A novel assessment method for COVID-19 humoral immunity duration using serial measurements in naturally-infected and vaccinated subjects.

Background: It is crucial for medical decision-making and vaccination strategies to collect information on sustainability of immune responses after infection or vaccination, and how long-lasting antibodies against SARS-COV-2 could provide a humoral and protective immunity, preventing reinfection with SARS-CoV-2 or its variants. The aim of this study is to present a novel method to quantitatively measure and monitor the diversity of SARS-CoV-2 specific antibody profiles over time. Methods: Two collections of serum samples were used in this study: A collection from 20 naturally-infected subjects (follow-ups to 1 year) and a collection from 83 subjects vaccinated with one or two doses of Pfizer BioNtech vaccine (BNT162b2/BNT162b2) (follow-ups to 6 months). The Multi-SARS-CoV-2 assay, a multiparameter serology test, developed for the serological confirmation of past-infections was used to determine the reactivity of six different SARS-CoV-2 antigens. For each patient sample, 3 dilutions (1/50, 1/400 and 1/3200) were defined as an optimal set over the six antigens and their respective linear ranges, allowing accurate quantitation of the corresponding six specific antibodies. Nonlinear mixed-effects modelling was applied to convert intensity readings from 3 determined dilutions to a single quantification value for each antibody. Results: Median half-life for the 20 naturally infected vs 74 vaccinated subjects (two doses) was respectively 120 vs 50 days for RBD, 127 vs 53 days for S1 and 187 vs 86 days for S2 antibodies. Respectively, 90% of the antibody concentration wanes after 158 vs 398 days for RBD, 171 vs 420 days for S1, and 225 vs 620 days for S2 after the second vaccine shot. Conclusion: The newly proposed method, based on a series of a limited number of dilutions, can convert a conventional qualitative assay into a quantitative assay. This conversion helps define the sustainability of specific immune responses against each relevant viral antigen and can help in defining the protection characteristics after an infection or a vaccination.

Correlation between cycle threshold and viral load through comparison of RT-PCR qualitative versus quantitative assay for SARS-CoV-2

Background and aims. Real-time reverse transcription polymerase chain reaction (RT-PCR) is the gold-standard assay to detect SARS-CoV-2, but it has limitations compared to viral load analysis. Quantitative detection improves surveillance, diagnosis, and prevention. We performed a comparative study of qualitative and quantitative tests for the diagnosis of COVID-19 on respiratory samples from patients screened for SARS-CoV-2 infection, and explored the correlation between viral load compared to the threshold cycle (Ct) value obtained in RT-PCR.Materials and methods. Sixty respiratory samples from patients affected by SARS-CoV-2 were subjected to both the qualitative (Allplex ™ 2019-nCoV Seegene) and the quantitative (Clonit® Quanty COVID-19) assays, and the relationship between viral load and Ct value was assessed by Spearman correlation analysis (ρ). In addition, the viral load of samples collected from a patient with symptomatic cancer was monitored. Results. The results show 100% agreement between the results obtained with quantitative assay and the reference standards, whereas 99.2% agreement was found for the qualitative test. A strong negative Spearman’s correlation between the Ct values of the N genes and RdRP gene was observed from qualitative assay values and viral loads.Conclusions. Quantitative assay has a higher sensitivity than qualitative assay, and viral load testing allows the clinicians to better orient themself in the choice of therapeutic treatment to be adopted. The constantly higher viral load of clinical cases considered, irrespective of the different therapies used, confirms that viral load monitoring could represent a great advantage in clinical practice.

PHYTOCHEMICAL STUDIES OF STAR FRUIT AVERRHOA CARAMBOLA L.

The paper deals with a phytochemical investigation on the fruit of Averrhoa carambola L. belonging to the family Oxalidaceae. Commonly known as “star fruit”. Fruits and leaves are used widely in Ayurveda preparations to pacify impaired Kapha, pitta, skin diseases, pruritis, worm infestations, diarrhea, vomiting, hemorrhoids, intermittent fever, over-perspiration, and general debility. In the present study fruits of Averrhoa carambola L. were screened for their phytochemical constituents following hot continuous and successive extraction by Soxhlet apparatus. A qualitative assay was done using a range of solvents. The extraction process was carried using different solvents successively in the order of increasing polarity. Qualitative analysis of the extracts using standard procedures revealed the presence of alkaloids, avonoids, tannins, saponins, glycosides, steroids&terpenoids, phenols, coumarins, and phytosterols. Preliminary screening of phytochemicals is a valuable step, in the detection of the bioactive principles present in medicinal plants and subsequently, may lead to drug discovery and development.

