key: cord-1001357-6p5ltn4w
authors: Ma, H.; Zhao, D.; Zeng, W.; Yang, Y.; Hu, X.; Zhou, P.; Weng, J.; Cheng, L.; Zheng, X.; Jin, T.
title: Decline of SARS-CoV-2 specific IgG, IgM and IgA in convalescent COVID-19 patients within 100 days after hospital discharge
date: 2020-08-21
journal: nan
DOI: 10.1101/2020.08.17.20175950
sha: c172569e827ac0a2c8c0a76510cadfd54fed4cdb
doc_id: 1001357
cord_uid: 6p5ltn4w

Monitoring the levels of SARS-CoV-2 specific antibodies such as IgG, M and A in COVID-19 patient is an alternative method for diagnosing SARS-CoV-2 infection and an simple way to monitor immune responses in convalescent patients and after vaccination. Here, we assessed the levels of SARS-CoV-2 RBD specific antibodies in twenty-seven COVID-19 convalescent patients over 28-99 days after hospital discharge. Almost all patient who had severe or moderate COVID-19 symptoms and a high-level of IgG during the hospitalization showed a significant reduction at revisit. The remaining patients who had a low-level IgG during hospitalization stayed low at revisit. As expected, IgM levels in almost all convalescent patients reduced significantly or stayed low at revisit. The RBD-specific IgA levels were also reduced significantly at revisit. We also attempted to estimate decline rates of virus-specific antibodies using a previously established exponential decay model of antibody kinetics after infection. The predicted days when convalescent patients' RBD-specific IgG reaches to an undetectable level are approximately 273 days after hospital discharge, while the predicted decay times are 150 days and 108 days for IgM and IgA, respectively. This investigation and report will aid current and future studies to develope SARS-CoV-2 vaccines that are potent and long-lasting.

Monitoring the levels of SARS-CoV-2 specific antibodies such as IgG, M and A in COVID-19 patient is 30 an alternative method for diagnosing SARS-CoV-2 infection and an simple way to monitor immune 31 responses in convalescent patients and after vaccination. Here, we assessed the levels of 32 SARS-CoV-2 RBD specific antibodies in twenty-seven COVID-19 convalescent patients over 28-99 33 days after hospital discharge. Almost all patient who had severe or moderate COVID-19 symptoms and 34 a high-level of IgG during the hospitalization showed a significant reduction at revisit. The remaining 35 patients who had a low-level IgG during hospitalization stayed low at revisit. As expected, IgM levels in 36 almost all convalescent patients reduced significantly or stayed low at revisit. The RBD-specific IgA 37 levels were also reduced significantly at revisit. We also attempted to estimate decline rates of 38 virus-specific antibodies using a previously established exponential decay model of antibody kinetics 39 after infection. The predicted days when convalescent patients' RBD-specific IgG reaches to an 40 undetectable level are approximately 273 days after hospital discharge, while the predicted decay 41 times are 150 days and 108 days for IgM and IgA, respectively. This investigation and report will aid 42 current and future studies to develope SARS-CoV-2 vaccines that are potent and long-lasting. 43 44 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The 2019 novel coronavirus (later renamed as SARS-CoV-2 in February 2020) infected over 12 million 46 people globally by early July and caused mild to severe COVID-19 patients in millions. Monitoring the 47 levels of antibodies such as immunoglobin (Ig) G, M and A that are specific to SARS-CoV-2 and 48 present in blood provides not only an alternative method for diagnosing SARS-CoV-2 infection 49 (including asymptomatic carriers), but also an simple way to monitor immune responses in 50 convalescent patients or after vaccination. A high and persistent level of SARS-CoV-2 specific 51 antibodies, especially those that can bind to and neutralize the virus, would be a strong indication that 52 an immunized host could resist to SRAS-CoV-2 infection. Currently, there are no effective drugs to 53 specifically prevent or cure SARS-CoV-2 infection; therefore, host immune responses and 54 antibody-based therapeutics will continue playing important roles in combating and later preventing 55 COVID-19. 

