Assessment of antiphospholipid antibodies and calprotectin as biomarkers for discriminating mild from severe COVID-19.

BACKGROUND: To explore the association of thrombo-inflammatory biomarkers with severity in coronavirus disease (COVID-19), we measured antiphospholipid antibodies (aPL) and calprotectin in sera of COVID-19 patients. METHODS: Anticardiolipin antibodies (aCL) and anti-ß2-glycoprotein I antibodies were measured using enzyme-linked immunosorbent assay (ELISA) and multiplex flow immunoassay (MFIA) in hospitalized COVID-19 patients (N = 105) and healthy controls (N = 38). Anti-phosphatidylserine/prothrombin antibodies, calprotectin, and C-reactive protein (CRP) levels were also measured. We assessed the potential correlation between calprotectin levels and various laboratory parameters that were measured during the hospitalization period. After stratifying COVID-19 patients into two groups by their oxygenation status or acute respiratory distress syndrome presentation, the discriminatory performance of each biomarker was evaluated. RESULTS: A high proportion of COVID-19 patients (29.5%, 31/105) had low aCL IgM titers that were detectable by ELISA but mostly below the detection limit of MFIA. Calprotectin levels in severe groups of COVID-19 were significantly higher than those in non-severe groups, while CRP levels revealed no significant differences. Serum calprotectin levels showed strong to moderate degree of correlation with other routinely used parameters including peak levels of CRP, ferritin, procalcitonin, BUN, and neutrophil-to-lymphocyte ratio, but a negative correlation with minimal lymphocyte count and CD4+ T cells. The discriminatory performance was highest for calprotectin in discriminating severe groups of COVID-19. CONCLUSIONS: Serum calprotectin levels were significantly elevated in severe COVID-19 cases. The prevalence of clinically significant aPL did not differ. The link between calprotectin and inflammatory pathway in COVID-19 may help improve the management and outcomes of COVID-19 patients.

Comparative analysis of mutational hotspots in the spike protein of SARS-CoV-2 isolates from different geographic origins.

The spike (S) protein mutations of SARS-CoV-2 are of major concern in terms of viral transmission and pathogenesis. Hence, we developed a PCR-based method to rapidly detect the 6 mutational hotspots (H49Y, G476S, V483A, H519Q, A520S, and D614G) in the S protein and applied this method to analyze the hotspots in the viral isolates from different geographical origins. Here, we identified that there was only the D614G mutation in the viral isolates. As of September 30, 2020, the analysis of 113,381 sequences available from the public repositories revealed that the SARS-CoV-2 variant carrying G614 has become the most prevalent form globally. Our results support recent epidemiological and genomic data demonstrating that the viral infectivity and transmission are enhanced by the S protein D614G mutation.

Novel indel mutation in the N gene of SARS-CoV-2 clinical samples that were diagnosed positive in a commercial RT-PCR assay.

Commercially available reverse transcription-polymerase chain reaction (RT-PCR) kits are being used as an important tool to diagnose SARS-CoV-2 infection in clinical laboratories worldwide. However, some kits lack sufficient clinical evaluation due to the need for emergency use caused by the current COVID-19 pandemic. Here we found that a novel insertion/deletion mutation in the nucleocapsid (N) gene of SARS-CoV-2 samples is a cause of negative results for the N gene in a widely used assay that received emergency use authorization (EUA) from US FDA and Conformite Europeenne-in vitro diagnostics (CE-IVD) from EU. Although SARS-CoV-2 is diagnosed positive by other target probes in the assay, our findings provide an evidence of the genetic variability and rapid evolution of SARS-CoV-2 as well as a reference in designing commercial RT-PCR assays.