Comparison of 2 fully automated tests detecting antibodies against nucleocapsid N and spike S1/S2 proteins in COVID-19.

Automated assays for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in coronavirus disease 2019 (COVID-19) diagnostics have recently come available. We compared the performance of the Elecsys® Anti-SARS-CoV-2 and LIAISON® SARS-CoV-2 S1/S2 IgG tests. The seroconversion panel comprised of 120 samples from 13 hospitalized COVID-19 patients. For the sensitivity and specificity testing, samples from COVID-19 outpatients >15 days after positive nucleic acid amplification test (NAAT) result (n = 35) and serum control samples collected before the COVID-19 era (n = 161) were included in the material. Samples for the detection of possible cross-reactions were also tested. Based on our results, the SARS-CoV-2 antibodies can be quite reliably detected 2 weeks after NAAT positivity and 3 weeks after the symptom onset with both tests. However, since some COVID-19 patients were positive only with Elecsys®, the antibodies should be screened against N-antigen (Elecsys®) and reactive samples confirmed with S antigen (LIAISON®), but both results should be reported. In some COVID-19 patients, the serology can remain negative.

Flinck H ，Rauhio A ，Luukinen B ，Lehtimäki T ，Haapala AM ，Seiskari T ，Aittoniemi J ... -  《-》

Quantitative SARS-CoV-2 Serology in Children With Multisystem Inflammatory Syndrome (MIS-C).

We aimed to measure severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological responses in children hospitalized with multisystem inflammatory syndrome in children (MIS-C) compared with those with coronavirus disease 2019 (COVID-19), those with Kawasaki disease (KD), and hospitalized pediatric controls. From March 17, 2020, to May 26, 2020, we prospectively identified hospitalized children with MIS-C (n = 10), symptomatic COVID-19 (n = 10), and KD (n = 5) and hospitalized controls (n = 4) at Children's Healthcare of Atlanta. With institutional review board approval, we obtained prospective and residual blood samples from these children and measured SARS-CoV-2 spike receptor-binding domain (RBD) immunoglobulin M and immunoglobulin G (IgG), full-length spike IgG, and nucleocapsid protein antibodies using quantitative enzyme-linked immunosorbent assays and SARS-CoV-2 neutralizing antibodies using live-virus focus-reduction neutralization assays. We statistically compared the log-transformed antibody titers among groups and performed linear regression analyses. All children with MIS-C had high titers of SARS-CoV-2 RBD IgG antibodies, which correlated with full-length spike IgG antibodies (R 2 = 0.956; P < .001), nucleocapsid protein antibodies (R 2 = 0.846; P < .001), and neutralizing antibodies (R 2 = 0.667; P < .001). Children with MIS-C had significantly higher SARS-CoV-2 RBD IgG antibody titers (geometric mean titer 6800; 95% confidence interval 3495-13 231) than children with COVID-19 (geometric mean titer 626; 95% confidence interval 251-1563; P < .001), children with KD (geometric mean titer 124; 95% confidence interval 91-170; P < .001), and hospitalized controls (geometric mean titer 85; P < .001). All children with MIS-C also had detectable RBD immunoglobulin M antibodies, indicating recent SARS-CoV-2 infection. RBD IgG titers correlated with the erythrocyte sedimentation rate (R 2 = 0.512; P < .046) and with hospital (R 2 = 0.548; P = .014) and ICU lengths of stay (R 2 = 0.590; P = .010). Quantitative SARS-CoV-2 serology may have a role in establishing the diagnosis of MIS-C, distinguishing it from similar clinical entities, and stratifying risk for adverse outcomes.

Rostad CA ，Chahroudi A ，Mantus G ，Lapp SA ，Teherani M ，Macoy L ，Tarquinio KM ，Basu RK ，Kao C ，Linam WM ，Zimmerman MG ，Shi PY ，Menachery VD ，Oster ME ，Edupuganti S ，Anderson EJ ，Suthar MS ，Wrammert J ，Jaggi P ... -  《-》

Validation of a new automated chemiluminescent anti-SARS-CoV-2 IgM and IgG antibody assay system detecting both N and S proteins in Japan.

Yokoyama R ，Kurano M ，Morita Y ，Shimura T ，Nakano Y ，Qian C ，Xia F ，He F ，Kishi Y ，Okada J ，Yoshikawa N ，Nagura Y ，Okazaki H ，Moriya K ，Seto Y ，Kodama T ，Yatomi Y ... -  《PLoS One》

Back to normal; serological testing for COVID-19 diagnosis unveils missed infections.

The gold standard for coronavirus disease (COVID-19) diagnosis has been the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA by nucleic acid amplification testing (NAAT). On the other hand, serological testing for COVID-19 may offer advantages in detecting possibly overlooked infections by NAAT. To evaluate seroconversion of NAAT-negative pneumonia patients, immunoglobulin M (IgM) and IgG targeting the spike protein of SARS-CoV-2 were semiquantified by an immunofluorescence assay. Seroconversion was confirmed by another serological method, targeting the nucleocapsid protein. Eight suspected but unconfirmed COVID-19 pneumonia patients (median age, 39 years; range, 21-55) were included. The median period between symptom onset and NAAT sample collection was 6 days (2-27 days). None of them had tested positive for SARS-CoV-2 by NAAT. In contrast, all eight patients revealed seropositivity with the two serological methods, indicating actual seroconversion against SARS-CoV-2. The median period between onset and blood sampling was 26.5 days (7-51 days). Eight patients with COVID-19 pneumonia, initially tested negative for SARS-CoV-2 by NAAT, were finally confirmed of the diagnosis by serological testing. To cover the whole spectrum of this heterogenous infectious disease, serology testing should be implemented to the multitiered diagnostic algorithm for COVID-19.

Tsuchida T ，Nitahara Y ，Suzuki S ，Komase Y ，Candray K ，Kido Y ，Nakagama Y ，Yamasaki Y ，Imamura M ，Kawahata K ，Kunishima H ，Fujitani S ，Mineshita M ，Matsuda T ... -  《-》

Serological Assays for Assessing Postvaccination SARS-CoV-2 Antibody Response.

Mahmoud SA ，Ganesan S ，Naik S ，Bissar S ，Zamel IA ，Warren KN ，Zaher WA ，Khan G ... -  《Microbiology Spectrum》