Analysis of the initial lot of the CDC 2019-Novel Coronavirus (2019-nCoV) real-time RT-PCR diagnostic panel.

At the start of the COVID-19 pandemic, the Centers for Disease Control and Prevention (CDC) designed, manufactured, and distributed the CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel for SARS-CoV-2 detection. The diagnostic panel targeted three viral nucleocapsid gene loci (N1, N2, and N3 primers and probes) to maximize sensitivity and to provide redundancy for virus detection if mutations occurred. After the first distribution of the diagnostic panel, state public health laboratories reported fluorescent signal in the absence of viral template (false-positive reactivity) for the N3 component and to a lesser extent for N1. This report describes the findings of an internal investigation conducted by the CDC to identify the cause(s) of the N1 and N3 false-positive reactivity. For N1, results demonstrate that contamination with a synthetic template, that occurred while the "bulk" manufactured materials were located in a research lab for quality assessment, was the cause of false reactivity in the first lot. Base pairing between the 3' end of the N3 probe and the 3' end of the N3 reverse primer led to amplification of duplex and larger molecules resulting in false reactivity in the N3 assay component. We conclude that flaws in both assay design and handling of the "bulk" material, caused the problems with the first lot of the 2019-nCoV Real-Time RT-PCR Diagnostic Panel. In addition, within this study, we found that the age of the examined diagnostic panel reagents increases the frequency of false positive results for N3. We discuss these findings in the context of improvements to quality control, quality assurance, and assay validation practices that have since been improved at the CDC.

High-throughput quantitation of SARS-CoV-2 antibodies in a single-dilution homogeneous assay.

SARS-CoV-2 emerged in late 2019 and has since spread around the world, causing a pandemic of the respiratory disease COVID-19. Detecting antibodies against the virus is an essential tool for tracking infections and developing vaccines. Such tests, primarily utilizing the enzyme-linked immunosorbent assay (ELISA) principle, can be either qualitative (reporting positive/negative results) or quantitative (reporting a value representing the quantity of specific antibodies). Quantitation is vital for determining stability or decline of antibody titers in convalescence, efficacy of different vaccination regimens, and detection of asymptomatic infections. Quantitation typically requires two-step ELISA testing, in which samples are first screened in a qualitative assay and positive samples are subsequently analyzed as a dilution series. To overcome the throughput limitations of this approach, we developed a simpler and faster system that is highly automatable and achieves quantitation in a single-dilution screening format with sensitivity and specificity comparable to those of ELISA.

Rapid development of neutralizing and diagnostic SARS-COV-2 mouse monoclonal antibodies.

The need for high-affinity, SARS-CoV-2-specific monoclonal antibodies (mAbs) is critical in the face of the global COVID-19 pandemic, as such reagents can have important diagnostic, research, and therapeutic applications. Of greatest interest is the ~ 300 amino acid receptor binding domain (RBD) within the S1 subunit of the spike protein because of its key interaction with the human angiotensin converting enzyme 2 (hACE2) receptor present on many cell types, especially lung epithelial cells. We report here the development and functional characterization of 29 nM-affinity mouse SARS-CoV-2 mAbs created by an accelerated immunization and hybridoma screening process. Differing functions, including binding of diverse protein epitopes, viral neutralization, impact on RBD-hACE2 binding, and immunohistochemical staining of infected lung tissue, were correlated with variable gene usage and sequence.

Efficacy analysis of hyperbaric oxygen therapy in the treatment of severe coronavirus disease 2019 patients

Objective To explore the potential mechanisms underlying the prominent efficiency of hyperbaric oxygen therapy (HBOT) in the treatment of severe coronavirus disease 2019 (COVID-19) patients. Methods Five COVID-19 patients, aged from 24 to 69 years old, received HBOT after routine therapies failed to stop the deterioration and progressive hypoxemia in General Hospital of the Yangtze River Shipping. The procedure of HBOT was as follows: compressed to 2.0 ATA (0.1 MPa gauge pressure, patient 1) or 1.6 ATA (0.06 MPa gauge pressure, patient 2-5) at a constant rate for 15 min, maintained for 90 min (first treatment) or 60 min (subsequent treatment), then decompressed to normal pressure for 20 min, once a day;the patients inhaled oxygen with the mask of Built-in-Breathing System continuously;and HBOT was ended when the daily mean pulse oxygen saturation (SpO2) in wards was above 95% for two days. The symptoms, respiratory rate (RR), SpO2, arterial blood gas analysis, blood routine, coagulation function, high-sensitivity C-reactive protein (hs-CRP) and chest computed tomography (CT) were collected. Paired t test was used to compare each index before and after treatment. Results After the first HBOT, the symptoms and signs of the five patients began to improve. Supine breathlessness disappeared after HBOT for four times, and digestive tract symptoms completely disappeared and only mild chest pain and breathlessness at rest and in motion remained after HBOT for five times. After finishing HBOT, the RR of the patients was significanlty lower than that before HBOT ([20.80±2.28] min-1 vs [27.20±5.40] min-1, P<0.05). After finishing HBOT, daily SpO2 in wards was increased day by day, and the daily mean SpO2 recovered to more than 95% after the first, second, third, third and sixth HBOT in the five patients, respectively. After the first HBOT decompression, SpO2 was (93.60±0.07)%, which was signficantly higher than that before HBOT ([73.20±6.42] %) (P<0.05). SpO2 values before compression of the second and third HBOT were signficantly higher than that before the first HBOT (both P<0.05). There was no significant difference in the SpO2 immediately before and after the third HBOT (P>0.05). Before HBOT, the arterial partial pressure of carbon dioxide (PaCO2) of the patients was (31.48±3.40) mmHg (1 mmHg=0.133 kPa), which was lower than the normal range (35-45 mmHg). After finishing HBOT, arterial partial pressure of oxygen ([130.20±18.58] mmHg), arterial oxygen saturation ([98.40±0.55]%), lymphocyte proportion (0.207 8±0.074 2) and lymphocyte count ([1.09±0.24]×109/L) were significantly higher than those before HBOT ([61.60±15.24] mmHg, [73.20±6.43]%, 0.094 6±0.062 1, and [0.61± 0.35]×109/L), while the levels of fibrinogen ([2.97±0.27] g/L) and hs-CRP ([7.76±6.95] mg/L) were significantly lower than those before HBOT ([4.45±0.94] g/L and [30.36±1.27] mg/L) (all P<0.05). The levels of lacttic acid and D-dimer were decreased after HBOT versus before HBOT ([1.13±0.10] mmol/L vs [2.16±1.71] mmol/L, [0.42±0.13] mg/L vs [1.84±1.29] mg/L), but the differences were not significant (both P>0.05). All the five patients had typical lung CT imaging changes of severe COVID-19 before HBOT, which were improved after HBOT. Conclusion Systemic hypoxia induced by persistent hypoxemia may be the main reason for the deterioration of severe COVID-19. The respiratory dysfunction of COVID-19 is mainly alveolar gas exchange dysfunction. HBOT may be the best way to correct the progressive hypoxemia which can not be controlled by atmospheric oxygen supply in severe COVID-19 patients. HBOT can provide enough oxygen supply for the continuous hypoxia tissues, and is beneficial to the recovery of immune function, circulatory function and stress level, so as to improve the condition of patients.