RADIOIMMUNOASSAY FOR DETECTION OF ANTI-RINDERPEST ANTIBODIES IN CATTLES

Liquid Phase Radioimmunoassay (RIA) was developed to detect and measure anti-rinderpest immunoglobulins in field animals sera, within two hours. Rinderpest virus adapted on Vero cell line culture and antigen purified by treatment with Triton-Gentron 13 Butanol, and, labeled with I isotope, using chloramin T iodination method. Comparative studies for detecting anti-rinderpest immunoglobulin in 80 calves sera samples, using the developed assay in parallel with virus neutralization test (VNT). The study showed 58.75 % agreement between the two methods. However, 71 % of seven months old, non-vaccinated calves showed anti rinderpest antibodies in their sera, also 81 % of 10 months old vaccinated calves were developed antibodies in their blood. These results demonstrate the development of sensitive, specific and rapid quantitative / qualitative radioimmunoassay, necessary for screening the development of immunity against rinderpest in cattle.

SARS-CoV-2 Antibodies Are Persisting in Saliva for More Than 15 Months After Infection and Become Strongly Boosted After Vaccination

SARS-CoV-2 antibodies in saliva serve as first line of defense against the virus. They are present in the mucosa, more precisely in saliva, after a recovered infection and also following vaccination. We report here the antibody persistence in plasma and in saliva up to 15 months after mild COVID-19. The IgG antibody response was measured every two months in 72 participants using an established and validated in-house ELISA assay. In addition, the virus inhibitory activity of plasma antibodies was assessed in a surrogate virus neutralization test before and after vaccination. SARS-CoV-2-specific antibody concentrations remained stable in plasma and saliva and the response was strongly boosted after one dose COVID-19 vaccination.

Waning antibody levels after vaccination with mRNA BNT162b2 and inactivated CoronaVac COVID-19 vaccines in Hong Kong blood donors

Both inactivated vaccine (CoronaVac; Sinovac) and mRNA vaccine (Comirnaty/BNT162b2; Fosun-Pharma/BioNTech) are available in Hong Kong’s COVID-19 Vaccination Programme. We reported waning antibody levels by enzyme-linked immunosorbent assays (ELISA) and surrogate virus neutralization test (sVNT) among 850 fully vaccinated blood donors (i.e., received two doses). The BNT162b2 group’s antibody levels remain over the 50% protection threshold within six months, and the CoronaVac’s group’s median antibody levels begin to fall below the 50% protection threshold two months after vaccination.

Differences in Post-mRNA Vaccination SARS-CoV-2 IgG Concentrations and Surrogate Virus Neutralization Test Response by HIV Status and Type of Vaccine: a Matched Case-Control Observational Study

Following SARS-CoV-2 mRNA vaccination, people living with HIV (PLWH) had lower surrogate virus neutralization test response (p=0.03) and a trend towards lower IgG response (p=0.08), particularly among those with lower CD4+T-cell counts and who received the BNT162b2 vaccine. Study of the impact of supplemental vaccine doses among PLWH is needed.

Evaluation of Humoral Immune Response after SARS-CoV-2 Vaccination Using Two Binding Antibody Assays and a Neutralizing Antibody Assay

The Siemens severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG (sCOVG; Siemens Healthcare Diagnostics Inc., NY, USA) and Abbott SARS-CoV-2 IgG II Quant (CoV-2 IgG II; Abbott Laboratories, Sligo, Ireland), which are automated, quantitative SARS-CoV-2-binding antibody assays, have been recently launched. This study aimed to evaluate the humoral immune response of BNT162b2 and ChAdOx1 nCoV-19 vaccines using sCOVG and CoV-2 IgG II and compare the quantitative values with the results of the GenScript surrogate virus neutralization test (cPASS; GenScript, USA Inc., NJ, USA).

SARS-CoV-2 exposure in wild white-tailed deer (Odocoileus virginianus)

Widespread human SARS-CoV-2 infections combined with human–wildlife interactions create the potential for reverse zoonosis from humans to wildlife. We targeted white-tailed deer (Odocoileus virginianus) for serosurveillance based on evidence these deer have angiotensin-converting enzyme 2 receptors with high affinity for SARS-CoV-2, are permissive to infection, exhibit sustained viral shedding, can transmit to conspecifics, exhibit social behavior, and can be abundant near urban centers. We evaluated 624 prepandemic and postpandemic serum samples from wild deer from four US states for SARS-CoV-2 exposure. Antibodies were detected in 152 samples (40%) from 2021 using a surrogate virus neutralization test. A subset of samples tested with a SARS-CoV-2 virus neutralization test showed high concordance between tests. These data suggest white-tailed deer in the populations assessed have been exposed to SARS-CoV-2.

Quantitative SARS-CoV-2 Spike Antibody Response in COVID-19 Patients Using Three Fully Automated Immunoassays and a Surrogate Virus Neutralization Test

Quantitative SARS-CoV-2 antibody assays against the spike (S) protein are useful for monitoring immune response after infection or vaccination. We compared the results of three chemiluminescent immunoassays (CLIAs) (Abbott, Roche, Siemens) and a surrogate virus neutralization test (sVNT, GenScript) using 191 sequential samples from 32 COVID-19 patients. All assays detected >90% of samples collected 14 days after symptom onset (Abbott 97.4%, Roche 96.2%, Siemens 92.3%, and GenScript 96.2%), and overall agreement among the four assays was 91.1% to 96.3%. When we assessed time-course antibody levels, the Abbott and Siemens assays showed higher levels in patients with severe disease (p < 0.05). Antibody levels from the three CLIAs were correlated (r = 0.763–0.885). However, Passing–Bablok regression analysis showed significant proportional differences between assays and converting results to binding antibody units (BAU)/mL still showed substantial bias. CLIAs had good performance in predicting sVNT positivity (Area Under the Curve (AUC), 0.959–0.987), with Abbott having the highest AUC value (p < 0.05). SARS-CoV-2 S protein antibody levels as assessed by the CLIAs were not interchangeable, but showed reliable performance for predicting sVNT results. Further standardization and harmonization of immunoassays might be helpful in monitoring immune status after COVID-19 infection or vaccination.