Quantitative Antibody Response Research Articles

A common NFKB1 variant detected through antibody analysis in UK Biobank predicts risk of infection and allergy

Infectious agents contribute significantly to the global burden of diseases through both acute infection and their chronic sequelae. We leveraged the UK Biobank to identify genetic loci that influence humoral immune response to multiple infections. From 45 genome-wide association studies in 9,611 participants from UK Biobank, we identified NFKB1 as a locus associated with quantitative antibody responses to multiple pathogens, including those from the herpes, retro-, and polyoma-virus families. An insertion-deletion variant thought to affect NFKB1 expression (rs28362491), was mapped as the likely causal variant and could play a key role in regulation of the immune response. Using 121 infection- and inflammation-related traits in 487,297UK Biobank participants, we show that the deletion allele was associated with an increased risk of infection from diverse pathogens but had a protective effect against allergic disease. We propose that altered expression of NFKB1, as a result of the deletion, modulates hematopoietic pathways and likely impacts cell survival, antibody production, and inflammation. Taken together, we show that disruptions to the tightly regulated immune processes maytip the balance between exacerbated immune responses and allergy, or increased risk of infection and impaired resolution of inflammation.

Exposure factors associated with SARS-CoV-2 seropositivity are not predictive for higher humoral immune responses: A cross-sectional cohort study in the general population

IntroductionHigher antibody levels, in particular antibodies directed against the receptor-binding domain (RBD) of the spike protein, protect against re-infection with SARS-CoV-2. Quantitative antibody response data provide insight into population immunity and are essential for decision-making on booster-vaccination strategies. We aimed to identify predictors for higher antibody responses such as gender, age, experienced COVID-19-compatible symptoms, disease severity and exposure to pre-determined risk factors associated with SARS-CoV-2 seropositivity. Materials and methodsQuantitative anti-S-RBD responses were analysed in seropositive vaccine-naive individuals (n = 1,857) from a study population of 10,001 adults, including healthcare workers (n = 211) and individuals with a known date of a positive PCR (n = 214). Regression models tested associations between age, gender, the period of symptoms, disease severity, pre-identified exposure factors associated with SARS-CoV-2 seropositivity, and anti-S-RBD responses. ResultsSymptoms of more severe disease (fever and/or dyspnoea: OR 2.42 [95%CI 1.76–3.34], and hospital admission: OR 11.41 [95%CI 4.66–27.97]), and a longer interval between COVID-19-compatible symptoms and serum collection (OR 3.17 [95%CI 1.32–7.63]) were predictive for anti-S-RBD levels ≥300 U/mL. Working in healthcare was inversely associated with anti-S-RBD levels ≥300 U/mL (OR 0.51 [95%CI 0.31–0.82]). None of the pre-identified exposure factors associated with SARS-CoV-2 seropositivity could be identified as predictive of higher anti-S-RBD responses. ConclusionNo exposure factors were identified as predictors of higher neutralising antibody responses. Nevertheless, higher neutralising antibody levels in individuals with more severe symptoms suggest better immunological protection against SARS-CoV-2 re-infection. In seroprevalence studies, that mainly include asymptomatic or mildly infected individuals, the determination of quantitative antibody responses may help in the interpretation of population immunity.

Timing and sequence of vaccination against COVID-19 and influenza (TACTIC): a single-blind, placebo-controlled randomized clinical trial.

