Antibody kinetics and serologic profiles of SARS-CoV-2 infection using two serologic assays

Immunoglobulins in COVID-19 pneumonia: from the acute phase to the recovery phase

BACKGROUND

COVID-19 pneumonia causes hyperinflammatory response that culminates in acute respiratory syndrome (ARDS) related to increased multiorgan dysfunction and mortality risk. Antiviral-neutralizing immunoglobulins production reflect the host humoral status and illness severity, and thus, immunoglobulin (Ig) circulating levels could be evidence of COVID-19 prognosis.

METHODS

The relationship among circulating immunoglobulins (IgA, IgG, IgM) and COVID-19 pneumonia was evaluated using clinical information and blood samples in a COVID-19 cohort composed by 320 individuals recruited during the acute phase and followed up to 4 to 8 weeks (n = 252) from the Spanish first to fourth waves.

RESULTS

COVID-19 pneumonia development depended on baseline Ig concentrations. Circulating IgA levels together with clinical features at acute phase was highly associated with COVID-19 pneumonia development. IgM was positively correlated with obesity (ρb = 0.156, P = 0.020), dyslipemia (ρb = 0.140, P = 0.029), COPD (ρb = 0.133, P = 0.037), cancer (ρb = 0.173, P = 0.007) and hypertension (ρb = 0.148, P = 0.020). Ig concentrations at recovery phase were related to COVID-19 treatments.

CONCLUSIONS

Our results provide valuable information on the dynamics of immunoglobulins upon SARS-CoV-2 infection or other similar viruses.

COVID-19 Vaccination and Serological Profile of a Brazilian University Population

BACKGROUND

COVID-19 led to the suspension academic activities worldwide, affecting millions of students and staff.

METHODS

In this study, we evaluated the presence of IgM and IgG anti-SARS-CoV-2 antibodies in an academic population during the return to classes after a one-year suspension. The study took place over five months at a Brazilian university and included 942 participants.

RESULTS

We found that most participants had reactive IgG and non-reactive IgM. All received at least one dose, and 940 received two or more doses, of different COVID-19 vaccines. We obtained a higher average of memory antibodies (IgG) in participants who received the CoronaVac/ChAdOx1 combination. IgG was consistently distributed for each vaccine group, but individuals who completed the vaccination schedule had higher levels. There were no differences between antibodies and gender, presence of symptoms, and previous COVID-19 infection, but older participants (>53 years) and contacts of infected individuals had higher IgM levels.

CONCLUSION

This study makes significant contributions to the assessment of antibodies in the academic environment, allowing us to infer that most participants had memory immunity and low indications of recent infection when returning to face-to-face classes, as well as demonstrating the need to monitor immunity and update vaccinations.

Clinical performance of SARS-CoV-2 antigen-detection rapid diagnostic test using SERS-based lateral flow immunoassay

Background

'ACROSIS COVID-19 Ag (NPS)' kit (SG Medical, Seoul, Korea) is a newly developed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen-detection rapid diagnostic test (Ag-RDT) using surface-enhanced Raman scattering (SERS)-based lateral flow immunoassay (LFIA). We evaluated its clinical performance compared with STANDARD Q COVID-19 Ag (SD Biosensor, Suwon, Korea), a previously approved Ag-RDT.

Methods

A total of 286 nasopharyngeal swab specimens were collected: 104 positive and 182 negative specimens in SARS-CoV-2 real-time reverse-transcription polymerase-chain-reaction (rRT-PCR). SARS-CoV-2-positive specimens were divided according to the cycle threshold (Ct) value in rRT-PCR. The clinical performance of ACROSIS was compared with that of STANDARD Q.

Results

ACROSIS showed significantly higher sensitivity than STANDARD Q (92.3% vs. 85.6%, P = 0.02), especially in specimens with 25 ≤ Ct < 30 (78.6% vs. 42.9%). The Ct values of RdRp/S genes for 95% detection rates by ACROSIS and STANDARD Q were 25.8 and 23.0, respectively.

