Journal of Clinical and Diagnostic Research, ISSN - 0973 - 709X

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Dr Mohan Z Mani

"Thank you very much for having published my article in record time.I would like to compliment you and your entire staff for your promptness, courtesy, and willingness to be customer friendly, which is quite unusual.I was given your reference by a colleague in pathology,and was able to directly phone your editorial office for clarifications.I would particularly like to thank the publication managers and the Assistant Editor who were following up my article. I would also like to thank you for adjusting the money I paid initially into payment for my modified article,and refunding the balance.
I wish all success to your journal and look forward to sending you any suitable similar article in future"



Dr Mohan Z Mani,
Professor & Head,
Department of Dermatolgy,
Believers Church Medical College,
Thiruvalla, Kerala
On Sep 2018




Prof. Somashekhar Nimbalkar

"Over the last few years, we have published our research regularly in Journal of Clinical and Diagnostic Research. Having published in more than 20 high impact journals over the last five years including several high impact ones and reviewing articles for even more journals across my fields of interest, we value our published work in JCDR for their high standards in publishing scientific articles. The ease of submission, the rapid reviews in under a month, the high quality of their reviewers and keen attention to the final process of proofs and publication, ensure that there are no mistakes in the final article. We have been asked clarifications on several occasions and have been happy to provide them and it exemplifies the commitment to quality of the team at JCDR."



Prof. Somashekhar Nimbalkar
Head, Department of Pediatrics, Pramukhswami Medical College, Karamsad
Chairman, Research Group, Charutar Arogya Mandal, Karamsad
National Joint Coordinator - Advanced IAP NNF NRP Program
Ex-Member, Governing Body, National Neonatology Forum, New Delhi
Ex-President - National Neonatology Forum Gujarat State Chapter
Department of Pediatrics, Pramukhswami Medical College, Karamsad, Anand, Gujarat.
On Sep 2018




Dr. Kalyani R

"Journal of Clinical and Diagnostic Research is at present a well-known Indian originated scientific journal which started with a humble beginning. I have been associated with this journal since many years. I appreciate the Editor, Dr. Hemant Jain, for his constant effort in bringing up this journal to the present status right from the scratch. The journal is multidisciplinary. It encourages in publishing the scientific articles from postgraduates and also the beginners who start their career. At the same time the journal also caters for the high quality articles from specialty and super-specialty researchers. Hence it provides a platform for the scientist and researchers to publish. The other aspect of it is, the readers get the information regarding the most recent developments in science which can be used for teaching, research, treating patients and to some extent take preventive measures against certain diseases. The journal is contributing immensely to the society at national and international level."



Dr Kalyani R
Professor and Head
Department of Pathology
Sri Devaraj Urs Medical College
Sri Devaraj Urs Academy of Higher Education and Research , Kolar, Karnataka
On Sep 2018




Dr. Saumya Navit

"As a peer-reviewed journal, the Journal of Clinical and Diagnostic Research provides an opportunity to researchers, scientists and budding professionals to explore the developments in the field of medicine and dentistry and their varied specialities, thus extending our view on biological diversities of living species in relation to medicine.
‘Knowledge is treasure of a wise man.’ The free access of this journal provides an immense scope of learning for the both the old and the young in field of medicine and dentistry as well. The multidisciplinary nature of the journal makes it a better platform to absorb all that is being researched and developed. The publication process is systematic and professional. Online submission, publication and peer reviewing makes it a user-friendly journal.
As an experienced dentist and an academician, I proudly recommend this journal to the dental fraternity as a good quality open access platform for rapid communication of their cutting-edge research progress and discovery.
I wish JCDR a great success and I hope that journal will soar higher with the passing time."



Dr Saumya Navit
Professor and Head
Department of Pediatric Dentistry
Saraswati Dental College
Lucknow
On Sep 2018




Dr. Arunava Biswas

"My sincere attachment with JCDR as an author as well as reviewer is a learning experience . Their systematic approach in publication of article in various categories is really praiseworthy.
Their prompt and timely response to review's query and the manner in which they have set the reviewing process helps in extracting the best possible scientific writings for publication.
It's a honour and pride to be a part of the JCDR team. My very best wishes to JCDR and hope it will sparkle up above the sky as a high indexed journal in near future."



