Detection of IgM and IgG antibodies in patients with coronavirus disease 2019

Longitudinal changes in IgG levels among COVID-19 recovered patients: A prospective cohort study

OBJECTIVES

To quantify SARS-CoV2 IgG antibody titers over time and assess the longevity of the immune response in a multi-ethnic population setting.

SETTING

This prospective study was conducted in a tertiary hospital in Abu Dhabi city, UAE, among COVID-19 confirmed patients. The virus-specific IgG were measured quantitatively in serum samples from the patients during three visits over a period of 6 months. Serum IgG levels ≥15 AU/ml was used to define a positive response.

PARTICIPANTS

113 patients were analyzed at first visit, with a mean (SD) age of participants of 45.9 (11.8) years 87.5% of the patients were men. 63 and 27 participants had data available for visits 2 and 3, respectively.

PRIMARY OUTCOME

Change in SARS-CoV2 IgG antibody titers over the visits.

RESULTS

No mortality or re-infection were reported. 69% of the patients developed positive IgG response within the first month after the onset of symptoms. The levels of IgG showed a consistent increase during the first three months with a peak level during the third month. Increasing trend in the levels of IgG were observed in 82.5%, 55.6% and 70.4% of patients between visit 1 to visit 2, visit 2 to visit 3, and from visit 1 to visit 3, respectively. Furthermore, about 64.3% of the patients showed sustained increase in IgG response for more than 120 days.

CONCLUSIONS

Our study indicates a sustained and prolonged positive immune response in COVID-19 recovered patients. The consistent rise in antibody and positive levels of IgG titers within the first 5 months suggest that immunization is possible, and the chances of reinfection minimal.

People Living with HIV Easily lose their Immune Response to SARS-CoV-2: Result From A Cohort of COVID-19 Cases in Wuhan, China

Background To date, whether the immune response for SARS-CoV-2 infection among people living with HIV(PLWH) is different from HIV-naïve individuals is still not clear. Methods In this cohort study, COVID-19 patients admitted to hospital in Wuhan between January 15 and April 1, 2020, were enrolled. Patients were categorized into PLWH and HIV-naïve group. All patients were followed up regularly (every fifteen days) until November 30, 2020, and the immune response towards SARS-CoV-2 was observed. Results Totally, 18 PLWH and 185 HIV-naïve individuals with COVID-19 were enrolled. The positive conversion rates of IgG were 56% in PLWH and 88% in HIV-naïve patients respectively, and the peak was on the 45th day after COVID-19 onset. However, the positive rate of IgG dropped to 12% in PLWH and 33% among HIV-naïve individuals by the end of the study. The positive conversion rate of IgG among asymptomatic carriers is significantly lower than that among moderate patients (AOR = 0.18, 95% CI: 0.05-0.65) and PLWH had a lower IgG seroconversion rate compared to the HIV-naive group (AOR = 0.22, 95% CI: 0.05-0.90). Patients with lower lymphocyte counts at onset had a higher positive conversion rate (AOR = 0.29, 95% CI: 0.09-0.90) and longer duration for IgG (AHR = 4.01, 95% CI: 1.78-9.02). Conclusions The positive conversion rate of IgG for SARS-CoV-2 was relatively lower and quickly lost in PLWH, which meant PLWH was in a disadvantaged situation when affected with COVID-19.

What Is the Antibody Response and Role in Conferring Natural Immunity After SARS-CoV-2 Infection? Rapid, Living Practice Points From the American College of Physicians (Version 1)

DESCRIPTION

The widespread availability of SARS-CoV-2 antibody tests raises important questions for clinicians, patients, and public health professionals related to the appropriate use and interpretation of these tests. The Scientific Medical Policy Committee (SMPC) of the American College of Physicians developed these rapid, living practice points to summarize the current and best available evidence on the antibody response to SARS-CoV-2 infection, antibody durability after initial infection with SARS-CoV-2, and antibody protection against reinfection with SARS-CoV-2.

METHODS

The SMPC developed these rapid, living practice points based on a rapid and living systematic evidence review done by the Portland VA Research Foundation and funded by the Agency for Healthcare Research and Quality. Ongoing literature surveillance is planned through December 2021. When new studies are identified and a full update of the evidence review is published, the SMPC will assess the new evidence and any effect on the practice points.

PRACTICE POINT 1

Do not use SARS-CoV-2 antibody tests for the diagnosis of SARS-CoV-2 infection.

PRACTICE POINT 2

Antibody tests can be useful for the purpose of estimating community prevalence of SARS-CoV-2 infection.

PRACTICE POINT 3

Current evidence is uncertain to predict presence, level, or durability of natural immunity conferred by SARS-CoV-2 antibodies against reinfection (after SARS-CoV-2 infection).

Antibody Response After SARS-CoV-2 Infection and Implications for Immunity : A Rapid Living Review

BACKGROUND

The clinical significance of the antibody response after SARS-CoV-2 infection remains unclear.

PURPOSE

To synthesize evidence on the prevalence, levels, and durability of detectable antibodies after SARS-CoV-2 infection and whether antibodies to SARS-CoV-2 confer natural immunity.

DATA SOURCES

MEDLINE (Ovid), Embase, CINAHL, Cochrane Central Register of Controlled Trials, ClinicalTrials.gov, World Health Organization global literature database, and Covid19reviews.org from 1 January through 15 December 2020, limited to peer-reviewed publications available in English.

STUDY SELECTION

Primary studies characterizing the prevalence, levels, and duration of antibodies in adults with SARS-CoV-2 infection confirmed by reverse transcriptase polymerase chain reaction (RT-PCR); reinfection incidence; and unintended consequences of antibody testing.

DATA EXTRACTION

Two investigators sequentially extracted study data and rated quality.

DATA SYNTHESIS

Moderate-strength evidence suggests that most adults develop detectable levels of IgM and IgG antibodies after infection with SARS-CoV-2 and that IgG levels peak approximately 25 days after symptom onset and may remain detectable for at least 120 days. Moderate-strength evidence suggests that IgM levels peak at approximately 20 days and then decline. Low-strength evidence suggests that most adults generate neutralizing antibodies, which may persist for several months like IgG. Low-strength evidence also suggests that older age, greater disease severity, and presence of symptoms may be associated with higher antibody levels. Some adults do not develop antibodies after SARS-CoV-2 infection for reasons that are unclear.

LIMITATIONS

Most studies were small and had methodological limitations; studies used immunoassays of variable accuracy.

CONCLUSION

Most adults with SARS-CoV-2 infection confirmed by RT-PCR develop antibodies. Levels of IgM peak early in the disease course and then decline, whereas IgG peaks later and may remain detectable for at least 120 days.

PRIMARY FUNDING SOURCE

Agency for Healthcare Research and Quality. (PROSPERO: CRD42020207098).

Laboratory tests for the detection of SARS-CoV-2 infection: basic principles and examples

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has circulated throughout the world causing the worst pandemic since 1918. All efforts have been marshalled towards testing different treatment approaches, obtaining clinical and epidemiological information, developing suitable diagnostic tests, and developing new vaccines. New ribonucleic acid (RNA)-based and viral vector-based vaccines have been developed and licensed under emergency use in many countries; however, there is a huge demand for vaccines, and it will take some time before a sufficient number of people are vaccinated to stop the circulation of the virus. Therefore, the proper diagnosis and identification of infected individuals are crucial for the isolation and treatment of these patients and tracing of their contacts. Many diagnostic tests and diag-nostic kits have been developed in a relatively short time. This review summarizes the principles of the available laboratory assays that are in use for the detection of SARS-CoV-2 RNA, antigens, or antibodies.

Antibody Responses and Clinical Outcomes in Adults Hospitalized With Severe Coronavirus Disease 2019 (COVID-19): A Post hoc Analysis of LOTUS China Trial

BACKGROUND

The characteristics of neutralizing antibodies (NAbs) and antibody against major antigen proteins related to clinical outcomes in severe coronavirus disease 2019 (COVID-19) patients were still less known.

METHODS

NAbs and antibodies targeting nucleocapsid (N), spike protein (S), and the receptor-binding domain (RBD) in longitudinal plasma samples from the LOTUS China trial were measured by microneutralization assay and enzyme-linked immunosorbent assay (ELISA). Viral load was determined by real-time reverse transcription polymerase chain reaction (RT-PCR). A total of 576 plasma and 576 throat swabs were collected from 191 COVID-19 patients. Antibody titers related to adverse outcome and clinical improvement were analyzed. Multivariable adjusted generalized linear mixed model for random effects were developed.

