SARS-CoV-2 specific T-cell immunity in COVID-19 convalescent patients and unexposed controls measured by ex vivo ELISpot assay

ObjectivesSARS-CoV-2 T-cell response characterization represents a crucial issue for defining the role of immune protection against COVID-19. The aim of the study was to assess the SARS-CoV-2 T-cell response in a cohort of COVID-19 convalescent patients and in a group of unexposed subjects.MethodsSARS-CoV-2 T-cell response was quantified from peripheral blood mononuclear cells (PBMCs) of 87 COVID-19 convalescent subjects (range 7–239 days after symptom onset) and 33 unexposed donors by ex vivo ELISpot assay. Follow-up of SARS-CoV-2 T-cell response was performed in ten subjects up to 12 months after symptom onset. The role of SARS-CoV-2 specific CD4 and CD8 T cells was characterized in a group of COVID-19 convalescent subjects. Moreover, neutralizing antibodies were determined in serum samples.ResultsIn 14/33 (42.4%) unexposed donors and 85/87 (97.7%) COVID-19 convalescent subjects a positive result for at least one SARS-CoV-2 antigen was observed. A positive response was observed up to 12 months after COVID-19 infection (median 246 days after symptom onset; range 118–362 days). Of note, SARS-CoV-2 T-cell response seems to be mainly mediated by CD4 T cells. A weak positive correlation was observed between Spike-specific T-cell response and neutralizing antibody titre (p 0.0028; r² = 0.2891) and positive SARS-CoV-2 T-cell response was observed in 8/9 (88.9%) COVID-19 convalescent subjects with undetectable SARS-CoV-2 neutralizing antibodies.DiscussionCross-reactive SARS-CoV-2 T-cell response in uninfected patients may be due to previous infections with other common coronaviruses. Our data suggest that long-term SARS-CoV-2 T-cell response might accompany a waning humoral response.     

Seroprevalence of SARS-CoV-2 among potential convalescent plasma donors and analysis of their deferral pattern: Experience from tertiary care hospital in western India

Background and objectivesSeroprevalence estimation of COVID-19 is quite necessary for controlling the transmission of SARS-CoV-2 infection. Seroprevalence rate in recovered COVID-19 patients help us to identify individual with anti-SARS-CoV-2 antibodies and its protective nature. The objective of present study was to evaluate seroprevalence of SARS-CoV-2 among potential convalescent plasma donors and analysis of their deferral reasons.Materials and methodsA total 400 potential convalescent plasma donors were enrolled over five-month period for this prospective study. Inclusion criteria were lab confirmed COVID-19 recovered patients and 14 days of symptoms free period. All prospective plasmapheresis donors were tested for IgG SARS-CoV-2 antibody through chemiluminescent microparticle immunoassay, CBC, serum protein, blood grouping along with other required test for normal blood donation as per Drugs & Cosmetics Act. After pre donation testing and medical examination if donor was found to be ineligible for plasmapheresis was deferred. Seroprevalence rate was calculated by positive IgG antibody test results among the potential plasma donors.ResultsSeroprevalence rate was 87% for IgG SARS-CoV-2 antibodies in prospective convalescent plasma donors (recovered COVID-19 patients). There was no significant difference in seroprevalence rate between different sub-groups with respect to gender, age, blood groups, Rh factor, mode of treatment, day of Ab testing and repeat plasma donation. Most common reason for their deferral was absent IgG SARS-CoV-2 antibodies (13%) followed by absenteeism of eligible screen donors (6.7%), low Hb (1.7%) and poor veins for plasmapheresis (1.7%). Till five-month study period none of the plasmapheresis develop symptoms of reinfection with COVID-19.ConclusionIn all, 13% recovered patients did not develop IgG antibodies after SARS-CoV-2 infection. SARS-CoV-2 IgG antibodies persist for quite some time and are protective against reinfection. More long-term serology studies are needed to understand better antibody response kinetics and duration of persistence of IgG antibodies.     