Dr. Arunava Biswas
MD, DM (Clinical Pharmacology)
Assistant Professor
Department of Pharmacology
Calcutta National Medical College & Hospital , Kolkata




Dr. C.S. Ramesh Babu
" Journal of Clinical and Diagnostic Research (JCDR) is a multi-specialty medical and dental journal publishing high quality research articles in almost all branches of medicine. The quality of printing of figures and tables is excellent and comparable to any International journal. An added advantage is nominal publication charges and monthly issue of the journal and more chances of an article being accepted for publication. Moreover being a multi-specialty journal an article concerning a particular specialty has a wider reach of readers of other related specialties also. As an author and reviewer for several years I find this Journal most suitable and highly recommend this Journal."
Best regards,
C.S. Ramesh Babu,
Associate Professor of Anatomy,
Muzaffarnagar Medical College,
Muzaffarnagar.
On Aug 2018




Dr. Arundhathi. S
"Journal of Clinical and Diagnostic Research (JCDR) is a reputed peer reviewed journal and is constantly involved in publishing high quality research articles related to medicine. Its been a great pleasure to be associated with this esteemed journal as a reviewer and as an author for a couple of years. The editorial board consists of many dedicated and reputed experts as its members and they are doing an appreciable work in guiding budding researchers. JCDR is doing a commendable job in scientific research by promoting excellent quality research & review articles and case reports & series. The reviewers provide appropriate suggestions that improve the quality of articles. I strongly recommend my fraternity to encourage JCDR by contributing their valuable research work in this widely accepted, user friendly journal. I hope my collaboration with JCDR will continue for a long time".



Dr. Arundhathi. S
MBBS, MD (Pathology),
Sanjay Gandhi institute of trauma and orthopedics,
Bengaluru.
On Aug 2018




Dr. Mamta Gupta,
"It gives me great pleasure to be associated with JCDR, since last 2-3 years. Since then I have authored, co-authored and reviewed about 25 articles in JCDR. I thank JCDR for giving me an opportunity to improve my own skills as an author and a reviewer.
It 's a multispecialty journal, publishing high quality articles. It gives a platform to the authors to publish their research work which can be available for everyone across the globe to read. The best thing about JCDR is that the full articles of all medical specialties are available as pdf/html for reading free of cost or without institutional subscription, which is not there for other journals. For those who have problem in writing manuscript or do statistical work, JCDR comes for their rescue.
The journal has a monthly publication and the articles are published quite fast. In time compared to other journals. The on-line first publication is also a great advantage and facility to review one's own articles before going to print. The response to any query and permission if required, is quite fast; this is quite commendable. I have a very good experience about seeking quick permission for quoting a photograph (Fig.) from a JCDR article for my chapter authored in an E book. I never thought it would be so easy. No hassles.
Reviewing articles is no less a pain staking process and requires in depth perception, knowledge about the topic for review. It requires time and concentration, yet I enjoy doing it. The JCDR website especially for the reviewers is quite user friendly. My suggestions for improving the journal is, more strict review process, so that only high quality articles are published. I find a a good number of articles in Obst. Gynae, hence, a new journal for this specialty titled JCDR-OG can be started. May be a bimonthly or quarterly publication to begin with. Only selected articles should find a place in it.
An yearly reward for the best article authored can also incentivize the authors. Though the process of finding the best article will be not be very easy. I do not know how reviewing process can be improved. If an article is being reviewed by two reviewers, then opinion of one can be communicated to the other or the final opinion of the editor can be communicated to the reviewer if requested for. This will help one’s reviewing skills.
My best wishes to Dr. Hemant Jain and all the editorial staff of JCDR for their untiring efforts to bring out this journal. I strongly recommend medical fraternity to publish their valuable research work in this esteemed journal, JCDR".



Dr. Mamta Gupta
Consultant
(Ex HOD Obs &Gynae, Hindu Rao Hospital and associated NDMC Medical College, Delhi)
Aug 2018




Dr. Rajendra Kumar Ghritlaharey

"I wish to thank Dr. Hemant Jain, Editor-in-Chief Journal of Clinical and Diagnostic Research (JCDR), for asking me to write up few words.
Writing is the representation of language in a textual medium i e; into the words and sentences on paper. Quality medical manuscript writing in particular, demands not only a high-quality research, but also requires accurate and concise communication of findings and conclusions, with adherence to particular journal guidelines. In medical field whether working in teaching, private, or in corporate institution, everyone wants to excel in his / her own field and get recognised by making manuscripts publication.


