Visible Light Photocatalytic Activity of Ag/WO3 Nanoparticles and its Antibacterial Activity Under Ambient Light and in The Dark

Nanomaterial such as metals and metal oxide photocatalysts have emerged as important tools for removing contaminants from wastewater and as antibacterial agents to prevent infections; this is mainly due to their stability under different irradiation conditions. Herein, the catalytic and antimicrobial activities of nanocrystalline silver (Ag), supported on tungsten oxide (WO3) nanoparticles prepared using the deposition-precipitation synthesis technique, are studied. The synthesized material was characterized as XRD, XPS, TEM, and TEM-EDS to investigate their physio-chemical properties. HRTEM, XPS analysis shows that the photocatalyst has a large sheet-like morphology with well-dispersed small metallic Ag particles (<3 nm) on the WO3 nanoparticle's surface, with most particles near the edges. Ultraviolet–visible spectra analysis observed a large redshift in the absorbing band edge and decreased bandgap energy from 2.6 to 2.1 eV. Photocatalytic analysis at different concentrations of 1% Ag/WO3 under visible light indicated a high degradation efficiency. The largest degradation efficiency of Methylene Blue (MB) under visible light irradiation was (∼80%) in 120 min at 1 g/L catalyst dosage. The photodegradation of MB under visible light as a function of catalyst dose followed the pseudo-first-order kinetics. In addition, the catalyst shows high degradation efficiency and significant dose-dependent inhibition of Gram-negative E. Coli and the Gram-positive S. aureus. Furthermore, the catalyst showed excellent stability and recyclability

Performance evaluation of novel fluorescent-based lateral immune flow assay (LIFA) for rapid detection and quantification of total anti-SARS-CoV-2 S-RBD binding antibodies in infected individuals.

The vast majority of the commercially available LFIA is used to detect SARS-CoV-2 antibodies qualitatively. Recently, a novel fluorescence-based LIFA test was developed for quantitative measurement of the total binding antibody units (BAU/mL) against the receptor-binding domain of the SARS-CoV-2 spike protein (S-RBD). To evaluate the performance of the fluorescence LIFA Finecare 2019-nCoV S-RBD test along with its reader (Model No.: FS-113). Plasma from 150 RT-PCR confirmed-positive individuals and 100 pre-pandemic samples were tested by FinCare to access sensitivity and specificity. For qualitative and quantitative validation of the FinCar measurements, the BAU/mL results of FinCare were compared with results of two reference assays: the surrogate virus-neutralizing test (sVNT, GenScript, USA), and the VIDAS®3 automated assay (BioMérieux, France). Finecare showed 92% sensitivity and 100% specificity compared to PCR. Cohen's Kappa statistic denoted moderate and excellent agreement with sVNT and VIDAS®3, ranging from 0.557 (95% CI: 0.32-0.78) to 0.731 (95% CI: 0.51-0.95), respectively. A strong correlation was observed between Finecare/sVNT (r=0.7, p<0.0001) and Finecare/VIDAS®3 (r=0.8, p<0.0001). Finecare is a reliable assay and can be used as a surrogate to assess binding and neutralizing antibody response post-infection or vaccination, particularly in none or small laboratory settings

Validation of Selected Commercial Serological Assays for Diagnosis of COVID-19

As researchers around the globe rush to put the available antibody tests to use, concerns have been raised about their precision. This study aimed to evaluate and compare the performance of selected commercial & automated serological assays, that are widely used in different clinical settings in Qatar. We validated the performance of five commercial IgG and IgM ELISA kits, three fully automated immunoassays, and two commercial rapid tests. The sensitivity of all assays was compared to RT-PCR and a surrogate virus neutralization test (sVNT). In addition, cross-reactivity was investigated. Among the evaluated kits, Lionex IgG assaydemonstrated the best performance (~88% sensitivity and ~99 specificity). All automated assays showed an excellent correlation with the neutralization test with an overall agreement of 93.6-98.5%. The rapid assays demonstrated a very good performance in detecting IgG antibodies (86.0-88.0% sensitivity and 98.0-100% specificity)

Low risk of serological cross-reactivity between the dengue virus and SARS-CoV-2 IgG antibodies using advanced detection assays.