High-throughput quantitation of SARS-CoV-2 antibodies in a single-dilution homogeneous assay

SARS-CoV-2 emerged in late 2019 and has since spread around the world, causing a pandemic of the respiratory disease COVID-19. Detecting antibodies against the virus is an essential tool for tracking infections and developing vaccines. Such tests, primarily utilizing the enzyme-linked immunosorbent assay (ELISA) principle, can be either qualitative (reporting positive/negative results) or quantitative (reporting a value representing the quantity of specific antibodies). Quantitation is vital for determining stability or decline of antibody titers in convalescence, efficacy of different vaccination regimens, and detection of asymptomatic infections. Quantitation typically requires two-step ELISA testing, in which samples are first screened in a qualitative assay and positive samples are subsequently analyzed as a dilution series. To overcome the throughput limitations of this approach, we developed a simpler and faster system that is highly automatable and achieves quantitation in a single-dilution screening format with sensitivity and specificity comparable to those of ELISA.

Seroprevalence study of SARS-CoV-2 antibodies in healthcare workers following the first wave of the COVID-19 pandemic in a tertiary-level hospital in the south of Ireland

ObjectiveThis study investigated seroprevalence of SARS-CoV-2-specific IgG antibodies, using the Abbott antinucleocapsid IgG chemiluminescent microparticle immunoassay (CMIA) assay, in five prespecified healthcare worker (HCW) subgroups following the first wave of the COVID-19 pandemic.SettingAn 800-bed tertiary-level teaching hospital in the south of Ireland.ParticipantsSerum was collected for anti-SARS-CoV-2 nucleocapsid IgG using the Abbott ARCHITECT SARS-CoV-2 IgG CMIA qualitative assay, as per the manufacturer’s specifications.The groups were as follows: (1) HCWs who had real-time PCR (RT-PCR) confirmed COVID-19 infection (>1-month postpositive RT-PCR); (2) HCWs identified as close contacts of persons with COVID-19 infection and who subsequently developed symptoms (virus not detected by RT-PCR on oropharyngeal/nasopharyngeal swab); (3) HCWs identified as close contacts of COVID-19 cases and who remained asymptomatic (not screened by RT-PCR); (4) HCWs not included in the aforementioned groups working in areas determined as high-risk clinical areas; and (5) HCWs not included in the aforementioned groups working in areas determined as low-risk clinical areas.ResultsSix of 404 (1.49%) HCWs not previously diagnosed with SARS-CoV-2 infection (groups 2–5) were seropositive for SARS-CoV-2 at the time of recruitment into the study.Out of the 99 participants in group 1, 72 had detectable IgG to SARS-CoV-2 on laboratory testing (73%). Antibody positivity correlated with shorter length of time between RT-PCR positivity and antibody testing.Quantification cycle value on RT-PCR was not found to be correlated with antibody positivity.ConclusionsSeroprevalence of SARS-CoV-2 antibodies in HCWs who had not previously tested RT-PCR positive for COVID-19 was low compared with similar studies.

IgG antibody response against Nucleocapsid and Spike protein post SARS-CoV-2 infection

Objectives: Coronavirus disease-19 (COVID-19) pandemic became the greatest public health challenge globally. Study of dynamicity and durability of naturally developed antibodies against SARS-CoV-2 are of great importance from an epidemiological viewpoint.Methods: In this observational cohort study, we have followed up the 76 individuals who tested positive for SARS-CoV-2 infection by real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) for 16 weeks (post enrollment) to record the periodic changes in titre, concentration, clinical growth and persistence of naturally developed SARS-CoV-2 antibodies. We collected serum samples from these individuals for 16 weeks with a frequency of weekly and fortnightly during each follow-up and tested them in two CLIA-based platforms (Abbott Architect i1000SR and Roche Cobas e411) for testing SARS-CoV-2 antibodies both qualitatively and quantitatively.Results: We recorded the antibody magnitude of these individuals 10 times between September 2020 and February 2021. We found a waning of antibodies against nucleocapsid antigen protein but not a complete disappearance by the end of 16 weeks. Out of 76 cases, 30 cases (39.47%) became seronegative in qualitative assay, although all the sera samples (100%) remained positive when tested in quantitative assay.Conclusion: The lower persistence of anti-nucleocapsid SARS-CoV-2 antibody may not be the exact phenomenon as those cases were still seropositive against spike protein and help in neutralizing the virus.