RESULTS

After day 28 post symptoms onset, the rate of antibody positivity reached 100% for RBD-immunoglobulin M (IgM), 97.8% for S-IgM, 100% for N-immunoglobulin G (IgG), 100% for RBD-IgG, 91.1% for N-IgM, and 91.1% for NAbs. The NAbs titers increased over time in both survivors and nonsurvivors and correlated to IgG antibodies against N, S, and RBD, whereas its presence showed no statistical correlation with death. N-IgG (slope -2.11, 95% confidence interval [CI] -3.04 to -1.18, P < .0001), S-IgG (slope -2.44, 95% CI -3.35 to -1.54, P < .0001), and RBD-IgG (slope -1.43, 95% CI -1.98 to -.88, P < .0001) were negatively correlated with viral load. S-IgG titers were lower in nonsurvivors than survivors (P = .020) at week 4 after symptoms onset.

CONCLUSIONS

IgM and IgG against N, S, and RBD and NAbs developed in most severe COVID-19 patients and do not correlate clearly with clinical outcomes. The levels of IgG antibodies against N, S, and RBD were related to viral clearance.

Design of an effective piezoelectric microcantilever biosensor for rapid detection of COVID-19

Acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, is one of the most contagious viruses resulting in a progressive pandemic. Since specific antiviral treatments have not been developed yet and its fatal rate is almost high, early and fast detection is critical for controlling the outbreak. In this study, a piezoelectric microcantilever biosensor has been designed for detecting COVID-19 samples directly without requiring preparation steps. The biosensor acts as a transducer and is coated with the related antibody. When the SARS-CoV-2 antigens adsorbed on the microcantilever top surface through their spike proteins, a surface stress due to the mass change would be prompted leading to the measurable tip deflection and floating voltage. To obtain a biosensor with optimum parameters, different shapes and piezoelectric materials have been assessed and it was concluded that a Poly (vinylidene fluoride) (PVDF) biosensor in a shape of a holed punched form triangle, represented the best result. Therefore, the highly sensitive microcantilever biosensor can detect COVID-19 in clinical samples with various viral loads, rapidly. Also, it is selective enough to differentiate SARS-CoV-2 from other viruses with similar symptoms.

Design and Numerical Analysis of a Graphene-Coated SPR Biosensor for Rapid Detection of the Novel Coronavirus

In this paper, a highly sensitive graphene-based multiple-layer (BK7/Au/PtSe2/Graphene) coated surface plasmon resonance (SPR) biosensor is proposed for the rapid detection of the novel Coronavirus (COVID-19). The proposed sensor was modeled on the basis of the total internal reflection (TIR) technique for real-time detection of ligand-analyte immobilization in the sensing region. The refractive index (RI) of the sensing region is changed due to the interaction of different concentrations of the ligand-analyte, thus impacting surface plasmon polaritons (SPPs) excitation of the multi-layer sensor interface. The performance of the proposed sensor was numerically investigated by using the transfer matrix method (TMM) and the finite-difference time-domain (FDTD) method. The proposed SPR biosensor provides fast and accurate early-stage diagnosis of the COVID-19 virus, which is crucial in limiting the spread of the pandemic. In addition, the performance of the proposed sensor was investigated numerically with different ligand-analytes: (i) the monoclonal antibodies (mAbs) as ligand and the COVID-19 virus spike receptor-binding domain (RBD) as analyte, (ii) the virus spike RBD as ligand and the virus anti-spike protein (IgM, IgG) as analyte and (iii) the specific probe as ligand and the COVID-19 virus single-standard ribonucleic acid (RNA) as analyte. After the investigation, the sensitivity of the proposed sensor was found to provide 183.33°/refractive index unit (RIU) in SPR angle (θSPR) and 833.33THz/RIU in SPR frequency (SPRF) for detection of the COVID-19 virus spike RBD; the sensitivity obtained 153.85°/RIU in SPR angle and 726.50THz/RIU in SPRF for detection of the anti-spike protein, and finally, the sensitivity obtained 140.35°/RIU in SPR angle and 500THz/RIU in SPRF for detection of viral RNA. It was observed that whole virus spike RBD detection sensitivity is higher than that of the other two detection processes. Highly sensitive two-dimensional (2D) materials were used to achieve significant enhancement in the Goos-Hänchen (GH) shift detection sensitivity and plasmonic properties of the conventional SPR sensor. The proposed sensor successfully senses the COVID-19 virus and offers additional (1 + 0.55) × L times sensitivity owing to the added graphene layers. Besides, the performance of the proposed sensor was analyzed based on detection accuracy (DA), the figure of merit (FOM), signal-noise ratio (SNR), and quality factor (QF). Based on its performance analysis, it is expected that the proposed sensor may reduce lengthy procedures, false positive results, and clinical costs, compared to traditional sensors. The performance of the proposed sensor model was checked using the TMM algorithm and validated by the FDTD technique.

Analytical Validation and Clinical Application of Rapid Serological Tests for SARS-CoV-2 Suitable for Large-Scale Screening

Recently, large-scale screening for COVID-19 has presented a major challenge, limiting timely countermeasures. Therefore, the application of suitable rapid serological tests could provide useful information, however, little evidence regarding their robustness is currently available. In this work, we evaluated and compared the analytical performance of a rapid lateral-flow test (LFA) and a fast semiquantitative fluorescent immunoassay (FIA) for anti-nucleocapsid (anti-NC) antibodies, with the reverse transcriptase real-time PCR assay as the reference. In 222 patients, LFA showed poor sensitivity (55.9%) within two weeks from PCR, while later testing was more reliable (sensitivity of 85.7% and specificity of 93.1%). Moreover, in a subset of 100 patients, FIA showed high sensitivity (89.1%) and specificity (94.1%) after two weeks from PCR. The coupled application for the screening of 183 patients showed satisfactory concordance (K = 0.858). In conclusion, rapid serological tests were largely not useful for early diagnosis, but they showed good performance in later stages of infection. These could be useful for back-tracing and/or to identify potentially immune subjects.

Review of Current COVID-19 Diagnostics and Opportunities for Further Development

Diagnostic testing plays a critical role in addressing the coronavirus disease 2019 (COVID-19) pandemic, caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Rapid and accurate diagnostic tests are imperative for identifying and managing infected individuals, contact tracing, epidemiologic characterization, and public health decision making. Laboratory testing may be performed based on symptomatic presentation or for screening of asymptomatic people. Confirmation of SARS-CoV-2 infection is typically by nucleic acid amplification tests (NAAT), which requires specialized equipment and training and may be particularly challenging in resource-limited settings. NAAT may give false-negative results due to timing of sample collection relative to infection, improper sampling of respiratory specimens, inadequate preservation of samples, and technical limitations; false-positives may occur due to technical errors, particularly contamination during the manual real-time polymerase chain reaction (RT-PCR) process. Thus, clinical presentation, contact history and contemporary phyloepidemiology must be considered when interpreting results. Several sample-to-answer platforms, including high-throughput systems and Point of Care (PoC) assays, have been developed to increase testing capacity and decrease technical errors. Alternatives to RT-PCR assay, such as other RNA detection methods and antigen tests may be appropriate for certain situations, such as resource-limited settings. While sequencing is important to monitor on-going evolution of the SARS-CoV-2 genome, antibody assays are useful for epidemiologic purposes. The ever-expanding assortment of tests, with varying clinical utility, performance requirements, and limitations, merits comparative evaluation. We herein provide a comprehensive review of currently available COVID-19 diagnostics, exploring their pros and cons as well as appropriate indications. Strategies to further optimize safety, speed, and ease of SARS-CoV-2 testing without compromising accuracy are suggested. Access to scalable diagnostic tools and continued technologic advances, including machine learning and smartphone integration, will facilitate control of the current pandemic as well as preparedness for the next one.

Anti-A and SARS-CoV-2: an intriguing association

BACKGROUND

Blood groups and anti-A isohemagglutinin may be involved in susceptibility to SARS-CoV-2 infection.

MATERIALS AND METHODS

We retrospectively studied 268 COVID-19 convalescent plasma donors and 162 COVID-19 inpatients (total 430 subjects, confirmed by RT-PCR) and 2,212 healthy volunteer first-time blood donors as a control group. These were further divided into two groups: those with anti-A (blood types O and B) and those without it (types A and AB). Titres of nucleoproteins, and neutralizing SARS-CoV-2 antibody were measured in the convalescent plasma donors and inpatients. Multivariate logistic regression and non-parametric tests were applied.

RESULTS

Persons having types O or B showed less infection prevalence than those of types A or AB (OR = 0·62, 95% CI 0·50-0·78; P < 0·001), but there was no difference when COVID-19 inpatients were analysed. Immunoglobulins M, G and A were lower in COVID-19 subjects of types O or B group than those of A or AB (0·16 vs. 0·19; P = 0·03, 2·11 vs. 2·55; P = 0·02, 0·23 vs. 0·32; P = 0·03, respectively).