Several studies have reported serological cross-reactivity of the immune responses between SARS-CoV-2 and DENV. Most of the available studies are based on the point of care (POC) rapid testing kits. However, some rapid test kits have low specificity and can generate false positives. Hence, we aimed to investigate the potential serological cross-reactivity between SARS-CoV-2 and DENV IgG antibodies using advanced assays including chemiluminescence immunoassay (CLIA) and ELISA test. A total of 90 DENV-IgG-ELISA positive and 90 negative pre-pandemic sera were tested for anti-SARS-CoV-2-IgG using the automated CL-900i CLIA assay. Furthermore, a total of 91 SARS-CoV-2-IgG-CLIA positive and 91 negative post-pandemic sera were tested for anti-DENV-IgG using the Novalisa ELISA assay. The DENV-IgG positive sera resulted in five positives and 85 negatives for SARS-CoV-2-IgG. Similarly, the DENV-IgG negative sera also resulted in five positives and 85 negatives for SARS-CoV-2-IgG. No statistically significant difference in specificity between the DENV-IgG positive and DENV-IgG negative sera was found (p-value=1.00). The SARS-CoV-2-IgG positive sera displayed 43 positives, 47 negatives, and one equivocal for DENV-IgG. Whereas the SARS-CoV-2-IgG negative sera resulted in 50 positives, 40 negatives, and one equivocal for DENV-IgG. No statistically significant difference in the proportion that is DENV-IgG positive between the SARS-CoV-2-IgG positive and SARS-CoV-2-IgG negative sera (p-value=0.58). In conclusion, there is a low risk of serological cross-reactivity between the DENV, and SARS-CoV-2 IgG antibodies when using advanced detection assays.  .L.J.A. acknowledges the support of the Biomedical Research Program and the Biostatistics, Epidemiology, and Biomathematics Research Core, both at Weill Cornell Medicine-Qatar. This work was made possible by Grant Nos. RRC-2-032 and UREP19-013-3-001 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. In addition, G.K.N. would also like to acknowledge funds from Qatar University’s internal Grant QUERG-CMED-2020-2

Comparison of antibody immune responses between BNT162b2 and mRNA-1273 SARS-CoV-2 vaccines in naïve and previously infected individuals.

Two mRNA vaccines, Pfizer-BNT162b2 and Moderna-mRNA-1273, obtained the Emergency Use Listing by WHO for preventing COVID-19. However, little is known about the difference in antibody responses induced by these two mRNA vaccines in naïve and previously infected (PI) individuals. We investigated the levels of anti-S-RBD (total, IgG and IgA) levels in naïve and PI individuals, 1-13 (median = 6) weeks following the second dose of either vaccine. Results in the naïve-vaccinated group, the mRNA-1273 vaccine induced significantly higher levels of anti-S-RBD total antibodies (3.5-fold; P < 0.001), IgG (2-fold, P < 0.01) and IgA (2.1-fold, P < 0.001) as compared with the BNT162b2 vaccine. In addition, both vaccines produced significantly higher anti-S-RBD total antibody levels in the PI-group compared with naïve-vaccinated group. The PI group elicited a higher level of anti-S-RBD IgG than the naïve-BNT162b2 (P = 0.05), but not more than the naïve-mRNA-1273 (P = 0.9) group. Interestingly, the PI vaccinated group elicited a comparable level of IgA ratio to the naïve-mRNA-1273 group but significantly higher than the naïve-BNT162b2 group (1.6-fold, P < 0.001). Our results showed that the PI-vaccinated group produces a higher level of antibodies than the naïve vaccinated group, particularly for those vaccinated with BNT162b2

Neutralizing antibodies against SARS-CoV-2 are higher but decline faster in mRNA vaccinees compared to individuals with natural infection.