Conclusions

This is the first study that evaluated the performance of ACROSIS compared with STANDARD Q. The overall clinical performance of ACROSIS was superior to that of STANDARD Q, especially in specimens with 25 ≤ Ct < 30. ACROSIS could be useful for SARS-CoV-2 Ag detection even in relatively low viral load specimens.

Performance and correlation of ten commercial immunoassays for the detection of SARS-CoV-2 antibodies

Accurate immunoassays with a good correlation to neutralizing antibodies are required to support SARS-CoV-2 diagnosis, management, vaccine deployment, and epidemiological investigation. We conducted a study to evaluate the performance and correlation of the surrogate virus neutralization test (sVNT) and other commercial immunoassays. We tested 107 sera of COVID-19 confirmed cases from three different time points, 58 confirmed non-COVID-19 sera, and 52 sera collected before the pandemic with two sVNTs, seven chemiluminescent assays, and one fluorescein assay. All assays achieved excellent sensitivity (95%-100%, ≥15 days after onset of illness), specificity (95.5%-100%), and showed moderate to high correlation with GenScript sVNT (r = 0.58 to r = 0.98), except Roche total antibodies (r = 0.48). Vazyme sVNT and Siemens total antibodies showed the highest correlation with GenScript sVNT (r = 0.98 and 0.88, respectively). Median indexes that may be used to estimate sera with the highest ability to inhibit SARS-CoV-2 and ACE-2 receptor attachment (GenScript sVNT inhibition 90%-100%) were 6.9 S/C (Abbott IgG), 161.9 COI (FREND™ IgG), 16.8 AU/ml (Snibe IgG), 40.1 S/CO (Beckman IgG), 281.9 U/ml (Mindray IgG), 712.2 U/ml (Mindray total antibodies), >10 index (Siemens total antibodies), and 95.3% inhibition (Vazyme sVNT). All ten commercial COVID-19 serology assays, with different targeting antigens, demonstrated a reliable performance, supporting the utility of those assays in clinical and research settings. However, further studies using more samples are needed to refine the results of evaluating the performances of these marketed serological assays. Reliable serological assays would be useful for clinicians, researchers and epidemiologists in confirming SARS-CoV-2 infections, observing SARS-CoV-2 transmission, and immune response post infection and vaccination, leading to better management and control of the disease.

Role of Antibodies against SARS-COV-2 in the Detection of Corona Virus, its Transmissibility and Immunological Status Determination among Different Population in Babylon Province

BACKGROUND: The fast worldwide spreading and the elevation of coronavirus disease-2019 (COVID-19) pandemic wave lead to decrease capacity of health-care units. It is important to add serology testing to assess viral transmissibility and the possibility of protection against reinfection. AIM: We aimed to assess the transmissibility of severe acute respiratory syndrome coronavirus-2 in the community and to assess the immunological response, qualitative assay of immunoglobulins (Ig) G and IgM, and the possibility of reinfection. MATERIALS AND METHODS: The present study included a total of 553 patients. We used a rapid test cassette of Biozek Medical Company/Netherland of COVID-19 IgG/IgM. It is a chromatographic immunoassay for the qualitative detection of IgG and IgM antibodies against the COVID-19 virus in human blood. Biozek Medical Company has created this highly accurate, UK approved, COVID-19 test, which provides high accuracy within 15 min. All required information were collected with the patients’ consent. The statistical analysis was performed using the IBM SPSS Statistics, 2016, Armonk, NY: IBM Corp. RESULTS: A total of 320 (57.9%) males and 233 (42.1%) females aged between 2 to 88 years. A significant correlation was found between the age of patients and chronic diseases. While most of the patients did not have any chronic diseases, the patients who had those diseases were mostly aged between their forties to more than 60 of age. A highly significant correlation was found between IgM level in the serum of the patient and the presence of symptoms. A significant correlation was found with chronic diseases and the level of IgG in the serum of patients. Furthermore, a significant correlation was found in patients with previous COVID-19 infections. CONCLUSIONS: Serological testing of IgM and IgG for COVID-19 is very helpful in diagnosing asymptomatic and symptomatic patients, evaluating the immunological status of individuals toward COVID-19 and giving an idea about the spreading of COVID-19 among different populations.

