Evaluation of serum IgM and IgG antibodies in COVID‐19 patients by enzyme linked immunosorbent assay

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is sweeping the world since the end of 2019. The titer change of antibodies against SARS-CoV-2 needs to be further clarified, the clinical and preventive value of antibodies still needs to be further investigated. An enzyme-linked immunosorbent assay (ELISA) was established by coating with SARS-CoV-2 recombinant spike protein and used to detect serum immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies against SARS-CoV-2 in coronavirus disease 2019 patients to evaluate the pattern of changes of antibodies. The specificity of the ELISA for detection SARS-CoV-2 IgM and IgG were 96% (144/150) and 100% (150/150), respectively. The sensitivity of ELISA was 100% (150/150) for IgM, and 99.3% (149/150) for IgG. SARS-CoV-2-SP-IgM and SP-IgG antibodies could be detected on Day 1 of hospitalization in 12.5%patients, and SP-IgM began to decrease after reaching its peak at around 22-28 days, and become negative at Month 3 in 30% patients and negative at Month 7 in 79% of these patients after onset; IgG reached its peak around Day 22-28 and kept at a high level within the longest observation period for 4 months, it dropped very sharply at 7 months. The positive rates of SP-IgM and SP-IgG were higher than those of reverse transcription-polymerase chain reaction on Day 7 and 4. The established indirect ELISA has good specificity and sensitivity. IgM and IgG against SARS-CoV-2 appeared almost simultaneously in the early stage, and the level of IgG antibodies could not maintain a high plateau in the observation period of 7 months.Our data will help develop the diagnosis and vaccine of SARS-CoV-2.

Understanding neutralising antibodies against SARS-CoV-2 and their implications in clinical practice

“…1 Humoral immune response (IgG, IgM, IgA) profiles of SARS-CoV-2 infections: onset and persistence of neutralising antibodies. a Onset within 10–14 days [ 27 – 32 ]; levels remain elevated for weeks [ 30 , 33 – 38 ]; peaks at around day 25 [ 26 ]. b Rises within the first week of infection [ 30 , 31 , 33 , 39 ]; lasts 1-2 months before gradually diminishing [ 15 , 30 , 38 ]; peaks at around 20–30 days post-symptom onset [ 40 ].…”

“…a Onset within 10–14 days [ 27 – 32 ]; levels remain elevated for weeks [ 30 , 33 – 38 ]; peaks at around day 25 [ 26 ]. b Rises within the first week of infection [ 30 , 31 , 33 , 39 ]; lasts 1-2 months before gradually diminishing [ 15 , 30 , 38 ]; peaks at around 20–30 days post-symptom onset [ 40 ]. c Onset within 6–8 days [ 39 ]; lasts 71 days [ 38 ]; peaks at around 20–22 days post-symptom onset [ 39 , 40 ]; high titres in severe COVID-19 cases [ 32 ] …”

“…IgG antibody then peaks at around day 25 [ 26 ] (Fig. 1 ), and remains high for weeks [ 30 , 33 – 38 ]. IgG has a half-life of only ~ 21 days—hence, sustained antibody titres observed are likely produced by long-lived plasma cells in the bone marrow [ 13 ].…”

“…Only 42.3% had detectable anti-N/anti-S IgM antibodies Wu et al [ 14 ] Wuhan, China Case series ( n = 349) Serum RT-PCR, CLIA, virus neutralisation assay IgM The positive rate for IgM-S reached a peak of 95% at week 5 and then rapidly decreased to 0% at week 13 fluctuating below 35% thereafter. IgM-N could be detected in 72% of subjects at week 3 Zhou et al [ 33 ] Hefei, Anhui, China Case series ( n = 165) Serum ELISA IgM SP–IgM showed a tendency to increase from days 1–28, and was detectable on the first day, with a positive rate of 46% and an OD value of 0.3128 ± 0.2365 from days 1–3 BCR Sequencing B cell receptor sequencing, C-ELISA Competitive enzyme-linked immunosorbent assay, CLIA chemiluminescent immunoassay, COVID-19 Coronavirus disease 2019, DPI days post infection, ELISA enzyme-linked immunosorbent assay, FRNT focus reduction neutralisation test, IFA immunofluorescence assay, IgM-ELISA IgM μ-chain capture method, LIPS assay fluid-phase luciferase immune precipitation assay, M-CSF macrophage colony-stimulating factor, MCLIA magnetic chemiluminescence immunoassay, OD optical density, PSO post symptom onset, RBD Receptor-binding domain, RDTs rapid diagnostic tests, RT-PCR Test reverse transcription polymerase chain reaction test , RT-qPCR reverse-transcription quantitative polymerase chain reaction, SARS-CoV-2 severe respiratory syndrome coronavirus 2, SCF stem cell factor, TRAIL TNF-related apoptosis-inducing ligand …”

Anti-SARS-COV-2 antibodies Amongst Asymptomatic Healthcare Workers and students of Tertiary Care hospital and Medical School in Pakistan

“…Out of 274 cases of contact history 80 (29.19%) were reactive and out of 169 with travel history 28 (16.5%) were reactive cases. Analysis of a study found that close contacts to confirm COVID-19 cases revealed a relatively short infectious period of COVID-19 and a higher transmission risk around the time of symptom onset of the index case, followed by a lower transmission risk at the later stage of disease [18]. Age difference in reactive and non-reactive subjects was non-significant in the study.…”