SARS-CoV-2 vaccine humoral response in adults with Down syndrome

ObjectivePeople with Down syndrome (DS) are particularly vulnerable to coronavirus disease 2019 (COVID-19) and show altered immune response to vaccination. We aimed to evaluate the immune response of a group of adults with DS treated with standard regimens of SARS-CoV-2 vaccine as compared with an age- and sex-matched group of persons without DS.MethodsWe compared antibody responses between 42 subjects with DS (41.6 ± 10.8 years, 57% male), and an age- and sex-matched comparison group of healthy health care workers (HCW) (41.4 ± 8.8 years, 54.8% male) after SARS-CoV-2 vaccination with the standard regimen of BNT162b2 mRNA COVID-19. Receptor binding domain (RBD) IgG antibodies were assessed at 4 time points (baseline, 21 days after the first dose, 21 days after the second dose, and 6 months after the first dose) with Siemens SARS-CoV-2 IgG (COV2G) antibody test.ResultsWe observed significantly different antibody responses at all time points after vaccination (HCW vs. DS: 7.9 ± 3.9 vs. 1.4 ± 3.6 IU/mL at 21 days after first dose; 358.5 ± 3.8 vs. 38.1 ± 3.0 IU/mL at 21 days after second dose; 34.6 ± 2.4 vs. 7.9 ± 3.1 IU/mL at 6 months after vaccination) and a significantly different time course of decline in antibody titers between the two groups.DiscussionSubjects with DS have a valid antibody response to SARS-CoV-2 vaccination. However, this response is lower than that of subjects in the HCW group. This finding could indicate a more rapid decline in the protective effects of the vaccination in subjects with DS and could suggest that people with DS may benefit from a booster dose of vaccine.     

Post–COVID-19 syndrome and humoral response association after 1 year in vaccinated and unvaccinated patients

ObjectivesThis study aimed to describe the impact of vaccination and the role of humoral responses on post–COVID-19 syndrome 1 year after the onset of SARS coronavirus type 2 (CoV-2).MethodsThis prospective study was conducted through interviews to investigate post–COVID-19 syndrome 6 and 12 months after disease onset in all adult in- and outpatients with COVID-19 at Udine Hospital (March–May 2020). Vaccination status and two different serological assays to distinguish between response to vaccination (receptor-binding domain (RBD) SARS-CoV-2 IgG) and/or natural infection (non-RBD-SARS-CoV-2 IgG) were also assessed.ResultsA total of 479 patients (52.6% female; mean age: 53 years) were interviewed 13.5 months (standard deviation: 0.6 months) after acute infection. Post–COVID-19 syndrome was observed in 47.2% of patients (n = 226) after 1 year. There were no significant differences in the worsening of post–COVID-19 symptoms (22.7% vs. 15.8%; p = 0.209) among vaccinated (n = 132) and unvaccinated (n = 347) patients. The presence of non-RBD SARS-CoV-2 IgG induced by natural infection showed a significant association with post–COVID-19 syndrome (OR: 1.35; 95% CI, 1.11–1.64; p = 0.003), and median non-RBD SARS-CoV-2 IgG titres were significantly higher in long haulers than in patients without symptoms (22 kAU/L (interquartile range, 9.7–37.2 kAU/L) vs. 14.1 kAU/L (interquartile range, 5.4–31.3 kAU/L); p = 0.009) after 1 year. In contrast, the presence of RBD SARS-CoV-2 IgG was not associated with the occurrence of post–COVID-19 syndrome (>2500 U/mL vs. 0.9–2500 U/mL; OR: 1.36; 95% CI, 0.62–3.00; p = 0.441), and RBD SARS-CoV-2 IgG titres were similar in long haulers as in patients without symptoms (50% values > 2500 U/mL vs. 55.6% values > 2500 U/mL; p = 0.451).DiscussionThe SARS-CoV-2 vaccination is not associated with the emergence of post–COVID-19 symptoms more than 1 year after acute infection. The persistence of high serological titre response induced by natural infection, but not vaccination, may play a role in long-haul COVID-19.     

SARS-CoV-2 neutralizing capacity among blood donors without prior COVID-19 symptomatic history vs. blood donors with prior COVID-19 symptomatic history: A comparative study

