Highlights d A linear epitope landscape of the SARS-CoV-2 Spike from 1,051 COVID-19 patients d Responsive epitopes are highly variable among patients and correlate with severity d The RBD lacks linear epitopes, but two other regions are rich in linear epitopes d Little neutralization activity is observed for the linear-epitopeelicited antibodies

Background/Aims: MicroRNA (miRNA) is a small non-coding RNA molecule that functions in regulation of gene expression by targeting mRNA to affect its stability and/or translation. The aim of this study was to evaluate the miRNAs involvement in gestational diabetes mellitus (GDM), a well known risk factor for fetal overgrowth. Methods: Differential microRNA expression in placental tissues of normal controls and women with GDM were identified by miRNA micorarray analysis and further confirmed by quantitative real-time PCR (qRT-PCR) on an independent set of normal and GDM placental tissues. Target genes of microRNAs were bioinformatically predicted and verified in vitro by Western blotting. Results: Our results uncovered 9 miRNAs that were significantly deregulated in GDM samples: miR-508-3p was up-regulated and miR-27a, miR-9, miR-137, miR-92a, miR-33a, miR-30d, miR-362-5p and miR-502-5p were down-regulated. Bioinformatic approaches revealed that the microRNAs signature identifies gene targets involved in EGFR (epidermal growth factor receptor)-PI3K (phosphoinositide 3-Kinase)-Akt (also known as protein kinase B) pathway, a signal cascade which plays important roles in placental development and fetal growth. We found that the protein levels of EGFR, PI3K and phospho-Akt were up-regulated and PIKfyve (a FYVE finger-containing phosphoinositide kinase), a negative regulator of EGFR signaling, was down-regulated significantly in GDM tissues. We also confirmed PIKfyve was a direct target of miR-508-3p. Conclusion: Our data identified a miRNA signature involvement in GDM which may contribute to macrosomia through enhancing EGFR signaling.

Serological tests play an essential role in monitoring and combating the COVID-19 pandemic. Recombinant spike protein (S protein), especially the S1 protein, is one of the major reagents used for serological tests. However, the high cost of S protein production and possible cross-reactivity with other human coronaviruses pose unavoidable challenges. By taking advantage of a peptide microarray with full spike protein coverage, we analyzed 2,434 sera from 858 COVID-19 patients, 63 asymptomatic patients and 610 controls collected from multiple clinical centers. Based on the results, we identified several S protein-derived 12-mer peptides that have high diagnostic performance. In particular, for monitoring the IgG response, one peptide (aa 1148–1159 or S2–78) exhibited a sensitivity (95.5%, 95% CI 93.7–96.9%) and specificity (96.7%, 95% CI 94.8–98.0%) comparable to those of the S1 protein for the detection of both symptomatic and asymptomatic COVID-19 cases. Furthermore, the diagnostic performance of the S2–78 (aa 1148–1159) IgG was successfully validated by ELISA in an independent sample cohort. A panel of four peptides, S1–93 (aa 553–564), S1–97 (aa 577–588), S1–101 (aa 601–612) and S1–105 (aa 625–636), that likely will avoid potential cross-reactivity with sera from patients infected by other coronaviruses was constructed. The peptides identified in this study may be applied independently or in combination with the S1 protein for accurate, affordable, and accessible COVID-19 diagnosis.