Profile of specific antibodies to SARS-CoV-2: The first report (2020)

•Profile of specific antibodies to virus in blood can assist diagnosis and reflect disease course.•The preliminary study explored the dynamic profile of IgM and IgG.•Serum IgM to SARS-COV-2 last more than a month indicating the prolonged virus replication in infected patients. A novel coronavirus (COVID-19) epidemic threatens the world.1Tang J.W. TAMbyah P.A. Hui D.S. Emergence of a novel coronavirus causing respiratory illness from Wuhan, China.J. Infect. 2020; (https://doi.org/)https://doi.org/10.1016/j.jinf.2020.01.014Abstract Full Text Full Text PDF Scopus (113) Google Scholar,2Zunyou W. Jennifer M.G. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in china: Summary of a report of 72,314 cases from the Chinese center for disease control and prevention.JAMA. 2020; (Published online February 24)https://doi.org/10.1001/jama.2020.2648Crossref Scopus (12455) Google Scholar Before this study, some studies reported cases of viral detection by RT-PCR at different timepoints throughout the disease course.3Zou L. Ruan F. Huang M. et al.SARS-CoV-2 viral load in upper respiratory specimens of infected patients.N Engl. J. Med. 2020; (Published online February 19)https://doi.org/10.1056/NEJMc2001737Crossref Scopus (3423) Google Scholar,4Pan Y. Zhang D.T. Yang P. et al.Viral load of SARS-CoV-2 in clinical samples.Lancet Infect Dis. 2020; (Published Online February 24)https://doi.org/10.1016/S1473-3099(20)30113-4Abstract Full Text Full Text PDF Scopus (1162) Google Scholar However, these reports monitored SARS-CoV-2 in the acute phase of infection. Currently no study reported the profile of specific antibodies to SARS-CoV-2 infection. Profile of specific antibodies in patients’ blood can assist diagnosis and reflect the disease course. Here, we first studied the profile of IgM and IgG for SARS-CoV-2 from 34 COVID-19 patients. A total of 34 hospitalized patients (admission date from Feb 1st to Feb 29th, 2020) with confirmed SARS-CoV-2 infection were included in this study. All enrolled patients were confirmed diagnosed of COVID-19 according to the diagnosis and treatment guideline for SARS-CoV-2 from Chinese National Health Committee (Version 5) and the interim guidance from Centers for Disease Control and Prevention.5Interim infection prevention and control recommendations for patients with confirmed coronavirus disease 2019 (COVID-19) or persons under investigation for COVID-19 in healthcare settings. (Update: February 21, 2020). https://www.cdc.gov/coronavirus/2019-ncov/hcp/infection-control.html.Google Scholar,6China National Health Commission Diagnosis and treatment of 2019-nCoV pneumonia in China; 2020. (Version 5) In Chinese. Published February 8Accessed March 3, 2020 http://www.nhc.gov.cn/yzygj/s7653p/202002/d4b895337e19445f8d728fcaf1e3e13a/files/ab6bec7f93e64e7f998d802991203cd6.pdfGoogle Scholar Blood samples were obtained at different date after onset of symptoms to detect the specific antibodies to SARS-CoV-2. IgM and IgG were analyzed by chemiluminescent immunoassay according to the manufacturer's protocol (Shenzhen Yahuilong Biotechnology Co., Ltd). All data (test dates and results of IgM and IgG) were collected up to the final follow-up date (March 3rd, 2020). Details of demographic characteristics and test dates and results of IgM and IgG were list in Table 1. Except for two patients (2 days and 3 days after symptoms onset), all included patients had IgM and IgG tests after 2 weeks from symptoms onset. We categorized patients by weeks according to the date of antibodies test after symptoms onset. In week 3 after symptoms onset, all patients were tested positive for IgM and IgG, with the mean value of 322.80AU/ml and 112.40AU/ml (Reference:<10AU/ml) respectively. In week 4, all the results were still positive for IgM and IgG. IgM declined while IgG