IntroductionThough moderate to severely ill COVID-19 patients are being treated using COVID Convalescent plasma across the world, there is a lack of standardization or information about the relative neutralizing capacity of antibodies from convalescent plasma donors. The current study aimed to compare the neutralizing antibody inhibition levels between COVID-Convalescent plasma from apheresis donors who had symptomatic COVID-19 history and asymptomatic blood donors, i.e., whole blood donors without prior any COVID-19 positive diagnosis nor symptoms/contact history related to COVID-19.MethodsObservational study conducted at the Blood Centre, Tertiary Care Hospital, South India on blood donor samples during the period July–December 2020. A total of 90 samples (43 convalescent plasma donors and 47 whole blood donors) were tested for SARS-CoV-2-IgG and Neutralising antibodies.ResultsNo significant difference in neutralization capacity was observed between these symptomatic vs. asymptomatic donors. Also, inhibition % appeared similar in the two groups with respect to age, gender, blood group, donation status, or type of donation without any statistical significance. On analyzing the correlation between the SARS-CoV-2-IgG levels and neutralizing antibodies among the WBD and CCP, both the groups showed a positive correlation, while neutralizing antibodies showed a significant correlation with SARS-CoV-2-IgG levels among the whole blood donors (Pearson correlation P = 0.000).ConclusionNo significant difference in neutralizing antibody capacity was observed in asymptomatic whole blood donors and convalescent plasma donors. Therefore, donors having adequate levels of SARS-CoV-2-IgG antibody levels on screening can be considered for convalescent plasma donation irrespective of prior COVID-19 diagnosis or COVID-related symptoms.     

Assessment of changes in immune status linked to COVID-19 convalescent and its clinical severity in patients and uninfected exposed relatives

IntroductionThe immune response during and after SARS-CoV-2 infection can be complex and heterogeneous, and it can be affected by the severity of the disease. It can also contribute to an unfavorable evolution and bring about short and long term effects. The aim of this study was to characterize the lymphocyte composition according to the severity of COVID-19, as well as its degree of relationship to the specific humoral response to SARS-CoV-2 in convalescents up to 106 days after the infection and in their exposed relatives.MethodsAn applied research was carried out with a cross-section analytical design, from March 11 to June 11, 2020 in Cuba. The sample consisted of 251 convalescents from COVID-19 over 18 years of age and 88 exposed controls who did not become ill. The B and T cell subpopulations, including memory T cells, as well as the relationship with the humoral immune response against SARS-CoV-2, were identified by flow cytometry and enzyme immunoassay.ResultsConvalescent patients, who evolved with severe forms, showed a decrease in frequency and a greater proportion of individuals with values ??lower than the minimum normal range of B cells, CD3 + CD4 + cells and the CD4 + / CD8 + ratio, as well as a higher frequency and a greater proportion of individuals with values ??above the normal maximum range of CD3 + CD8 + and NK cells. Convalescent patients with severe forms of COVID-19 that exhibited IgG / RBD titers ≥ 1/200 had a lower frequency of TEMRA CD8 + cells (p = 0.0128) and TEMRA CD4 + (p = 0.0068). IgG / RBD titers were positively correlated with the relative frequency of CD4 + CM T memory cells (r = 0.4352, p = 0.0018).ConclusionsThe identified alterations of B and T lymphocytes suggest that convalescent patients with the severe disease could be vulnerable to infectious, autoimmune or autotinflammatory processes; therefore, these individuals need medical follow-up after recovering from the acute disease. Furthermore, the role of T cells CD4 + CM in the production of antibodies against SARS-CoV-2 is confirmed, and it is noted that the defect of memory T cells CD8 + TEMRA could contribute to the development of severe forms of COVID-19.     

Longitudinal neutralizing antibody responses after SARS-CoV-2 infection: A convalescent cohort study in Taiwan

BackgroundUnderstanding the neutralizing antibody (NAb) titer against COVID-19 over time is important to provide information for vaccine implementation. The longitudinal NAb titer over one year after SARS-CoV-2 infection is still unclear. The purposes of this study are to evaluate the duration of the neutralizing NAb titers in COVID-19 convalescents and factors associated with the titer positive duration.MethodsA cohort study followed COVID-19 individuals diagnosed between 2020 and 2021 May 15th from the COVID-19 database from the Taiwan Centers for Disease Control. We analyzed NAb titers from convalescent SARS-CoV-2 individuals. We used generalized estimating equations (GEE) and a Cox regression model to summarize the factors associated with NAb titers against COVID-19 decaying in the vaccine-free population.ResultsA total of 203 convalescent subjects with 297 analytic samples were followed for a period of up to 588 days. Our study suggests that convalescent COVID-19 in individuals after more than a year and four months pertains to only 25% of positive titers. The GEE model indicates that longer follow-up duration was associated with a significantly lower NAb titer. The Cox regression model indicated the disease severity with advanced condition was associated with maintaining NAb titers (adjusted hazard ratio: 2.01, 95% CI: 1.11–3.63) and that smoking was also associated with higher risk of negative NAb titers (adjusted hazard ratio: 0.55, 95% CI: 0.33–0.92).ConclusionsNeutralizing antibody titers diminished after more than a year. The antibody titer response against SARS-CoV-2 in naturally convalescent individuals provides a reference for vaccinations.     