Novel mRNA-based vaccines have been used to protect against SARS-CoV-2, especially in vulnerable populations who also receive an annual influenza vaccination. The TACTIC study investigated potential immune interference between the mRNA COVID-19 booster vaccine and the quadrivalent influenza vaccine, and determined if concurrent administration would have effects on safety or immunogenicity. TACTIC was a single-blind, placebo-controlled randomized clinical trial conducted at the Radboud University Medical Centre, the Netherlands. Individuals ≥60 years, fully vaccinated against COVID-19 were eligible for participation and randomized into one of four study groups: 1) 0.5ml influenza vaccination Vaxigrip Tetra followed by 0.3ml BNT162b2 COVID-19 booster vaccination 21 days later, (2) COVID-19 booster vaccination followed by influenza vaccination, (3) influenza vaccination concurrent with the COVID-19 booster vaccination, and (4) COVID-19 booster vaccination only (reference group). Primary outcome was the geometric mean concentration (GMC) of IgG against the spike (S)-protein of the SARS-CoV-2 virus, 21 days after booster vaccination. We performed a non-inferiority analysis of concurrent administration compared to booster vaccines alone with a predefined non-inferiority margin of-0.3 on the log10-scale. 154 individuals participated from October, 4, 2021, until November, 5, 2021. Anti-S IgG GMCs for the co-administration and reference group were 1684 BAU/ml and 2435 BAU/ml, respectively. Concurrent vaccination did not meet the criteria for non-inferiority (estimate-0.1791, 95% CI -0.3680 to-0.009831) and antibodies showed significantly lower neutralization capacity compared to the reference group. Reported side-effects were mild and did not differ between study groups. Concurrent administration of both vaccines is safe, but the quantitative and functional antibody responses were marginally lower compared to booster vaccination alone. Lower protection against COVID-19 with concurrent administration of COVID-19 and influenza vaccination cannot be excluded, although additional larger studies would be required to confirm this. EudraCT: 2021-002186-17. The study was supported by the ZonMw COVID-19 Programme.

Reduced serological response to COVID-19 booster vaccine is associated with reduced B cell memory in patients with Inflammatory Bowel Disease; VARIATION (VAriability in Response in IBD AgainsT SARS-COV-2 ImmunisatiON).

Patients with inflammatory bowel disease (IBD) have an attenuated response to initial COVID-19 vaccination. We sought to characterise the impact of IBD and its treatment on responses after third vaccine against SARS-CoV-2. Prospective multicentre observational study of patients with IBD (n=202) and healthy controls (HC, n=92). Serological response to vaccination was assessed by quantification of anti-spike protein (SP) immunoglobulin (Ig)G levels (anti-SPIgG) and in-vitro neutralisation of binding to Angiotensin-Converting-Enzyme (ACE2). Peripheral blood B-cell phenotype populations were assessed by flow cytometry. SARS-CoV-2 antigen specific B-cell responses were assessed in ex-vivo culture. Median anti-SP IgG post-third vaccination in our IBD cohort is significantly lower than HCs (7,862 versus 19,622 AU/mL, p <0.001) as is ACE2 binding inhibition (p <0.001). IBD patients previously infected with COVID-19 (30%) have similar quantitative antibody response as HCs previously infected with COVID-19 (p = 0.12). Lowest anti-SP IgG titres and neutralisation are seen in IBD patients on anti-TNF agents, without prior COVID-19 infection but all IBD patients show attenuated vaccine response compared to HCs. Patients with IBD have reduced memory B-cell populations and attenuated B-cell responses to SARS-CoV-2 antigens if not previously infected with COVID-19 (p = 0.01). Higher anti-TNF drug levels and zinc levels < 65ng/ml are associated with significantly lower serologic response. Patients with IBD have an attenuated response to three doses of SARS-CoV-2 vaccine. Physicians should consider patients with higher anti-TNF drug levels and/or zinc deficiency as potentially at higher risk of attenuated response to vaccination.

BA.1, BA.2 and BA.2.75 variants show comparable replication kinetics, reduced impact on epithelial barrier and elicit cross-neutralizing antibodies.

The Omicron variant of SARS-CoV-2 is capable of infecting unvaccinated, vaccinated and previously-infected individuals due to its ability to evade neutralization by antibodies. With multiple sub-lineages of Omicron emerging in the last 12 months, there is inadequate information on the quantitative antibody response generated upon natural infection with Omicron variant and whether these antibodies offer cross-protection against other sub-lineages of Omicron variant. In this study, we characterized the growth kinetics of Kappa, Delta and Omicron variants of SARS-CoV-2 in Calu-3 cells. Relatively higher amounts infectious virus titers, cytopathic effect and disruption of epithelial barrier functions was observed with Delta variant whereas infection with Omicron sub-lineages led to a more robust induction of interferon pathway, lower level of virus replication and mild effect on epithelial barrier. The replication kinetics of BA.1, BA.2 and BA.2.75 sub-lineages of the Omicron variant were comparable in cell culture and natural infection in a subset of individuals led to a significant increase in binding and neutralizing antibodies to the Delta variant and all the three sub-lineages of Omicron but the level of neutralizing antibodies were lowest against the BA.2.75 variant. Finally, we show that Cu2+, Zn2+ and Fe2+ salts inhibited in vitro RdRp activity but only Cu2+ and Fe2+ inhibited both the Delta and Omicron variants in cell culture. Thus, our results suggest that high levels of interferons induced upon infection with Omicron variant may counter virus replication and spread. Waning neutralizing antibody titers rendered subjects susceptible to infection by Omicron variants and natural Omicron infection elicits neutralizing antibodies that can cross-react with other sub-lineages of Omicron and other variants of concern.