CONCLUSION

In this retrospective cohort, COVID-19 individuals were less likely to belong to blood types O and B, and also had lower SARS-CoV-2 antibody titres than A and AB individuals. COVID-19 severity did not associate with the blood groups.

Diagnostics for SARS-CoV-2 infections

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread to nearly every corner of the globe, causing societal instability. The resultant coronavirus disease 2019 (COVID-19) leads to fever, sore throat, cough, chest and muscle pain, dyspnoea, confusion, anosmia, ageusia and headache. These can progress to life-threatening respiratory insufficiency, also affecting the heart, kidney, liver and nervous systems. The diagnosis of SARS-CoV-2 infection is often confused with that of influenza and seasonal upper respiratory tract viral infections. Due to available treatment strategies and required containments, rapid diagnosis is mandated. This Review brings clarity to the rapidly growing body of available and in-development diagnostic tests, including nanomaterial-based tools. It serves as a resource guide for scientists, physicians, students and the public at large.

COVID-2019 fundamentals

BACKGROUND

A novel coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified at the end of 2019. The disease caused by SARS-CoV-2 was named COVID-19. The main purpose of this review was to provide an overview of SARS-CoV-2.

METHODS

The authors searched the MEDLINE database for clinical studies related to virus characteristics, pathogenesis, diagnosis, transmission mechanisms, and treatment options.

RESULTS

As of January 27, 2021, the number of infected people and deaths associated with COVID-19 worldwide were approximately 100 million and 2 million, respectively. The manifestations of COVID-19 are variable, and the severity is affected by age and preexisting medical conditions. Children and adolescents are usually asymptomatic or have mild symptoms. Older adults, in comparison, may experience severe illness and have disproportionally elevated mortality. Among those who survive, some may experience enduring deficits. The viral load is particularly elevated in saliva and oropharynx, which constitute potential sources of infection. The diagnosis of the disease may be confounded by factors related to the replicating cycle of the virus, viral load, and sensitivity of the diagnostic method used. As of January 2021, COVID-19 has no cure but can be prevented. Its treatment is based on supportive care along with antiviral medications and monoclonal antibodies. In severe cases with multiorgan involvement, mechanical ventilation, dialysis, and hemodynamic support may be necessary.

CONCLUSIONS

COVID-19 is a transmittable disease with a variable course. A substantial number of patients, particularly children, remain asymptomatic. Important advances have been made in the development of new treatments. However, the mortality in vulnerable populations remains elevated.

PRACTICAL IMPLICATIONS

The elevated viral load in the oral cavity and pharynx suggests that oral health care professionals could get infected through occupational exposure. Providers should understand the variables that influence the yield of diagnostic studies because false-negative results can occur.

IL-33 expression in response to SARS-CoV-2 correlates with seropositivity in COVID-19 convalescent individuals

Our understanding of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still developing. We perform an observational study to investigate seroprevalence and immune responses in subjects professionally exposed to SARS-CoV-2 and their family members (155 individuals; ages 5-79 years). Seropositivity for SARS-CoV-2 Spike glycoprotein aligns with PCR results that confirm the previous infection. Anti-Spike IgG/IgM titers remain high 60 days post-infection and do not strongly associate with symptoms, except for fever. We analyze PBMCs from a subset of seropositive and seronegative adults. TLR7 agonist-activation reveals an increased population of IL-6⁺TNF^-IL-1β⁺ monocytes, while SARS-CoV-2 peptide stimulation elicits IL-33, IL-6, IFNa2, and IL-23 expression in seropositive individuals. IL-33 correlates with CD4⁺ T cell activation in PBMCs from convalescent subjects and is likely due to T cell-mediated effects on IL-33-producing cells. IL-33 is associated with pulmonary infection and chronic diseases like asthma and COPD, but its role in COVID-19 is unknown. Analysis of published scRNAseq data of bronchoalveolar lavage fluid (BALF) from patients with mild to severe COVID-19 reveals a population of IL-33-producing cells that increases with the disease. Together these findings show that IL-33 production is linked to SARS-CoV-2 infection and warrant further investigation of IL-33 in COVID-19 pathogenesis and immunity.

Assessment of humoral responses in COVID-19 using various quantitative antibody tests

Background

Quantitative antibody tests are expected to be useful in diagnostics of COVID-19 and investigation of herd immunity against SARS-CoV-2. To make it proper to perform them, understanding of the immunological aspects is critically important. The present study aimed to assess humoral responses in COVID-19 using various quantitative antibody tests.

Methods

Four quantitative antibody tests that are different in targeted antigens, detectable immunoglobulin classes and avidity were used. Diagnosis was confirmed by RT-PCR for SARS-CoV-2 detection. Antibody titres of 117 samples collected from 24 COVID-19 patients and 23 non-COVID-19 patients were measured to evaluate correlations between different tests. For 24 COVID-19 patients, antibody titres measured at various time points after the onset or the RT-PCR diagnosis were subjected to assessment of humoral responses.

Results

Correlations between tests were observed to some degree, although there were discrepancies putatively due to differences in measurement principle. Seronegative COVID-19 was diagnosed for some patients, in whom antibody titres were less than the cut-off value in each test throughout the time courses. IgG seroconversion without prior IgM seroconversion most frequently occurred, while predominance of IgM responses over IgG responses was observed in some severe cases. Viral burdens estimated according to threshold cycle values at the RT-PCR seemed to impact antibody responses.

Conclusions

The results provide insights into the nature of humoral responses to SARS-CoV-2 and diagnostic performance of antibody tests.

SARS-CoV-2 Infection among the Dental Staff from Lombardy Region, Italy

Dentists have been supposed to be among the healthcare workers at greatest risk of SARS-CoV-2 infection. However, scant data are available on the issue. The aim of this study is to quantify the SARS-CoV-2 antibody prevalence and determinants in a sample of dentists, dental hygienists, and other personnel employed among the dental staff in Lombardy region. We used an accurate rapid diagnostic test kit detecting immunoglobulins (Ig) in 504 adults. Of the 499 participants who obtained a valid antibody test, 54 (10.8%) had a SARS-CoV-2 positive test (0.4% IgM+, 1.8% both IgM+ and IgG+, and 8.6% IgG+). A statistically significant association with infection was found for geographic area (compared to Milan, adjusted odds ratio was 2.79, 95% confidence interval, CI: 1.01–7.68 for eastern and 2.82, 95% CI: 1.34–5.94, for southern Lombardy). The clinical staff did not result positive to SARS-CoV-2 more frequently than the administrative staff. This is the first study using antibody test in the dental staff personnel. It shows that the prevalence of SARS-CoV-2 infection in Lombardy region was around 10%, in line with estimates on other healthcare professionals. Despite the close physical contact with the patient, dentists have been able to scrupulously manage and effectively use protective devices.

Clinical characteristics and antibody response to SARS-CoV-2 spike 1 protein using VITROS Anti-SARS-CoV-2 antibody tests in COVID-19 patients in Japan

Introduction. Serological tests for COVID-19 are important in providing results for surveillance and supporting diagnosis. Investigating the serological response in COVID-19 patients with different disease severity is important for assessing the clinical utility of serological assays.Gap Statement. However, few studies have investigated the clinical utility of antibody assays for COVID-19 or differences in antibody response in association with disease severity.Aim. The study aimed to evaluate the clinical characteristics and clinical utility of VITROS SARS-CoV-2 antibody tests according to COVID-19 severity in patients in Japan.Methodology. We analysed 255 serum specimens from 130 COVID-19 patients and examined clinical records and laboratory data. Presence of total (IgA, IgM, and IgG) and specific IgG antibody for the spike 1 antigen of SARS-CoV-2 was determined using VITROS Anti-SARS-CoV-2 antibody tests.Results. Overall, 98 (75.4 %) and 32 (24.6 %) patients had mild and severe COVID-19, respectively. On admission, 76 (58.5 %) and 45 (34.6 %) patients were positive for total and IgG antibody assays. Among 91 patients at discharge, 90 (98.9 %) and 81 (89.0 %) were positive for total and IgG antibody, respectively. Clinical background and laboratory findings on admission, but not the prevalence or concentration of total or IgG antibody, were associated with disease prognosis. Total and IgG antibody intensities were significantly higher in severe cases than in mild cases in serum collected >11 days after onset, but not within 10 days.Conclusion. VITROS Anti-SARS-CoV-2 total and IgG assays will be useful as supporting diagnostic and surveillance tools and for evaluation of humoral immune response to COVID-19. Optimal prediction of disease prognosis is made from considering both clinical history and laboratory findings.

