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The Production and Clinical Implications of SARS-CoV-2 Antibodies
19 Pages Posted: 30 Apr 2020
More...Abstract
Background: Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2), a novel betacoronavirus, has caused an outburst of pneumonia cases in Wuhan, China. We report the production of specific IgM and IgG antibodies after the infection of SARS-CoV-2 and its implication for the diagnosis, pathology and the course of the disease as well as the recurrence of positive nucleic acid tests after discharge.
Methods: Test results for SARS-CoV-2 IgM and IgG antibodies of 221 confirmed COVID-19 patients were retrospectively examined, and their clinical data were collected and analyzed based on various subgroups. SARS-CoV-2 IgM and IgG antibodies were determined with the chemiluminescence method.
Findings: The concentration (S/CO) of SARS-CoV-2 IgM and IgG antibodies peaked on day 19-21 after symptom onset, with a median of 17.38 (IQR 4·39-36·4) for IgM and 5·59 (IQR 0·73-13·65) for IgG. Detection rates reached highest on day 16-18 and day 19-21 for IgM and IgG, which were 73·6% and 98·6%, respectively, with significantly higher concentration of IgG in critically ill patients than in those with mild to moderate disease (P=0·027). The concentration of the antibodies on day 16-21 is not correlated with the course or outcome of the disease (Spearman r < 0·20, P > 0·05). Nasopharyngeal swabs revealed positive SARS-CoV-2 RNA in up to 52.7% of recovered patients after discharge, whose IgG proved to be significantly lower than that of those with negative RNA results (P = 0·009). IgG and IgM were tested twice within 14 days after discharge with a 7-day interval, and the second testing of these antibodies displayed a decrease in concentration of 21·2% (IQR, 11·2%,34·48%) for IgG and 23.05% (IQR, -27·96%,46·13%) for IgM, without statistical significance between the patients with re-detectable positive RNA results and those with negative RNA results after discharge; however, those with positive results experienced a count decrease in lymphocyte subsets.
Interpretation: The concentration of SARS-CoV-2 IgM and IgG antibodies peaked on day 19-21 after symptom onset, and antibody testing on day 16-21 is associated with increased detection rates, but the antibody concentration does not affect the course and outcome of the infection. Recovering patients with re-detectable positive SARS-CoV-2 RNA displayed lower concentration of IgG, but the downward trend of IgG during recovery indicated its limited duration of protection, and the protective effect of IgG remains to be investigated.
Funding Statement: This work is funded by Chongqing Education Board “new coronavirus infection and prevention” emergency scientific research project (KYYJ202006). Chongqing Science and Technology Bureau “new crown pneumonia epidemic emergency science and technology special” the fourth batch of projects. Famous teacher project of Chongqing talent plan.
Declaration of Interests: The authors declare no competing interests.
Ethics Approval Statement: This study was approved by the Medical Ethical Committee of the First Affiliated Hospital of Chongqing Medical University (approval number 20200601). Due to the special reasons of the epidemic, the patients’ informed consent was not obtained.
Keywords: severe acute respiratory syndrome coronavirus 2; Corona virus disease 2019; IgG antibody; IgM antibody; clinical implication
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