Field evaluation of seven SARS-COV-2 antigen assays

There is a global demand for rapid diagnostic tests (RDTs) for Coronavirus disease 2019 (COVID-19), and the interest in their clinical compliance is growing. In this study, we evaluated the clinical compliance of seven different severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antigen RDTs. Nasopharyngeal/oropharyngeal swab specimens from COVID-19-confirmed cases and reverse-transcription PCR (RT-PCR) screening were used to evaluate the performance of seven RDTs. Using the RT-PCR and RDT results, we predicted the cycle threshold (Ct) of each target gene (E, RdRP, and N genes) which 50% (Ct₅₀) and 95% (Ct₉₅) detection rates were achieved in the RDTs. A total of 482 specimens were enrolled in our study: 316 specimens from COVID-19-confirmed cases and 166 RT-PCR-negative specimens. The median values of Ct₅₀ and Ct₉₅ for the seven RDTs were in the ranges of ranged 24.3-30.9 and 19.3-22.6 for E, 25.5-31.5 and 20.9-24.0 for RdRP, and 26.8-32.3 and 22.7-25.7 for N, respectively. The RDTs showed acceptable compliance only for specimens with high viral burdens (Ct < 20). However, the false-negative rate increased by more than 50% for most of the RDTs in low-viral burden specimens (Ct> 30). These results suggest that RDTs should not be used without molecular assays for COVID-19 screening for asymptomatic patients because of their high false-negative rates.

SARS-CoV-2/COVID-19 laboratory biosafety practices and current molecular diagnostic tools

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)/coronavirus disease 2019 (COVID-19) pandemic has crippled several countries across the globe posing a serious global public health challenge. Despite the massive rollout of vaccines, molecular diagnosis remains the most important method for timely isolation, diagnosis, and control of COVID-19. Several molecular diagnostic tools have been developed since the beginning of the pandemic with some even gaining emergency use authorization from the United States (US) Food and Drug Administration for in vitro diagnosis of SARS-CoV-2. Herein, we discuss the working principles of some commonly used molecular diagnostic tools for SARS-CoV-2 including nucleic acid amplification tests, isothermal amplification tests, and rapid diagnostic tests. To ensure successful detection while minimizing the risk of cross-infection and misdiagnosis when using these diagnostic tools, laboratories should adhere to proper biosafety practices. Hence, we also present the common biosafety practices that may ensure the successful detection of SARS-CoV-2 from specimens while protecting laboratory workers and non-suspecting individuals from being infected. From this review article, it is clear that the SARS-CoV-2 pandemic has led to an increase in molecular diagnostic tools and the formation of new biosafety protocols that may be important for future and ongoing outbreaks.

Assessment of avidity related to IgG subclasses in SARS-CoV-2 Brazilian infected patients