Dynamics and Correlation Among Viral Positivity, Seroconversion, and Disease Severity in COVID-19 : A Retrospective Study

BACKGROUND

The understanding of viral positivity and seroconversion during the course of coronavirus disease 2019 (COVID-19) is limited.

OBJECTIVE

To describe patterns of viral polymerase chain reaction (PCR) positivity and evaluate their correlations with seroconversion and disease severity.

DESIGN

Retrospective cohort study.

SETTING

3 designated specialty care centers for COVID-19 in Wuhan, China.

PARTICIPANTS

3192 adult patients with COVID-19.

MEASUREMENTS

Demographic, clinical, and laboratory data.

RESULTS

Among 12 780 reverse transcriptase PCR tests for severe acute respiratory syndrome coronavirus 2 that were done, 24.0% had positive results. In 2142 patients with laboratory-confirmed COVID-19, the viral positivity rate peaked within the first 3 days. The median duration of viral positivity was 24.0 days (95% CI, 18.9 to 29.1 days) in critically ill patients and 18.0 days (CI, 16.8 to 19.1 days) in noncritically ill patients. Being critically ill was an independent risk factor for longer viral positivity (hazard ratio, 0.700 [CI, 0.595 to 0.824]; P < 0.001). In patients with laboratory-confirmed COVID-19, the IgM-positive rate was 19.3% in the first week, peaked in the fifth week (81.5%), and then decreased steadily to around 55% within 9 to 10 weeks. The IgG-positive rate was 44.6% in the first week, reached 93.3% in the fourth week, and then remained high. Similar antibody responses were seen in clinically diagnosed cases. Serum inflammatory markers remained higher in critically ill patients. Among noncritically ill patients, a higher proportion of those with persistent viral positivity had low IgM titers (<100 AU/mL) during the entire course compared with those with short viral positivity.

LIMITATION

Retrospective study and irregular viral and serology testing.

CONCLUSION

The rate of viral PCR positivity peaked within the initial few days. Seroconversion rates peaked within 4 to 5 weeks. Dynamic laboratory index changes corresponded well to clinical signs, the recovery process, and disease severity. Low IgM titers (<100 AU/mL) are an independent risk factor for persistent viral positivity.

PRIMARY FUNDING SOURCE

None.

Infection with SARS-CoV-2 in primary care health care workers assessed by antibody testing

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic threat of public health during the last month causing more than 10 million infections and 500 000 deceased patients worldwide. Nevertheless, data about risk of infection for health care workers are sparse.

METHODS

In a large primary care facility, 151 workers underwent SARS-CoV-2 immunoglobulin G (IgG) testing. In addition, participants had to complete a survey regarding symptoms and their individual risk of infection.

RESULTS

Symptoms suspicious for COVID-19 occurred in 72%, fever in 25% of all subjects. Four workers (2.6%, 95% confidence interval 0.8-7.1%) had a positive SARS-CoV-2 antibody testing. None of these was free from COVID-19 suspicious symptoms. Source of infection was presumably professional in three of four individuals.

CONCLUSION

Our systematic analysis of SARS-CoV-2 infection in a cohort of health care workers in a large outpatient centre revealed an apparently low rate of 2.6% past SARS-CoV-2 infections. Relative risk for infection following health care profession cannot be derived as data about infection rates in the corresponding general population are lacking.

Microfluidic-based virus detection methods for respiratory diseases

With the recent SARS-CoV-2 outbreak, the importance of rapid and direct detection of respiratory disease viruses has been well recognized. The detection of these viruses with novel technologies is vital in timely prevention and treatment strategies for epidemics and pandemics. Respiratory viruses can be detected from saliva, swab samples, nasal fluid, and blood, and collected samples can be analyzed by various techniques. Conventional methods for virus detection are based on techniques relying on cell culture, antigen-antibody interactions, and nucleic acids. However, these methods require trained personnel as well as expensive equipment. Microfluidic technologies, on the other hand, are one of the most accurate and specific methods to directly detect respiratory tract viruses. During viral infections, the production of detectable amounts of relevant antibodies takes a few days to weeks, hampering the aim of prevention. Alternatively, nucleic acid-based methods can directly detect the virus-specific RNA or DNA region, even before the immune response. There are numerous methods to detect respiratory viruses, but direct detection techniques have higher specificity and sensitivity than other techniques. This review aims to summarize the methods and technologies developed for microfluidic-based direct detection of viruses that cause respiratory infection using different detection techniques. Microfluidics enables the use of minimal sample volumes and thereby leading to a time, cost, and labor effective operation. Microfluidic-based detection technologies provide affordable, portable, rapid, and sensitive analysis of intact virus or virus genetic material, which is very important in pandemic and epidemic events to control outbreaks with an effective diagnosis.

Moderate vs. mild cases of overseas-imported COVID-19 in Beijing: a retrospective cohort study

This study compared the differences in the clinical manifestations, treatment courses and clinical turnover between mild and moderate coronavirus disease 2019 (COVID-19). Clinical data of the patients with imported COVID-19 admitted to Beijing Xiaotangshan Designated Hospital between March 15 and April 30, 2020, were retrospectively analysed. A total of 53 COVID-19 patients were included, with 21 mild and 32 moderate cases. Compared with the mild group, the moderate group showed significant differences in breathing frequency, lymphocyte count, neutrophil percentage, neutrophil/lymphocyte ratio, procalcitonin, C-reactive protein, and dynamic erythrocyte sedimentation rate. In the moderate group, 87.5% exhibited ground-glass opacities, 14% exhibited consolidative opacities, 53.1% exhibited local lesions and 68.8% exhibited unilateral lesions. The proportion of patients who received antiviral or antibiotic treatment in the moderate group was higher than that in the mild group, and the number of cases that progressed to severe disease in the moderate group was also significantly higher (18.7% vs. 0%, p = 0.035). Compared with patients with mild COVID-19, those with moderate COVID-19 exhibited more noticeable inflammatory reactions, more severe pulmonary imaging manifestations and earlier expression of protective antibodies. The overall turnover of the moderate cases was poorer than that of the mild cases.

Comparison of Antibody Class-Specific SARS-CoV-2 Serologies for the Diagnosis of Acute COVID-19

Accurate diagnosis of acute severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is critical for appropriate management of patients with this disease. We examined the possible complementary role of laboratory-developed class-specific clinical serology in assessing SARS-CoV-2 infection in hospitalized patients. Serological tests for immunoglobulin G (IgG), IgA, and IgM antibodies against the receptor binding domain (RBD) of SARS-CoV-2 were evaluated using samples from real-time reverse transcription-quantitative PCR (qRT-PCR)-confirmed inpatient coronavirus disease 2019 (COVID-19) cases. We analyzed the influence of timing and clinical severity on the diagnostic value of class-specific COVID-19 serology testing. Cross-sectional analysis revealed higher sensitivity and specificity at lower optical density cutoffs for IgA in hospitalized patients than for IgG and IgM serology (IgG area under the curve [AUC] of 0.91 [95% confidence interval {CI}, 0.89 to 0.93] versus IgA AUC of 0.97 [95% CI, 0.96 to 0.98] versus IgM AUC of 0.95 [95% CI, 0.92 to 0.97]). The enhanced performance of IgA serology was apparent in the first 2 weeks after symptom onset and the first week after PCR testing. In patients requiring intubation, all three tests exhibit enhanced sensitivity. Among PCR-negative patients under investigation for SARS-CoV-2 infection, 2 out of 61 showed clear evidence of seroconversion IgG, IgA, and IgM. Suspected false-positive results in the latter population were most frequently observed in IgG and IgM serology tests. Our findings suggest the potential utility of IgA serology in the acute setting and explore the benefits and limitations of class-specific serology as a complementary diagnostic tool to PCR for COVID-19 in the acute setting.

Clinical Evaluation of an Immunochromatographic-Based IgM/IgG Antibody Assay (GenBody™ COVI040) for Detection of Antibody Seroconversion in Patients with SARS-CoV-2 Infection

There is a need for accurate diagnostic tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the cause of coronavirus disease (COVID-19). This study aimed to evaluate the diagnostic accuracy of an immunochromatography-based immunoglobulin G (IgG)/immunoglobulin M (IgM) antibody assay (GenBody™ COVI040) for detecting SARS-CoV-2 antibody seroconversion in COVID-19 patients. A total of 130 samples, serially collected from patients with confirmed COVID-19, and 100 negative control samples were tested for anti-SARS-CoV-2 IgM and IgG using the GenBody™ COVI040 assay following the South Korean Ministry of Food and Drug Safety guidelines on the review and approval of in vitro diagnostic devices for COVID-19. Reverse-transcription polymerase chain reaction results were used as the comparator. The overall sensitivity of the GenBody™ COVI040 assay was 97.69% (95% confidence interval (CI): 93.40–99.52%). The sensitivity of the assay increased with time post symptom onset (PSO) (sensitivity ≤6 days PSO: 78.57%, 95% CI: 49.20–95.34%; sensitivity 7–13 days PSO: 100%, 95% CI: 87.23–100%; and sensitivity ≥14 days PSO: 100%, 95% CI: 95.94–100%). The specificity of the assay was 100% (95% CI: 96.38–100%). The GenBody™ COVI040 assay showed high sensitivity and specificity, making it a promising diagnostic test to monitor COVID-19.

