Immunogenicity and safety of mixed COVID-19 vaccine regimens in patients with immune-mediated inflammatory diseases: a single-centre prospective cohort study.

OBJECTIVE: Among persons with immune-mediated inflammatory diseases (IMIDs) who received SARS-CoV-2 vaccines, we compared postvaccine antibody responses and IMID disease activity/states. DESIGN: Single-centre prospective cohort study. SETTING: Specialty ambulatory clinics in central Canada. PARTICIPANTS: People with inflammatory arthritis (n=78; 77% rheumatoid arthritis), systemic autoimmune rheumatic diseases (n=84; 57% lupus), inflammatory bowel disease (n=93; 43% Crohn's) and multiple sclerosis (n=72; 71% relapsing-remitting) (female 79.4%, white 84.7%, mean (SD) age 56.0 (14.3) years) received COVID-19 vaccinations between March 2021 and September 2022. PRIMARY OUTCOME: Postvaccination anti-spike, anti-receptor binding domain (anti-RBD) and anti-nucleocapsid (anti-NC) IgG antibodies tested by multiplex immunoassays compared across vaccine regimens and with responses in 370 age-matched and sex-matched vaccinated controls. SECONDARY OUTCOMES: COVID-19 infection and self-reported IMID disease activity/state. RESULTS: Most (216/327, 66.1%) received homologous messenger RNA (mRNA) (BNT162b2 or mRNA1273) vaccines, 2.4% received homologous ChAdOx1 and 30.6% received heterologous vaccines (23.9% ChAdOx1/mRNA, 6.4% heterologous mRNA) for their first two vaccines (V1, V2). Seroconversion rates were 52.0% (91/175) for post-V1 anti-spike and 58.9% (103/175) for anti-RBD; 91.5% (214/234) for post-V2 anti-spike and 90.2% (211/234) for anti-RBD; and were lower than controls (post-V2 anti-spike 98.1% (360/370), p<0.0001). Antibody titres decreased 3 months after V2 but increased 1 month after the third vaccine (V3) and 1 month after the fourth vaccine (V4) (BAU/mL median (IQR), anti-spike 1835 (2448) 1 month post-V2, 629.1 (883.4) 3 months post-V2, 4757.5 (7033.1) 1 month post-V3 and 4356.0 (9393.4) 1 month post-V4; anti-RBD 1686.8 (2199.44) 1 month post-V2, 555.8 (809.3) 3 months post-V2, 4280.3 (6380.6) 1 month post-V3 and 4792.2 (11 673.78) 1 month post-V4). If primed with a vector vaccine, an mRNA vaccine increased antibody titres to those comparable to homologous mRNA vaccines. Anti-RBD and anti-spike titres were higher in anti-NC seropositive (n=31; 25 participants) versus seronegative samples (BAU/mL median (IQR) anti-RBD 11 755.3 (20 373.1) vs 1248.0 (53 278.7); anti-spike 11 254.4 (15 352.6) vs 1313.1 (3106.6); both p<0.001). IMID disease activity/state and rates of self-reported moderate or severe IMID flare were similar across vaccinations. CONCLUSION: Heterologous COVID-19 vaccination improves seroconversion rates following a vector vaccine and does not lead to IMID disease flare. IMIDs benefit from at least three vaccines.

Comparative performance data for multiplex SARS-CoV-2 serological assays from a large panel of dried blood spot specimens.

The extent of the COVID-19 pandemic will be better understood through serosurveys and SARS-CoV-2 antibody testing. Dried blood spot (DBS) samples will play a central role in large scale serosurveillance by simplifying biological specimen collection and transportation, especially in Canada. Direct comparative performance data on multiplex SARS-CoV-2 assays resulting from identical DBS samples are currently lacking. In our study, we aimed to provide performance data for the BioPlex 2200 SARS-CoV-2 IgG (Bio-Rad), V-PLEX SARS-CoV-2 Panel 2 IgG (MSD), and Elecsys Anti-SARS-CoV-2 (Roche) commercial assays, as well as for two highly scalable in-house assays (University of Ottawa and Mount Sinai Hospital protocols) to assess their suitability for DBS-based SARS-CoV-2 DBS serosurveillance. These assays were evaluated against identical panels of DBS samples collected from convalescent COVID-19 patients (n = 97) and individuals undergoing routine sexually transmitted and bloodborne infection (STBBI) testing prior to the COVID-19 pandemic (n = 90). Our findings suggest that several assays are suitable for serosurveillance (sensitivity >97% and specificity >98%). In contrast to other reports, we did not observe an improvement in performance using multiple antigen consensus-based rules to establish overall seropositivity. This may be due to our DBS panel which consisted of samples collected from convalescent COVID-19 patients with significant anti-spike, -receptor binding domain (RBD), and -nucleocapsid antibody titers. This study demonstrates that biological specimens collected as DBS coupled with one of several readily available assays are useful for large-scale COVID-19 serosurveillance.