Outbreak of SARS-CoV-2 B.1.617.2 (delta) variant in a nursing home 28 weeks after two doses of mRNA anti-COVID-19 vaccines: evidence of a waning immunity

ObjectivesTo describe a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.617.2 (Delta) variant outbreak among residents (n = 69) and health workers (n = 69) of a small nursing home in northeastern Italy, with full vaccination coverage of 91% and 82%, respectively. Evaluation of the anti-Spike IgG titres 28 weeks after the mRNA vaccine booster dose against SARS-CoV-2 infection and severe coronavirus disease 2019 (COVID-19).Materials and methodsSera were collected within 48 hours from the index case; anti-Spike IgG was determined (expressed as WHO binding antibody units (BAU)/mL) through a commercial quantitative assay; SARS-CoV-2 was diagnosed using RT-PCR, and full-genome sequencing was performed for lineage characterization. Residents were grouped according to anti-Spike IgG titres (≤50, 51–1000 and > 1000 BAU/mL) and the resulting protection against infection and severe disease was measured.ResultsNone of the health workers and 14 of the 59 (24%) residents fully vaccinated and without a previous SARS-CoV-2 infection showed anti-Spike IgG ≤50 BAU/mL (one-sided Fisher exact test, p 0.011). Among these residents, a level of anti-Spike IgG ≤50 BAU/mL resulted in a higher risk of SARS-CoV-2 infection (relative risk 1.55, 95% CI 1.17–2.05) and severe COVID-19 (relative risk 5.33, 95% CI 1.83–15.57).ConclusionLow levels of SARS-CoV-2 neutralizing anti-Spike IgG in serum 28 weeks after the administration of the second dose parallel the waning of vaccine protection.     

B-cell malignancies and COVID-19: a narrative review

BackgroundCOVID-19 has been extensively characterized in immunocompetent hosts and to a lesser extent in immunocompromised populations. Among the latter, patients treated for B-cell malignancies have immunosuppression generated by B-cell lymphodepletion/aplasia resulting in an increased susceptibility to respiratory virus infections and poor response to vaccination. The consequence is that these patients are likely to develop severe or critical COVID-19.ObjectivesTo examine the overall impact of COVID-19 in patients treated for a B-cell malignancy or receiving chimeric antigen receptor T (CAR-T) immunotherapy administered in case of relapsed or refractory disease.SourcesWe searched in the MEDLINE database to identify relevant studies, trials, reviews, or meta-analyses focusing on SARS-CoV-2 vaccination or COVID-19 management in patients treated for a B-cell malignancy or recipients of CAR-T cell therapy up to 8 July 2022.ContentThe epidemiology and outcomes of COVID-19 in patients with B-cell malignancy and CAR-T cell recipients are summarized. Vaccine efficacy in these subgroups is compiled. Considering the successive surges of variants of concern, we propose a critical appraisal of treatment strategies by discussing the use of neutralizing monoclonal antibodies, convalescent plasma therapy, direct-acting antiviral drugs, corticosteroids, and immunomodulators.ImplicationsFor patients with B-cell malignancy, preventive vaccination against SARS-CoV-2 remains essential and the management of COVID-19 includes control of viral replication because of protracted SARS-CoV-2 shedding. Passive immunotherapy (monoclonal neutralizing antibody therapy and convalescent plasma therapy) and direct-active antivirals, such as remdesivir and nirmatrelvir/ritonavir are the best currently available treatments. Real-world data and subgroup analyses in larger trials are warranted to assess COVID-19 therapeutics in B-cell depleted populations.     