Determination of the Concentration of IgG against the Spike Receptor-Binding Domain That Predicts the Viral Neutralizing Activity of Convalescent Plasma and Serum against SARS-CoV-2

Several hundred millions of people have been diagnosed of coronavirus disease 2019 (COVID-19), causing millions of deaths and a high socioeconomic burden. SARS-CoV-2, the causative agent of COVID-19, induces both specific T- and B-cell responses, being antibodies against the virus detected a few days after infection. Passive immunization with hyperimmune plasma from convalescent patients has been proposed as a potentially useful treatment for COVID-19. Using an in-house quantitative ELISA test, we found that plasma from 177 convalescent donors contained IgG antibodies specific to the spike receptor-binding domain (RBD) of SARS-CoV-2, although at very different concentrations which correlated with previous disease severity and gender. Anti-RBD IgG plasma concentrations significantly correlated with the plasma viral neutralizing activity (VN) against SARS-CoV-2 in vitro. Similar results were found using an independent cohort of serum from 168 convalescent health workers. These results validate an in-house RBD IgG ELISA test in a large cohort of COVID-19 convalescent patients and indicate that plasma from all convalescent donors does not contain a high enough amount of anti-SARS-CoV-2-RBD neutralizing IgG to prevent SARS-CoV-2 infection in vitro. The use of quantitative anti-RBD IgG detection systems might help to predict the efficacy of the passive immunization using plasma from patients recovered from SARS-CoV-2.

COVID-19 Antibody Tests: A Valuable Public Health Tool with Limited Relevance to Individuals

Antibody tests for detecting past infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have many uses for public health decision making, but demand has largely come from individual consumers. This review focuses on the individual relevance of antibody tests: their accuracy in detecting prior infection, what past SARS-CoV-2 infection can currently infer about future immunity or possible medical sequelae, and the potential future importance of antibody tests for vaccine selection and medical screening. Given uncertainty about the antibody tests (quality, accuracy level, positive predictive value) and what those tests might indicate immunologically (durability of antibodies and necessity for protection from reinfection), seropositive test results should not be used to inform individual decision making, and antibody testing should remain a tool of public health at this time.

Immune response following infection with SARS-CoV-2 and other coronaviruses: A rapid review

In this review, we systematically searched and summarized the evidence on the immune response and reinfection rate following SARS-CoV-2 infection. We also retrieved studies on SARS-CoV and MERS-CoV to assess the long-term duration of antibody responses. A protocol based on Cochrane rapid review methodology was adhered to and databases were searched from 1/1/2000 until 26/5/2020. Of 4744 citations retrieved, 102 studies met our inclusion criteria. Seventy-four studies were retrieved on SARS-CoV-2. While the rate and timing of IgM and IgG seroconversion were inconsistent across studies, most seroconverted for IgG within 2 weeks and 100% (N = 62) within 4 weeks. IgG was still detected at the end of follow-up (49-65 days) in all patients (N = 24). Neutralizing antibodies were detected in 92%-100% of patients (up to 53 days). It is not clear if reinfection with SARS-CoV-2 is possible, with studies more suggestive of intermittent detection of residual RNA. Twenty-five studies were retrieved on SARS-CoV. In general, SARS-CoV-specific IgG was maintained for 1-2 years post-infection and declined thereafter, although one study detected IgG up to 12 years post-infection. Neutralizing antibodies were detected up to 17 years in another study. Three studies on MERS-CoV reported that IgG may be detected up to 2 years. In conclusion, limited early data suggest that most patients seroconvert for SARS-CoV-2-specific IgG within 2 weeks. While the long-term duration of antibody responses is unknown, evidence from SARS-CoV studies suggest SARS-CoV-specific IgG is sustained for 1-2 years and declines thereafter.

Seroprevalence of SARS-CoV-2 IgG antibodies among health care workers prior to vaccine administration in Europe, the USA and East Asia: A systematic review and meta-analysis

BACKGROUND

Knowing the seroprevalence of SARS-CoV-2 IgG antibodies across geographic regions before vaccine administration is one key piece of knowledge to achieve herd immunity. While people of all ages, occupations, and communities are at risk of getting infected with SARS-CoV-2, the health care workers (HCWs) are possibly at the highest risk. Most seroprevalence surveys with HCWs conducted worldwide have been limited to Europe, North America, and East Asia. We aimed to understand how the seroprevalence of SARS-CoV-2 IgG antibodies varied across these geographic regions among HCWs based on the available evidences.

METHODS

By searching through PubMed, ScienceDirect, and Google Scholar databases, eligible studies published from January 1, 2020 to January 15, 2021 were included for the systematic review and meta-analysis. The random-effects model was used to estimate the pooled proportion of IgG seropositive HCWs. Publication bias was assessed by funnel plot and confirmed by Egger's test. Heterogeneity was quantified using I2 statistics. We performed sensitivity analyses based on sample size, diagnostic method and publication status. The study protocol was registered with PROSPERO (CRD42020219086).

FINDINGS

A total of 53 peer-reviewed articles were selected, including 173,353 HCWs (32.7% male) from the United States, ten European, and three East Asian countries. The overall seropositive prevalence rate of IgG antibodies was 8.6% in these regions (95% CI= 7.2-9.9%). Pooled seroprevalence of IgG antibodies was higher in studies conducted in the USA (12.4%, 95% CI= 7.8-17%) than in Europe (7.7%, 95% CI=6.3-9.2%) and East Asia (4.8%, 95% CI=2.9-6.7%). The subgroup study also estimated that male HCWs had 9.4% (95% CI= 7.2-11.6%) IgG seroconversion, and female HCWs had 7.8% (95% CI=5.9-9.7%). The study exhibits a high prevalence of IgG antibodies among HCWs under 40 years in the USA, conversely, it was high in older HCWs (≥40 years of age) in Europe and East Asia. In the months February-April 2020, the estimated pooled seroprevalence was 5.7% (4.0-7.4%) that increased to 8·2% (6.2-10%) in April-May and further to 9.9% (6.9-12.9%) in the May-September time-period.

INTERPRETATION

In the view of all evidence to date, a significant variation in the prevalence of SARS-CoV-2 antibodies in HCWs is observed in regions of Europe, the United States, and East Asia. The patterns of IgG antibodies by time, age, and gender suggest noticeable regional differences in transmission of the virus. Based on the insights driven from the analysis, priority is required for effective vaccination for older HCWs from Europe and East Asia. A considerable high seroprevalence of IgG among HCWs from the USA suggests a high rate of past infection that indicates the need to take adequate measures to prevent hospital spread. Moreover, the seroprevalence trend was not substantially changed after May 2020, suggesting a slow progression of long-term SARS-CoV-2 immunity. Routine testing of HCWs for SARS-CoV-2 should be considered even after the rollout of vaccination to identify the areas of increased transmission.

FUNDING

None.

Serological antibody testing in the COVID-19 pandemic: their molecular basis and applications

The ongoing COVID-19 pandemic has placed an overwhelming burden on the healthcare system, and caused major disruption to the world economy. COVID-19 is caused by SARS-CoV-2, a novel coronavirus that leads to a variety of symptoms in humans, including cough, fever and respiratory failure. SARS-CoV-2 infection can trigger extensive immune responses, including the production of antibodies. The detection of antibody response by serological testing provides a supplementary diagnostic tool to molecular tests. We hereby present a succinct yet comprehensive review on the antibody response to SARS-CoV-2 infection, as well as molecular mechanisms behind the strengths and limitations of serological antibody tests. The presence of antibodies can be detected in patient sera within days post symptom onset. Serological tests demonstrate superior sensitivity to molecular tests in some periods of time during disease development. Compared with the molecular tests, serological tests can be used for point-of-care testing, providing faster results at a lower cost. Commercially available serological tests show variable sensitivity and specificity, and the molecular basis of these variabilities are analysed. We discuss assays of different complexities that are used to specifically quantitate neutralising antibodies against SARS-CoV-2, which has important implications for vaccine development and herd immunity. Furthermore, we discuss examples of successful applications of serological tests to contact tracing and community-level sero-surveying, which provide invaluable information for pandemic management and assessment.

