Stability of SARS-CoV-2 IgG in multiple laboratory conditions and blood sample types

Potential of a Bead-Based Multiplex Assay for SARS-CoV-2 Antibody Detection

Serological assays for SARS-CoV-2 play a pivotal role in the definition of whether patients are infected, the understanding of viral epidemiology, the screening of convalescent sera for therapeutic and prophylactic purposes, and in obtaining a better understanding of the immune response towards the virus. The aim of this study was to investigate the performance of a bead-based multiplex assay. This assay allowed for the simultaneous testing of IgG antibodies against SARS-CoV-2 spike, S1, S2, RBD, and nucleocapsid moieties and S1 of seasonal coronaviruses hCoV-22E, hCoV-HKU1, hCoV-NL63, and hCoV-OC43, as well as MERS and SARS-CoV. We compared the bead-based multiplex assay with commercial ELISA tests. We tested the sera of 27 SARS-CoV-2 PCR-positive individuals who were previously tested with different ELISA assays. Additionally, we investigated the reproducibility of the results by means of multiple testing of the same sera. Finally, the results were correlated with neutralising assays. In summary, the concordance of the qualitative results ranged between 78% and 96% depending on the ELISA assay and the specific antigen. Repeated freezing-thawing cycles resulted in reduced mean fluorescence intensity, while the storage period had no influence in this respect. In our test cohort, we detected up to 36% of sera positive for the development of neutralising antibodies, which is in concordance with the bead-based multiplex and IgG ELISA.

Is there an immunological cross-reactivity of antibodies to the myelin oligodendrocyte glycoprotein and coronaviruses?

Recent reports indicated that myelin oligodendrocyte glycoprotein antibody-associated disease might be a rare complication after severe acute respiratory syndrome coronavirus 2 infection or vaccination. It is unclear whether this is an unspecific sequel of infection or vaccination or caused by possible immunological cross-reactivity of severe acute respiratory syndrome coronavirus 2 proteins and myelin oligodendrocyte glycoprotein. The aim of this study was therefore to elucidate whether there is an immunological cross-reactivity between severe acute respiratory syndrome coronavirus 2 spike or nucleocapsid proteins and myelin oligodendrocyte glycoprotein and to explore the relation of antibody responses against myelin oligodendrocyte glycoprotein and severe acute respiratory syndrome coronavirus 2 and other coronaviruses. We analysed serum samples from patients with severe acute respiratory syndrome coronavirus 2 infection and neurological symptoms with (myelin oligodendrocyte glycoprotein antibody-associated disease, n = 12) or without myelin oligodendrocyte glycoprotein-antibodies (n = 10); severe acute respiratory syndrome coronavirus 2 infection without neurological symptoms (n = 32); vaccinated patients with no history of severe acute respiratory syndrome coronavirus 2 infection and neurological symptoms with (myelin oligodendrocyte glycoprotein antibody-associated disease, n = 10) or without myelin oligodendrocyte glycoprotein-antibodies (n = 9); and severe acute respiratory syndrome coronavirus 2 negative/naïve unvaccinated patients with neurological symptoms with (myelin oligodendrocyte glycoprotein antibody-associated disease, n = 47) or without myelin oligodendrocyte glycoprotein-antibodies (n = 20). All samples were analysed for serum antibody responses to myelin oligodendrocyte glycoprotein, severe acute respiratory syndrome coronavirus 2, and other common coronaviruses (CoV-229E, CoV-HKU1, CoV-NL63 and CoV-OC43). Based on sample amount and antibody titres, 21 samples were selected for analysis of antibody cross-reactivity between myelin oligodendrocyte glycoprotein and severe acute respiratory syndrome coronavirus 2 spike and nucleocapsid proteins using affinity purification and pre-absorption. Whereas we found no association of immunoglobulin G and A myelin oligodendrocyte glycoprotein antibodies with coronavirus antibodies, infections with severe acute respiratory syndrome coronavirus 2 correlated with an increased immunoglobulin M myelin oligodendrocyte glycoprotein antibody response. Purified antibodies showed no cross-reactivity between severe acute respiratory syndrome coronavirus 2 spike protein and myelin oligodendrocyte glycoprotein. However, one sample of a patient with myelin oligodendrocyte glycoprotein antibody-associated disease following severe acute respiratory syndrome coronavirus 2 infection showed a clear immunoglobulin G antibody cross-reactivity to severe acute respiratory syndrome coronavirus 2 nucleocapsid protein and myelin oligodendrocyte glycoprotein. This patient was also seropositive for other coronaviruses and showed immunological cross-reactivity of severe acute respiratory syndrome coronavirus 2 and CoV-229E nucleocapsid proteins. Overall, our results indicate that an immunoglobulin G antibody cross-reactivity between myelin oligodendrocyte glycoprotein and severe acute respiratory syndrome coronavirus 2 proteins is rare. The presence of increased myelin oligodendrocyte glycoprotein-immunoglobulin M antibodies after severe acute respiratory syndrome coronavirus 2 infection may either be a consequence of a previous infection with other coronaviruses or arise as an unspecific sequel after viral infection. Furthermore, our data indicate that myelin oligodendrocyte glycoprotein-immunoglobulin A and particularly myelin oligodendrocyte glycoprotein-immunoglobulin M antibodies are a rather unspecific sequel of viral infections. Finally, our findings do not support a causative role of coronavirus infections for the presence of myelin oligodendrocyte glycoprotein-immunoglobulin G antibodies.

