The level of anti-S Abs in the blood was highly positively correlated with nAbs (r = 0.652, P < 0.0001) (Physique 2 ). hospital, and the levels of anti-S Abs in the blood were highly positively correlated with nAbs (r = 0.652, P < 0.0001). The positivity rate of nAbs for patients with anti-S Abs positive was 100%. Conclusions There is a good agreement between anti-S Abs detected by GICA and nAbs detected by CMIA. It indicates that anti-S Abs detected by GICA may be used as a cheaper screening strategy for detectable SARS-CoV-2 nAbs in COVID-19 convalescent individuals. Keywords: COVID-19, SARS-CoV-2, Colloidal gold immunochromatographic assay (GICA), Neutralizing antibody Introduction The ongoing global SARS-CoV-2 pandemic has placed an enormous burden around the global public health system and the economy at large. Each day, hundreds of thousands of new confirmed cases are IACS-8968 S-enantiomer recorded worldwide (WHO, 2021). Concurrently, many patients are in recovery, some of whom are still at risk of reinfection after rehabilitation due to the lack of or inability to produce adequate protective antibodies (Hall et al., 2021, Lumley et al., 2021). Therefore, there have been efforts to develop effective vaccines as the primary means to curtail the detrimental effects of the SARS-CoV-2 contamination; so far, millions of people have been vaccinated globally (Chung et al., 2021, Mohammad, 2021). To inform vaccination and optimize immunization strategies, rapid assessment of the level and duration of protective antibodies in natural post-infected and recovered patients make sense. However, the plaque reduction neutralization test (PRNT) and the microneutralization assay (NT), the gold standards for determining antibody neutralizing activity against SARS-CoV-2, cannot be widely adopted because of their low flux, time-consuming, and fussy operation (CDC, 2021). Recently, several companies have developed reagents such as chemiluminescent microparticle immunoassay (CMIA) kits based on the theory of competitive inhibition to detect SARS-CoV-2 nAbs. The reagents could be widely used because of their high throughput and sensitivity properties (Bonelli et al., 2020, Taylor et al., 2021). However, limited by expensive instruments, it is hard to widely serve undeveloped countries and regions with backward economies. Therefore, cheap, accurate, simple, and rapid methods for quantifying serum nAbs in recovered patients are valuable to determine the duration of antibody response after contamination, which can guideline the development and refinement of vaccine and public immunization strategies. Herein, we reported a good agreement between anti-S Abs detected by colloidal gold immunochromatographic assay (GICA) and nAbs detected by CMIA. Furthermore, all positive anti-S Abs results identified by GICA were also nAbs positive, indicating that this method can be used as IACS-8968 S-enantiomer a cheaper screening strategy for SARS-CoV-2 nAbs. Methods Study participants In this study, 306 patients recovered from COVID-19 admitted at the Tongji Hospital, Huazhong University of Science and Technology, Wuhan, China, were enrolled. The patients were admitted to the hospital between January and February 2020 and had no reinfection during the follow-up period (Li et al., 2020). The diagnosis was confirmed based on positive high-throughput sequencing of nasopharyngeal swab specimens or nucleic acid detection using real-time reverse transcription-polymerase chain reaction (RT-PCR), according to interim guidelines of the World Health Business (WHO, 2020). All patients IACS-8968 S-enantiomer were tested multiple occasions throughout to ensure diagnostic accuracy. All patients were followed up after discharge to ensure no reinfection occurred. Serum samples were collected six months after discharge for assessment of IACS-8968 S-enantiomer protective antibody levels. Disease grading The grading of disease on admission was based on the Chinese management guidelines for COVID-19 (version 7.0) (NHC, 2020). Mild cases were defined as patients with moderate clinical symptoms and pneumonia manifestation undetectable by imaging examination. Moderate cases were defined as patients presenting with clinical symptoms and pneumonia features detectable by imaging tools. Severe cases were those presenting with any of the following: respiratory distress with RR 30 occasions/min; pulse oxygen saturation (SpO2) 93% at rest; arterial partial pressure of oxygen (PaO2)/fraction of inspired oxygen (FiO2) 300 mmHg (1 mmHg = 0.133 kPa). Crucial cases were those showing one of the following features: respiratory failure that needs mechanical ventilation, shock, multiple organ failures that call for monitoring of intensive care unit (ICU), or death. Detection of total antibodies Six months after discharged from the hospital, blood samples were collected from patients undergoing rehabilitation by experienced doctors. The blood samples were centrifuged to obtain serum which was stored at 4 C. All antibody assessments were performed within 24 h after sample collection. The colloidal gold immunochromatographic assay (GICA) reagents (Wondfo, Guangzhou, China, batch number: W19501002), which specifically target the spike glycoprotein (S-protein) antibody, were used to measure the total antibody of SARS-CoV-2 in serum (IgM and IgG). Briefly, 10 l serum samples and 80 l diluting water Rabbit Polyclonal to EFEMP1 (about 2C3 drops) were added to the hole of the test card, and the test results were observed after15C20 min. If the sample contained IgM or/and IgG antibodies of COVID-19, the antibodies would bind to the recombinant.