Trimer IgG and neutralising antibody response to COVID-19 mRNA vaccination in individuals with sarcoidosis.

BackgroundIndividuals with sarcoidosis are at higher risk for infection owing to underlying disease pathogenesis and need for immunosuppressive treatment. Current knowledge as to how subjects with sarcoidosis respond to different forms of vaccination is limited. We examined quantitative and functional antibody response to COVID-19 vaccination in infection-naive subjects with and without sarcoidosis.MethodsOur prospective cohort study recruited 14 subjects with biopsy-proven sarcoidosis and 27 age-gender matched controls who underwent a 2-shot series of the BNT162b2 mRNA vaccine at the University of Illinois at Chicago. Baseline, 4-week, and 6-month trimer spike protein IgG and neutralising antibody (nAb) titers were assessed. Correlation and multivariate regression analysis was conducted.ResultsSarcoidosis subjects had a significant increase in short term antibody production to a level comparable to controls, however IgG titers significantly declined back to baseline levels by 6 months. Corresponding neutralising assays revealed robust nAb titers in sarcoidosis subjects that persisted at 6 months. A significant and strong correlation between IgG and nAb titers across all time points was observed in the control group. However within the sarcoidosis group, a significant but weak correlation between antibody levels was found. Overall, IgG levels were poor predictors of nAb titers at short or long term time points.ConclusionsSarcoidosis subjects exhibit nAb induced by the BNT162b2 mRNA SARS-CoV-2 vaccine at levels comparable to controls that persists at 6 months. Trimer IgG levels are poor predictors of nAb in subjects with sarcoidosis. Studies of further antibody immunoglobulins and subtypes warrant investigation.

230.5: Antibody Response and Molecular Graft Surveillance in Kidney Transplant Recipients Following SARS-CoV-2 Vaccination

Introduction: Preliminary studies suggest that kidney transplant recipients (KTRs) show diminished humoral responses to SARS-CoV-2 vaccination. Although reports of allograft rejection around the time of SARS-CoV-2 vaccination have been rare, there is no recommended framework for monitoring for potential vaccine-related allograft injury. Here, we describe an approach for longitudinal assessment of immunogenicity and safety of SARS-COV-2 vaccination in KTRs. Methods: KTRs eligible for SARS-CoV-2 vaccination were identified through medical records, beginning March 12, 2021. Baseline and weekly blood samples were collected for routine assessment, SARS-CoV-2 spike protein antibody titers, dd-cfDNA (AlloSure, CareDx) and gene expression profiling (GEP) (AlloMap, CareDx) for 12 weeks. HLA DSA testing was performed at baseline, 2 weeks after completion of vaccine doses and at week 12. Antibody response was defined as a 10-fold increase in total binding IgG titers. Results: 49 KTRs were identified for analysis. Patient demographics are summarized in Table 1. 10 patients (20.4%) demonstrated a spike antibody response following completion of the vaccine series. Patients with a prior history of COVID-19 were more likely to mount a spike antibody response (n=8, 53.3%) compared to those with no reported history of COVID-19 (n=2, 5.8%). The odds ratio was 18.3 (95% CI 3.2, 105.0, p=0.0005). Median dd-cfDNA levels did not differ between pre- and post-vaccination (0.23% versus 0.21% respectively; Table 2). There was no significant difference between pre- and post-vaccination GEP scores (9.85 versus 10.4 respectively; Table 2). No patients developed clinically significant DSA, eGFR decline or allograft rejection following vaccination. Conclusions: Quantitative antibody responses were strongly associated with a diagnosis of prior SARS-CoV-2 infection. Stability of eGFR, dd-cfDNA, GEP profiles and lack of allosensitization reinforce the safety profile of SARS-CoV-2 vaccination in KTRs. Further studies are needed to better understand immunogenicity in SARS-CoV-2 naïve individuals, including whether cellular responses are protective in the absence of humoral responses.