Perspectives About Modulating Host Immune System in Targeting SARS-CoV-2 in India

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the causative agent of coronavirus induced disease-2019 (COVID-19), is a type of common cold virus responsible for a global pandemic which requires immediate measures for its containment. India has the world's largest population aged between 10 and 40 years. At the same time, India has a large number of individuals with diabetes, hypertension and kidney diseases, who are at a high risk of developing COVID-19. A vaccine against the SARS-CoV-2, may offer immediate protection from the causative agent of COVID-19, however, the protective memory may be short-lived. Even if vaccination is broadly successful in the world, India has a large and diverse population with over one-third being below the poverty line. Therefore, the success of a vaccine, even when one becomes available, is uncertain, making it necessary to focus on alternate approaches of tackling the disease. In this review, we discuss the differences in COVID-19 death/infection ratio between urban and rural India; and the probable role of the immune system, co-morbidities and associated nutritional status in dictating the death rate of COVID-19 patients in rural and urban India. Also, we focus on strategies for developing masks, vaccines, diagnostics and the role of drugs targeting host-virus protein-protein interactions in enhancing host immunity. We also discuss India's strengths including the resources of medicinal plants, good food habits and the role of information technology in combating COVID-19. We focus on the Government of India's measures and strategies for creating awareness in the containment of COVID-19 infection across the country.

Development of a SERS-based lateral flow immunoassay for rapid and ultra-sensitive detection of anti-SARS-CoV-2 IgM/IgG in clinical samples

The accurate and rapid screening of serum antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the key to control the spread of 2019 coronavirus disease (COVID-19). In this study, we reported a surface-enhanced Raman scattering-based lateral flow immunoassay (SERS-LFIA) for the simultaneous detection of anti-SARS-CoV-2 IgM/IgG with high sensitivity. Novel SERS tags labeled with dual layers of Raman dye were fabricated by coating a complete Ag shell on SiO₂ core (SiO₂@Ag) and exhibited excellent SERS signals, good monodispersity, and high stability. Anti-human IgM and IgG were immobilized onto the two test lines of the strip to capture the formed SiO₂@Ag-spike (S) protein-anti-SARS-CoV-2 IgM/IgG immunocomplexes. The SERS signal intensities of the IgM and IgG test zones were easily recorded by a portable Raman instrument and used for the high-sensitivity analysis of target IgM and IgG. The limit of detection of SERS-LFIA was 800 times higher than that of standard Au nanoparticle-based LFIA for target IgM and IgG. The SERS-LFIA biosensor was tested on 19 positive serum samples from COVID-19 patients and 49 negative serum samples from healthy people to demonstrate the clinical feasibility of our proposed assay. The results revealed that the proposed method exhibited high accuracy and specificity for patients with SARS-CoV-2 infection.

Role of IgG against N-protein of SARS-CoV2 in COVID19 clinical outcomes

The Nucleocapsid Protein (N Protein) of severe acute respiratory syndrome Coronavirus 2 (SARS-CoV2) is located in the viral core. Immunoglobulin G (IgG) targeting N protein is detectable in the serum of infected patients. The effect of high titers of IgG against N-protein on clinical outcomes of SARS-CoV2 disease has not been described. We studied 400 RT-PCR confirmed SARS-CoV2 patients to determine independent factors associated with poor outcomes, including Medical Intensive Care Unit (MICU) admission, prolonged MICU stay and hospital admissions, and in-hospital mortality. We also measured serum IgG against the N protein and correlated its concentrations with clinical outcomes. We found that several factors, including Charlson comorbidity Index (CCI), high levels of IL6, and presentation with dyspnea were associated with poor clinical outcomes. It was shown that higher CCI and higher IL6 levels were independently associated with in-hospital mortality. Anti-N protein IgG was detected in the serum of 55 (55%) patients at the time of admission. A high concentration of antibodies, defined as signal to cut off ratio (S/Co) > 1.5 (75 percentile of all measurements), was found in 25 (25%) patients. The multivariable logistic regression models showed that between being an African American, higher CCI, lymphocyte counts, and S/Co ratio > 1.5, only S/Co ratio were independently associated with MICU admission and longer length of stay in hospital. This study recommends that titers of IgG targeting N-protein of SARS-CoV2 at admission is a prognostic factor for the clinical course of disease and should be measured in all patients with SARS-CoV2 infection.

Evaluation of Antibody Response in Symptomatic and Asymptomatic COVID-19 Patients and Diagnostic Assessment of New IgM/IgG ELISA Kits

This study aims to study the immune response and evaluate the performances of four new IgM and five IgG enzyme-linked immunosorbent assay (ELISA) kits for detecting anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies against different antigens in symptomatic and asymptomatic coronavirus disease 2019 (COVID-19) patients. A total of 291 samples collected from symptomatic and asymptomatic RT-PCR-confirmed patients were used to evaluate the ELISA kits' performance (EDI, AnshLabs, DiaPro, NovaLisa, and Lionex). The sensitivity was measured at three different time-intervals post symptoms onset or positive SARS-CoV-2 RT-PCR test (≤14, 14-30, >30 days). The specificity was investigated using 119 pre-pandemic serum samples. The sensitivity of all IgM kits gradually decreased with time, ranging from 48.7% (EDI)-66.4% (Lionex) at ≤14 days, 29.1% (NovaLisa)-61.8% (Lionex) at 14-30 days, and 6.0% (AnshLabs)-47.9% (Lionex) at >30 days. The sensitivity of IgG kits increased with time, peaking in the latest interval (>30 days) at 96.6% (Lionex). Specificity of IgM ranged from 88.2% (Lionex)-99.2% (EDI), while IgG ranged from 75.6% (DiaPro)-98.3% (Lionex). Among all RT-PCR-positive patients, 23 samples (7.9%) were seronegative by all IgG kits, of which only seven samples (30.4%) had detectable IgM antibodies. IgM assays have variable and low sensitivity, thus considered a poor marker for COVID-19 diagnosis. IgG assays can miss at least 8% of RT-PCR-positive cases.

Joint Investigation of 2-Month Post-diagnosis IgG Antibody Levels and Psychological Measures for Assessing Longer Term Multi-Faceted Recovery Among COVID-19 Cases in Northern Cyprus

Following the outbreak of COVID-19, multidisciplinary research focusing on the long-term effects of the COVID-19 infection and the complete recovery is still scarce. With regards to long-term consequences, biomarkers of physiological effects as well as the psychological experiences are of significant importance for comprehensively understanding the complete COVID-19 recovery. The present research surveys the IgG antibody titers and the impact of COVID-19 as a traumatic experience in the aftermath of the active infection period, around 2 months after diagnosis, in a subset of COVID-19 patients from the first wave (March-April 2020) of the outbreak in Northern Cyprus. Associations of antibody titers and psychological survey measures with baseline characteristics and disease severity were explored, and correlations among various measures were evaluated. Of the 47 serology tests conducted for presence of IgG antibodies, 39 (83%) were positive. We identified trends demonstrating individuals experiencing severe or critical COVID-19 disease and/or those with comorbidities are more heavily impacted both physiologically and mentally, with higher IgG titers and negative psychological experience compared to those with milder disease and without comorbidities. We also observed that more than half of the COVID-19 cases had negative psychological experiences, being subjected to discrimination and verbal harassment/insult, by family/friends. In summary, as the first study co-evaluating immune response together with mental status in COVID-19, our findings suggest that further multidisciplinary research in larger sample populations as well as community intervention plans are needed to holistically address the physiological and psychological effects of COVID-19 among the cases.

A longitudinal study of SARS-CoV-2-infected patients reveals a high correlation between neutralizing antibodies and COVID-19 severity

Understanding the immune responses elicited by SARS-CoV-2 infection is critical in terms of protection against reinfection and, thus, for public health policy and vaccine development for COVID-19. In this study, using either live SARS-CoV-2 particles or retroviruses pseudotyped with the SARS-CoV-2 S viral surface protein (Spike), we studied the neutralizing antibody (nAb) response in serum samples from a cohort of 140 SARS-CoV-2 qPCR-confirmed infections, including patients with mild symptoms and also more severe forms, including those that required intensive care. We show that nAb titers correlated strongly with disease severity and with anti-spike IgG levels. Indeed, patients from intensive care units exhibited high nAb titers; conversely, patients with milder disease symptoms had heterogeneous nAb titers, and asymptomatic or exclusive outpatient-care patients had no or low nAbs. We found that nAb activity in SARS-CoV-2-infected patients displayed a relatively rapid decline after recovery compared to individuals infected with other coronaviruses. Moreover, we found an absence of cross-neutralization between endemic coronaviruses and SARS-CoV-2, indicating that previous infection by human coronaviruses may not generate protective nAbs against SARS-CoV-2. Finally, we found that the D614G mutation in the spike protein, which has recently been identified as the current major variant in Europe, does not allow neutralization escape. Altogether, our results contribute to our understanding of the immune correlates of SARS-CoV-2-induced disease, and rapid evaluation of the role of the humoral response in the pathogenesis of SARS-CoV-2 is warranted.