Salivary testing of COVID-19: evaluation of serological testing following positive salivary results

Background Salivary detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been proposed as an alternative to nasopharyngeal or oropharyngeal swab testing. Our group previously published a study demonstrating that both testing methods identified SARS-CoV-2 using polymerase chain reaction (PCR)-based detection methodology. We therefore conducted a follow-up study using antibody testing to evaluate the accuracy of saliva versus swabs for COVID-19 detection and the durability of antibody response. Methods Venous blood samples were collected from consenting participants and the presence of serum antibodies for SARS-CoV-2 was evaluated on a large, automated immunoassay platform by the Roche anti-SARS-CoV-2 qualitative assay (Roche Diagnostics, Laval Quebec). Individuals with a serum antibody cut-off index (COI) ≥ 1.0 were considered positive. Results In asymptomatic and mildly symptomatic patients with a previously positive standard swab and/or saliva SARS-CoV-2 PCR-test, 42 demonstrated antibodies with 13 patients positive by swab alone, and 8 patients positive by saliva alone. Conclusions Despite their status as ‘current standard’ for COVID-19 testing, these findings highlight limitations of PCR-based tests.

An HIV Diagnostic Testing Algorithm Using the cobas HIV-1/HIV-2 Qualitative Assay for HIV Type Differentiation and Confirmation

HIV-1 and HIV-2 diagnostic testing algorithms recommended by the Centers for Disease Control involve up to three tests and rely mostly on detection of viral antigen and host antibody responses. HIV-1 p24 antigen/HIV-1/2 antibody reactive specimens are confirmed with an immunochromatographic HIV-1/HIV-2 antibody differentiation assay and negative or indeterminate results from the differentiation assay are resolved by an HIV-1-specific nucleic acid amplification test (NAT). The performance of a proposed alternative algorithm using the cobas HIV-1/HIV-2 Qualitative NAT as the differentiation assay was evaluated in subjects known to be infected with HIV-1 (N=876) or HIV-2 (N=139), at low (N=6017) or high (N=1020) risk of HIV-1 infection, or at high-risk for HIV-2 infection (N=498) (Study A). The performance of the cobas HIV-1/HIV-2 Qualitative test was also evaluated by comparison to an HIV-1 or HIV-2 alternative NAT (Study B). The HIV-1 and HIV-2 overall percent agreements (OPA) in Study A ranged from 95%-100% in all groups. The positive percent agreements (PPA) for HIV-1 and HIV-2 were 100% (876/876) and 99.4% (167/168) respectively for known positive groups. The negative percent agreement in the HIV low-risk group was 100% for both HIV-1 and HIV-2. In Study B, the HIV-1 and HIV-2 OPA ranged from 99%-100% in all groups evaluated (N: 183 to 1030), and the PPA for HIV-1 and HIV-2 were 100% and 99.5% respectively for known positive groups. The cobas HIV-1/HIV-2 Qualitative Assay can discriminate between HIV-1 and HIV-2 based on HIV RNA, and can be included in an alternative diagnostic algorithm for HIV.

Dramatic Rise of Seroprevalence Rates of SARS-CoV-2 Antibodies among Healthy Blood Donors: The evolution of a Pandemic

Background: The coronavirus disease 2019 (COVID-19) pandemic has resulted in more than 106 million cases of confirmed infection and more than 2.3 million deaths worldwide as of February 11th 2021. Seroprevalence studies are extremely useful in studying and assessing the epidemiological status in the community and the degree of spread. They help decision makers in implementing or relaxing mitigating measures to contain the disease in addition to other benefits. Objective: To study the seroprevalence rates of SARS-CoV-2 antibodies among healthy blood donors in Jordan, at various points of time as the pandemic evolves in the community. Methods: A total of 1374 blood donor were tested for the SARS-CoV-2 antibodies in 3 groups. The first group of 746 and the second of 348 individuals were tested in June and September of 2020 respectively. The 3rd group of 292 were tested in early February of 2021. We utilized a qualitative assay that uses Electrochemiluminescence method (ECLIA) that has a specificity and sensitivity of 99.8% and 100% respectively. Results: The first 2 groups representing the months of January to September of 2020, where the number of confirmed Covid-19 cases were several hundred to 3000 showed a seroprevalence rate of 0% (95% CI 0.00%, 0.51%). The 3rd group representing late January and early February 2021 when the number of reported confirmed case has reached 100 folds the numbers of September 2020, showed a seroprevalence of 27.4% (95% CI 22.5% and 32.9%). Conclusions: a dramatic rise in seroprevalence of SARS-CoV-2 antibodies was seen among healthy blood donors in Jordan in parallel with wide-spread intracommunity transmission of the disease. This information is useful to assess the degree of herd immunity and provides for better understanding of the pandemic.