Evaluation of QuantiFERON SARS-CoV-2 interferon-γ release assay following SARS-CoV-2 infection and vaccination

Humoral and cellular response of two different vaccines against SARS-CoV-2 in a group of healthcare workers: An observational study

On March 13, 2021, Tunisia started a widespread immunization program against SARS-CoV-2 utilizing different vaccinations that had been given emergency approval. Herein, we followed prospectively a cohort of participant who received COVID-19 vaccine (Pfizer BioNTech and Sputnik-Gameleya V). The goal of this follow-up was to define the humoral and cellular immunological profile after immunization by assessing neutralizing antibodies and IFN- γ release. 26 vaccinated health care workers by Pfizer BioNTech (n=12) and Sputnik-Gameleya V (n=14) were enrolled from June to December 2021 in Military hospital of Tunis. All consenting participants were sampled for peripheral blood after three weeks of vaccination. The humoral response was investigated by the titer of anti-SARS-CoV-2 immunoglobulin G (IgG) antibodies to S1 protein. The CD4 and CD8 T cell responses were evaluated by the QuantiFERON® SARS-CoV-2 (Qiagen® Basel, Switzerland). Regardless the type of vaccine, the assessment of humoral and cellular response following vaccination showed a strong involvement of the later with expression of IFN-γ as compared to antibodies secretion. Moreover, we showed that people with past SARS-CoV-2 infection developed high levels of antibodies than those who are not previously infected. However, no significant difference was detected concerning interferon gamma (IFN-γ) expression by CD4 and CD8 T cells in health care worker (HCW) previously infection or not with COVID-19 infection. Analysis of immune response according to the type of vaccine, we found that Pfizer BioNTech induced high level of humoral response (91.66%) followed by Sputnik-Gameleya V (64.28%). However, adenovirus vaccine gave a better cellular response (57.14%) than mRNA vaccine (41.66%). Regarding the immune response following vaccine doses, we revealed a significant increase of neutralizing antibodies and IFN-γ release by T cells in patients fully vaccinated as compared to those who have received just one vaccine. Collectively, our data revealed a similar immune response between Pfizer BioNTech and Sputnik-Gameleya V vaccine with a slight increase of humoral response by mRNA vaccine and cellular response by adenovirus vaccine. It's evident that past SARS-CoV-2 infection was a factor that contributed to the vaccination's increased immunogenicity. However, the administration of full doses of vaccines (Pfizer BioNTech or Sputnik-Gameleya V) induces better humoral and cellular responses detectable even more than three months following vaccination.

Cellular Immunity of SARS-CoV-2 in the Borriana COVID-19 Cohort: A Nested Case-Control Study

Our goal was to determine the cellular immune response (CIR) in a sample of the Borriana COVID-19 cohort (Spain) to identify associated factors and their relationship with infection, reinfection and sequelae. We conducted a nested case-control study using a randomly selected sample of 225 individuals aged 18 and older, including 36 individuals naïve to the SARS-CoV-2 infection and 189 infected patients. We employed flow-cytometry-based immunoassays for intracellular cytokine staining, using Wuhan and BA.2 antigens, and chemiluminescence microparticle immunoassay to detect SARS-CoV-2 antibodies. Logistic regression models were applied. A total of 215 (95.6%) participants exhibited T-cell response (TCR) to at least one antigen. Positive responses of CD4+ and CD8+ T cells were 89.8% and 85.3%, respectively. No difference in CIR was found between naïve and infected patients. Patients who experienced sequelae exhibited a higher CIR than those without. A positive correlation was observed between TCR and anti-spike IgG levels. Factors positively associated with the TCR included blood group A, number of SARS-CoV-2 vaccine doses received, and anti-N IgM; factors inversely related were the time elapsed since the last vaccine dose or infection, and blood group B. These findings contribute valuable insights into the nuanced immune landscape shaped by SARS-CoV-2 infection and vaccination.

Systems vaccinology studies - achievements and future potential

Human immune responses to vaccination are variable both within and between populations. Systems vaccinology, which is the application of multi-omics technologies to vaccine studies, seeks to understand such variation and predict responses to optimise vaccine strategies. Here, we outline new approaches to systems vaccinology, focusing on the incorporation of additional cohorts, endpoints and technologies.

A quest for universal anti-SARS-CoV-2 T cell assay: systematic review, meta-analysis, and experimental validation

Measuring SARS-CoV-2-specific T cell responses is crucial to understanding an individual's immunity to COVID-19. However, high inter- and intra-assay variability make it difficult to define T cells as a correlate of protection against COVID-19. To address this, we performed systematic review and meta-analysis of 495 datasets from 94 original articles evaluating SARS-CoV-2-specific T cell responses using three assays - Activation Induced Marker (AIM), Intracellular Cytokine Staining (ICS), and Enzyme-Linked Immunospot (ELISPOT), and defined each assay's quantitative range. We validated these ranges using samples from 193 SARS-CoV-2-exposed individuals. Although IFNγ ELISPOT was the preferred assay, our experimental validation suggested that it under-represented the SARS-CoV-2-specific T cell repertoire. Our data indicate that a combination of AIM and ICS or FluoroSpot assay would better represent the frequency, polyfunctionality, and compartmentalization of the antigen-specific T cell responses. Taken together, our results contribute to defining the ranges of antigen-specific T cell assays and propose a choice of assay that can be employed to better understand the cellular immune response against viral diseases.