Performance and validation of an adaptable multiplex assay for detection of serologic response to SARS-CoV-2 infection or vaccination

Measurement of quantitative antibody responses are increasingly important in evaluating the immune response to infection and vaccination. In this study we describe the validation of a quantitative, multiplex serologic assay utilising an electrochemiluminescence platform, which measures IgG against the receptor binding domain (RBD), spike S1 and S2 subunits and nucleocapsid antigens of SARS-CoV-2. The assay displayed a sensitivity ranging from 73 to 91% and specificity from 90 to 96% in detecting previous infection with SARS-CoV-2 depending on antigenic target and time since infection, and this assay highly correlated with commercially available assays. The within-plate coefficient of variation ranged from 3.8–3.9% and the inter-plate coefficient of variation from 11 to 13% for each antigen.

Estimating typhoid incidence from community-based serosurveys: a multicohort study

SummaryBackgroundThe incidence of enteric fever, an invasive bacterial infection caused by typhoidal Salmonellae (Salmonella enterica serovars Typhi and Paratyphi), is largely unknown in regions without blood culture surveillance. The aim of this study was to evaluate whether new diagnostic serological markers for typhoidal Salmonella can reliably estimate population-level incidence.MethodsWe collected longitudinal blood samples from patients with blood culture-confirmed enteric fever enrolled from surveillance studies in Bangladesh, Nepal, Pakistan, and Ghana between 2016 and 2021 and conducted cross-sectional serosurveys in the catchment areas of each surveillance site. We used ELISAs to measure quantitative IgA and IgG antibody responses to hemolysin E and S Typhi lipopolysaccharide. We used Bayesian hierarchical models to fit two-phase power-function decay models to the longitudinal antibody responses among enteric fever cases and used the joint distributions of the peak antibody titres and decay rate to estimate population-level incidence rates from cross-sectional serosurveys.FindingsThe longitudinal antibody kinetics for all antigen-isotypes were similar across countries and did not vary by clinical severity. The seroincidence of typhoidal Salmonella infection among children younger than 5 years ranged between 58·5 per 100 person-years (95% CI 42·1–81·4) in Dhaka, Bangladesh, to 6·6 per 100 person-years (4·3–9·9) in Kavrepalanchok, Nepal, and followed the same rank order as clinical incidence estimates.InterpretationThe approach described here has the potential to expand the geographical scope of typhoidal Salmonella surveillance and generate incidence estimates that are comparable across geographical regions and time.FundingBill & Melinda Gates Foundation.TranslationsFor the Nepali, Bengali and Urdu translations of the abstract see Supplementary Materials section.

Factors affecting the serologic response to SARS-CoV-2 vaccination in patients with solid tumors: A prospective study

ObjectiveTo evaluate the factors affecting seropositivity and antibody levels after SARS-CoV-2 vaccines in patients with cancer because they were excluded from clinical studies of SARS-CoV-2 vaccines. MethodsThis prospective, observational, single-center study included 290 patients with solid tumors followed up in our medical oncology clinic between March 2021 and August 2021. SARS-CoV-2 antibody status was determined before the first dose of vaccine. Fifty-one patients with positive prevaccine baseline antibody tests were excluded from the study, regardless of whether they had previously confirmed SARS-CoV-2 PCR positivity. To determine the quantitative IgG antibody response of the vaccines, blood samples were collected at least 28 days after each dose of vaccine. Quantitative IgG levels against virus spike protein receptor binding domain (RBD) were measured using chemiluminescent enzyme immunoassay (CLIA). Demographic and clinical features affecting seropositivity were analyzed. ResultsOne hundred and fifty-one (69.3%) patients were vaccinated with two doses of CoronaVac followed by one dose of BNT162b2 (Biontech) (group 1). Sixty-seven (30.7%) patients were vaccinated with three doses of BNT162b2 (group 2). The proportion of patients who developed seropositivity was significantly higher in group 2 (78.6% vs. 54.9%, p < 0.012). Antibody response increased significantly after the second dose of vaccine in both groups. Female sex, being younger than 65 years, and chemotherapy status were significantly related to higher anti-SARS-CoV-2 S antibody levels (p = 0.033, p = 0.036, and p = 0.047, respectively). Antibody levels were significantly higher in patients who had previously received chemotherapy than in patients receiving active chemotherapy (p = 0.042). ConclusionsOur study is the first to evaluate basal SARS-CoV-2 IgG levels before the first dose of vaccine and after three doses in patients with solid tumors. The rate of development of seropositivity with two doses of mRNA vaccine was found to be higher than with two doses of inactivated SARS-CoV-2 vaccine. More attention should be paid to preventive measures in addition to vaccination in patients aged over 65 years and men with cancer diagnoses.

