Patient-derived monoclonal antibodies to SARS-CoV-2 nucleocapsid protein N-terminal and C-terminal domains cross-react with their counterparts of SARS-CoV, but not other human betacoronaviruses.

Introduction: SARS-CoV-2 nucleocapsid (N) protein plays a key role in multiple stages of the viral life cycle such as viral replication and assembly. This protein is more conserved than the Spike protein of the virus and can induce both humoral and cell-mediated immune responses, thereby becoming a target for clinical diagnosis and vaccine development. However, the immunogenic characteristics of this protein during natural infection are still not completely understood. Methods: Patient-derived monoclonal antibodies (mAbs) against SARS-CoV-2 N protein were generated from memory B cells in the PBMCs using the antigen-specific B cell approach. For epitope mapping of the isolated hmAbs, a panel of series-truncated N proteins were used , which covered the N-terminal domain (NTD, aa 46-174 ) and C-terminal domain (CTD, aa 245-364 ), as well as the flanking regions of NTD and CTD. NTD- or CTD-specific Abs in the plasma from COVID-19 patients were also tested by ELISA method. Cross-binding of hmAbs or plasma Abs in COVID-19 patients to other human ß-CoV N proteins was determined using the capture ELISA. Results: We isolated five N-specific monoclonal antibodies (mAbs) from memory B cells in the peripheral blood of two convalescent COVID-19 patients. Epitope mapping revealed that three of the patient-derived mAbs (N3, N5 and N31) targeted the C-terminal domain (CTD), whereas two of the mAbs (N83 and 3B7) targeted the N-terminal domain (NTD) of SARS-CoV-2 N protein. All five patient-derived mAbs were cross-reactive to the N protein of SARS-CoV but showed little to no cross-reactivity to the N proteins of other human beta coronaviruses (ß-CoVs). We also tested 52 plasma samples collected from convalescent COVID-19 patients for Abs against the N proteins of human ß-CoVs and found that 78.8% of plasma samples showed detectable Abs against the N proteins of SARS-CoV-2 and SARS-CoV. No plasma sample had cross-reactive Abs to the N protein of MERS-CoV. Cross-reactive Abs to the N proteins of OC43 and HKU1 were detected in 36.5% (19/52) and 19.2% (10/52) of plasma samples, respectively. Discussion: These results suggest that natural SARS-CoV-2 infection elicits cross-reactive Abs to the N protein of SARS-CoV and that the five patient-derived mAbs to SARS-CoV-2 N protein NTD and CTD cross-react with their counterparts of SARS-CoV, but not other human ß-CoVs. Thus, these five patient-derived mAbs can potentially be used for developing the next generation of COVID-19 At-Home Test kits for rapid and specific screening of SARS-CoV-2 infection.

Clinical characteristics and immune profile alterations in vaccinated individuals with breakthrough Delta SARS-CoV-2 infections.

Despite timely immunization programs, and efficacious vaccines conveying protection against SARS-CoV-2 infection, breakthrough infections in vaccinated individuals have been reported. The Delta variant of concern (VOC) outbreak in Guangzhou resulted in local transmission in vaccinated and non-vaccinated residents, providing a unique opportunity to study the protective effects of the inactivated vaccines in breakthrough infection. Here, we find that the 2-dose vaccinated group has similar peak viral titers and comparable speeds of viral RNA clearance to the non-vaccinated group but accelerated viral suppression in the middle course of the disease. We quantitatively demonstrate that peak viral pneumonia is significantly mitigated in the 2-dose vaccine group (median 0.298%) compared with the non-vaccinated (5.77%) and 1-dose vaccine (3.34%) groups. Pneumonia absorbance is approximately 6 days ahead in the 2-dose group (median 10 days) than in the non-vaccinated group (16 days) (p = 0.003). We also observe reduced cytokine inflammation and markedly undisturbed gene transcription profiles of peripheral blood mononuclear cells (PBMCs) in the 2-dose group. In short, our study demonstrates that prior vaccination substantially restrains pneumonia development, reduces cytokine storms, and facilitates clinical recovery.

[Cardiac presentations in severe and critical coronavirus disease 2019].