Waning protection against emerging SARS-CoV-2 variants by pre-existing antibodies elicited due to current vaccination or natural infection is a global concern. Whether this is due to the waning of immunity to SARS-COV-2 remains unclear. We aimed to investigate the dynamics of antibody isotype responses among vaccinated naïve (VN) and naturally infected (NI) individuals. We followed up antibody levels in COVID-19 mRNA-vaccinated subjects without prior infection (VN, n = 100) in two phases: phase-I (P-I) at ~ 1.4 and phase-II (P-II) at ~ 5.3 months. Antibody levels were compared to those of unvaccinated and naturally infected subjects (NI, n = 40) at ~ 1.7 (P-1) and 5.2 (P-II) months post-infection. Neutralizing antibodies (NTAb), anti-S-RBD-IgG, -IgM, and anti-S-IgA isotypes were measured. The VN group elicited significantly greater antibody responses (p < 0.001) than the NI group at P-I, except for IgM. In the VN group, a significant waning in antibody response was observed in all isotypes. There was about ~ a 4-fold decline in NTAb levels (p < 0.001), anti-S-RBD-IgG (~5-folds, p < 0.001), anti-S-RBD-IgM (~6-folds, p < 0.001), and anti-S1-IgA (2-folds, p < 0.001). In the NI group, a significant but less steady decline was notable in S-RBD-IgM (~2-folds, p < 0.001), and a much smaller but significant difference in NTAb (<2-folds, p < 0.001) anti-S-RBD IgG (<2-folds, p = 0.005). Unlike the VN group, the NI group mounted a lasting anti-S1-IgA response with no significant decline. Anti-S1-IgA, which were ~ 3 folds higher in VN subjects compared to NI in P-1 (p < 0.001), dropped to almost the same levels, with no significant difference observed between the two groups in P-II. While double-dose mRNA vaccination boosted antibody levels, vaccinated individuals' 'boost' was relatively short-lived.This work was made possible by WHO grant numbers COVID-19-22-43 and UREP28–173–3-057 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors

Diagnostic Efficiency of Three Fully Automated Serology Assays and Their Correlation with a Novel Surrogate Virus Neutralization Test in Symptomatic and Asymptomatic SARS-COV-2 Individuals

Abstract: To support the deployment of serology assays for population screening during the COVID-19 pandemic, we compared the performance of three fully automated SARS-CoV-2 IgG assays: Mindray CL-900i® (target: spike [S] and nucleocapsid [N]), BioMérieux VIDAS®3 (target: receptor-binding domain [RBD]) and Diasorin LIAISON®XL (target: S1 and S2 subunits). A total of 111 SARS-CoV-2 RT-PCR- positive samples collected at ≥ 21 days post symptom onset, and 127 prepandemic control samples were included. Diagnostic performance was assessed in correlation to RT-PCR and a surrogate virus-neutralizing test (sVNT). Moreover, cross-reactivity with other viral antibodies was investigated. Compared to RT-PCR, LIAISON®XL showed the highest overall specificity (100%), followed by VIDAS®3 (98.4%) and CL-900i® (95.3%). The highest sensitivity was demonstrated by CL-900i® (90.1%), followed by VIDAS®3 (88.3%) and LIAISON®XL (85.6%). The sensitivity of all assays was higher in symptomatic patients (91.1–98.2%) compared to asymptomatic patients (78.4–80.4%). In correlation to sVNT, all assays showed excellent sensitivities (92.2–96.1%). In addition, VIDAS®3 demonstrated the best correlation (r = 0.75) with the sVNT. The present study provides insights on the performance of three fully automated assays, which could help diagnostic laboratories in the choice of a particular assay according to the intended us

Performance evaluation of five ELISA kits for detecting anti-SARS-COV-2 IgG antibodies

ObjectivesTo evaluate and compare the performances of five commercial ELISA assays (EDI, AnshLabs, Dia.Pro, NovaTec, and Lionex) for detecting anti-SARS-CoV-2 IgG. Methods70 negative control samples (collected before the COVID-19 pandemic) and samples from 101 RT-PCR-confirmed SARS-CoV-2 patients (collected at different time points from symptoms onset: ≤7, 8-14, and >14 days) were used to compare the sensitivity, specificity, agreement, positive and negative predictive values of each assay with RT-PCR. A concordance assessment between the five assays was also conducted. Cross-reactivity with other HCoV, non-HCoV respiratory viruses, non-respiratory viruses, and nuclear antigens was investigated. ResultsLionex showed the highest specificity (98.6%, 95%CI: 92.3-99.8), followed by EDI and Dia.Pro (97.1%, 95%CI: 90.2-99.2), NovaTec (85.7%, 95%CI: 75.7-92.1), then AnshLabs (75.7%, 95%CI: 64.5-84.2). All ELISA kits cross-reacted with one anti-MERS IgG positive sample except Lionex. The sensitivity was low during the early stages of the disease but improved over time. After 14 days from symptoms onset, Lionex and NovaTec showed the highest sensitivity at 87.9% (95%CI: 72.7-95.2) and 86.4% (95%CI: 78.5-91.7), respectively. The agreement with RT-PCR results based on Cohen’s kappa was as follows: Lionex (0.89)> NovaTec (0.70)> Dia.Pro (0.69)> AnshLabs (0.63)> EDI (0.55). ConclusionThe Lionex ELISA, which measures antibodies solely to the S1 protein, demonstrated the best performance.This work was made possible by grant No. RRC-2-032 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. GKN would like to acknowledge funds from Qatar University's internal grant QUERG-CMED-2020-2