Enhanced SARS-CoV-2 IgG durability following COVID-19 mRNA booster vaccination and comparison of BNT162b2 with mRNA-1273

BackgroundBNT162b2 (Pfizer/BioNTech, Comirnaty) and mRNA-1273 (Moderna, Spikevax) are messenger RNA (mRNA) vaccines that elicit antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike receptor-binding domain (S-RBD) and have been approved by the US Food and Drug Administration to combat the coronavirus disease 2019 (COVID-19) pandemic. Because vaccine efficacy and antibody levels waned over time after the 2-shot primary series, the US Food and Drug Administration authorized a booster (third) dose for both mRNA vaccines to adults in the fall of 2021.ObjectiveTo evaluate the magnitude and durability of S-RBD immunoglobulin (Ig)G after the booster mRNA vaccine dose in comparison to the primary series. We also compared S-RBD IgG levels after BNT162b2 and mRNA-1273 boosters and explored effects of age and prior infection.MethodsSurrounding receipt of the second and third homologous mRNA vaccine doses, adults in an employee-based cohort provided serum and completed questionnaires, including information about previous COVID-19 infection. The IgG to S-RBD was measured using an ImmunoCAP-based system. A subset of samples were assayed for IgG to SARS-CoV-2 nucleocapsid by commercial assay.ResultsThere were 228 subjects who had samples collected between 7 and 150 days after their primary series vaccine and 117 subjects who had samples collected in the same time frame after their boost. Antibody levels from 7 to 31 days after the primary series and booster were similar, but S-RBD IgG was more durable over time after the boost, regardless of prior infection status. In addition, mRNA-1273 post-boost antibody levels exceeded BNT162b2 out to 5 months.ConclusionThe COVID-19 mRNA vaccine boosters increase antibody durability, suggesting enhanced long-term clinical protection from SARS-CoV-2 infection compared with the 2-shot regimen.     

Impact of dexamethasone on SARS-CoV-2 concentration kinetics and antibody response in hospitalized COVID-19 patients: results from a prospective observational study

ObjectivesDexamethasone has become the standard of care for severe coronavirus disease 2019 (COVID-19), but its virological impact is poorly understood. The objectives of this work were to characterize the kinetics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) concentration in the upper respiratory tract (URT) and the antibody response in patients with (D⁺) and without (D^–) dexamethasone treatment.MethodsData and biosamples from hospitalized patients with severe COVID-19, enrolled between 4th March and 11th December 2020 in a prospective observational study, were analysed. SARS-CoV-2 virus concentration in serial URT samples was measured using RT-PCR. SARS-CoV-2-specific immunoglobulins A and G (IgA and IgG) were measured in serum samples using S1-ELISA.ResultsWe compared 101 immunocompetent patients who received dexamethasone (according to the inclusion criteria and dosage determined in the RECOVERY trial) to 93 immunocompetent patients with comparable disease severity from the first months of the pandemic, who had not been treated with dexamethasone or other glucocorticoids. We found no inter-group differences in virus concentration kinetics, duration of presence of viral loads >10⁶ viral copies/mL (D⁺ median 17 days (IQR 13–24), D^– 19 days (IQR 13–29)), or time from symptom onset until seroconversion (IgA: D⁺ median 11.5 days (IQR 11–12), D^– 14 days (IQR 11.5–15.75); IgG: D⁺ 13 days (IQR 12–14.5), D^– 12 days (IQR 11–15)).ConclusionDexamethasone does not appear to lead to a change in virus clearance or a delay in antibody response in immunocompetent patients hospitalized with severe COVID-19.     

Evaluation of the correlation between the access SARS-CoV-2 IgM and IgG II antibody tests with the SARS-CoV-2 surrogate virus neutralization test

Fully automated immunoassays for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies that are strongly correlated with neutralization antibodies (nAbs) are clinically important because they enable the assessment of humoral immunity after infection and vaccination. Access SARS-CoV-2 immunoglobulin M (IgM) and immunoglobulin G (IgG) II antibody tests are semi-quantitative, fully automated immunoassays that detect anti-receptor-binding domain (RBD) antibodies and might reflect nAb levels in coronavirus disease 2019 (COVID-19). However, no studies have investigated the clinical utility of these tests in association with nAbs to date. To evaluate the clinical utility of Access SARS-CoV-2 IgM and IgG II antibody tests and their correlation with the SARS-CoV-2 surrogate virus neutralization test (sVNT) that measures nAbs in patients with COVID-19, we analyzed 54 convalescent serum samples from COVID-19 patients and 89 serum samples from non-COVID-19 patients. The presence of anti-RBD antibodies was detected using Access SARS-CoV-2 IgM and IgG II antibody tests, while nAbs were measured by sVNT. The sensitivity and specificity of sVNT were 94.4% and 98.9%, respectively. There were strong positive correlations between the inhibition values of sVNT and the results of the Access SARS-CoV-2 IgM (R = 0.95, R² = 0.90, p < 0.001) and IgG II antibody tests (R = 0.96, R² = 0.92, p < 0.001). In terms of the presence of nAbs, the sensitivity and specificity were 98.1% and 98.9% in the IgM assay and 100.0% and 100.0% in the IgG II assay, respectively. The Access SARS-CoV-2 IgM and IgG II antibody tests showed high sensitivity and specificity for the detection of nAbs in COVID-19 patients and might be alternatives for measuring nAbs.     