Authors are the souls of any journal, and deserve much respect. To publish a journal manuscripts are needed from authors. Authors have a great responsibility for producing facts of their work in terms of number and results truthfully and an individual honesty is expected from authors in this regards. Both ways its true "No authors-No manuscripts-No journals" and "No journals–No manuscripts–No authors". Reviewing a manuscript is also a very responsible and important task of any peer-reviewed journal and to be taken seriously. It needs knowledge on the subject, sincerity, honesty and determination. Although the process of reviewing a manuscript is a time consuming task butit is expected to give one's best remarks within the time frame of the journal.
Salient features of the JCDR: It is a biomedical, multidisciplinary (including all medical and dental specialities), e-journal, with wide scope and extensive author support. At the same time, a free text of manuscript is available in HTML and PDF format. There is fast growing authorship and readership with JCDR as this can be judged by the number of articles published in it i e; in Feb 2007 of its first issue, it contained 5 articles only, and now in its recent volume published in April 2011, it contained 67 manuscripts. This e-journal is fulfilling the commitments and objectives sincerely, (as stated by Editor-in-chief in his preface to first edition) i e; to encourage physicians through the internet, especially from the developing countries who witness a spectrum of disease and acquire a wealth of knowledge to publish their experiences to benefit the medical community in patients care. I also feel that many of us have work of substance, newer ideas, adequate clinical materials but poor in medical writing and hesitation to submit the work and need help. JCDR provides authors help in this regards.
Timely publication of journal: Publication of manuscripts and bringing out the issue in time is one of the positive aspects of JCDR and is possible with strong support team in terms of peer reviewers, proof reading, language check, computer operators, etc. This is one of the great reasons for authors to submit their work with JCDR. Another best part of JCDR is "Online first Publications" facilities available for the authors. This facility not only provides the prompt publications of the manuscripts but at the same time also early availability of the manuscripts for the readers.
Indexation and online availability: Indexation transforms the journal in some sense from its local ownership to the worldwide professional community and to the public.JCDR is indexed with Embase & EMbiology, Google Scholar, Index Copernicus, Chemical Abstracts Service, Journal seek Database, Indian Science Abstracts, to name few of them. Manuscriptspublished in JCDR are available on major search engines ie; google, yahoo, msn.
In the era of fast growing newer technologies, and in computer and internet friendly environment the manuscripts preparation, submission, review, revision, etc and all can be done and checked with a click from all corer of the world, at any time. Of course there is always a scope for improvement in every field and none is perfect. To progress, one needs to identify the areas of one's weakness and to strengthen them.
It is well said that "happy beginning is half done" and it fits perfectly with JCDR. It has grown considerably and I feel it has already grown up from its infancy to adolescence, achieving the status of standard online e-journal form Indian continent since its inception in Feb 2007. This had been made possible due to the efforts and the hard work put in it. The way the JCDR is improving with every new volume, with good quality original manuscripts, makes it a quality journal for readers. I must thank and congratulate Dr Hemant Jain, Editor-in-Chief JCDR and his team for their sincere efforts, dedication, and determination for making JCDR a fast growing journal.
Every one of us: authors, reviewers, editors, and publisher are responsible for enhancing the stature of the journal. I wish for a great success for JCDR."



Thanking you
With sincere regards
Dr. Rajendra Kumar Ghritlaharey, M.S., M. Ch., FAIS
Associate Professor,
Department of Paediatric Surgery, Gandhi Medical College & Associated
Kamla Nehru & Hamidia Hospitals Bhopal, Madhya Pradesh 462 001 (India)
E-mail: drrajendrak1@rediffmail.com
On May 11,2011




Dr. Shankar P.R.

"On looking back through my Gmail archives after being requested by the journal to write a short editorial about my experiences of publishing with the Journal of Clinical and Diagnostic Research (JCDR), I came across an e-mail from Dr. Hemant Jain, Editor, in March 2007, which introduced the new electronic journal. The main features of the journal which were outlined in the e-mail were extensive author support, cash rewards, the peer review process, and other salient features of the journal.
Over a span of over four years, we (I and my colleagues) have published around 25 articles in the journal. In this editorial, I plan to briefly discuss my experiences of publishing with JCDR and the strengths of the journal and to finally address the areas for improvement.
My experiences of publishing with JCDR: Overall, my experiences of publishing withJCDR have been positive. The best point about the journal is that it responds to queries from the author. This may seem to be simple and not too much to ask for, but unfortunately, many journals in the subcontinent and from many developing countries do not respond or they respond with a long delay to the queries from the authors 1. The reasons could be many, including lack of optimal secretarial and other support. Another problem with many journals is the slowness of the review process. Editorial processing and peer review can take anywhere between a year to two years with some journals. Also, some journals do not keep the contributors informed about the progress of the review process. Due to the long review process, the articles can lose their relevance and topicality. A major benefit with JCDR is the timeliness and promptness of its response. In Dr Jain's e-mail which was sent to me in 2007, before the introduction of the Pre-publishing system, he had stated that he had received my submission and that he would get back to me within seven days and he did!
Most of the manuscripts are published within 3 to 4 months of their submission if they are found to be suitable after the review process. JCDR is published bimonthly and the accepted articles were usually published in the next issue. Recently, due to the increased volume of the submissions, the review process has become slower and it ?? Section can take from 4 to 6 months for the articles to be reviewed. The journal has an extensive author support system and it has recently introduced a paid expedited review process. The journal also mentions the average time for processing the manuscript under different submission systems - regular submission and expedited review.
Strengths of the journal: The journal has an online first facility in which the accepted manuscripts may be published on the website before being included in a regular issue of the journal. This cuts down the time between their acceptance and the publication. The journal is indexed in many databases, though not in PubMed. The editorial board should now take steps to index the journal in PubMed. The journal has a system of notifying readers through e-mail when a new issue is released. Also, the articles are available in both the HTML and the PDF formats. I especially like the new and colorful page format of the journal. Also, the access statistics of the articles are available. The prepublication and the manuscript tracking system are also helpful for the authors.
Areas for improvement: In certain cases, I felt that the peer review process of the manuscripts was not up to international standards and that it should be strengthened. Also, the number of manuscripts in an issue is high and it may be difficult for readers to go through all of them. The journal can consider tightening of the peer review process and increasing the quality standards for the acceptance of the manuscripts. I faced occasional problems with the online manuscript submission (Pre-publishing) system, which have to be addressed.
Overall, the publishing process with JCDR has been smooth, quick and relatively hassle free and I can recommend other authors to consider the journal as an outlet for their work."