Comparison of capillary blood self-collection using the Tasso-SST device with venous phlebotomy for anti-SARS-CoV-2 antibody measurement

Measuring seroprevalence over time is a valuable epidemiological tool for improving our understanding of COVID-19 immunity. Due to the large number of collections required for population surveillance as well as concerns about potential infection risk to the collectors, self-collection approaches are being increasingly pursued. To advance this methodology, we collected paired venous and capillary blood samples by routine phlebotomy and Tasso-SST device respectively from 26 participants and measured total immunoglobulin (Ig) and IgG antibodies to the SARS-CoV-2 receptor binding domain (RBD) by enzyme-linked immunosorbent assay (ELISA) on both specimens. Qualitatively, no discrepancies were noted in binary results between Tasso and venipuncture-derived plasma. Furthermore, in vaccinated participants, correlation between Tasso and venous total Ig and IgG specific antibody quantitative levels was high (Total Ig: Spearman ρ = 0.72, 95% CI (0.39,0.90); IgG: Spearman ρ = 0.85, 95% CI (0.54, 0.96)). Our results support the use of Tasso at-home collection devices for antibody testing.

Preanalytical stability of SARS-CoV-2 anti-nucleocapsid antibodies

OBJECTIVES

Anti-nucleocapsid (NC) antibodies are produced in response to SARS-CoV-2 infection. Therefore, they are well suited for the detection of a previous infection. Especially in the case of seroprevalence studies or during the evaluation of a novel in-vitro diagnostic test, samples have been stored at <-70 °C (short- and long-term) or 2-10 °C (short-term) before analysis. This study aimed to assess the impact of different storage conditions relevant to routine biobanking on anti-NC antibodies.

METHODS

The preanalytical impact of short-term storage (84 [58-98] days) on <-70 °C and for 14 days at 2-10 °C was evaluated using samples from 111 donors of the MedUni Vienna Biobank. Long-term effects (443 [409-468] days) were assessed using 208 samples from Biobank Graz and 49 samples from Biobank Vienna. Anti-Nucleocapsid antibodies were measured employing electrochemiluminescence assays (Roche Anti-SARS-CoV-2).

RESULTS

After short-term storage, the observed changes did not exceed the extent that could be explained by analytical variability. In contrast, results after long-term storage were approximately 20% higher and seemed to increase with storage duration. This effect was independent of the biobank from which the samples were obtained. Accordingly, the sensitivity increased from 92.6 to 95.3% (p=0.008). However, comparisons with data from Anti-Spike protein assays, where these deviations were not apparent, suggest that this deviation could also be explained by the analytical variability of the qualitative Anti-NC assay.