Prevalence of SARS-CoV-2 Antibody in 2,935 Healthcare Workers at 6 Major Hospitals,Daegu, Korea

BackgroundIn Korea, the first community outbreak of coronavirus disease 2019 (COVID-19) occurred in Daegu on February 18, 2020. This study was performed to investigate the prevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) antibodies in healthcare workers (HCWs) at 6 major hospitals in Daegu.MethodsBlood specimens of 2,935 HCWs at 6 major hospitals in Daegu from January 2021 to February 2021 were collected. Every specimen was tested for antibody against SARS-CoV-2 using both Elecsys Anti-SARS-CoV-2 electrochemiluminescence immunoassay (Roche Diagnostics, Rotkreuz, Switzerland) and R-FIND COVID-19 IgG/M/A enzyme-linked immunosorbent assay kit (SG medical Inc., Seoul, Korea) as screening tests. If 1 or more of these screening test results was positive, 2 additional antibody tests were performed using Abbott Anti-SARS-CoV-2 IgG assay (Abbott, Abbott Park, IL, USA) and cPass SARS-CoV-2 Neutralization Antibody Detection Kit (GenScript USA Inc., Piscataway, NJ, USA). If 2 or more of the total 4 test results were positive, it was determined as positive for the antibody against SARS-CoV-2.ResultsAccording to the criteria of SARS-CoV-2 antibody positivity determination, 12 subjects were determined as positive. The overall positive rate of the SARS-CoV-2 antibody was 0.41% (12/2,935). Of the 12 subjects determined as positive, 7 were diagnosed with COVID-19, and the remaining 5 were nondiagnosed cases of COVID-19.ConclusionIn early 2021, the overall seroprevalence of SARS-CoV-2 antibody among HCW located in Daegu was 0.41%, and 0.17% excluding COVID-19 confirmed subjects. These results were not particularly high compared with the general public and were much lower than HCWs in other countries.     

Anti-SARS-CoV-2 IgG levels in relation to disease severity of COVID-19

The durability of infection-induced severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity has crucial implications for reinfection and vaccine effectiveness. However, the relationship between coronavirus disease 2019 (COVID-19) severity and long-term anti-SARS-CoV-2 immunoglobulin G (IgG) antibody level is poorly understood. Here, we measured the longevity of SARS-CoV-2-specific IgG antibodies in survivors who had recovered from COVID-19 1 year previously. In a cohort of 473 survivors with varying disease severity (asymptomatic, mild, moderate, or severe), we observed a positive correlation between virus-specific IgG antibody titers and COVID-19 severity. In particular, the highest virus-specific IgG antibody titers were observed in patients with severe COVID-19. By contrast, 74.4% of recovered asymptomatic carriers had negative anti-SARS-CoV-2 IgG test results, while many others had very low virus-specific IgG antibody titers. Our results demonstrate that SARS-CoV-2-specific IgG persistence and titer depend on COVID-19 severity.     

Antibody response against SARS-CoV-2 spike protein and nucleoprotein evaluated by four automated immunoassays and three ELISAs