The positive rate of IgM and IgG antibodies against SARS-CoV-2 is similar in severe and non-severe COVID-19 patients

Background: Coronavirus disease 2019 (COVID-19) has spread rapidly in China and globally. In order to control the spread of the epidemic, it is important to find an efficient diagnostic method.

Objectives: The aim of this study was to assess the responses of antibodies during SARS-CoV-2 infection in relation to disease severity and to evaluate the association between the positive rate of antibody detection and nucleic acid test.

Methods: Ninety patients with SARS-CoV-2 infection were recruited in this retrospective observational study. Demographic, clinical data, and SARS-CoV-2 IgM and IgG antibodies in serum specimens were detected at 4 and 6 weeks after diagnosis.

Results: IgM and IgG antibody levels showed a decreased tendency, the titers at week 4 were higher than the titers at week 6: The positive rates of IgM at week 4 and 6 were 92.9% and 67.9%, respectively. The positive rates of IgG at week 4 and week 6 were 100%. No association was found between the positive rate of antibody detection at week 4 or 6 and that of nucleic acid test (P>0.05). No difference between the positive rate of antibodies against SARS-CoV-2 in severe and non-severe COVID-19 patients was observed.

Conclusions: Antibody detection is an effective means in the diagnosis of COVID-19. The titer and positive rate of IgM are lower than those of IgG in the first six weeks after infection. Positive rate of antibodies was not different between severe and non-severe patients.

Comprehensive analysis of COVID-19 during pregnancy

The COVID-19 pandemic resulting from the emergence of the coronavirus SARS-CoV-2 remains a major global health concern. Pregnant individuals are more likely to develop severe COVID-19 and a number of pregnancy complications have been observed in COVID-19 patients. To date, little is known about the impact of COVID-19 on pregnancy. In this review, we examine key aspects of pregnancy that may be impacted by COVID-19 and summarize the current literature on SARS-CoV-2 infection of the placenta and in utero vertical transmission. Furthermore, we highlight recent studies exploring the role of the maternal antibody response to SARS-CoV-2 during pregnancy and the passive transfer of maternal antibodies from mothers with COVID-19 to fetus.

Nanotechnology Enabled Solutions to Combat Covid-19: Prevention, Treatment and Diagnosis

Changes in human lifestyles and environmental deterioration globally causes emergence of new viruses posing research challenges. Recent outburst of disease COVID-19 (nCoV19) is a recent example wherein effective management of virus using conventional medication or adopting preventive and effective diagnostic measures is a challenge. While many ongoing strategies from vaccine development to drug repurposing, are currently being investigated, a targeted approach with nanotechnology can be helpful to meet the demand for preventive and diagnostic measures. The significant results of nanotechnology in resolving better efficacy in pharmaceutical drugs is expected to be helpful in combating nCoV19 by using nanotechnology-based solutions preventive, treatment, and diagnosis. As vaccine development involves long clinical trial procedures, preventive measures such as masks, disinfectants, sanitizers, and personal protective equipment's are gaining popularity for effective management. The present write-up addresses the dire need of the nanotechnology-based solutions in present pandemic and studies of the ongoing innovation and existing patents for developing better solutions. Multiple applications of nanotechnology is expected to be helpful in preventive and diagnostic measures, immune response modulation and immunity boosters along with projecting a pathway for industry and academic researchers for addressing such pandemic.

Immunological perspectives on the pathogenesis, diagnosis, prevention and treatment of COVID-19

Coronavirus disease 2019 (COVID-19) is an acute respiratory disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). COVID-19 can spread to the entire body and cause multiple organ failure. It is a daunting challenge to control the fast growing worldwide pandemic because effective prevention and treatment strategies are unavailable currently. Generally, the immune response of the human body triggered by viral infection is essential for the elimination of the virus. However, severe COVID-19 patients may manifest dysregulated immune responses, such as lymphopenia, lymphocyte exhaustion, exacerbated antibody response, cytokine release syndrome (CRS), etc. Understanding of these immunological characteristics may help identify better approaches for diagnosis, prognosis and treatment of COVID-19 patients. As specific anti-viral agents are notoriously difficult to develop, strategies for modulating the immune responses by either developing novel vaccines or using immunotherapy hold great promise to improve the management of SARS-CoV-2 infection.

Evaluation of five immunoassays and one lateral flow immunochromatography for anti-SARS-CoV-2 antibodies detection

INTRODUCTION

In order to deal with the current pandemic caused by the novel SARS-CoV-2 coronavirus several serological immunoassays have been recently developed with the objective of being used as a complementary diagnostic tool and to support the RT-PCR technique currently considered the "gold-standard" method. However, these new assays need to be evaluated and validated. The purpose of this study was to assess the performance of five immunoassays (two ELISA and three CLIA assays) and one rapid immunochromatographic test for the detection of anti-SARS-CoV-2 antibodies.

METHODS

Five semiquantitative immunoassays (MENARINI®, PALEX®, VIRCLIA®, ROCHE® and SIEMENS®) and one lateral flow rapid test (WONDFO®) were performed. A total of 124 samples were studied. Case serum samples (n=78) were obtained from COVID-19 patients confirmed by real-time RT-PCR/epidemiological-clinical-radiological criteria, and control non-SARS-CoV-2 samples (n=46) belonged to healthy healthcare workers involved in a seroprevalence study.

RESULTS

Overall, the tests showed sensitivities around 70-90% and specificities greater than 95%, including the immunochromatographic test. In addition, we observed very good agreements among them, being better for the detection of IgG than for IgM antibodies (Cohen's kappa index of 0.95 for VIRCLIA® IgG with ROCHE®), as well as good diagnostic power of the tests as determined by the ROC curves.

CONCLUSIONS

This study demonstrates the proper performance of the different immunoassays in order to be applied in the clinical practice as support in the diagnostic approach and in the development of vaccines and seroepidemiological studies of COVID-19.

Narrative review of the novel coronavirus SARS-CoV-2: update on genomic characteristics, transmissions and animal model

Two outbreaks of severe respiratory infection caused by severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV) caused global pandemics and highlighted the importance of preparedness for respiratory CoVs. Recently, a third highly pathogenic CoV, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was first identified in Wuhan, Hubei, China and posed a public health crisis worldwide. Here, we focus on the recent advances of the novel CoV, and discuss its genomic similarity with other CoVs, transmission, animal model and clinical treatment of coronavirus disease 2019 (COVID-19) induced by SARS-CoV-2, which help epidemic prevention and control, and guide treatment strategies.

Development of an Automated Chemiluminescence Assay System for Quantitative Measurement of Multiple Anti-SARS-CoV-2 Antibodies

Objectives

Serological tests for COVID-19 have been instrumental in studying the epidemiology of the disease. However, the performance of the currently available tests is plagued by the problem of variability. We have developed a high-throughput serological test capable of simultaneously detecting total immunoglobulins (Ig) and immunoglobulin G (IgG) against nucleocapsid protein (NP) and spike protein (SP) and report its performance in detecting COVID-19 in clinical samples.

Methods

We designed and prepared reagents for measuring NP-IgG, NP-Total Ig, SP-IgG, and SP-Total Ig (using N-terminally truncated NP (ΔN-NP) or receptor-binding domain (RBD) antigen) dedicated automated chemiluminescent enzyme immunoassay analyzer AIA-CL1200. After determining the basal thresholds based on 17 sera obtained from confirmed COVID-19 patients and 600 negative sera, the clinical validity of the assay was evaluated using independent 202 positive samples and 1,000 negative samples from healthy donors.

Results

All of the four test parameters showed 100% specificity individually (1,000/1,000; 95%CI, 99.63–100). The sensitivity of the assay increased proportionally to the elapsed time from symptoms onset, and all the tests achieved 100% sensitivity (153/153; 95%CI, 97.63–100) after 13 days from symptoms onset. NP-Total Ig was the earliest to attain maximal sensitivity among the other antibodies tested.

Conclusion

Our newly developed serological testing exhibited 100% sensitivity and specificity after 13 days from symptoms onset. Hence, it could be used as a reliable method for accurate detection of COVID-19 patients and to evaluate seroprevalence and possibly for surrogate assessment of herd immunity.