Identification of host\u2013pathogen-disease relationships using a scalable multiplex serology platform in UK Biobank

Certain infectious agents are recognised causes of cancer and other chronic diseases. To understand the pathological mechanisms underlying such relationships, here we design a Multiplex Serology platform to measure quantitative antibody responses against 45 antigens from 20 infectious agents including human herpes, hepatitis, polyoma, papilloma, and retroviruses, as well as Chlamydia trachomatis, Helicobacter pylori and Toxoplasma gondii, then assayed a random subset of 9695 UK Biobank participants. We find seroprevalence estimates consistent with those expected from prior literature and confirm multiple associations of antibody responses with sociodemographic characteristics (e.g., lifetime sexual partners with C. trachomatis), HLA genetic variants (rs6927022 with Epstein-Barr virus (EBV) EBNA1 antibodies) and disease outcomes (human papillomavirus-16 seropositivity with cervical intraepithelial neoplasia, and EBV responses with multiple sclerosis). Our accessible dataset is one of the largest incorporating diverse infectious agents in a prospective UK cohort offering opportunities to improve our understanding of host-pathogen-disease relationships with significant clinical and public health implications.

Reduced Serological Response to COVID-19 Vaccines in Patients with IBD is Further Diminished by TNF Inhibitor Therapy; Early Results of the VARIATION study [VAriability in Response in IBD Against SARS-COV-2 ImmunisatiON

Background and AimsEvidence suggests patients with inflammatory bowel disease (IBD) receiving TNF-antagonists have attenuated response to vaccination against COVID-19. We sought to determine the impact of IBD and various medications for treatment of IBD on antibody responses to vaccination against COVID-19.MethodsPatients with IBD (n=270) and healthy controls (HC, n=116) were recruited prospectively and quantitative antibody responses assessed following COVID-19 vaccination. The impact of IBD and medications for treatment of IBD on vaccine response rates was investigated.Results100% of HC seroconverted post-complete vaccination with two vaccine doses. 2% of patients with IBD failed to seroconvert. Median anti-spike protein (SP) immunoglobulin (Ig)G levels post-complete vaccination in our IBD cohort was significantly lower than HC (2,613 AU/mL versus 6,871 AU/mL, p=<0.001). A diagnosis of IBD was independently associated with lower anti-SP IgG levels (β coefficient -0.2, p = 0.001). Use of mRNA vaccines was independently associated with higher anti-SP IgG levels (β coefficient 0.25, p = < 0.001). Patients with IBD receiving TNF-inhibitors had significantly lower anti-SP IgG levels (2,445AU/mL) than IBD patients not receiving TNF-inhibitors (3868AU/mL)(p = < 0.001). Patients with IBD not receiving TNF-inhibitors still showed attenuated responses compared to HC (3868AU/mL versus 8747AU/mL p = 0.001).ConclusionsPatients with IBD have attenuated serological responses to SARS-CoV-2 vaccination. Use of anti-TNF therapy negatively impacts anti-SP IgG levels further. Patients who do not seroconvert post-vaccination are a particularly vulnerable cohort. Impaired responses to vaccination in our study highlight the importance of booster vaccination programmes for patients with IBD.

Dried blood spots as option to monitor the anti-sars-cov-2 antibody response after infection or vaccination

Rationale: Anti-SARS-CoV-2 antibody responses elicited by infection or vaccination vary among individuals and over time. Their knowledge is of particular importance in, amongst others, elite sport. Can dried blood spots serve as a minimally-invasive, low-cost, decentralized tool to monitor the quantitative antibody response and thus represent an alternative to full blood tests? Methods: Cross-validation of dried blood and venous blood samples of 27 individuals post-infection and 96 individuals post-vaccination, longitudinal antibody monitoring of 27 individuals after vaccination using different vaccines and vaccine schedules and detection of seropositive individuals in a cohort of 557 people using self-collected DBS (dried blood spots) and two commercial immunoassays. Findings: Plasma and DBS values were highly correlated allowing for extrapolation of plasma values from DBS using a factor of a least 10 following the presented procedure. Capillary volumetric sampling and self-sampling produced reliable results. After vaccination, participants showed heterogenous antibody responses but a consistent increase after the second dose. DBS allowed for the analysis of a huge sample volume in a timely manner by limited laboratory personnel. Discussion: DBS offer the possibility of infection and vaccination traceability of individuals and cohorts via minimally-invasive self-sampling. This way, they allow to screen and monitor the presence and evolution of anti-SARS-CoV-2 antibodies in a qualitative and quantitative manner. Using two commercial, automated assays enables large-scale and frequent testing, global implementation and comparability of results.