Dr. P. Ravi Shankar
KIST Medical College, P.O. Box 14142, Kathmandu, Nepal.
E-mail: ravi.dr.shankar@gmail.com
On April 2011
Anuradha

Dear team JCDR, I would like to thank you for the very professional and polite service provided by everyone at JCDR. While i have been in the field of writing and editing for sometime, this has been my first attempt in publishing a scientific paper.Thank you for hand-holding me through the process.


Dr. Anuradha
E-mail: anuradha2nittur@gmail.com
On Jan 2020

Important Notice

Original article / research
Year : 2022 | Month : March | Volume : 16 | Issue : 3 | Page : LC37 - LC42 Full Version

Antibody Response Profile in COVID-19 Infection in Healthcare Workers: Insights from a Study at a Reference Laboratory


Published: March 1, 2022 | DOI: https://doi.org/10.7860/JCDR/2022/52061.16166
Trupti Shetty , Anupa Dixit , Amar Dasgupta , Vineeth Nair , Heena Satam , Aditi Arora , Sanjay Arora

1. Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India. 2. Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India. 3. Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India. 4. Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India. 5. Molecular Biologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India. 6. Resident, Department of Pathology, Tata Memorial Hospital, Mumbai, Maharashtra, India. 7. Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India.

Correspondence Address :
Dr. Amar Dasgupta,
Pathologist, Department of Pathology, Suburban Diagnostics, Mumbai, Maharashtra, India.
E-mail: amar.dasgupta@suburbandiagnostics.com

Abstract

Introduction: The Coronavirus Disease 2019 (COVID-19) pandemic has imposed an unprecedented burden on our healthcare system. Serological testing for Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) antibodies serves as useful marker for determining an infection by the virus in the recent past and the immune response. The immune response, including the humoral response to the infection is one of them and the knowledge in this area is still evolving. Virus specific antibodies are expected to help in eliminating the virus and to provide protective immunity against reinfection.

Aim: To serially monitor the total antibody response to SARS-CoV-2 in order to gain better insight into the duration of antibody persistence.

Materials and Methods: This prospective observational and analytical study was conducted in 66 Healthcare Workers (HCW) with a history of Reverse Transcription-Polymerase Chain Reaction (RT-PCR) proven COVID-19 infection. The study was conducted between May 2020 to April 2021 at the Suburban diagnostics Central Processing Laboratory, Mumbai, Maharashtra, India. Serum samples were serially examined for the presence of total antibodies against the Nucleocapsid (N) protein of SARS-CoV-2 upto 180 days postinfection. A further follow-up examination was done at 360 days. A qualitative Electrochemiluminescence Immunoassay (ECLIA) was used for assessment of the antibody response. The Chi-square or Fisher-exact test was used to compare categorical variables and the Mann-Whitney U test, Kruskal Wallis test and student t-test were used to compare continuous variables across groups. For assessing relationship between variables, the Pearson test or Linear regression were used as appropriate.

Results: Out of 66 healthcare workers, 32 were male (48.5%) and 34 were females (51.5%) with the median age of 29.5 years. Out of 66 cases, 62 (94%) cases developed antibodies against SARS-CoV-2 at different time intervals, 48 cases during the 14-30 day interval, 10 cases during the 31-60 day interval, three cases during the 61-90 day interval and one case during the 90-120 days interval. Out of 35, 31 (88.6%) subjects could be followed-up at 360 days showed persistence of antibodies. No patient reported symptoms which would warrant a repeat RT-PCR test.

Conclusion: This study showed that the antibody response to SARS-CoV-2 virus was sustained for 12 months postinfection in most cases. The absence of fresh infection in these cases during the study period suggests that the antibodies might protect against reinfection with the virus. So, it may be safe to defer vaccination in postinfection cases by 6-9 months thereby saving precious resources.

Keywords

Coronavirus disease 2019, Immunity, Nucleocapsid, Reinfections, Severe acute respiratory syndrome coronavirus-2

The beginning of 2020 saw the emergence of Coronavirus Disease 2019 (COVID-19) pandemic caused by a novel coronavirus, Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), that belongs to lineage B of the beta-coronavirus family. The respiratory illness caused by the virus was termed “The Corona Virus Disease 2019; COVID-19” by the World Health Organisation (WHO) (1).

