21 Background: At present, PCR-based nucleic acid detection cannot meet the demands 22 for coronavirus infectious disease (COVID-19) diagnosis. Immunosorbent Assay (ELISA) kits based on recombinant SARS-CoV-2 nucleocapsid 27 protein (rN) and spike protein (rS) were used for detecting IgM and IgG antibodies, 28 and their diagnostic feasibility was evaluated.29 Results: Among the 214 patients, 146 (68.2%) and 150 (70.1%) were successfully 30 diagnosed with the rN-based IgM and IgG ELISAs, respectively; 165 (77.1%) and 31 159 (74.3%) were successfully diagnosed with the rS-based IgM and IgG ELISAs, 32 respectively. The positive rates of the rN-based and rS-based ELISAs for antibody 33 (IgM and/or IgG) detection were 80.4% and 82.2%, respectively. The sensitivity of 34 the rS-based ELISA for IgM detection was significantly higher than that of the 35 rN-based ELISA. We observed an increase in the positive rate for IgM and IgG with 36 an increasing number of days post-disease onset (d.p.o.), but the positive rate of IgM 37 dropped after 35 d.p.o. The positive rate of rN-based and rS-based IgM and IgG 38 ELISAs was less than 60% during the early stage of the illness 0-10 d.p.o., and that of 39 IgM and IgG was obviously increased after 10 d.p.o.40 Conclusions: ELISA has a high sensitivity, especially for the detection of serum 41 samples from patients after 10 d.p.o, it can be an important supplementary method for 42 on June 9, 2020 by guest http://jcm.asm.org/ Downloaded from COVID-19 diagnosis.43

21 Background: At present, PCR-based nucleic acid detection cannot meet the demands 22 for coronavirus infectious disease (COVID-19) diagnosis. Immunosorbent Assay (ELISA) kits based on recombinant SARS-CoV-2 nucleocapsid 27 protein (rN) and spike protein (rS) were used for detecting IgM and IgG antibodies, 28 and their diagnostic feasibility was evaluated. 29 Results: Among the 214 patients, 146 (68.2%) and 150 (70.1%) were successfully 30 diagnosed with the rN-based IgM and IgG ELISAs, respectively; 165 (77.1%) and 31 159 (74.3%) were successfully diagnosed with the rS-based IgM and IgG ELISAs, 32 respectively. The positive rates of the rN-based and rS-based ELISAs for antibody 33 (IgM and/or IgG) detection were 80.4% and 82.2%, respectively. The sensitivity of 34 the rS-based ELISA for IgM detection was significantly higher than that of the 35 rN-based ELISA. We observed an increase in the positive rate for IgM and IgG with 36 an increasing number of days post-disease onset (d.p.o.), but the positive rate of IgM 37 dropped after 35 d.p.o. The positive rate of rN-based and rS-based IgM and IgG 38 ELISAs was less than 60% during the early stage of the illness 0-10 d.p.o., and that of 39 IgM and IgG was obviously increased after 10 d.p.o.40Conclusions: ELISA has a high sensitivity, especially for the detection of serum

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30Background The outbreak of the recently emerged novel corona virus disease 2019

Highlights Chemiluminescence Microparticle Immunoassay has high sensitivity and specificity. The CMIA can provide important complementation to RNA assay for COVID-19 diagnosis. The age and gender do not affect the production of antibodies. The days of post onset was the main factor to influences the antibodies production. The disease-severity of COVID-19 patients affect the antibodies levels.

