Poor immunogenicity upon SARS-CoV-2 mRNA vaccinations in autoimmune SLE patients is associated with pronounced EF-mediated responses and anti-BAFF/Belimumab treatment. (preprint)

Novel mRNA vaccines have resulted in a reduced number of SARS-CoV-2 infections and hospitalizations. Yet, there is a paucity of studies regarding their effectiveness on immunocompromised autoimmune subjects. In this study, we enrolled subjects naive to SARS- CoV-2 infections from two cohorts of healthy donors (HD, n=56) and systemic lupus erythematosus (SLE, n=69). Serological assessments of their circulating antibodies revealed a significant reduction of potency and breadth of neutralization in the SLE group, only partially rescued by a 3rd booster dose. Immunological memory responses in the SLE cohort were characterized by a reduced magnitude of spike-reactive B and T cell responses that were strongly associated with poor seroconversion. Vaccinated SLE subjects were defined by a distinct expansion and persistence of a DN2 spike-reactive memory B cell pool and a contraction of spike-specific memory cTfh cells, contrasting with the sustained germinal center (GC)-driven activity mediated by mRNA vaccination in the healthy population. Among the SLE-associated factors that dampened the vaccine responses, treatment with the monoclonal antibody anti-BAFF/Belimumab (a lupus FDA- approved B cell targeting agent) profoundly affected the vaccine responsiveness by restricting the de novo B cell responses and promoting stronger extra-follicular (EF)-mediated responses that were associated with poor immunogenicity and impaired immunological memory. In summary, this study interrogates antigen-specific responses and characterized the immune cell landscape associated with mRNA vaccination in SLE. The identification of factors associated with reduced vaccine efficacy illustrates the impact of SLE B cell biology on mRNA vaccine responses and provides guidance for the management of boosters and recall vaccinations in SLE patients according to their disease endotype and modality of treatment.

Rapid, High Throughput, Automated Detection Of SARS-Cov-2 Neutralizing Antibodies Against Native-Like Vaccine And Delta Variant Spike Trimers (preprint)

Traditional cellular and live-virus methods for detection of SARS-CoV-2 neutralizing antibodies (nAbs) are labor- and time-intensive, and thus not suited for routine use in the clinical lab to predict vaccine efficacy and natural immune protection. Here, we report the development and validation of a rapid, high throughput method for measuring SARS-CoV-2 nAbs against native-like trimeric spike proteins. This assay uses a blockade of hACE-2 binding (BoAb) approach in an automated digital immunoassay on the Quanterix HD-X platform. BoAb assays using vaccine and delta variant viral strains showed strong correlation with cell-based pseudovirus and live-virus neutralization activity. Importantly, we were able to detect similar patterns of delta variant resistance to neutralization in samples with paired vaccine and delta variant BoAb measurements. Finally, we screened clinical samples from patients with or without evidence of SARS-CoV-2 exposure by a single-dilution screening version of our assays, finding significant nAb activity only in exposed individuals. In principle, these assays offer a rapid, robust, and scalable alternative to time-, skill-, and cost-intensive standard methods for measuring SARS-CoV-2 nAb levels.

Nucleocapsid antigenemia is a marker of acute SARS-CoV-2 infection (preprint)

BackgroundReliable detection of SARS-CoV-2 infection is essential for diagnosis and treatment of disease as well as infection control and prevention during the ongoing COVID-19 pandemic. Existing nucleic acid tests do not reliably distinguish acute from resolved infection, as residual RNA is frequently detected in the absence of replication-competent virus. We hypothesized that viral nucleocapsid in serum or plasma may be a specific biomarker of acute infection that could enhance isolation and treatment strategies at an individualized level. MethodsSamples were obtained from a retrospective serological survey using a convenience sampling method from adult inpatient and outpatient encounters from January through March 2021. Samples were categorized along a timeline of infection (e.g. acute, late presenting, convalescent) based on timing of available SARS-CoV-2 testing and symptomatology. Nucleocapsid was quantified by digital immunoassay on the Quanterix HD-X platform. ResultsIn a large sample of 1860 specimens from 1607 patients, the highest level and frequency of antigenemia were observed in samples obtained during acute SARS-CoV-2 infection. Levels of antigenemia were highest in samples from seronegative individuals and in those with more severe disease. Using ROC analysis, we found that antigenemia exhibited up to 85.8% sensitivity and 98.6% specificity as a biomarker for acute COVID-19. ConclusionsNucleocapsid antigenemia is a sensitive and specific biomarker for acute SARS-CoV-2 infection and may aid in individualized assessment of SARS-CoV-2 infection resolution or persistence, although interpretation is limited by absence of a diagnostic gold standard for active infection.

Quantifying post-vaccination protective anti-SARS-CoV-2 IgG antibodies in blood and saliva with a fully automated, high throughput digital immunoassay (preprint)

Background: Antibodies induced by COVID-19 vaccination have been shown to wane over time. Current tests for assessing virus-neutralizing antibodies are complex and time-intensive. There is a need for a simple diagnostic test that measures levels of protective antibodies to help monitor immunity status. Method: Using a commercially available FDA-authorized semi-quantitative SARS-CoV-2 IgG test, we monitored the duration of the immune response in dried blood microsamples (DBS) and saliva to vaccination by 3 different vaccines across prospective cohorts of 8 COVID-19 naive and 29 COVID-19 recovered individuals over a six-month period. We correlated the results to a binding blockade assay validated to a live virus neutralization assay to validate the test for measurement of protective antibodies. Results: The immune response characteristics between the two mRNA vaccines were similar over the 6-month period in both the COVID-19 naive and recovered cohorts. IgG titers in DBS were generally 3-4 orders of magnitude higher than in saliva, and longitudinal profiles were highly correlated between the two matrices (Rm = 0.80). Median IgG concentrations post-vaccination declined to <10% neutralization capacity with all vaccines by six months. Conclusions: The potential of a simple, fully automated high throughput anti-SARS-CoV-2 IgG test to quantitatively measure protective antibodies in samples collected remotely or at the point of care was demonstrated. The IgG immune response and protective immunity was shown to decline significantly by six months.