Higher correlation between neutralizing antibodies and surrogate neutralizing or binding antibodies in COVID-19 patients than vaccine recipients.

This study determined the seropositive rates and levels of antibodies to severe acute respiratory syndrome coronavirus-2 in 50 patients and 108 vaccinees using microneutralization test (MNT), surrogate virus neutralization test (sVNT), chemiluminescent microparticle immunoassay (CMIA), and electrochemiluminescence immunoassay (ECLIA). MNT, as the reference method, employed living clade S and Delta viruses to measure neutralizing (NT) antibodies, while sVNT employed wild type strain and Delta receptor-binding domains (RBD) as the test antigens to measure sVNT antibodies. CMIA and ECLIA employed only one version of RBD to measure the binding antibodies. Our study performed S gene sequencing of the test virus to exclude undesired mutants that might lead to changes in antibody levels in MNT assay. We showed that spike protein amino acid sequences of our Delta virus contained 13 amino acid changes, with 3 related to the reduced neutralization. The MNT assay showed a significant reduction in seropositive rates and antibody levels in the patients' sera when the Delta variant replaced clade S as the test virus. In contrast, the seropositive rates determined by sVNT assay using wild type strain RBD and Delta RBD were non-significantly different, suggesting that sVNT assay could not identify the difference between the antigenicity of wild type RBD and Delta RBD. Furthermore, the correlation between the levels of NT and sVNT antibodies was moderate with the patients' sera but modest with the post-vaccination sera. The seropositive rates in the patients, as determined by CMIA or ECLIA, were not different from the MNT assay using clade S, but not Delta, as the test virus. In all analyses, the correlations between the antibody levels measured by MNT and the other 3 assays were modest to moderate, with the r-values of 0.3500-0.7882.

Investigation of the activity of baicalein towards Zika virus.

BACKGROUND: Zika virus (ZIKV) is a mosquito transmitted virus spread primarily by Aedes species mosquitoes that can cause disease in humans, particularly when infection occurs in pregnancy where the virus can have a significant impact on the developing fetus. Despite this, there remains no prophylactic agent or therapeutic treatment for infection. Baicalein is a trihydroxyflavone, that is found in some traditional medicines commonly used in Asia, and has been shown to have several activities including antiviral properties. Importantly, studies have shown baicalein to be safe and well tolerated in humans, increasing its potential utilization. METHODS: This study sought to determine the anti-ZIKV activity of baicalein using a human cell line (A549). Cytotoxicity of baicalein was determined by the MTT assay, and the effect on ZIKV infection determined by treating A549 cells with baicalien at different time points in the infection process. Parameters including level of infection, virus production, viral protein expression and genome copy number were assessed by flow cytometry, plaque assay, western blot and quantitative RT-PCR, respectively. RESULTS: The results showed that baicalein had a half-maximal cytotoxic concentration (CC50) of > 800 µM, and a half-maximal effective concentration (EC50) of 124.88 µM. Time-of-addition analysis showed that baicalein had an inhibitory effect on ZIKV infection at the adsorption and post-adsorption stages. Moreover, baicalein also exerted a significant viral inactivation activity on ZIKV (as well as on dengue virus and Japanese encephalitis virus) virions. CONCLUSION: Baicalein has now been shown to possess anti-ZIKV activity in a human cell line.

Seroprevalence of anti-SARS-CoV-2 antibodies in Thai adults during the first three epidemic waves.

This study determined the presence of anti-SARS-CoV-2 antibodies in 4964 individuals, comprising 300 coronavirus disease-19 (COVID-19) prepandemic serum samples, 142 COVID-19 patients, 2113 individuals at risk due to their occupations, 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, and 553 Thai citizens returning after spending extended periods of time in countries with a high disease prevalence. We recruited participants between May 2020 and May 2021, which spanned the first two epidemic waves and part of the third wave of the COVID-19 outbreaks in Thailand. Their sera were tested in a microneutralization and a chemiluminescence immunoassay for IgG against the N protein. Furthermore, we performed an immunofluorescence assay to resolve discordant results between the two assays. None of the prepandemic sera contained anti-SARS-CoV-2 antibodies, while antibodies developed in 88% (15 of 17) of the COVID-19 patients at 8-14 days and in 94-100% of the patients between 15 and 60 days after disease onset. Neutralizing antibodies persisted for at least 8 months, longer than IgG antibodies. Of the 2113 individuals at risk due to their occupation, none of the health providers, airport officers, or public transport drivers were seropositive, while antibodies were present in 0.44% of entertainment workers. Among the 1856 individuals at risk due to sharing workplaces or communities with COVID-19 patients, seropositivity was present in 1.9, 1.5, and 7.5% of the Bangkok residents during the three epidemic waves, respectively, and in 1.3% of the Chiang Mai people during the first epidemic wave. The antibody prevalence varied between 6.5 and 47.0% in 553 Thai people returning from high-risk countries. This serosurveillance study found a low infection rate of SARS-CoV-2 in Thailand before the emergence of the Delta variant in late May 2021. The findings support the Ministry of Public Health's data, which are based on numbers of patients and contact tracing.

Evaluation of different platforms for the detection of anti-SARS coronavirus-2 antibodies, Thailand.

BACKGROUND: Antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) help determine previous infection in individuals, regardless of whether they are asymptomatic or symptomatic. The detection of antibodies serves several purposes, including supporting other assays for disease diagnosis, conducting seroepidemiological studies, and evaluating vaccines. Many platforms of immunological methods for anti-SARS-CoV-2 antibody detection and their performance require validation. METHODS: This study evaluated the test performance of three autoanalyzer-based assays (Architect IgG, Vitros IgG, and Vitros total Ig) and one manual ELISA (Wantai total Ig) against a microneutralization (microNT) assay on the detection of SARS-CoV-2 antibodies. Furthermore, an indirect immunofluorescence assay verified the discordant results between the microNT and commercial assays. The test sensitivity, specificity, positive predictive value, and negative predictive value were determined based on four groups of 1005 serum samples: 102 COVID-19 prepandemic sera, 45 anti-SARS-CoV-2 positive sera, 366 sera of people at risk, and 492 sera of citizens returning from countries with a high prevalence of infection. RESULTS: The analyses as a whole showed that the performance of these commercial assays was comparable. Each group was also analysed separately to gain further insight into test performance. The Architect did not detect two positive sera of people at risk (prevalence of infection 0.55%). The other methods correctly identified these two positive sera but yielded varying false-positive results. The group of returning travellers with an infection rate of 28.3% (139 of 492) better differentiated the test performance of individual assays. CONCLUSIONS: High-throughput Architect and Vitros autoanalyzers appear appropriate for working on large sample sizes in countries that can afford the cost. The Wantai ELISA, while requiring more individual time and technical skill, may provide reliable results at a lower cost. The selection of assays will depend on the laboratory facilities and feasibility.