continued to go up, with the mean value of 147.92AU/ml and 157.01AU/ml respectively. In week 5, however, all patients were positive for IgG, while 2 patients (16.7%) got negative results for IgM. IgM level kept going down to 78.03AU/ml and IgG continued up to 163.56AU/ml. At the end of observation (7 weeks), 2 patients (33.3%) got negative results for IgM, while all patients positive for IgG, with the mean value of 21.83AU/ml and 167.16AU/ml respectively. (Fig. 1)Table 1Characteristics of demographic and specific antibodies in COVID-19 patients (N = 34).PatientsAgeGenderIgM AU/mlIgG AU/mlTest days, after onsetWeekMean IgM AU/mlSEMMean IgG AU/mlSEMPatient182Female3.562.48212.241.331.960.53Patient287Female0.911.433Patient359Female122.73163.85143322.80127.65112.4021.43Patient472Male924187.414Patient532Female111.78110.1716Patient663Male207.3955.4317Patient769Male401.1978.7117Patient864Male169.7278.8221Patient965Female104.77187.94224147.9294.50157.0112.40Patient1039Male16.63152.8823Patient1152Male89.31179.1823Patient1249Male41.55128.7524Patient1335Male62.5103.8927Patient1431Male11.26193.8328Patient1558Female709.39152.5728Patient1644Male36.57190.8530578.0333.55163.5615.95Patient1726Female14.37277.9130Patient1857Male1.6576.8530Patient1945Male35.44165.2730Patient2062Female3.38200.9531Patient2165Male119.35155.2932Patient2283Male18.95158.3233Patient2343Male48.8873.6433Patient2453Male134.24135.5433Patient2533Female54.39162.0133Patient2664Male422.78159.3834Patient2760Female46.34206.734Patient2873Male5.27134.94366–721.835.72167.1612.24Patient2925Female15.11179.2336Patient3071Male36.11184.5637Patient3156Female34.07121.0837Patient3254Male42.28216.9638Patient3347Male11.2176.7338Patient3454Male8.75156.5949Abbreviations: SEM, standard error of mean. *Reference of IgG and IgM are 10AU/ml. Open table in a new tab Abbreviations: SEM, standard error of mean. *Reference of IgG and IgM are 10AU/ml. Genomic studies have shown that SARS-CoV-2 shared around 80% identity sequencing with SARS-CoV, which caused a global epidemic with 8096 confirmed cases worldwide in 2002–2003.7Summary of probable SARS cases with onset of illness from 1 November 2002 to 31 July 2003. Geneva: World Health Organization 2004 https://www.who.int/csr/sars/country/table2004_04_21/en/.Google Scholar Study of case series suggested the viral nucleic acid shedding pattern of patients infected with SARS-CoV-2 is different from SARS-CoV.3Zou L. Ruan F. Huang M. et al.SARS-CoV-2 viral load in upper respiratory specimens of infected patients.N Engl. J. Med. 2020; (Published online February 19)https://doi.org/10.1056/NEJMc2001737Crossref Scopus (3423) Google Scholar For SARS-CoV, studies revealed that IgM reached the highest point within 4 weeks and was not detectable on 3 months after onset of symptoms. IgG were persistently detectable up to 24 months.8Mo H.Y. Zeng G.Q. Ren X.L. et al.Longitudinal profile of antibodies against SARS-coronavirus in SARS patients and their clinical significance.Respirology. 2006; 11: 49-53Crossref PubMed Scopus (140) Google Scholar Our results suggested that the profile of specific antibodies to SARS-CoV-2 is similar to SARS-CoV. Detectable and continuous high level of IgM indicated the acute phase of infection. Furthermore, IgM last more than a month indicating the prolonged virus replication in SARS-CoV-2 infected patients. IgG responded later than IgM and persisted high in our study, indicating the humoral immune reaction to protect the body against SARS-CoV-2 virus. The detection and profile of specific antibodies to SARS-CoV-2 will provide valuable information for rapid screening of suspects, assist diagnosis and evaluate the disease course. Furthermore, concentrated IgG antibody may be informative in vaccine development and treatment for SARS-CoV-2. All authors declare that there are no conflicts of interest. No funding resources to declare for this study.