CONCLUSIONS

Results from anti-NC antibodies are stable during short-term storage at <-70 °C and 2-10 °C. After long-term storage, a slight increase in sensitivity could not be ruled out.

Preserved SARS-CoV-2 neutralizing IgG activity of in-house manufactured COVID-19 convalescent plasma

PURPOSE

In the current study, we aimed to evaluate the neutralizing IgG activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as well as the coagulation factors of convalescent plasmas which we manufactured in-house without a fast-freezing technique.

METHODS

We collected plasmas from eligible participants who had confirmed certain titers of neutralizing antibodies. The plasmas were frozen and stored in the ordinary biofreezer without a fast-freezing function. The purified-IgG neutralizing activity of 20 samples from 19 participants and the coagulation factors of 49 samples from 40 participants were evaluated before and after freezing.

RESULTS

Purified-IgG maintained its neutralizing activities, with the median 50 % inhibitory concentration (IC50) of 10.11 mg/ml (IQR 6.53-18.19) before freezing and 8.90 m g/ml (IQR 6.92-28.27) after thawing (p = 0.956). On the contrary, fibrinogen and factor Ⅷ decreased significantly after freezing and thawing in our environment. No significant temperature deviation was observed during the storage period.

CONCLUSION

Neutralizing IgG activity, which largely contributes to the antiviral activity of convalescent plasma, did not change through our in-house manufacturing, without fastfreezing and storage conditions for more than 200 days. Ordinary freezers without the fast-freezing function are suitable enough to manufacture and store convalescent plasmas. Hospitals or facilities without specified resources could easily collect and store convalescent plasmas in case of upcoming emerging or re-emerging infectious diseases on-demand with appropriate neutralizing antibody levels measurements.

Evolution of anti-SARS-CoV-2 spike protein titers after two-dose of COVID-19 vaccination among people living with HIV

Background

A community COVID-19 outbreak caused by the B.1.1.7 SARS-CoV-2 variant occurred in Taiwan in May 2021. High-risk populations such as people living with HIV (PLWH) were recommended to receive two doses of COVID-19 vaccines. While SARS-CoV-2 vaccines have demonstrated promising results in general population, real-world information on the serological responses remains limited among PLWH.

Methods

PLWH receiving the first dose of SARS-CoV-2 vaccine from 2020 to 2021 were enrolled. Determinations of anti-SARS-CoV-2 spike IgG titers were performed every one to three months, the third dose of the SARS-CoV-2 vaccine or confirmed SARS-CoV-2 infection. All serum samples were tested for anti-nucleocapsid antibody and those tested positive were excluded from analysis.

Results

A total of 1189 PLWH were enrolled: 829 (69.7%) receiving two doses of the AZD1222 vaccine, 232 (19.5%) of the mRNA-1273 vaccine, and 128 (10.8%) of the BNT162b2 vaccine. At all time-points, PLWH receiving two doses of mRNA vaccines had consistently higher antibody levels than those receiving the AZD1222 vaccine (p <0.001 for all time-point comparisons). Factors associated with failure to achieve an anti-spike IgG titer >141 BAU/mL within 12 weeks, included type 2 diabetes mellitus (DM) (adjusted odds ratio [aOR], 2.24; 95% CI, 1.25-4), a CD4 T cell count <200 cells/mm³ upon receipt of the first dose of vaccination (aOR, 3.43; 95% CI, 1.31-9) and two homologous AZD1222 vaccinations (aOR, 16.85; 95%CI, 10.13-28). For those receiving two doses of mRNA vaccines, factors associated with failure to achieve an anti-spike IgG titer >899 BAU/mL within 12 weeks were a CD4 T cell count <200 cells/mm³ on first-dose vaccination (aOR, 3.95; 95% CI, 1.08-14.42) and dual BNT162b2 vaccination (aOR, 4.21; 95% CI, 2.57-6.89).