P040 Reduced serological response to COVID-19 vaccines in patients with IBD is further diminished by TNF inhibitor therapy; Early results of the VARIATION study (VAriability in Response in IBD Against SARS-COV-2 ImmunisatiON)

BackgroundPatients with inflammatory bowel disease (IBD) have attenuated responses to current vaccinations. There is a limited body of evidence suggesting patients with IBD receiving TNF antagonists have an attenuated response to vaccination against COVID-19. We sought to determine the impact of IBD and various medications for the treatment of IBD on antibody responses to vaccination against COVID-19.MethodsPatients with IBD (n=270) and healthy controls (HC, n=116) were recruited prospectively and quantitative antibody responses were assessed following 1st and 2nd doses of COVID-19 vaccination. The impact of IBD and medications for treatment of IBD on vaccine response rates was investigated.ResultsAll HC seroconverted post complete vaccination [100%]. A small proportion of patients with IBD failed to seroconvert [2%]. Median IgG spike protein (SP) antibody levels post-complete vaccination in our IBD cohort was significantly lower than HC [2,613 AU/mL versus 6,871 AU/mL, p=<0.001]. A diagnosis of IBD and viral-vector vaccine use were independently associated with lower IgG SP antibody levels. Patients with IBD receiving anti-TNF therapy had significantly lower IgG SP antibody levels [2444.6 AU/mL] than IBD patients not receiving these agents [3867.6 AU/mL]. Patients with IBD not receiving TNF inhibitors still showed attenuated responses compared to HC receiving a similar vaccine [p = < 0.001].[Figure 1]. IgG SP antibody levels in our IBD cohort reduced rapidly during follow up. ConclusionPatients with IBD who do not seroconvert post-vaccination against COVID-19 are a vulnerable cohort. Patient with IBD have attenuated serological responses to SARS-CoV-2 vaccination. Use of anti-TNF therapy further impacts IgG SP antibody levels. Impaired response to vaccination in our study highlights the importance of booster vaccination programmes for patients with IBD.

A new testing platform using fingerstick blood for quantitative antibody response evaluation after SARS-CoV-2 vaccination

ABSTRACT Testing and vaccination have been major components of the strategy for combating the ongoing COVID-19 pandemic. In this study, we have developed a quantitative anti-SARS-CoV-2 spike (S1) IgG antibody assay using a fingerstick dried blood sample. We evaluated the feasibility of using this high-throughput and quantitative anti-SARS-CoV-2 spike (S1) IgG antibody testing assay in vaccinated individuals. Fingerstick blood samples were collected and analyzed from 137 volunteers before and after receiving the Moderna or Pfizer mRNA vaccine. Anti-SARS-CoV-2 S1 IgG antibody could not be detected within the first 7 days after receiving the first vaccine dose, however, the assay reliably detected antibodies from day 14 onwards. In addition, no anti-SARS-CoV-2 nucleocapsid (N) protein IgG antibody was detected in any of the vaccinated or healthy participants, indicating that the anti-SARS-CoV-2 S1 IgG assay is specific for the mRNA vaccine-induced antibodies. The S1 IgG levels detected in fingerstick samples correlated with the levels found in venous blood plasma samples and with the efficacy of venous blood plasma samples in the plaque reduction neutralization test (PRNT). The assay displayed a limit of quantification (LOQ) of 0.59 μg/mL and was found to be linear in the range of 0.51-1000 μg/mL. Finally, its clinical performance displayed a Positive Percent Agreement (PPA) of 100% (95% CI: 0.89-1.00) and a Negative Percent Agreement (NPA) of 100% (95% CI: 0.93-1.00). In summary, the assay described here represents a sensitive, precise, accurate, and simple method for the quantitative detection and monitoring of post-vaccination anti-SARS-CoV-2 spike IgG responses.