OBJECTIVE: To investigate the cardiac presentations and the possible influencing factors of severe and critical coronavirus disease 2019 (COVID-19). METHODS: A retrospective study was conducted. Patients with severe and critical COVID-19 admitted to the Eighth People's Hospital of Guangzhou from January 21st to February 24th 2020 were enrolled. According to the clinical classification, the patients were divided into severe group and critical group. The myocardial injury markers, such as lactate dehydrogenase (LDH), aspartate aminotransferase (AST), creatine kinase (CK), cardiac troponin I (cTnI), myoglobin (MYO), MB isoenzyme of creatine kinase (CK-MB), B-type natriuretic peptide (BNP) and electrocardiogram (ECG) changes were compared between the two groups. RESULTS: A total of 55 COVID-19 patients were selected, including 15 critical cases and 40 severe cases. The patients with severe and critical COVID-19 were male-dominated (61.8%), the average age was (61.2±13.0) years old, 83.6% (46 cases) of them had contact history of Hubei, 38.2% (21 cases) of them were complicated with hypertension. There was no significant difference in baseline data between the critical group and the severe group. Myocardial injury markers of critical and severe COVID-19 patients were increased in different proportion, LDH increased in most patients (20 severe cases and 7 critical cases), followed by AST (16 severe cases and 5 critical cases). There was significant difference in the number of patients with elevated CK between severe group and critical group (cases: 1 vs. 4, P = 0.027). Abnormal ECG was found in 39 of 42 patients with ECG examination. Nonspecific change of T wave was the most common. Before and after treatment, 9 of 15 patients with changes of ECG and myocardial injury markers had oxygenation index less than 100 mmHg (1 mmHg = 0.133 kPa), and the prominent changes of ECG were heart rate increasing and ST-T change. CONCLUSIONS: The increase of myocardial injury markers and abnormal ECG were not specific to the myocardial injury of severe and critical COVID-19 patients. At the same time, the dynamic changes of myocardial injury markers and ECG could reflect the situation of myocardial damage.

No Evidence of Re-infection or Person-to-Person Transmission in Cured COVID-19 Patients in Guangzhou, a Retrospective Observational Study.

Objectives: To clarify the clinical characteristics of cured patients with coronavirus disease (COVID-19), and to clarify the re-infection and person-to-person transmission in the cured. Methods: A total of 187 cured COVID-19 patients with antibody test were followed up every 2 weeks in this retrospective observational study. Assessment for general condition, symptoms, epidemiological contact history, polymerase chain reaction (PCR) assay, and antibody tests were performed and recorded. Information from Guangzhou CDC was also screened. Results: There were 33 (17.6%) patients with negative results for IgG and 35 (18.7%) patients with positive results for IgM. The average days of antibody detection from disease onset were 53.0. PCR assay was positive in 10 (5.3%) patients during the follow-up. Neither IgG nor IgM results showed a relationship with PCR test results (all P > 0.05). Neither re-infection nor person-to-person transmission was found in the cured patients. Factors associated with appearance of antibody comprised hospitalization days (OR: 1.06, 95%CI: 1.02-1.11, P = 0.006) and antibiotics treatment (OR: 3.50, 95%CI: 1.40-8.77, P = 0.007). Conclusions: In our study, no evidence of person-to-person transmission was found in cured COVID-19 patients. There seemed to be no re-infection in the cured COVID-19 patients in Guangzhou. These finding suggest that the cured do not cause the spread of disease. Additionally, neither IgG nor IgM can be used to replace the PCR test in cured patients.

Detectable 2019-nCoV viral RNA in blood is a strong indicator for the further clinical severity.

The novel coronavirus (2019-nCoV) infection caused pneumonia. we retrospectively analyzed the virus presence in the pharyngeal swab, blood, and the anal swab detected by real-time PCR in the clinical lab. Unexpectedly, the 2109-nCoV RNA was readily detected in the blood (6 of 57 patients) and the anal swabs (11 of 28 patients). Importantly, all of the 6 patients with detectable viral RNA in the blood cohort progressed to severe symptom stage, indicating a strong correlation of serum viral RNA with the disease severity (p-value = 0.0001). Meanwhile, 8 of the 11 patients with annal swab virus-positive was in severe clinical stage. However, the concentration of viral RNA in the anal swab (Ct value = 24 + 39) was higher than in the blood (Ct value = 34 + 39) from patient 2, suggesting that the virus might replicate in the digestive tract. Altogether, our results confirmed the presence of virus RNA in extra-pulmonary sites.