The number of COVID-19 cases worldwide has surpassed 160 million confirmed cases including more than 3.4 million deaths at the time of writing (2). Healthcare Workers (HCW) are at a higher risk of SARS-CoV-2 infection due to increased occupational exposure to SARS-CoV-2 (3). The highly contagious nature of the virus, the huge number of active patient population in the world and the high rate of morbidity and mortality associated with the disease make an early and correct diagnosis mandatory in all suspected cases. Detection of the virus in the upper respiratory tract samples by real time Reverse Transcription- Polymerase Chain Reaction (RT-PCR) is at present the gold standard method for diagnosis in the early stages of infection as viral nucleic acids are present in adequate quantity in the respiratory tract samples.

Inspite of a large body of information on SARS-CoV-2 infection there are several aspects of this infection that are still not well understood. The immune response, including the humoral response to the infection is one of them and the knowledge in this area is still evolving. Virus specific antibodies produced by the human body have already been found to play an important role in our fight against the pandemic. These antibodies are expected to help in eliminating the virus and to provide protective immunity against reinfection.

Longitudinal serological studies that examine persistence of antibodies in patients who have recovered from COVID-19 infection are required for answering several unresolved questions, specifically with regards to the duration of immune response and the protection offered by the antibodies to reinfection with SARS-CoV-2 vis-à-vis that offered by vaccination. Although recent studies by L’Huillier AG et al., and Favresse J et al., have indicated persistence of antibody response to be for at least 6-10 months following an infection (4),(5), the same following vaccination is still unknown. The present study was therefore, undertaken to understand the trend of antibody values (increasing/decreasing), the duration of the antibody response following natural infection by SARS-CoV-2 and to understand the association, if any, between the immune response post SARS-CoV-2 infection (seroconversion interval) and viral dynamics during infection (cycle threshold-value/viral load, symptomatic/asymptomatic infection).

Material and Methods

This prospective observational and analytical study to understand the antibody response profile in COVID-19 was conducted over a total period of 12 months from May 2020 to April 2021 at Suburban Diagnostic’s Central Processing Laboratory in Mumbai, Maharashtra, India. The study was conducted on HCW who were employees at Suburban Diagnostics India Private Limited after obtaining approval for the study from the Institutional Committee constituted for this purpose (IC-Sub/Approval/003/2020). Informed consent was obtained from the patients, prior to their inclusion in the study.

Inclusion criteria: The HCW working at Suburban Diagnostics India Pvt. Ltd., with no co-morbidities, who contracted COVID-19 (proven by a positive RT-PCR result from nasopharyngeal/oropharyngeal swab) between April 15th and April 30th 2020 and who volunteered to be part of the study were included.

Exclusion criteria: The HCW who were vaccinated during the study period were automatically excluded from the study.

Out of a total of 85 subjects who contracted COVID-19 in the stipulated time period, 66 fulfilled the inclusion criteria and were included in the study. All subjects received standard care treatment as per ICMR guidelines. All safety protocols were followed for collection of samples.

Procedure

All the subjects included in the study had been diagnosed using RT-PCR qualitative assay for SARS-CoV-2 performed using TaqPath RT-PCR kit from Applied Biosystems targeting Orf1ab, N and S genes. The instructions mentioned in the TaqPath kit literature were strictly followed while performing the tests. The RNA extraction was performed on Kingfisher flex 96 automated magnetic bead-based extractor from Thermo Fisher (USA), Amplification of RNA was carried out on Quantstudio 5 from Thermo Fisher. A cycle threshold-value >35 was considered as RT-PCR negative. Examples of positive and negative RT-PCR amplification curves are shown in (Table/Fig 1), (Table/Fig 2), respectively.

For the purposes of analysis, the Ct-values of the positive RT-PCR at time of diagnosis were used as an indicator for the viral load in the patient.

This antibody response profile was studied with serial serum sampling done till October 2020 with a final follow-up and sampling done at 360 days from the date of infection. Serum samples collected from these subjects were analysed for anti SARS-CoV-2 nucleocapsid total antibody on the fully automated Cobas 8000 analyser employing the Elecsys Anti SARS-CoV-2 assay kit (Roche Diagnostics, Switzerland). The Roche Elecsys Anti SARS-CoV-2 assay is an immunoassay for in-vitro qualitative detection of antibodies (including IgA, IgG and IgM)) against the SARS-CoV-2 nucleoprotein. The test requires a minimum of 100 μL of serum or plasma. Qualitative results and index values reported by the analyser as positive {Cut-off Index (COI) >1} and negative (COI <1) were used for reporting the results and as surrogate markers for antibody levels in this analysis.

The subjects in the study by Long QX et al., had shown positivity rate of 100% for IgG within 19 days. However, IgM positivity rate reached >94% only after 23 days (6). Keeping this fact in mind, for the purpose of analysis in the current study, immune response in the subjects was analysed by categorising them into the following categories based on the time of appearance of antibody positivity as detected by the assay:

• Seroconverted within 30 days-early responders,
• Seroconverted post 30 days-late responders,
• No seroconversion-non responders

The 30 day cut-off used in this study for categorising the immune response in COVID-19 patients was based on the data published by Long QX et al., which, as mentioned above, showed appearance of the antibody response up to three weeks postinfection in 100% of the subjects (6).

