PONE-D-20-31485

Seroprevalence of anti-SARS-CoV-2 antibodies in Japanese COVID-19 patients

PLOS ONE

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PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Partly

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have provided the seroprevalence of anti-SARS-CoV-2 IgG and IgM antibodies in 34 symptomatic Japanese COVID-19 patients and concluded that a serologic anti-SARS-CoV-2 antibody analysis can complement PCR for diagnosing COVID-19 14 days after symptom onset.

The immunological characteristic of COVID-19 patients has been intensively studied, such as cross-reactivity of anti-RBD, anti-Spike and anti-nucleocapsid and effector mechanisms of different subclasses of antibody. However, the author failed to summarize all the knowledge in the introduction.

There is pre-existing SARS-CoV-2 nucleocapsid-specific immunity in people infected by seasonal “common cold” HCoV-OC43 and HCoV-NL63 viruses. Therefore, the anti-SARS-CoV-2 antibody test requires negative control samples including seasonal "common cold" HCoV-OC43 and HCoV-NL63 viruses. Furthermore, effector mechanisms should be discussed. Antibodies of different subclasses activate different effector mechanisms in response to RBD antigens. Therefore, a combination of IgG1 and IgG2 subclasses against the RBD may enhance this effect and reduce disease severity. The detection of anti-RBD subclasses is important to clinical research. [Tackling COVID19 by exploiting pre-existing cross-reacting spike-specific immunity. Mol Ther. 2020 Nov 4; 28(11): 2314–2315.]

The authors used Abbott SARS-CoV-2 IgG assay which detects anti-nucleocapsid antibody. The Abbott assay results constitute false-positive reactions due to cross-reactivity to nucleocapsid as reported in Lancet [Testing for responses to the wrong SARS-CoV-2 antigen?. Lancet 2020; published online August 28. http://dx.doi.org/10.1016/S0140-6736(20)31830-4.] and Science Translational Medicine [https://stm.sciencemag.org/content/12/559/eabc3103/tab-e-letters]. To further clarify this issue, the study should include anti-SARS-CoV-2 RBD antibody detection methods.

Reviewer #2: 1. Authors have mentioned that IgG antibodies were detectable in 5- 10 days, is it possible to detect the antibodies with a high percentage of antibodies in asymptomatic patients?

2. Authors have mentioned that clinical data includes patients that have major comorbidities, what are the major comorbidities were diagnosed in COVI-19 patients, is these comorbidities play a key role in antibody production?

3. Why have authors selected only male candidates for the selection for this study?

4. In table 2, Compared to severe and critical samples shows a higher percentage of positive results than mild and moderate is this kit only gives accuracy in severe/critical cases?

5. Authors have mentioned that these two kits are complementary PCR for COVID-19 detection. But the SARS-CoV-2 infected individuals are identified by RT-PCR and the nasopharyngeal sampling was positive in approximately 89% (95% CI 83 to 93) of tests within 4 days of either symptom onset. But these two kits do not detect the antibodies in the mild cases. Then how authors have justified these kits are used as complementary methods.

6. In table 3, The IC result shows, the percentage of IgG and IgM in mild and moderate shows very less content in the starting period of the study. Is this starting period the initial stage of the COVID-19 infection?

7. Compared to PCR how much accuracy is noticed in these two kits. Any evidence?

8. If the infection was detected in the initial stage it could be more effective, but these two kits do not detect any antibodies in initial or mild to moderate cases, how could it be more effective than PCR?

9. Did authors find differences in the percentage of IgG and IgM in patients with comorbidities and without any comorbidity?

Reviewer #3: Hiki and team had summarized their findings on seroprevalence of anti-SARS-CoV-2 antibodies in Japanese COVID-19 patients using CMIA. According to their report, the antibodies were developed within 2 weeks of onset of the disease; however, there were numbers of patients who were at severe to critical stage after the development of the IgG. It is suggested to report the clinical manifestations of the included patients and correlate their recovery with the clinical improvement and developed antibodies.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Seroprevalence of anti-SARS-CoV-2 antibodies in Japanese COVID-19 patients

PONE-D-20-31485R1

Dear Dr. Naito,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Kind regards,

Chandrabose Selvaraj, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The authors have provided the seroprevalence of anti-SARS-CoV-2 IgG and IgM antibodies in 34 symptomatic Japanese COVID-19 patients and concluded that a serologic anti-SARS-CoV-2 antibody analysis can complement PCR for diagnosingCOVID-19 14 days after symptom onset.

The immunological characteristic of COVID-19 patients has been intensively discussed, such as cross-reactivity of anti-RBD, anti-Spike and anti-nucleocapsid and effector mechanisms of different subclasses of antibody.

Reviewer #2: authors have explained all the quires with significant justification to the reviewer comments, and authors have used well standard statistical methods and maintain the good language throughout the manuscript.

Reviewer #3: The authors addressed the comments made to improve the quality of the article to meet the journal standard. Thank you.

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: Yes: Yang Xu, MD, PhD

Reviewer #2: No

Reviewer #3: No