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted August 21, 2020. . https://doi.org/10.1101/2020.08.17.20175950 doi: medRxiv preprint after hospital discharge, we used the same kits for detecting RBD-specific IgG, IgM and IgA levels in 72 blood of patients in this cohort as we did for them during the hospitalization (Ma et al., 2020) . remaining patients who had a low-level IgG during hospitalization stayed low at revisit. As expected, 86

IgM levels in these convalescent patients reduced significantly or stayed low at revisit, except #14 (B). 87

The RBD-specific IgA levels were also reduced significantly at revisit (C), except patient #10 who also 88 had an increased IgG, but not IgM. Few exceptional cases will need further studies. 89 90 We also attempted to estimate decline rates of virus-specific antibodies using a previously established 91 exponential decay model of antibody kinetics after infection (Teunis et al., 2016) . Based on the 92 combined data of COI ratios before and after discharge for each of the 27 patients, we plotted decay 93 curves for RBD-specific IgG, IgM and IgA over time (Figure 1D-F) . The predicted days when 94 convalescent patients' RBD-specific IgG reaches to an undetectable level are approximately 273 days 95 (ranging from 134-304 days or 4.5-10 months) after hospital discharge (D), while the predicted decay 96 times are 150 days and 108 days for IgM and IgA, respectively. 97 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted August 21, 2020. . https://doi.org/10.1101/2020.08.17.20175950 doi: medRxiv preprint

In summary, the initial data of this longitudinal study showed that the levels of SARS-CoV-2 99 RBD-specific antibodies in most COVID-19 convalescent patients reduced significantly or remained 100 low within the first 100 days after discharge. A mathematical modeling and extrapolation predicts that 101 the virus-specific IgG in this group of convalescent patients will disappear in 273 days (~ 9 months). designing as how to achieve long-last humoral immune response and memory. One way is to seek 119 immunogens and adjuvants that show very strong immune responses such as virus-specific IgG 120 induction that can be easily monitored. For example, a recent clinical trial showed that an 121 experimental vaccine using inactivated SARS-CoV-2 viruses with alum as the adjuvant only elicited 122 comparable to, but not much higher virus-specific IgG production than what we and others observed in 123 hospitalized COVID-19 patients . Using more potent immunogens and adjuvants to 124 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted August 21, 2020. . https://doi.org/10.1101/2020.08.17.20175950 doi: medRxiv preprint indication for effective development of SARS-CoV-2 vaccines that are highly potent and long-lasting. 126

Although long-term data beyond 99 days after discharge are still in progress and needed to confirm our 127 modeling, our current report provides timely information and fills the gap of knowledge to assess the 128 persistence of antibody levels in response to this novel human coronavirus. A rapid reduction of 129 antibodies (IgG, IgM and IgA) specific to SARS-CoV-2 we observed in convalescent patients examined 130 4-14 weeks after discharge warrants timely and close attention; however, one shall interpret our 131 current data cautiously. First, we had data so far from a relatively small group of COVID-19 132 convalescent patients, who were first chosen because we can compare changes of the virus-specific 133 antibodies after discharge. Second, we measured only the antibodies specific to SARS-CoV-2 RBD 134 in the study subjects. Third, we have not examined cellular immune responses in this cohort of is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted August 21, 2020. 

Authors declare that they have no conflicts of interest. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted August 21, 2020. . https://doi.org/10.1101/2020.08.17.20175950 doi: medRxiv preprint are presented as Cut-Off Index (COI) which is calculated as RLU signal divided by the Cut-Off value 203 previously set for each of IgG, IgM and IgA, respectively. The p values for the difference between 204 discharge and revisit are < 0.0001, 0.0023 and 0.0020 for IgG, IgM and IgA, respectively. (D-F) Decline 205 curves for RBD-specific IgG (D), IgM (E) and IgA (F) over time, based on a mathematical model of 206 exponential decay after its peak at recovery (soon before or at discharge). The ratios of COI at 207 revisit versus discharge (day 0) is plotted by log10 scale for each patient's IgG, IgM and IgA separately, 208 as a function of time (days after discharge). See more details in supplemental Methods. The decay 209 curve is marked as a blue line, and 95% confidence interval is marked as a grey zone for each type of 210 SARS-CoV-2 specific antibodies. 211 212 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted August 21, 2020. . https://doi.org/10.1101/2020.08.17.20175950 doi: medRxiv preprint

Disappearance of antibodies to 165 SARS-associated coronavirus after recovery

Targets of T Cell Responses to SARS-CoV-2

Coronavirus in Humans with COVID-19 Disease and Unexposed Individuals

SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, 173 and uninfected controls

Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections

Serum IgA, IgM, and IgG responses in COVID-19

Detection of SARS-CoV-2-Specific Humoral and Cellular Immunity in COVID-19 Convalescent 182 Individuals

Convergent antibody responses to SARS-CoV-2 in 185 convalescent individuals

Linking 187 the seroresponse to infection to within-host heterogeneity in antibody production

Neutralizing antibody responses to SARS-CoV-2 in a COVID-19 recovered patient cohort and their 191 implications. medRxiv, 2020.03.30

Effect of an Inactivated Vaccine Against SARS-CoV-2 on Safety and Immunogenicity 194 Outcomes: Interim Analysis of 2 Randomized Clinical Trials