It was noteworthy in this context that even though the assay is a qualitative one, the results of positive samples, i.e., those above the cut-off, were expressed as numeric values by the assay. Serum samples were collected from each subject according to predetermined intervals i.e., at 14-30 days, 31-60 days, 61-90 days, 91-120 days, 121-150 days and 151-180 days. The intervals for the subjects were counted from the day of onset of symptoms in symptomatic individuals and from the day of confirmation of infection in asymptomatic cases.

In April 2021, a follow-up antibody testing was done at the 360-day mark in 45 of the 66 cases. Total 21 subjects were lost to follow-up due to change of employment, travel and strict country-wide lockdown. A close telephonic and in-person (wherever possible) follow-up of the subjects was maintained on a fortnightly basis during the entire study period to pick-up recurrence of symptoms that warranted RT-PCR testing.

Statistical Analysis

The collected data was entered in Microsoft Excel 2019, exported to and then analysed using Statistical Package for the Social Sciences (SPSS) version 25.0 (IBM SPSS Statistics, Chicago, IL). Continuous variables are expressed as median and categorical variables as whole numbers and percentages. The Chi-square or Fisher-exact test was used to compare categorical variables and the Mann-Whitney U-test, Kruskal-Wallis test and student t-test were used to compare continuous variables across groups. For assessing relationship between variables, the Pearson test or Linear regression were used as appropriate.

Results

A total of 66 HCW were included in the study with 32 males (48.5%) and 34 females (51.5%). The ages ranged from 17-64 years with the median age being 29.5 years.

PHASE I: Serial Sampling up to Day 180

Using the numeric values above the cut-off index, we monitored the changes in the antibodies in each case as they went up, stabilised and then came down with passage of time in the first 180 days.

Rate of antibody positivity and seroconversion interval: Sixty two of the total 66 cases (93.9%) enrolled in the study became antibody reactive during the 180 day period of the study and 4/66 (6.1%) remained antibody non reactive (non responders) during this period. Forty eight of the 62 responders (77.4%) first showed the presence of antibodies between 14-30 days from the date of RT-PCR testing (early responders), while 14/62 (22.5%) were late responders. Of the 14 late responders, 10 became antibody positive in the 31-60 day period, three became antibody positive in 61-90 day period and one became positive in 91-120 day period (Table/Fig 3).

No significant association was seen between the age and the time to seroconversion (p-value=0.054), and between gender and seroconversion interval (p-value=0.322). There was a statistical association between the presence of influenza like symptoms and the time to seroconversion. The individuals who had a symptomatic infection were more likely to have seroconverted in less than 30 days post onset of symptoms (p-value=0.031).

The most common symptom reported during the infection by the subjects was fever which was seen in 39 out of 45 patients. The complete breakdown of reported symptoms is listed in (Table/Fig 4).

All the responders showed peaks at different intervals as depicted in (Table/Fig 5). No significant association was noted between the time of the antibody response and the time to attainment of the peak response (p-value=0.762).

At the end of 180 days, 14.5% (9/62) of the responders had antibody values lower than the initial antibody level at the time of seroconversion whereas the remaining 53 responders had antibody levels higher than the initial antibody level at the time of seroconversion. The trends of the antibody values are depicted in a Sankey diagram (Table/Fig 6).

Correlation of antibody response with Ct-value: Out of 66, 45 (68.2%) patients were symptomatic and the remaining 21 (31.8%) were asymptomatic. All four non responders (6%) had an asymptomatic infection The Ct-value at the time of diagnosis in the total patient population ranged from 12.05-34.92 with median Ct-value being 23.79. Ct-value ranged from 14-34.76 with a median of 23.52 for asymptomatic subjects and ranged from 12.05-34.92 with a median of 23.99 for symptomatic subjects. There was no statistically significant difference in the Ct-values between symptomatic and asymptomatic patients (p-value=0.618). Similarly, no statistically significant difference was seen in the age between symptomatic and asymptomatic patients (p-value=0.544).

No significant correlation was identified between Ct-values in RT-PCR assays at the time of diagnosis and peak antibody value (p-value=0.309, Pearson correlation coefficient=0.128). Further analysis showed that there was no significant difference in peak antibody values (p-value=0.168) or Ct-values (p-value=0.663) across symptomatic and asymptomatic cases.

PHASE II: Follow-up at 360 Days

All the 66 subjects were contacted around 360 days following their infection. Due to an on-going lockdown and logistic constraints, day 360 samples could be obtained from 45 of the 66 subjects. Twenty-one cases were lost to follow-up. Of these 45 subjects in whom day 360 samples could be collected, 10 were excluded from further analysis as they had been vaccinated in the 180-360 day period with inactivated whole virus vaccine that produces antibodies against multiple antigenic determinants of the virus similar to that induced by natural infection. Hence, a total of 35 cases were included for follow-up at 360 days.