SARS-CoV-2 is considered a global emergency, resulting in an exacerbated crisis in the health public in the world. Although there are advances in vaccine development, it is still limited for many countries. On the other hand, an immunological response that mediates protective immunity or indicates that predict disease outcome in SARS-CoV-2 infection remains undefined. This work aimed to assess the antibody levels, avidity, and subclasses of IgG to RBD protein, in symptomatic patients with severe and mild forms of COVID-19 in Brazil using an adapted in-house RBD-IgG ELISA. The RBD IgG-ELISA showed 100% of specificity and 94.3% of sensibility on detecting antibodies in the sera of hospitalized patients. Patients who presented severe COVID-19 had higher anti-RBD IgG levels compared to patients with mild disease. Additionally, most patients analyzed displayed low antibody avidity, with 64.4% of the samples of patients who recovered from the disease and 84.6% of those who died in this avidity range. Our data also reveals an increase of IgG1 and IgG3 levels since the 8th day after symptoms onset, while IgG4 levels maintained less detectable during the study period. Surprisingly, patients who died during 8–14 and 15–21 days also showed higher anti-RBD IgG4 levels in comparison with the recovered (P < 0.05), suggesting that some life-threatening patients can elicit IgG4 to RBD antibody response in the first weeks of symptoms onset. Our findings constitute the effort to clarify IgG antibodies' kinetics, avidity, and subclasses against SARS-CoV-2 RBD in symptomatic patients with COVID-19 in Brazil, highlighting the importance of IgG antibody avidity in association with IgG4 detection as tool laboratory in the follow-up of hospitalized patients with more significant potential for life-threatening.

Determinants of IgG antibodies kinetics after severe and critical COVID-19

The kinetics of IgG antibodies after coronavirus disease 2019 (COVID-19) remain poorly understood. We investigated factors influencing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibody levels and time to seronegativation during the follow-up of severe and critically ill patients. We retrospectively reviewed serological evaluations drawn during the follow-up of severe or critical laboratory-proven COVID-19 patients hospitalized at a large academic hospital. Specific IgG titers were measured using a chemiluminescent assay targeting anti-spike and anti-nucleocapsid protein IgG. The influence of time, demographic factors, clinical and paraclinical characteristics, and COVID-19 therapeutics on IgG levels were assessed through linear regression using a mixed-effect model, and delay until IgG negativation through a Weibull regression model. The cohort included 116 patients with a total of 154 IgG measurements drawn at a median of 79 days after diagnosis. IgG antibodies were increased with age (p = 0.005) and decreased significantly over time (p = 0.0002). Using elapsed time and age as covariates, we demonstrated higher IgG levels in patients with a higher body mass index (BMI) (p = 0.0026) and lower IgG levels in immunocompromised patients (p = 0.032). A high BMI was further found to delay and immunodeficiency to hasten significantly seronegativation, whereas no significant effect was observed with corticosteroids. These data highlight the waning over time of IgG antibodies after severe or critical COVID-19. Age, BMI, and immunosuppression also appear to influence the IgG kinetics, while short-term corticotherapy does not. Those data improve the understanding of SARS-CoV-2 serology while further research should determine the determinants of long-term seroprotection.

Clinical and epidemiologic characteristics of inconclusive results in SARS-CoV-2 RT-PCR assays

Background

Inconclusive results in SARS-CoV-2 molecular assays cause confusion among clinicians and delay appropriate infection prevention and control. In this study, we aimed to characterize the respiratory specimens associated with inconclusive SARS-CoV-2 molecular assay results.

Methods

We re-evaluated inconclusive specimens by 3 additional RT-PCR assays and attempted to detect subgenomic RNA (sgRNA) in these specimens.

Results

Among follow-up tests from confirmed SARS-CoV-2 cases, 36.3% of the inconclusive results were classified as presumptive positive results (45/124). However, none of the specimens from 36 screening cases was classified as a presumptive positive result. Among 160 inconclusive specimens, sgRNAs were detected in 78 samples (48.8%): 58 were confirmed cases (58/124, 46.8%) and 20 were screening cases (20/36, 55.6%).

Conclusions

The results of our study suggest the recommendation of considering inconclusive results as positive results for confirmed SARS-CoV-2 cases. In screening cases, viral remnants could be partially amplified in PCR assays, and these inconclusive results could be related to previous infections. In addition, sgRNAs were detected in about half of the inconclusive specimens; however, the clinical significance of sgRNA is not yet clear.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06534-5.