Evaluation of Three Anti-SARS-CoV-2 Serologic Immunoassays for Post-Vaccine Response.

BackgroundIn North America, both messenger RNA (mRNA) vaccines, Pfizer-BioNTech BNT162b2, and Moderna mRNA-1273, each utilizing a 2-dose regimen, have started to be administered to individuals.MethodsWe evaluated the quantitative serologic antibody response following administration of either a single dose or both doses of an mRNA severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in a cohort of 98 participants (88 healthcare workers [HCW] and 10 solid organ transplant [SOT] recipients). Antibody levels were compared across 3 immunoassays: Elecsys Anti-SARS-CoV-2 S (Roche Diagnostics), SARS-CoV-2 TrimericS IgG (DiaSorin), and SARS-CoV-2 IgG II Quant (Abbott).ResultsAmong HCW, sensitivity ranged from 100% (Roche), 99% (Abbott) and 98% (DiaSorin). The SARS-CoV-2 IgG II Quant and SARS-CoV-2 TrimericS IgG assays showed good agreement with a Pearson correlation coefficient of R = 0.95. Pearson correlation coefficients of R = 0.82 and 0.83 were obtained for Elecsys Anti-SARS-CoV-2 S vs SARS-CoV-2 TrimericS IgG and SARS-CoV-2 IgG II Quant vs Elecsys Anti-SARS-CoV-2 S, respectively. Significant differences in antibody levels between HCW and SOT recipients were observed. A decrease in antibody levels from time of vaccine administration to blood draw was evident. Among those with a second dose, an increase in antibody levels with increased time between administration of the first and second dose was observed.ConclusionsThe absolute values generated from each of the assay platforms are not interchangeable. Antibody levels differed with increased time between vaccine administration and with increased time between administration of the first and second dose. Further, significant differences in antibody levels between HCW and SOT recipients were observed.

Increases in HPV-16/18 antibody avidity and HPV-specific memory B-cell response in mid-adult aged men post-dose three of the quadrivalent HPV vaccine

Strong quantitative and functional antibody responses to the quadrivalent human papillomavirus (HPV) vaccine were reported in mid-adult aged men, but there are limited data on the avidity of the antibody response and the memory B-cell response following vaccination. Although circulating antibodies induced by vaccination are believed to be the main mediators of protection against infection, evaluation of avidity of antibodies and memory B cell responses are critical for a better understanding of the vaccine immunogenicity mechanisms. Both the modified enzyme-linked immunosorbent assay (ELISA) and the enzyme-linked immunosorbent spot (ELISpot) assay are tools to measure the humoral and cellular immune responses post vaccination to characterize vaccine immunogenicity. The avidity of HPV-16 and HPV-18 specific IgG in the serum of mid-adult aged men (N = 126) who received three quadrivalent HPV vaccine doses was examined using a modified ELISA. HPV-16 memory B-cell responses were assessed via ELISpot at month 0 (prior to vaccination) and 1-month post-dose three of the vaccine (month 7). The quadrivalent vaccine induced an increase in HPV-16 and HPV-18 antibody avidity at month 7. HPV-18 avidity levels moderately correlated with anti-HPV-18 antibody titers, but no association was observed for HPV-16 antibody titers and avidity levels. The HPV-16-specific memory B-cell response was induced following three vaccine doses, however, no association with anti-HPV-16 antibody avidity was observed. Three doses of quadrivalent HPV vaccine increased antibody affinity maturation for HPV-16/18 and increased the frequency of anti-HPV-16 memory B-cells in mid-adult aged men.

Antibody responses to SARS-CoV-2 vaccines in 45,965 adults from the general population of the United Kingdom

We report that in a cohort of 45,965 adults, who were receiving either the ChAdOx1 or the BNT162b2 SARS-CoV-2 vaccines, in those who had no prior infection with SARS-CoV-2, seroconversion rates and quantitative antibody levels after a single dose were lower in older individuals, especially in those aged >60 years. Two vaccine doses achieved high responses across all ages. Antibody levels increased more slowly and to lower levels with a single dose of ChAdOx1 compared with a single dose of BNT162b2, but waned following a single dose of BNT162b2 in older individuals. In descriptive latent class models, we identified four responder subgroups, including a ‘low responder’ group that more commonly consisted of people aged >75 years, males and individuals with long-term health conditions. Given our findings, we propose that available vaccines should be prioritized for those not previously infected and that second doses should be prioritized for individuals aged >60 years. Further data are needed to better understand the extent to which quantitative antibody responses are associated with vaccine-mediated protection.