Conclusions

Two doses of homologous mRNA vaccination achieved significantly higher serological responses than vaccination with AZD1222 among PLWH. Those with CD4 T cell counts <200 cells/mm³ and DM had consistently lower serological responses.

Type of mRNA COVID-19 vaccine and immunomodulatory treatment influence humoral immunogenicity in patients with inflammatory rheumatic diseases

Patients with inflammatory rheumatic diseases (IRD) are at increased risk for worse COVID-19 outcomes. Identifying whether mRNA vaccines differ in immunogenicity and examining the effects of immunomodulatory treatments may support COVID-19 vaccination strategies. We aimed to conduct a long-term, model-based comparison of the humoral immunogenicity following BNT162b2 and mRNA-1273 vaccination in a cohort of IRD patients. Patients from the Swiss IRD cohort (SCQM), who assented to mRNA COVID-19 vaccination were recruited between 3/2021-9/2021. Blood samples at baseline, 4, 12, and 24 weeks post second vaccine dose were tested for anti-SARS-CoV-2 spike IgG (anti-S1). We examined differences in antibody levels depending on the vaccine and treatment at baseline while adjusting for age, disease, and past SARS-CoV-2 infection. 565 IRD patients provided eligible samples. Among monotherapies, rituximab, abatacept, JAKi, and TNFi had the highest odds of reduced anti-S1 responses compared to no medication. Patients on specific combination therapies showed significantly lower antibody responses than those on monotherapy. Irrespective of the disease, treatment, and past SARS-CoV-2 infection, the odds of higher antibody levels at 4, 12, and 24 weeks post second vaccine dose were, respectively, 3.4, 3.8, and 3.8 times higher with mRNA-1273 versus BNT162b2 (p < 0.0001). With every year of age, the odds ratio of higher peak humoral immunogenicity following mRNA-1273 versus BNT162b2 increased by 5% (p < 0.001), indicating a particular benefit for elderly patients. Our results suggest that in IRD patients, two-dose vaccination with mRNA-1273 versus BNT162b2 results in higher anti-S1 levels, even more so in elderly patients.

Development of chemiluminescent lab-on-fiber immunosensors for rapid point-of-care testing of anti-SARS-CoV-2 antibodies and evaluation of longitudinal immune response kinetics following three-dose inactivation virus vaccination

Developing reliable, rapid, and quantitative point-of-care testing (POCT) technology of SARS-CoV-2-specific antibodies and understanding longitudinal vaccination response kinetics are highly required to restrain the ongoing coronavirus disease 2019 (COVID-19) pandemic. We demonstrate a novel portable, sensitive, and rapid chemiluminescent lab-on-fiber detection platform for detection of anti-SARS-CoV-2 antibodies: the chemiluminescent lab-on-fiber immunosensor (c-LOFI). Using SARS-CoV-2 Spike S1 RBD protein functionalized fiber bio-probe, the c-LOFI can detect anti-SARS-CoV-2 immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies with high sensitivity based on their respective horseradish peroxidase-labeled secondary antibodies. The limits of detection of anti-SARS-CoV-2 IgG and IgM antibodies were 0.6 and 0.3 ng/ml, respectively. The c-LOFI was successfully applied for direct detection of anti-SARS-CoV-2 antibodies in whole blood samples with simple dilution, which can serve as a finger prick test to rapidly detect antibodies. Furthermore, the longitudinal immune response (>12 months) kinetics following three-dose inactivated virus vaccines was evaluated based on anti-SARS-CoV-2 IgG detection results, which can provide important significance for understanding the immune mechanism against COVID-19 and identify individuals who may benefit from the vaccination and booster vaccination. The c-LOFI has great potential to become a sensitive, low-cost, rapid, high-frequency POCT tool for the detection of both SARS-CoV-2-specific antibodies and other biomarkers.