High diagnostic accuracy of quantitative SARS-CoV-2 spike-binding-IgG assay and correlation with in vitro viral neutralizing activity

Background

Antibody testing can easily evaluate the clinical status of patients, aid in the diagnosis of multisystem inflammatory syndrome, and monitor the immunity level in the population. However, the applicability of serological tests in detecting antibodies against the severe acute respiratory syndrome 2 (SARS-CoV-2) spike-binding protein remains limited. This study aimed to quantify both serum-derived neutralizing immunoglobulin-G (IgG) antibody activity and the amount of anti-SARS-CoV-2 Spike-IgG (S-IgG) in convalescent sera/plasmas and evaluate the direct correlation between the in vitro IgG-EC50 values and S-IgG values.

Methods

We evaluated the neutralizing activity of purified IgG (IgG-EC50), quantified S-IgG in the serum/plasma of consecutive COVID-19 convalescent individuals using a cell-based virus-neutralizing assay, and determined the correlation between IgG-EC50 and S-IgG. In addition, we evaluated rational cut-off values using the receiver operating characteristic (ROC) curve and calculated the sensitivity and specificity of the quantitative S-IgG assay for moderate and high IgG-EC50.

Results

A high correlation was observed between S-IgG and IgG-EC50 with a Spearman's ρ value of -0.748 (95 % confidence interval [CI]: -0.804-0.678). Using an IgG-EC50 of 50 μg/mL and 20 μg/mL as the cut-off values for moderate and high in vitro neutralizing activity, respectively, the Youden's index values of 287.5 binding antibody units (BAU)/mL and 454.1 BAU/mL determined from the ROC curve showed the highest diagnostic accuracy, with Kappa values of 0.884 (95 % CI: 0.823-0.946) and 0.920 (95 % CI: 0.681-0.979), respectively.

Conclusions

Quantitative S-IgG tests are a useful and convenient tool for estimating in vitro virus-neutralizing activity, with a high correlation with IgG-EC50 when the rational cut-off value is carefully determined.

Trends of participants in convalescent plasma donation for COVID-19 in Japan as the pandemic evolved

Background

We aimed to investigate chronological changes in the characteristics of participants in a coronavirus disease 2019 convalescent plasma donation study that may benefit optimal collection methods in the future.

Methods

Data from a convalescent plasma donation study from April 30, 2020 to November 5, 2021 were collected and analyzed. After August 23, 2021, an interim analysis of factors linked to higher antibody titers led us to restrict our participant recruitment criteria to participants who were within 4 months of disease onset and to patients who were otherwise most likely to have sufficiently high antibody titers. Overall, 1299 samples from 1179 patients were analyzed.

Results

Over the duration of the study, 35.9% of the samples were deemed eligible for convalescent plasma collection. The overall eligibility rate initially declined, dipping to <20% after one year. During this period, the proportion of enrolled samples from patients who had severe illness also declined, and the proportion of samples from participants who were >120 days post disease onset increased. After the addition of days from onset and vaccination status to our participant recruitment criteria, the eligibility rate improved significantly.

Conclusions

As outbreaks of emerging infectious disease occur, it is desirable to construct and implement a scheme for convalescent plasma donation promptly and to monitor the eligibility rate over time. If it declines, promptly analyze and resolve the associated factors. Additionally, vaccine development and infection prevalence are likely to influence the effective recruitment of participants with high antibody titers.

Efficacy of convalescent plasma therapy for COVID-19 in Japan: An open-label, randomized, controlled trial

BACKGROUND

Convalescent plasma is a potential therapeutic option for patients with coronavirus disease 2019 (COVID-19). Despite its use for treating several viral infections, we lack comprehensive data on its efficacy against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

METHODS

We conducted a multicenter, open-label, randomized controlled trial of convalescent plasma therapy with high neutralizing activity against SARS-CoV-2 in high-risk patients within five days after the onset of COVID-19 symptoms. The primary endpoint was the time-weighted average change in the SARS-CoV-2 viral load in nasopharyngeal swabs from days 0-5.