Quantitative SARS-CoV-2 anti-spike responses to Pfizer–BioNTech and Oxford–AstraZeneca vaccines by previous infection status

ObjectivesWe investigated determinants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) anti-spike IgG responses in healthcare workers (HCWs) following one or two doses of Pfizer–BioNTech or Oxford–AstraZeneca vaccines. MethodsHCWs participating in regular SARS-CoV-2 PCR and antibody testing were invited for serological testing prior to first and second vaccination, and 4 weeks post-vaccination if receiving a 12-week dosing interval. Quantitative post-vaccination anti-spike antibody responses were measured using the Abbott SARS-CoV-2 IgG II Quant assay (detection threshold: ≥50 AU/mL). We used multivariable logistic regression to identify predictors of seropositivity and generalized additive models to track antibody responses over time. Results3570/3610 HCWs (98.9%) were seropositive >14 days post first vaccination and prior to second vaccination: 2706/2720 (99.5%) were seropositive after the Pfizer–BioNTech and 864/890 (97.1%) following the Oxford–AstraZeneca vaccines. Previously infected and younger HCWs were more likely to test seropositive post first vaccination, with no evidence of differences by sex or ethnicity. All 470 HCWs tested >14 days after the second vaccination were seropositive. Quantitative antibody responses were higher after previous infection: median (IQR) >21 days post first Pfizer–BioNTech 14 604 (7644–22 291) AU/mL versus 1028 (564–1985) AU/mL without prior infection (p < 0.001). Oxford–AstraZeneca vaccine recipients had lower readings post first dose than Pfizer–BioNTech recipients, with and without previous infection, 10 095 (5354–17 096) and 435 (203–962) AU/mL respectively (both p < 0.001 versus Pfizer–BioNTech). Antibody responses >21 days post second Pfizer vaccination in those not previously infected, 10 058 (6408–15 582) AU/mL, were similar to those after prior infection followed by one vaccine dose. ConclusionsSARS-CoV-2 vaccination leads to detectable anti-spike antibodies in nearly all adult HCWs. Whether differences in response impact vaccine efficacy needs further study.

Profile of Humoral and Cellular Immune Responses to Single BNT162b2 or ChAdOx1 Vaccine in Residents and Staff Within Residential Care Homes (VIVALDI Study)

Background: Residents of long-term care facilities (LTCF) have experienced high mortality rates from SARS-CoV-2 infection and as such have been prioritized for Covid-19 vaccination. Several countries have implemented an extended interval of up to 12 weeks between first and second vaccine doses to increase population coverage after single administration. Methods: Spike-specific immune responses that were induced following single administration of BNT162b2 or ChAdOx1 were studied in 89 staff and 35 residents within LTCFs. Quantitative antibody and cellular responses were determined as well as antibody inhibition of spike protein-ACE2 binding from viral variants. Results: 20% of staff and 34% of residents were found to have serological evidence of prior SARS-CoV-2 infection and all of these donors demonstrated strong antibody responses that were independent of age. Antibody responses were detectable within 99% and 79% of ‘infection-naive’ staff and residents respectively but were 8.2-fold lower within residents. This effect resulted from slower kinetics of antibody generation within residents which reached levels comparable to staff after only 42 days. In contrast spike-specific cellular responses were equivalent between both groups. Antibody inhibition activity against the B.1.351 and P.1 viral variants of concern was low using serum from ‘infection-naive’ older donors. Prior history of natural infection thus has a marked impact on the magnitude and quality of antibody response after a single Covid-19 vaccine in care home residents. Interpretation: Residents who are infection-naive have delayed antibody responses to the first dose of vaccine and might be considered for an early second vaccine where possible. Funding: UK Government Department of Health and Social CareDeclaration of Interests: LS reports grants from the Department of Health and Social Care during the conduct of the study and is a member of the Social Care Working Group, which reports to the Scientific Advisory Group for Emergencies. AH is a member of the New and Emerging Respiratory Virus Threats Advisory Group at the Department of Health.Ethics Approval Statement: Ethical approval for this study was obtained from the South Central - Hampshire B Research Ethics Committee, REC Ref: 20/SC/023.