Omicron infection-associated T- and B-cell immunity in antigen-naive and triple-COVID-19-vaccinated individuals

Comparative analysis of eleven SARS-CoV-2 immunoassays and neutralisation data: time to enhance standardisation and correlation of protection

BACKGROUND

To infer a reliable SARS-CoV-2 antibody protection level from a serological test, an appropriate quantitative threshold and solid equivalence across serological tests are needed. Additionally, tests should show a solid correlation with neutralising assays and with the protection observed in large population cohorts even against emerging variants.

OBJECTIVES

We studied convalescent and vaccinated populations using 11 commercial antibody assays. Results were compared to evaluate discrepancies across tests. Neutralisation capacity was measured in a subset of the samples with a lentiviral-based assay.

METHODS

Serum from convalescent (n = 121) and vaccinated individuals (n = 471, 260 with Comirnaty, 110 with Spikevax, and 96 with Vaxzevria) was assessed using 11 different assays, including two from Abbott, Euroimmun, Liaison, Roche, and Vircell, and one from Siemens. A spike protein-lentiviral vector with a fluorescent reporter was used for neutralisation assay of serum from convalescent (n = 26) and vaccinated (n = 39) individuals.

RESULTS

Positivity ranged between 81.3 and 94.3% after infection and 99.4 and 99.7% after vaccination, depending on the assay. Both cohorts showed a high level of qualitative agreement across tests (Fleiss' kappa = 0.598 and 0.719 for convalescent and vaccinated respectively). Spikevax vaccine recipients showed the highest level of antibodies in all tests. Effectiveness of each test predicting SARS-CoV-2 neutralising capacity depended on assay type and target, with CLIA and anti-S being more effective than ELISA and anti-N assays, respectively.

CONCLUSIONS

High-throughput immunoassays are good predictors of neutralising capacity. Updated targets and better standardisation would be required to find an effective correlate of protection, especially to account for antibodies against new variants.

The Effect of Exposure to SARS-CoV-2 Vaccination and Infection on Humoral and Cellular Immunity in a Cohort of Patients with Immune-Mediated Diseases: A Pilot Study

Immunization against COVID-19 is needed in patients with immune-mediated inflammatory diseases (IMIDs). However, data on long-term immunity kinetics remain scarce. This study aimed to compare the humoral and cellular response to COVID-19 in patients with immune-mediated inflammatory diseases (IMIDs) compared to healthy controls. We compared the humoral and cellular response to SARS-Cov-2 elicited by vaccination and/or infection in a prospective cohort of 20 IMID patients compared with a group of 21 healthcare workers (HCWs). We assessed immunity before and after the third and fourth dose of BNT162b2 or after COVID-19 infection using quantitative IgG anti-SARS-CoV-2 Spike antibody (anti-S-IgG), neutralization assay, and specific interferon-gamma (IFN-g) release assay (IGRA). The responses were compared with those of healthy controls. The two groups were similar in age and total exposure, becoming infected for the first time, mainly after the third dose. Neutralizing antibodies and IGRA were negative in 9.5% of IMID patients but not in any HCWs. No significant difference was found between neutralization titers to BA.1 in the IMID and the HCW groups. The study highlights the SARS-CoV-2 immunological responses in healthy controls and IMID patients, suggesting that the combined stimuli of vaccination and infection in IMID patients could promote a more profound immunological response.

Immune cell populations and induced immune responses at admission in patients hospitalized with vaccine breakthrough SARS-CoV-2 infections

Background

Vaccine breakthrough SARS-CoV-2 infections are common and of clinical and public health concern. However, little is known about the immunological characteristics of patients hospitalized due to these infections. We aimed to investigate and compare immune cell subpopulations and induced immune responses in vaccinated and non-vaccinated patients hospitalized with severe COVID-19.

Methods

A nested case-control study on adults (≥ 18 years) who received at least two doses of a mRNA-COVID-19 vaccine and were hospitalized with SARS-CoV-2 breakthrough infections and severe COVID-19 between January 7, 2021, and February 1, 2022, were eligible for inclusion. Age- and sex-matched non-vaccinated controls were identified. Immunophenotyping was performed using a custom-designed 10-color flow cytometry prefabricated freeze-dried antibody panel (DuraClone, Beckman Coulter (BC), Brea, Calif). TruCulture (Myriad RBM, Austin, USA) was used to assess induced immune response in whole blood, revealing different critical signaling pathways as a proxy for immune function. All samples were obtained within 48 hours of admission.

Results

In total, 20 hospitalized patients with severe COVID-19 and a breakthrough SARS-CoV-2 infection were included, ten vaccinated and ten non-vaccinated patients. Vaccinated patients had lower concentrations of CD19 B cells (p = 0.035), naïve CD4 T cells (p = 0.015), a higher proportion of γδ1 T cells (p = 0.019), and higher unstimulated immune cell release of IL-10 (p = 0.015).

Conclusion

We observed immunological differences between vaccinated and non-vaccinated patients hospitalized due to severe COVID-19 that indicate that vaccinated patients had lower B cell concentrations, lower concentrations of CD4 naïve T cells, a skewed gamma-delta V1/V2 ratio, and an exaggerated IL-10 response at admission. These results could indicate a suboptimal immune response involved in SARS-CoV-2 breakthrough infections that cause severe COVID-19 in vaccinated adults. However, the sample size was small, and further research is needed to confirm these results.

Impact of Exposure to Vaccination and Infection on Cellular and Antibody Response to SARS-CoV-2 in CVID Patients Through COVID-19 Pandemic

PURPOSE

The purpose of this study is to investigate the kinetics of response against SARS-CoV-2 elicited by vaccination and/or breakthrough infection (occurred after 3 doses of BNT162b2) in a cohort CVID patients.

METHODS

We measured humoral and cellular immunity using quantitative anti-spike antibody (anti-S-IgG) and neutralization assay and specific interferon-gamma release assay (IGRA) before and after the third or fourth dose of BNT162b2 and/or after COVID-19.

RESULTS

In CVID, 58.3% seroconverted after 2 doses that increased to 77.8% after 3 doses. Between the second and third dose, there was a decline in humoral compartment that led to titers below the cutoff of 1:10 (MNA90%) in CVID. This was paralleled by a significantly lower proportion (30%) and reduced magnitude of the residual cellular response among CVID. The third dose achieved a lower titer of anti-S and nAb against the Wuhan strain than HC and significantly decreased the rate of those showing solely a positive neutralizing activity and those with simultaneous negativity of IGRA and nAbs; the differences in IGRA were overall reduced with respect to HC. At further sampling after breakthrough SARS-COV-2 infection, mostly in the omicron era, or fourth dose, 6 months after the last event, the residual nAb titer to Wuhan strain was still significantly higher in HC, while there was no significant difference of nAbs to BA.1. The rate of IGRA responders was 65.5% in CVID and 90.5% in HC (p=0.04), while the magnitude of response was similar. None of CVID had double negativity to nAbs and IGRA at the last sampling.

CONCLUSION

This data shows an increase of adaptive immunity in CVID after mRNA vaccination in parallel to boosters, accrual number of exposures and formation of hybrid immunity.