry to measure binding of antibodies to spike proteins and receptor-binding domains (RBDs) from VOCs in 12,000 sera. Effects of sera on RBD-ACE2 interactions were measured as a proxy for neutralizing antibodies. The samples were obtained from healthy individuals or patients on immunosuppressive therapy who had received two to four doses of COVID-19 vaccines and from COVID-19 convalescents. The results show that anti-RBDwt titers correlate with the levels of binding- and neutralizing antibodies against the Alpha, Beta, Gamma, Delta, Epsilon and Omicron variants. The benefit of multiplexed analysis lies in the ability to measure a wide range of anti-RBD titers using a single dilution of serum for each assay. The reactivity patterns also yield an internal reference for neutralizing activity and binding antibody units per milliliter (BAU/ml). Results obtained with sera from vaccinated healthy individuals and patients confirmed and extended results from previous studies on time-dependent waning of antibody levels and effects of immunosuppressive agents. We conclude that anti-RBDwt titers correlate with levels of neutralizing antibodies against VOCs and propose that our method may be implemented to enhance the precision and throughput of immunomonitoring.

Long COVID affects home-isolated young patients (preprint)

Long-term complications following COVID-19 are common in hospitalised patients, but the spectrum of symptoms in milder cases remains unclear. In a Norwegian prospective cohort study of 312 patients, 61% of COVID-19 patients (247 home-isolated and 65 hospitalised) had persistent symptoms at six months, most commonly fatigue (37%), impaired concentration (26%), disturbed smell and/or taste (25%), memory loss (24%) and dyspnoea (21%). In young home-isolated adults, aged 16–30, 52% had symptoms at six months, with fatigue (21%), dyspnoea (13%), impaired concentration (13%) and memory loss (11%) posing particular challenges. Pre-existing chronic lung disease and high convalescent antibody titres predicted persistent symptoms, particularly fatigue. Our finding that young, home-isolated adults with mild COVID-19 are at risk of long-lasting dyspnoea and cognitive symptoms highlights the importance of infection control measures, such as vaccination.