Validation of a Novel Fluorescent Lateral Flow Assay for Rapid Qualitative and Quantitative Assessment of Total Anti-SARS-CoV-2 S-RBD Binding Antibody Units (BAU) from Plasma or Fingerstick Whole-Blood of COVID-19 Vaccinees

Background: Limited commercial LFA assays are available to provide a reliable quantitative measurement of the total binding antibody units (BAU/mL) against the receptor-binding domain of the SARS-CoV-2 spike protein (S-RBD). Aim: This study aimed to evaluate the performance of the fluorescence LFA FinecareTM 2019-nCoV S-RBD test along with its reader (Model No.: FS-113) against the following reference methods: (i) the FDA-approved GenScript surrogate virus-neutralizing assay (sVNT); and (ii) three highly performing automated immunoassays: BioMérieux VIDAS®3, Ortho VITROS®, and Mindray CL-900i®. Methods: Plasma from 488 vaccinees was tested by all aforementioned assays. Fingerstick whole-blood samples from 156 vaccinees were also tested by FinecareTM. Results and conclusions: FinecareTM showed 100% specificity, as none of the pre-pandemic samples tested positive. Equivalent FinecareTM results were observed among the samples taken from fingerstick or plasma (Pearson correlation r = 0.9, p < 0.0001), suggesting that fingerstick samples are sufficient to quantitate the S-RBD BAU/mL. A moderate correlation was observed between FinecareTM and sVNT (r = 0.5, p < 0.0001), indicating that FinecareTM can be used for rapid prediction of the neutralizing antibody (nAb) post-vaccination. FinecareTM BAU results showed strong correlation with VIDAS®3 (r = 0.6, p < 0.0001) and moderate correlation with VITROS® (r = 0.5, p < 0.0001) and CL-900i® (r = 0.4, p < 0.0001), suggesting that FinecareTM can be used as a surrogate for the advanced automated assays to measure S-RBD BAU/mL.This work was made possible by grant number UREP28-173-3-057 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors

Are commercial antibody assays substantially underestimating SARS-CoV-2 ever infection? An analysis on a population-based sample in a high exposure setting

AbstractBackgroundPerformance of three automated commercial serological IgG-based assays was investigated for assessing SARS-CoV-2 ever (past or current) infection in a population-based sample in a high exposure setting.MethodsPCR and serological testing was performed on 394 individuals.ResultsSARS-CoV-2-IgG seroprevalence was 42.9% (95% CI 38.1%-47.8%), 40.6% (95% CI 35.9%-45.5%), and 42.4% (95% CI 37.6%-47.3%) using the CL-900i, VidasIII, and Elecsys assays, respectively. Between the three assays, overall, positive, and negative percent agreements ranged between 93.2%-95.7%, 89.3%-92.8%, and 93.8%-97.8%, respectively; Cohen kappa statistic ranged from 0.86-0.91; and 35 specimens (8.9%) showed discordant results. Among all individuals, 12.5% (95% CI 9.6%-16.1%) had current infection, as assessed by PCR. Of these, only 34.7% (95% CI 22.9%-48.7%) were seropositive by at least one assay. A total of 216 individuals (54.8%; 95% CI 49.9%-59.7%) had evidence of ever infection using antibody testing and/or PCR during or prior to this study. Of these, only 78.2%, 74.1%, and 77.3% were seropositive in the CL-900i, VidasIII, and Elecsys assays, respectively.ConclusionsAll three assays had comparable performance and excellent agreement, but missed at least 20% of individuals with past or current infection. Commercial antibody assays can substantially underestimate ever infection, more so when infection rates are high.</jats:sec