Kinetics of SARS-CoV-2 specific IgM and IgG responses in COVID-19 patients

Abstract

The emerging COVID-19 caused by SARS-CoV-2 infection poses severe challenges to global public health. Serum antibody testing is becoming one of the critical methods for the diagnosis of COVID-19 patients. We investigated IgM and IgG responses against SARS-CoV-2 nucleocapsid (N) and spike (S) protein after symptom onset in the intensive care unit (ICU) and non-ICU patients. 130 blood samples from 38 COVID-19 patients were collected. The levels of IgM and IgG specific to N and S protein were detected by ELISA. A series of blood samples were collected along the disease course from the same patient, including 11 ICU patients and 27 non-ICU patients for longitudinal analysis. N and S specific IgM and IgG (N-IgM, N-IgG, S-IgM, S-IgG) in non-ICU patients increased after symptom onset. N-IgM and S-IgM in some non-ICU patients reached a peak in the second week, while N-IgG and S-IgG continued to increase in the third week. The combined detection of N and S specific IgM and IgG could identify up to 75% of SARS-CoV-2 infected patients in the first week. S-IgG was significantly higher in non-ICU patients than in ICU patients in the third week. In contrast, N-IgG was significantly higher in ICU patients than in non-ICU patients. The increase of S-IgG positively correlated with the decrease of C-reactive protein (CRP) in non-ICU patients. N and S specific IgM and IgG increased gradually after symptom onset and can be used for detection of SARS-CoV-2 infection. Analysis of the dynamics of S-IgG may help to predict prognosis.

S protein-reactive IgG and memory B cell production after human SARS-CoV-2 infection includes broad reactivity to the S2 subunit

“…IgG MBCs are more broadly reactive than Abs generated against the same antigen, they persist after circulating Ab levels wane, and they are readily activated to generate strong Ab responses or seed germinal centers for additional rounds of affinity maturation (14). Concurrent early production of virus-specific IgM and IgG in the response to SARS-CoV-2 infection suggests a response mediated by IgG MBCs as well as naïve B cells (9,(15)(16)(17). This picture is supported by identification of B cell subsets with high and low immunoglobulin V gene mutation frequencies during the response to SARS-CoV-2 infection (18).…”

Temporal antibody responses to SARS-CoV-2 in patients of coronavirus disease 2019

“…IgG antibody can be detected 10 days from illness onset, which may last for a longer period 4 . It was also shown that antibody titers are higher and longer-lived in more severely ill patients than in mildly ill patients 5 , some of the latter do not develop a detectable antibody response 6 . However, data on the simultaneous evaluation of cellular immune response, cytokine production, and specific antibody were lacking 7 .…”

No evidence of SARS‐CoV‐2 RNA among blood donors: A multicenter study in Hubei, China

“…2 The origin of its etiological agent, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was targeted quickly. 3,4 The virus transmits from human to human mainly through respiratory droplets and it also has been found in feces, urine, and conjunctival secretions of infected cases or animal models, [5][6][7][8][9][10] especially in the early stage of COVID-19. 11 Moreover, viral RNA, although usually with a very low viral load, could be detected in plasma, serum, or whole blood.…”

“…11 Moreover, viral RNA, although usually with a very low viral load, could be detected in plasma, serum, or whole blood. 8,12,13 Viral dynamic analysis has proved that the viral load of the new coronavirus in blood ranged from 2 to 4 log copies per milliliter, which is much lower than that of the respiratory tract or stool samples and before the onset of any symptoms, viral RNA could be detected in blood. 8,14 Therefore, the risk of viral transmission via blood indeed exists but it is only a kind of theoretical possibility now.…”

“…8,12,13 Viral dynamic analysis has proved that the viral load of the new coronavirus in blood ranged from 2 to 4 log copies per milliliter, which is much lower than that of the respiratory tract or stool samples and before the onset of any symptoms, viral RNA could be detected in blood. 8,14 Therefore, the risk of viral transmission via blood indeed exists but it is only a kind of theoretical possibility now. Generally, prolonged or short asymptomatic blood-borne phase, the infectious agent in collected blood or components, and its ability to cause infection by the intravenous route are three key points to evaluate whether an emerging infection could transmit via transfusion.…”