Introduction Monitoring of laboratory indicators is important for predicting changes in disease severity and clinical outcomes. We aimed to identify the critical predictors that can effectively assess the disease conditions of patients with COVID‐19 by analyzing the clinical characteristics and laboratory findings of patients with SARS‐CoV‐2 infection. Methods All consecutive patients (n = 294) with confirmed SARS‐CoV‐2 infection admitted to the General Hospital of Central Theater Command of the PLA from February 6 to February 21, 2020, were enrolled. These patients were divided into the severe group and the nonsevere group according to disease severity during hospitalization. Results The median neutrophil‐to‐lymphocyte ratio (NLR) value of the severe patients was dramatically higher than that of the nonsevere patients (10.4 vs 2.6; P < .001). The NLR value equal to 5 was a boundary value worthy of reference, because more than 80% severe patients had an NLR value greater than 5 and over 80% nonsevere patients had an NLR value less than 5. The NLR value of these COVID‐19 patients was positively and respectively correlated with the values of C‐reactive protein (R = .5921, P < .001), lactate dehydrogenase (R = .4509, P < .001), procalcitonin (R = .5504, P < .001), fibrinogen (R = .4710, P < .001), and D‐dimers (R = .4425, P < .001). However, the NLR value was merely and positively correlated with the interleukin‐6 value (R = .3594, P < .05), but had no correlations with the values of interleukin‐10, interleukin‐4, interleukin‐17, interferon‐γ, and tumor necrosis factor‐α (P > .05). Discussion Neutrophil‐to‐lymphocyte ratio is a critical predictor for assessment of disease severity in patients with COVID‐19, and it has a close relation with the laboratory indicators related to disease conditions.

IntroductionWe aimed to identify the associations between the lymphocytes (LYM) absolute count on admission and clinical outcomes in COVID‐19 patients.MethodsIn this retrospective study, 224 COVID‐19 patients who were admitted to General Hospital of Central Theater Command of the PLA from January 22 to April 4, 2020, were consecutively included. These patients were divided into the lymphopenia group and the nonlymphopenia group according to whether the LYM count on admission was below the normal range.ResultsDuring hospitalization, patients in the lymphopenia group have a much higher all‐cause mortality (14.5% vs 0.0%; P < .001) and an evidently longer length of hospital stay (24.0 vs 17.5 days; P < .001) than patients in the nonlymphopenia group. The correlation analysis results indicated that the LYM count was negatively correlated with the values of NEU (R = −.2886, P < .001), PT (R = −.2312, P < .001), FIB (R = −.2954, P < .001), D‐D (R = −.3554, P < .001), CRP (R = −.4899, P < .001), IL‐6 (R = −.5459, P < .001), AST (R = −.2044, P < .01), Cr (R = −.1350, P < .05), CPK (R = −.2119, P < .01), CK‐Mb (R = −.1760, P < .01), and LDH (R = −.4330, P < .001), and was positively correlated with the count of PLT (R = .2679, P < .001). In addition, LYM as a continuous variable was associated with 97% decreased risk of in‐hospital mortality in the fully adjusted models (OR = 0.03, 95%CI, 0.00‐0.37, P < .001).DiscussionLYM screening on admission is a critical predictor for assessment of disease severity and clinical outcomes in patients with COVID‐19, and lymphopenia substantially correlates with poor clinical outcomes.

Although the SARS-CoV-2 vaccine has been widely used worldwide, not all individuals can produce neutralization antibodies, so it is still urgent to find and prepare neutralization antibodies for COVID-19 prevention or treatment. In this study, we created a new strategy to effectively obtain neutralizing antibodies or complementary determining region 3 (CDR3) of neutralizing antibodies against SARS-CoV-2. We first predicted and synthesized several B cell epitopes on RBD and adjacent RBD of S protein, then the B cell epitopes were used to prepare affinity chromatography columns respectively and purify the binding IgG from serum samples of convalescent COVID-19 patients. After these IgGs were identified to have neutralizing activity, the peptide sequences of the antigen-binding regions (variable region) of neutralizing antibodies were analyzed by protein mass spectrometry. Subsequently, the B cells from the same individual were sorted and used to obtain their full BCR repertoire by 5′ RACE combined with high-throughput of PacBio sequencing method. Then, the peptide sequence of neutralizing antibody variable region by protein mass spectrometry was mapped to the full BCR repertoire and found the full variable region sequence of neutralizing antibodies. Finally, we obtained and synthesized numerous CDR3 peptides of neutralizing antibodies to confirm the neutralizing activity for SARS-CoV-2 infection. Our results indicate that the novel scheme will be suitable for rapid screening of neutralizing antibodies, including screening neutralizing antibodies against SARS-CoV-2 and other pathogenic microorganisms.