Dynamic Assay for Profiling Anti-SARS-CoV-2 Antibodies and Their ACE2/Spike RBD Neutralization Capacity

Serological assays have been widely employed during the coronavirus disease 2019 (COVID-19) pandemic to measure antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and to track seroconversion in populations. However, currently available assays do not allow determination of neutralization capacity within the assay protocol. Furthermore, commercial serology assays have a high buy-in cost that is inaccessible for many research groups. We have replicated the serological enzyme-linked immunosorbent assay for the detection of SARS-CoV-2 antibody isotypes, developed at the Icahn School of Medicine at Mount Sinai, New York. Additionally, we have modified the protocol to include a neutralization assay with only a minor modification to this protocol. We used this assay to screen local COVID-19 patient sera (n = 91) and pre-COVID-19 control sera (n = 103), and obtained approximate parity with approved commercial anti-nucleoprotein-based assays with these sera. Furthermore, data from our neutralization assay closely aligns with that generated using a spike-based pseudovirus infection model when a subset of patient sera was analyzed.

Multicenter evaluation of four immunoassays for the performance of early diagnosis of COVID-19 and assessment of antibody responses of patients with pneumonia in Taiwan

Background/purpose

Our study goals were to evaluate the diagnostic performance of four anti-SARS-CoV-2 antibodies tests and the differences in dynamic immune responses between COVID-19 patients with and without pneumonia.

Methods

We collected 184 serum samples from 70 consecutively qRT-PCR-confirmed COVID-19 patients at four participating hospitals from 23 January 2020 to 30 September 2020. COVID-19 pneumonia was defined as the presence of new pulmonary infiltration. Serum samples were grouped by the duration after symptom onset on a weekly basis for antibody testing and analysis. The four immunoassays: Beckman SARS-CoV-2 IgG/IgM (Beckman Test), Siemens (ADVIA Centaur®) SARS-CoV-2 Total (COV2T) (Siemens Test), SBC COVID-19 IgG ELISA (SBC Test) and EliA SARS-CoV-2-Sp1 IgG/IgM/IgA P2 Research (EliA Test) were used for detecting the SARS-CoV-2 specific antibodies.

Results

The sensitivity of all tests reached 100% after 42 days of symptom onset. Siemens Test, the only test detecting total anti-SARS-CoV-2 antibodies, had the best performance in the early diagnosis of COVID-19 infection (day 0–7: 77%; day 8–14: 95%) compared to the other 3 serological tests. All tests showed 100% specificity except SBC Test (98%). COVID-19 patients with pneumonia had significantly higher testing signal values than patients without pneumonia (all p values < 0.05, except EliA IgM Test). However, Siemens Test and SBC Test had highest probability in early prediction of the presence of COVID-19 pneumonia.

Conclusion

Chronological analysis of immune response among COVID-19 patients with different serological tests provides important information in the early diagnosis of SARS-CoV-2 infection and prediction of the risk of pneumonia after infection.

Serological Profile of Children and Young Adults with at Least One SARS-CoV-2 Positive Cohabitant: An Observational Study

At the end of 2019, a new disease caused by the novel coronavirus SARS-CoV-2 appeared in Wuhan Province in China. Children seemed to be infected less frequently than adults, and family clusters seemed to play an important role in the spread of the pandemic. The aim of this study is to evaluate the serological profile of children and young adults between 4 and 16 years of age in order to assess the transmission patterns of COVID-19 between cohabitants. The subjects lived with at least one cohabitant who tested positive for the disease using a nasopharyngeal swab. To avoid contact with the disease, families were interviewed by telephone. Forty-nine children and adolescents with a mean age of 11 years were then subjected to a rapid lateral flow chromatographic test. Of them, seven (14.3%) were immunoglobulin G (IgG)-positive, and four (8.2%) were immunoglobulin M (IgM)-positive. In total, 16.3% of the tested sample had antibodies against SARS-CoV-2: this may confirm the lower vulnerability of children to COVID-19, despite the small sample size. The time from the negativization of the cohabitant until the test day may have influenced the results, especially when this timeframe is wide.

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.