T cell immune memory after covid-19 and vaccination

The T cell memory response is a crucial component of adaptive immunity responsible for limiting or preventing viral reinfection. T cell memory after infection with the SARS-CoV-2 virus or vaccination is broad, and spans multiple viral proteins and epitopes, about 20 in each individual. So far the T cell memory response is long lasting and provides a high level of cross reactivity and hence resistance to viral escape by variants of the SARS-CoV-2 virus, such as the omicron variant. All current vaccine regimens tested produce robust T cell memory responses, and heterologous regimens will probably enhance protective responses through increased breadth. T cell memory could have a major role in protecting against severe covid-19 disease through rapid viral clearance and early presentation of epitopes, and the presence of cross reactive T cells might enhance this protection. T cell memory is likely to provide ongoing protection against admission to hospital and death, and the development of a pan-coronovirus vaccine might future proof against new pandemic strains.

T-Cell Immunity Against Severe Acute Respiratory Syndrome Coronavirus 2 Measured by an Interferon-γ Release Assay Is Strongly Associated With Patient Outcomes in Vaccinated Persons Hospitalized With Delta or Omicron Variants

BACKGROUND

We measured T-cell and antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in vaccinated patients hospitalized for coronavirus disease 2019 (COVID-19) and explored their potential value to predict outcomes.

METHODS

This was a prospective, longitudinal study including vaccinated patients hospitalized with Delta and Omicron SARS-CoV-2 variants. TrimericS-IgG antibodies and SARS-CoV-2 T-cell response were measured using a specific quantitative interferon-γ release assay (IGRA). Primary outcome was all-cause 28-day mortality or need for intensive care unit (ICU) admission. Cox models were used to assess associations with outcomes.

RESULTS

Of 181 individuals, 158 (87.3%) had detectable SARS-CoV-2 antibodies, 92 (50.8%) showed SARS-CoV-2-specific T-cell responses, and 87 (48.1%) had both responses. Patients who died within 28 days or were admitted to ICU were less likely to have both unspecific and specific T-cell responses in IGRA. In adjusted analyses (adjusted hazard ratio [95% confidence interval]), for the entire cohort, having both T-cell and antibody responses at admission (0.16 [.05-.58]) and Omicron variant (0.38 [.17-.87]) reduced the hazard of 28-day mortality or ICU admission, whereas higher Charlson comorbidity index score (1.27 [1.07-1.51]) and lower oxygen saturation to fraction of inspired oxygen ratio (2.36 [1.51-3.67]) increased the risk.

CONCLUSIONS

Preexisting immunity against SARS-CoV-2 is strongly associated with patient outcomes in vaccinated individuals requiring hospital admission for COVID-19. Persons showing both T-cell and antibody responses have the lowest risk of severe outcomes.

Improved Performance of the QuantiFERON-SARS-CoV-2 Assay with the Extended Set

Multiple assays have been developed for the characterization of the functional activation of SARS-CoV-2 specific T-cells. This study was conducted to assess the post-vaccination and post-infection T cell response, as detected by the QuantiFERON-SARS-CoV-2 assay using the combination of three SARS-CoV-2 specific antigens (Ag1, Ag2 and Ag3). An amount of 75 participants with different infection and vaccination backgrounds were recruited for the evaluation of humoral and cellular immune responses. An elevated IFN-γ response in at least one Ag tube was observed in 69.2% of convalescent subjects and 63.9% of vaccinated ones. Interestingly, in a healthy unvaccinated case and three convalescents with negative IgG-RBD, we detected a positive QuantiFERON test after stimulation with Ag3. The majority of the T cell responders reacted simultaneously to the three SARS-CoV-2 specific antigens, and Ag3 demonstrated the highest rate of reactivity. At univariable analysis, the only factor that was associated with an absence of a cellular response was time from blood collection, being less than 30 days (OR:3.5, CI95% [1.15-10.50], p = 0.028). Overall, the inclusion of Ag3 improved the performance of the QuantiFERON-SARS-CoV-2 and showed a particular interest among subjects who fail to achieve a measurable antibody response after infection or vaccination.

Comparative analysis between STANDARD-E Covi-FERON ELISA with pre-existing IFN-γ release assays and determination of the optimum cutoff value for assessment of T-Cell response to SARS-CoV-2

BACKGROUND

Interferon-gamma (IFN-γ) release assays (IGRAs) are useful for the assessment of the T-cell response to severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). We aimed to assess the performance of the newly developed IGRA ELISA test compared to the pre-existing assays and to validate the cutoff value in real-world conditions.

METHODS

We enrolled 219 participants and assessed agreement between STANDARD-E Covi-FERON ELISA with Quanti-FERON SARS-CoV-2 (QFN SARS-CoV-2), as well as with T SPOT Discovery SARS-CoV-2 based on Cohen's kappa-index. We further determined the optimal cutoff value for the Covi-FERON ELISA according to the immune response to vaccinations or infections.

RESULTS

We found a moderate agreement between Covi-FERON ELISA and QFN SARS-CoV-2 before vaccination (kappa-index = 0.71), whereas a weak agreement after the first (kappa-index = 0.40) and second vaccinations (kappa-index = 0.46). However, the analysis between Covi-FERON ELISA and T SPOT assay demonstrated a strong agreement (kappa-index >0.7). The cut-off value of the OS (original spike) marker was 0.759 IU/mL with a sensitivity of 96.3% and specificity of 78.7%, and that of the variant spike (VS) marker was 0.663 IU/mL with a sensitivity and specificity of 77.8% and 80.6%, respectively.

CONCLUSION

The newly determined cut-off value may provide an optimum value to minimize and prevent the occurrence of false-negative or false-positive during the assessment of T-cell immune response using Covi-FERON ELISA under real-world conditions.