ObjectivesThe aim was to determine the antibody response against SARS-CoV-2 spike protein and nucleoprotein using four automated immunoassays and three ELISAs for the detection of total Ig antibodies (Roche) or IgG (Abbott, Diasorin, Snibe, Euroimmun, Mikrogen) in COVID-19 patients.MethodsSensitivity and dynamic trend to seropositivity were evaluated in 233 samples from 114 patients with moderate, severe or critical COVID-19 confirmed with PCR on nasopharyngeal swab. Specificity was evaluated in 113 samples collected before January 2020, including 24 samples from patients with non-SARS coronavirus infection.ResultsSensitivity for all assays was 100% (95% confidence interval 83.7–100) 3 weeks after onset of symptoms. Specificity varied between 94.7% (88.7–97.8) and 100% (96.1–100). Calculated at the cut-offs that corresponded to a specificity of 95% and 97.5%, Roche had the highest sensitivity (85.0% (79.8–89.0) and 81.1% (76.6–85.7), p < 0.05 except vs. Abbott). Seroconversion occurred on average 2 days earlier for Roche total Ig anti-N and the three IgG anti-N assays (Abbott, Mikrogen, Euroimmun) than for the two IgG anti-S assays (Diasorin, Euroimmun) (≥50% seroconversion day 9–10 vs. day 11–12 and p < 0.05 for percent seropositive patients day 9–10 to 17–18). There was no significant difference in the IgG antibody time to seroconversion between critical and non-critical patients.DiscussionSeroconversion occurred within 3 weeks after onset of symptoms with all assays and on average 2 days earlier for assays detecting IgG or total Ig anti-N than for IgG anti-S. The specificity of assays detecting anti-N was comparable to anti-S and excellent in a challenging control population.     

Immunological imprint of COVID-19 on human peripheral blood leukocyte populations

Background

SARS-CoV-2 has triggered a pandemic that is now claiming many lives. Several studies have investigated cellular immune responses in COVID-19-infected patients during disease but little is known regarding a possible protracted impact of COVID-19 on the adaptive and innate immune system in COVID-19 convalescent patients.

Methods

We used multiparametric flow cytometry to analyze whole peripheral blood samples and determined SARS-CoV-2-specific antibody levels against the S-protein, its RBD-subunit, and viral nucleocapsid in a cohort of COVID-19 convalescent patients who had mild disease ~10 weeks after infection (n = 109) and healthy control subjects (n = 98). Furthermore, we correlated immunological changes with clinical and demographic parameters.

Results

Even ten weeks after disease COVID-19 convalescent patients had fewer neutrophils, while their cytotoxic CD8⁺ T cells were activated, reflected as higher HLA-DR and CD38 expression. Multiparametric regression analyses showed that in COVID-19-infected patients both CD3⁺CD4⁺ and CD3⁺CD8⁺ effector memory cells were higher, while CD25⁺Foxp3⁺ T regulatory cells were lower. In addition, both transitional B cell and plasmablast levels were significantly elevated in COVID-19-infected patients. Fever (duration, level) correlated with numbers of central memory CD4⁺ T cells and anti-S and anti-RBD, but not anti-NC antibody levels. Moreover, a “young immunological age” as determined by numbers of CD3⁺CD45RA⁺CD62L⁺CD31⁺ recent thymic emigrants was associated with a loss of sense of taste and/or smell.

Conclusion

Acute SARS-CoV-2 infection leaves protracted beneficial (ie, activation of T cells) and potentially harmful (ie, reduction of neutrophils) imprints in the cellular immune system in addition to induction of specific antibody responses.

     

Multicenter evaluation of four immunoassays for the performance of early diagnosis of COVID-19 and assessment of antibody responses of patients with pneumonia in Taiwan

Background/purposeOur study goals were to evaluate the diagnostic performance of four anti-SARS-CoV-2 antibodies tests and the differences in dynamic immune responses between COVID-19 patients with and without pneumonia.MethodsWe collected 184 serum samples from 70 consecutively qRT-PCR-confirmed COVID-19 patients at four participating hospitals from 23 January 2020 to 30 September 2020. COVID-19 pneumonia was defined as the presence of new pulmonary infiltration. Serum samples were grouped by the duration after symptom onset on a weekly basis for antibody testing and analysis. The four immunoassays: Beckman SARS-CoV-2 IgG/IgM (Beckman Test), Siemens (ADVIA Centaur®) SARS-CoV-2 Total (COV2T) (Siemens Test), SBC COVID-19 IgG ELISA (SBC Test) and EliA SARS-CoV-2-Sp1 IgG/IgM/IgA P2 Research (EliA Test) were used for detecting the SARS-CoV-2 specific antibodies.ResultsThe sensitivity of all tests reached 100% after 42 days of symptom onset. Siemens Test, the only test detecting total anti-SARS-CoV-2 antibodies, had the best performance in the early diagnosis of COVID-19 infection (day 0–7: 77%; day 8–14: 95%) compared to the other 3 serological tests. All tests showed 100% specificity except SBC Test (98%). COVID-19 patients with pneumonia had significantly higher testing signal values than patients without pneumonia (all p values < 0.05, except EliA IgM Test). However, Siemens Test and SBC Test had highest probability in early prediction of the presence of COVID-19 pneumonia.ConclusionChronological analysis of immune response among COVID-19 patients with different serological tests provides important information in the early diagnosis of SARS-CoV-2 infection and prediction of the risk of pneumonia after infection.     