Two subjects who were non reactive at 180 days seroconverted by 360 days. The remaining two subjects who had been non reactive at the end of the 180 days continued to be non reactive. The antibody levels of additional two subjects who were reactive at the end of 180 days had dropped in the interim to become non reactive at 360 days. Interestingly, one of these subjects had an asymptomatic infection whereas the other had symptomatic infection.

Comparison of antibody level at 150-180 days and at 360 days: As mentioned above, after excluding patients who were vaccinated and those who were lost to follow-up, 35 cases remained who were followed-up at 360 days. Out of 35, 31 (88.6%) subjects who could be tested at 360 days showed the presence of antibodies at the end of 360 days. This includes the two cases which had seroconverted in the 180-360 day period. The antibody levels in 26 out of 31 cases had gone below the levels seen at 150-180 days.

Comparison of antibody levels at seroconversion versus at 360 days: When the antibody levels at 360 days were compared with the initial antibody level at the time of seroconversion, it was noted that 17 subjects out of the 31 had lower antibody levels (not including the two cases which had gone from reactive to non reactive during the 180-360 day period). By the same token, 12 subjects, not including the two cases which become reactive in the 180-360 day period, had higher antibody values (Table/Fig 7). This indicates that despite the fall in values in many cases, the majority of patients showed persistence of antibody response up to one year from the time of infection.

The results were analysed for the rise or fall of antibody value with respect to initial seroconversion value and it was found that rise or fall had no association with the presence or absence of symptoms (p-value=0.142). Similarly, there was no association with age (p-value=0.287), peak antibody value (p-value=0.760) or Ct-value at time of diagnosis (p-value=0.304).

Notably, during the entire study period, no patient reported symptoms which would warrant a repeat RT-PCR test.

Discussion

World Health Organisation defines health workers as all people engaged in actions whose primary intent is to enhance health (7). In the fight against the COVID-19 pandemic, HCWs are the forefront with the substantial task of diagnosing and treating an exponentially growing number of acutely ill patients (8). Measuring host immune response to SARS-CoV-2 infection is one of the key approaches for identifying past COVID-19 infection and to determine the response to a vaccine. The initial testing criteria implemented by the healthcare authorities in India that involved testing of symptomatic cases only, had left a number of COVID-19 asymptomatic patients untested. These cases were subsequently shown to have had the infection by antibody positivity thereby highlighting the role of antibody testing to determine the seroprevalence. Identification of convalescent plasma donors is another known indication of antibody testing.

In a study conducted in China by Huang CG et al., it was found that strong antibody response depends on the relative persistence of the virus instead of the absolute virus amount. The antibody response is found to be weak if a large amount of virus is cleared quickly (9).

The Coronavirus has four structural proteins, namely, spike (S), envelope (E), membrane (M) and nucleocapsid (N) proteins. The SARS-CoV-2 virus uses the S protein to bind to the receptor on host cells to trigger cell entry and infection. The S protein consists of S1 and S2 subunits. The S1 subunit interacts with the host cells via the Receptor Binding Domain (RBD) which binds to Angiotensin-Converting Enzyme 2 (ACE 2) receptor and is highly immunogenic (10). Most individuals infected with COVID-19 develop antibodies to S and Nucleocapsid (N) proteins, which are therefore, used as antigens in clinical serology assays. Following SARS-CoV-2 infection specific immune response in the form of IgA, IgM, IgG antibodies is observed. Sethuraman N et al., found that testing for the combination of IgA, IgM and IgG i.e., total antibody testing can make an early diagnosis and support evaluation of the stage of infection (11),(12).

Burbelo PD et al., in their review reported that the antibody to the N protein of SARS-CoV-2 is a more sensitive marker for detecting early infection than the S protein antibody (13). Anti-S and anti-RBD antibodies can block the interaction between the RBD domain of the S protein and the host cell leading to viral neutralisation and, as such, are better markers of functional immune responses (10),(14).

Long QX et al., reported that asymptomatic subjects have a significantly longer duration of viral shedding than the symptomatic ones (log-rank p=0.028). It has also been reported that the virus-specific IgG levels among asymptomatic cases were significantly lower (p=0.005) relative to the symptomatic cases in the acute phase (15). But in the current study, no association was found between presence of symptoms and peak antibody response. However, an association was found between the presence of symptoms and seroconversion interval; individuals with a symptomatic infection tended to seroconvert early. The present study did not show any correlation between the Ct-values of RT-PCR assays (ostensibly representing viral load) and the antibody response.

Only a very small percentage (4/66; 6%) of our cases did not show any antibody response till the end of the 180 day period. Most infected individuals (RT-PCR-positive) begin to have detectable seroconversion 10-14 days after symptom onset, but antibody levels in some mild cases can be low or undetectable (16). Low or undetectable antibodies do not necessarily represent a poor immune response. Although the absolute quantity of the antibody in these patients is low, the neutralisation efficacy per unit of antibody is equivalent to that of the group with higher antibody levels, indicating that patients with low antibody quantities also have a considerable number of mature B cells secreting effective antibodies (9). In the present study, though categorised as non responders, all the six cases had an uneventful recovery and none of them had associated co-morbidities or were re-infected during the study period.