RESULTS

Between February 24, 2021, and November 30, 2021, 25 patients were randomly assigned to either convalescent plasma (n = 14) or standard of care (n = 11) groups. Four patients discontinued their allocated convalescent plasma, and 21 were included in the modified intention-to-treat analysis. The median interval between the symptom onset and plasma administration was 4.5 days (interquartile range, 3-5 days). The primary outcome of the time-weighted average change in the SARS-CoV-2 viral load in nasopharyngeal swabs did not significantly differ between days 0-5 (1.2 log₁₀ copies/mL in the convalescent plasma vs. 1.2 log₁₀ copies/mL in the standard of care (effect estimate, 0.0 [95% confidence interval, -0.8-0.7]; P = 0.94)). No deaths were observed in either group.

CONCLUSIONS

The early administration of convalescent plasma with high neutralizing activity did not contribute to a decrease in the viral load within five days compared with the standard of care alone.

Engineering a Membrane-binding Protein to Trimerize and Induce High Membrane Curvature

The annexins are a family of Ca²⁺-dependent peripheral membrane proteins. Several annexins are implicated in plasma membrane repair and are overexpressed in cancer cells. Annexin A4 (ANXA4) and Annexin A5 (ANXA5) form trimers that induce high curvature on a membrane surface, a phenomenon deemed to accelerate membrane repair. Despite being highly homologous to ANXA4, Annexin A3 (ANXA3) does not form trimers on the membrane surface. Using molecular dynamics (MD) simulations, we have reverse-engineered an ANXA3-mutant (ANXA3-MUT) to trimerize on the surface of the membrane and induce high curvature reminiscent of ANXA4. In addition, AFM images show that like ANXA4, the engineered protein forms crystalline arrays on a supported lipid membrane. In spite of the trimer-forming and curvature-inducing properties of the engineered ANXA3, it does not accumulate near a membrane lesion in laser-punctured cells and is unable to repair the lesion. Our investigation provides insights into the factors which drive annexin-mediated membrane repair and shows that the membrane repairing property of trimer-forming annexins also necessitates high membrane binding affinity, other than trimer formation and induction of negative membrane curvature.

Factors associated with anti-SARS-CoV-2 IgG antibody production in patients convalescing from COVID-19

Introduction

Among patients with coronavirus disease 2019 (COVID-19), the factors that affect anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody production remain unclear. This study aimed to identify such factors among patients convalescing from COVID-19.

Methods

This study comprised patients who had been diagnosed with COVID-19 between January 1 and June 30, 2020 and gave consent for anti-SARS-CoV-2 spike protein antibody measurement using enzyme-linked immunosorbent assay during their acute and/or convalescent phases. Factors related to elevated antibody titers and the relationship between the days from disease onset and the development of antibody titers were assessed.

Results

A total of 84 participants enrolled in the study. Nineteen participants had antibody titers measured during the convalescent phase only, and 65 participants had antibody titers measured during the acute and convalescent phases. The antibody titers peaked in weeks 5 and 6. The stepwise multivariate log-normal analysis revealed that male sex (P = 0.04), diabetes mellitus (P = 0.03), and high C-reactive protein levels during the disease course (P < 0.001) were associated with elevated IgG antibodies. Glucocorticoid use was not associated with antibody titers.

Conclusion

The study found that high values of maximum CRP levels during the acute phase, male sex, and diabetes mellitus were associated with elevated antibody titers. Antibody titers tended to be highest in the first 5 or 6 weeks after the onset of symptoms.

[Benign clear cell tumor of the lung diagnosed by transbronchial biopsy]

A 26-year-old woman had an abnormal shadow on chest X-ray films during a general medical examination. A chest roentgenogram showed a nodular shadow 8 mm in diameter in the middle field of the right lung. Transbronchial biopsy specimens revealed that the coin lesion was a benign clear cell tumor. Benign clear cell tumors of the lung are rare; only 21 cases, including the present case, have been reported in Japan. Although the diagnosis in most of the cases reported required an open thoracotomy, for our patient the diagnosis was based solely on the findings of a transbronchial biopsy.

[Determination of tangshenoside I in Codonopsis pilosula Nannf. by TLC-UV spectrophotometric method]

A method of thin layer chromatographic separation and ultraviolet spectrophotometric determination of tangshenoside I in Codonopsis pilosula is described. A comparison of the contents in various samples is made. The contents of tangshenoside I in frosted sample have been found to be twice as much as in normal drug. The recovery of tangshenoside I is 99.92% and the coefficient of variation of eight samplings is 1.77%.