Possible correlation of electrochemiluminescence based numerical cut off index value with concentration of anti-SARS-CoV-2 antibody: Is it worth reporting?

Background: Many laboratories are reporting a numerical cutoff index value (COI) value for most anti-SARS-CoV-2 qualitative tests. These numerical values in patients' report ultimately created great confusion in the public and physicians, therefore this study was designed to evaluate the correlation of electrochemiluminescence (ECLIA) based numerical COI values with quantitative ELISA of anti-SARS-CoV-2 antibody. Design and Methods: Two hundred and twenty-eight (228) recovered COVID-19 patients were included; their serum samples were analyzed by quantitative ELISA and ECLIA for anti-SARSCOV- 2 antibodies. Results: One hundred and seventy-three (75.8%) patients tested positive by ECLIA and ELISA assay and thirty-seven (6.2%) were tested negative by both methods. A weak positive correlation (r=0.37) was found between numerical COI value of ECLIA with ELISA concentration, which was statistically significant with p<0.001. All values were dispersed on scatter plot and there was no significant linear relationship between ECLIA and ELISA assay. Conclusions: As both testing techniques are base upon the same immunological phenomena of detecting antibodies against nucleocapsid protein. We suggest that COI values are not meant to describe the immunity level of the individuals thus the physicians should not consider it as a quantitative value for antibody levels in COVID-19 patients.

Serological tests for COVID-19: Potential opportunities

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is a novel betacoronavirus, caused a pandemic leading to a standstill of nearly all global activities. There are some controversies on the production of specific immunoglobulin M (IgM) and IgG antibodies after the infection with SARS‐CoV‐2. This paper seeks to elaborate on the potential application of IgM and IgG antibodies and the viral antigens for the diagnosis and the course of the disease as well as the recurrence of positive nucleic acid tests after discharge.

Characteristics of COVID-19 Patients Based on the Results of Nucleic Acid and Specific Antibodies and the Clinical Relevance of Antibody Levels

Combination of nucleic acid and specific antibody testing is often required in the diagnosis of COVID-19, but whether patients with different nucleic acid and antibody results have different laboratory parameters, severities and clinical outcomes, has not yet been comprehensively investigated. Thus, according to different groups of nucleic acid and antibody results, we aimed to investigate the differences in demographic characteristics, and laboratory parameters among the different groups and predict their clinical outcomes. In our study, nasopharyngeal swab nucleic acids and antibodies were detected by reverse-transcription polymerase chain reaction and chemiluminescence, respectively. Patients with confirmed COVID-19 with different severities, were divided into the PCR+Ab+, PCR+Ab-, and PCR-Ab+ groups. Demographic characteristics, symptoms, comorbidities, laboratory parameters, and clinical outcomes were compared among the three groups. The correlation of antibodies with laboratory parameters and clinical outcomes was also explored, and antibodies were used to predict the timing of nucleic acid conversion. We found that a total of 364 COVID-19 patients were included in the final analysis. Of these, a total of 184, 37, and 143 patients were assigned to the PCR+Ab+, PCR+Ab-, and PCR-Ab+ groups, respectively. Compared to patients in the PCR+Ab- or PCR- Ab+ groups, patients in the PCR+Ab+ group presented worse symptoms, more comorbidities, more laboratory abnormalities, and worse clinical outcomes (P < 0.05). In addition, the levels of IgG, IgM, and IgA were all significantly correlated with the days of hospitalization, days of PCR turning negative, and multiple laboratory parameters (P < 0.05). Meanwhile, combined IgM, IgA, and IgG predicted the days of PCR turning negative within 1 week. The best performance was achieved when the cut-off values of IgM, IgG, and IgA were 3.2, 1.8 and 0.5, respectively, with a sensitivity of 73% and specificity of 82%. In conclusion, COVID-19 patients who were both positive for nucleic acids and antibodies presented with worse clinical features, laboratory abnormalities, and clinical outcomes. The three specific antibodies were positively correlated with clinical outcomes and most laboratory parameters. Furthermore, antibody levels can predict the time of nucleic acid conversion.

Recent Developments on Therapeutic and Diagnostic Approaches for COVID-19

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made a serious public health threat worldwide with millions of people at risk in a growing number of countries. Though there are no clinically approved antiviral drugs and vaccines for COVID-19, attempts are ongoing for clinical trials of several known antiviral drugs, their combination, as well as development of vaccines in patients with confirmed COVID-19. This review focuses on the latest approaches to diagnostics and therapy of COVID-19. We have summarized recent progress on the conventional therapeutics such as antiviral drugs, vaccines, anti-SARS-CoV-2 antibody treatments, and convalescent plasma therapy which are currently under extensive research and clinical trials for the treatment of COVID-19. The developments of nanoparticle-based therapeutic and diagnostic approaches have been also discussed for COVID-19. We have assessed recent literature data on this topic and made a summary of current development and future perspectives.

Advances in emergent biological recognition elements and bioelectronics for diagnosing COVID-19

Coronaviruses pose a serious threat to public health. Tremendous efforts are dedicated to advance reliable and effective detection of coronaviruses. Currently, the coronavirus disease 2019 (COVID-19) diagnosis mainly relies on the detection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genetic materials by using reverse transcription-polymerase chain reaction (RT-PCR) assay. However, simpler and more rapid and reliable alternatives are needed to meet high demand during the pandemic. Biosensor-based diagnosis approaches become alternatives for selectively and rapidly detecting virus particles because of their biorecognition elements consisting of biomaterials that are specific to virus biomarkers. Here, we summarize biorecognition materials, including antibodies and antibody-like molecules, that are designed to recognize SARS-CoV-2 biomarkers and the advances of recently developed biosensors for COVID-19 diagnosis. The design of biorecognition materials or layers is crucial to maximize biosensing performances, such as high selectivity and sensitivity of virus detection. Additionally, the recent representative achievements in developing bioelectronics for sensing coronavirus are included. This review includes scholarly articles, mainly published in 2020 and early 2021. In addition to capturing the fast development in the fields of applied materials and biodiagnosis, the outlook of this rapidly evolving technology is summarized. Early diagnosis of COVID-19 could help prevent the spread of this contagious disease and provide significant information to medical teams to treat patients.

Persistence of SARS-CoV-2-specific antibodies in COVID-19 patients

To better understand humoral immunity following SARS-CoV-2 infection, 114 hospitalised COVID-19 patients with antibody monitored over 8 weeks from symptom onset were retrospectively investigated. A total of 445 serum samples were assessed via chemiluminescence immunoassay. Positive rate of virus-specific IgM reached up to over 80% from the second week to the eighth week after symptom onset, then declined quickly to below 30% in the twelfth week. Concentrations of IgG remained high for at least 3 months before subsequently declining. As compared with the non-severe group, serum IgM level from week 3 to week 8 was significantly higher among the patients with severe clinical symptoms (P = 0.012) but not IgG (P = 0.053). Serum IgM level from week 3 to week 8 was correlated with positive virus RNA test (r = 0.201, P = 0.044), albumin level (r = -0.295, P = 0.003), lactic dehydrogenase (LDH) level (r = 0.292, P = 0.003), alkaline phosphatase (ALP) level (r = 0.254, P = 0.010), C-reactive protein (CRP) level (r = 0.281, P = 0.004) during the same course, while serum IgG level was correlated with age (r = 0.207, P = 0.038). This presented results provide insight into duration of SARS-CoV-2 antibodies and interaction between the virus and host systems.

An accurate, high-speed, portable bifunctional electrical detector for COVID-19

Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has rapidly spread and caused a severe global pandemic. Because no specific drugs are available for COVID-19 and few vaccines are available for SARS-CoV-2, accurate and rapid diagnosis of COVID-19 has been the most crucial measure to control this pandemic. Here, we developed a portable bifunctional electrical detector based on graphene fieldeffect transistors for SARS-CoV-2 through either nucleic acid hybridization or antigen-antibody protein interaction, with ultra-low limits of detection of ~0.1 and ~1 fg mL^-1 in phosphate buffer saline, respectively. We validated our method by assessment of RNA extracts from the oropharyngeal swabs of ten COVID-19 patients and eight healthy subjects, and the IgM/IgG antibodies from serum specimens of six COVID-19 patients and three healthy subjects. Here we show that the diagnostic results are in excellent agreement with the findings of polymerase chain reaction-based optical methods; they also exhibit rapid detection speed (~10 min for nucleic acid detection and ~5 min for immunoassay). Therefore, our assay provides an efficient, accurate tool for high-throughput point-of-care testing.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material is available in the online version of this article at 10.1007/s40843-020-1577-y.