A scalable serology solution for profiling humoral immune responses to SARS-CoV-2 infection and vaccination.

Objectives: Antibody testing against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been instrumental in detecting previous exposures and analyzing vaccine-elicited immune responses. Here, we describe a scalable solution to detect and quantify SARS-CoV-2 antibodies, discriminate between natural infection- and vaccination-induced responses, and assess antibody-mediated inhibition of the spike-angiotensin converting enzyme 2 (ACE2) interaction. Methods: We developed methods and reagents to detect SARS-CoV-2 antibodies by enzyme-linked immunosorbent assay (ELISA). The main assays focus on the parallel detection of immunoglobulin (Ig)Gs against the spike trimer, its receptor binding domain (RBD) and nucleocapsid (N). We automated a surrogate neutralisation (sn)ELISA that measures inhibition of ACE2-spike or -RBD interactions by antibodies. The assays were calibrated to a World Health Organization reference standard. Results: Our single-point IgG-based ELISAs accurately distinguished non-infected and infected individuals. For seroprevalence assessment (in a non-vaccinated cohort), classifying a sample as positive if antibodies were detected for ≥ 2 of the 3 antigens provided the highest specificity. In vaccinated cohorts, increases in anti-spike and -RBD (but not -N) antibodies are observed. We present detailed protocols for serum/plasma or dried blood spots analysis performed manually and on automated platforms. The snELISA can be performed automatically at single points, increasing its scalability. Conclusions: Measuring antibodies to three viral antigens and identify neutralising antibodies capable of disrupting spike-ACE2 interactions in high-throughput enables large-scale analyses of humoral immune responses to SARS-CoV-2 infection and vaccination. The reagents are available to enable scaling up of standardised serological assays, permitting inter-laboratory data comparison and aggregation.

Dried blood spot specimens for SARS-CoV-2 antibody testing: A multi-site, multi-assay comparison.

The true severity of infection due to COVID-19 is under-represented because it is based on only those who are tested. Although nucleic acid amplifications tests (NAAT) are the gold standard for COVID-19 diagnostic testing, serological assays provide better population-level SARS-CoV-2 prevalence estimates. Implementing large sero-surveys present several logistical challenges within Canada due its unique geography including rural and remote communities. Dried blood spot (DBS) sampling is a practical solution but comparative performance data on SARS-CoV-2 serological tests using DBS is currently lacking. Here we present test performance data from a well-characterized SARS-CoV-2 DBS panel sent to laboratories across Canada representing 10 commercial and 2 in-house developed tests for SARS-CoV-2 antibodies. Three commercial assays identified all positive and negative DBS correctly corresponding to a sensitivity, specificity, positive predictive value, and negative predictive value of 100% (95% CI = 72.2, 100). Two in-house assays also performed equally well. In contrast, several commercial assays could not achieve a sensitivity greater than 40% or a negative predictive value greater than 60%. Our findings represent the foundation for future validation studies on DBS specimens that will play a central role in strengthening Canada's public health policy in response to COVID-19.

Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals.

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific against the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS). When exposed to SARS-CoV-2 or a vaccine against SARS-CoV-2, the immune system responds by expressing antibodies at levels that can be detected and monitored to identify the fraction of the population potentially immunized against SARS-CoV-2 and support efforts to deploy a vaccine strategically. A SPR sensor coated with a peptide monolayer and functionalized with various sources of SARS-CoV-2 recombinant proteins expressed in different cell lines detected human anti-SARS-CoV-2 IgG antibodies in clinical samples. Nucleocapsid expressed in different cell lines did not significantly change the sensitivity of the assays, whereas the use of a CHO cell line to express spike ectodomain led to excellent performance. This bioassay was performed on a portable SPR instrument capable of measuring 4 biological samples within 30 minutes of sample/sensor contact and the chip could be regenerated at least 9 times. Multi-site validation was then performed with in-house and commercial ELISA, which revealed excellent cross-correlations with Pearson's coefficients exceeding 0.85 in all cases, for measurements in DBS and plasma. This strategy paves the way to point-of-care and rapid testing for antibodies in the context of viral infection and vaccine efficacy monitoring.