Long term SARS-CoV-2-specific cellular immunity after COVID-19 in liver transplant recipients

PurposeLong-term immunity after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in immunosuppressed patients is not well characterized. We aimed to explore the long-term natural immunity against SARS-CoV-2 in liver transplant (LT) recipients compared to the non-transplanted population (control group).MethodsFifteen LT recipients and 15 controls matched according to variables associated with disease severity were included at 12 months following the coronavirus disease 2019 (COVID-19) onset. Peripheral blood mononuclear cells were stimulated with peptide pools covering spike (S), nucleocapside (N), and membrane (M) proteins. Reactive CD4+ and CD8+ T cells were identified using flow cytometry, and cytokine production was evaluated in the culture supernatants using cytometric bead array. Serum anti-N and anti-S IgG antibodies were detected with chemiluminescence.ResultsThe percentage of patients with a positive response in both CD4+ and CD8+ T cells against each viral protein and IL2, IL10, TNF-α, and IFN-γ levels was similar between LT recipients and controls. IFN-γ levels were positively correlated with the percentage of reactive CD4+ (p = 0.022) and CD8+ (p = 0.043) T cells to a mixture of M + N + S peptide pools. The prevalence and levels of anti-N and anti-S IgG antibodies were slightly lower in the LT recipients, but the difference was not statistically significant.ConclusionLT recipients exhibited a similar T cell response compared to non-transplanted individuals one year after COVID-19 diagnosis.     

HLA-E*01:01 + HLA-E*01:01 genotype confers less susceptibility to COVID-19, while HLA-E*01:03 + HLA-E*01:03 genotype is associated with more severe disease

BackgroundHLA-E interaction with inhibitory receptor, NKG2A attenuates NK-mediated cytotoxicity. NKG2A overexpression by SARS-CoV-2 exhausts NK cells function, whereas virus-induced down-regulation of MHC-Ia reduces its derived-leader sequence peptide levels required for proper binding of HLA-E to NKG2A. This leads HLA-E to become more complex with viral antigens and delivers them to CD8⁺ T cells, which facilitates cytolysis of infected cells. Now, the fact that alleles of HLA-E have different levels of expression and affinity for MHC Ia-derived peptide raises the question of whether HLA-E polymorphisms affect susceptibility to COVID-19 or its severity.Methods104 COVID-19 convalescent plasma donors with/without history of hospitalization and 18 blood donors with asymptomatic COVID-19, all were positive for anti-SARS-CoV-2 IgG antibody as well as a group of healthy control including 68 blood donors with negative antibody were subjected to HLA-E genotyping. As a privilege, individuals hadn’t been vaccinated against COVID-19 and therefore naturally exposed to the SARS-CoV-2.ResultsThe absence of HLA-E*01:03 allele significantly decreases the odds of susceptibility to SARS-CoV-2 infection [p = 0.044; OR (95 %CI) = 0.530 (0.286 – 0.983)], suggesting that HLA-E*01:01 + HLA-E*01:01 genotype favors more protection against SARS-CoV-2 infection. HLA-E*01:03 + HLA-E*01:03 genotype was also significantly associated with more severe COVID-19 [p = 0.020; 2.606 (1.163 – 5.844)ConclusionHere, our observation about lower susceptibility of HLA-E*01:01 + HLA-E*01:01 genotype to COVID-19 could be clinical evidence in support of some previous studies suggesting that the lower affinity of HLA-E*01:01 to peptides derived from the leader sequence of MHC class Ia may instead shift its binding to virus-derived peptides, which then facilitates target recognition by restricted conventional CD8⁺ T cells and leads to efficient cytolysis. On the other hand, according to other studies, less reactivity of HLA-E*01:01 with NKG2A abrogates NK cells or T cells inhibition, which may also lead to a greater cytotoxicity against SARS-CoV-2 infected cells compared to HLA-E*01:03. Taken together given HLA-E polymorphisms, the data presented here may be useful in identifying more vulnerable individuals to COVID-19 for better care and management. Especially since along with other risk factors in patients, having HLA-E*01:03 + HLA-E*01:03 genotype may also be associated with the possibility of severe cases of the disease.