There could be several explanations for the slow or poor immune response in some patients after being infected by SARS-CoV-2. It is possible that these patients were unable to produce antibodies due to some form of undetected or transient immunodeficiency. Since, the immune apparatus in such cases were not investigated by most studies reporting this finding (14),(17), this possibility is somewhat conjectural. The fact that most patients with poor antibody response have an uneventful recovery from COVID-19 infection points to the role of cellular and other constituents of immune apparatus in the recovery process (18).

Concrete data explaining the relationship between a humoral immune response to SARS-CoV-2 infection and protection against reinfection by this virus is still awaited. Several studies like, Favresse J et al., Chia WN et al., Figueirado-Campos P et al., have assessed the dynamics and duration of antibody response in SARS-CoV-2 infection (5),(18),(19). These findings are not uniform, with some claiming rapid waning and others showing antibody persistence, partly due to the fact that different groups have measured different antibodies using different types of reagent/platform combinations and most studies were done at an early stage of convalescence (18). Figueirado-Campos P et al., in their study found that SARS-CoV-2 antibodies peak around week three postinfection, and although antibody titres do decline, IgG antibodies remain detectable and show virus neutralisation activity for at least six months post-SARS-CoV-2 infection (19). It is interesting to observe in this context that, in the present study, the majority of patients who were retested beyond 6 months (180-360 days) by the same method used during the study period referred to above, showed persistence of the antibody response up to 12 months. The findings of present study therefore, indicate that the antibody response to the natural infection is of longer duration than that hitherto reported in the literature (4),(5). This is an important finding as far as acquired immunity to the virus through natural infection is concerned and might lead to more efficient scheduling of vaccination in patients who have recovered from COVID-19 infection. This would help us prioritise the potential beneficiaries of the vaccine better and conserve precious resources, including the vaccines which have unpredictable supply flow in India. The possible influence of reagents used in the antibody assay in correctly capturing the duration of the antibody response as suggested by a recent report (5) does not seem relevant in our cases since the reagent/platform combination used by us was shown to result in data similar to that reported by this study.

Recent studies like Masiá M et al., have reported that viral replication determines the magnitude of the humoral immune response and that high viral load predicts an earlier antibody response, while non seroconversion is linked with very low replication. In addition, the kinetics of the humoral immune response predicts the speed of viral elimination (20). No such association was observed in the current study. However, further studies with larger datasets will be required to examine the association between viral dynamics and host immune response.

The antibody response in COVID-19 infection provides a window to the immune response to vaccines currently being used in India, especially the inactivated whole virus vaccine (Bharat Biotech). While the AstraZeneca vaccine induces a specific set of antibodies against the receptor binding site of the spike protein (S1-RBD), the Bharat Biotech vaccine produces an antibody response that is similar to that following an infection with the virus. Therefore, antibody response to the inactivated SARS-CoV-2 vaccine will be difficult to distinguish from the postinfection antibody response due to the similarity of the antigenic constituents of the attenuated and the live viruses respectively. Post-vaccination antibody response in a person already carrying antibodies to SARS-CoV-2 from a past COVID-19 infection in the past 6-9 months could be significantly heightened. The clinical and epidemiological implications of this summation effect should be considered while interpreting any sero-surveillance and/or vaccine response data. Laboratories performing anti-SARS-CoV-2 antibody assays also need to communicate the clinical utility and limitations of the many assays that are available at present to the physicians and to the public at large.

Limitation(s)

In view of small sample number, the findings of this study need to be confirmed by examination of a larger population of COVID-19 patients.

Conclusion

This study showed that the antibody response to SARS-CoV-2 virus although variable, is sustained for at least 12 months postinfection in most cases. The fact that none of the patients had a recurrence of the infection during the 12 months postinfection, even though they were HCW and continued to live and work in high-risk environment, could suggest that the antibodies to SARS-CoV-2 virus acquired following an infection do provide immunity to the infection. This possibility is of great epidemiological value to the population at large and to the governing authorities in planning and prioritising the vaccination program. However, further research and clinical trials will be required to understand the type and nature of the immune response that will be required for imparting a long-lasting and robust immunity which in turn will help us manage the pandemic better.

Acknowledgement

Authors would like to thank the study participants for their involvement and their co-operation during the course of this study. Authors also acknowledge the efforts of Dr. Shweta Naik in processing and reporting RT-PCR samples and Mr. Rohit Kumar in his assistance with regards to data analysis.

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DOI and Others

DOI: 10.7860/JCDR/2022/52061.16166

Date of Submission: Sep 06, 2021
Date of Peer Review: Oct 28, 2021
Date of Acceptance: Jan 09, 2022
Date of Publishing: Mar 01, 2022

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. NA

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