Monitoring of Both Humoral and Cellular Immunities Could Early Predict COVID-19 Vaccine Efficacy Against the Different SARS-CoV2 Variants.

Reliable immunoassays are essential to early predict and monitor vaccine efficacy against SARS-CoV-2. The performance of an Interferon Gamma Release Assay (IGRA, QuantiFERON® SARS-CoV-2), and a current anti-spike serological test, compared to a plaque reduction neutralization test (PRNT) taken as gold standard were compared. Eighty vaccinated individuals, whose 16% had a previous history of COVID-19, were included in a longitudinal prospective study and sampled before and two to four weeks after each dose of vaccine. In non-infected patients, 2 doses were required for obtaining both positive IGRA and PRNT assays, while serology was positive after one dose. Each dose of vaccine significantly increased the humoral and cellular response. By contrast, convalescent subjects needed a single dose of vaccine to be positive on all 3 tests. Both IGRA and current serology assay were found predictive of a positive titer of neutralizing antibodies that is correlated with vaccine protection. Patients over 65 or 80 years old had a significantly reduced response. The response tended to be better with the heterologous scheme (vs. homologous) and with the mRNA-1273 vaccine (vs. BNT162b2) in the homologous group, in patients under 55 and under 65 years old, respectively. Finally, decrease intensity or absence of IGRA response and to a less extent of anti-spike serology were also correlated to reinfection which has occurred during the follow up. In conclusion, both IGRA and current anti-spike serology assays could be used at defined thresholds to monitor the vaccine response against SARS-CoV-2 and to simply identify non-responding individuals after a complete vaccination scheme. Two available specific tests (IGRA and anti-spike antibodies) could early assess the vaccine-induced immunity against SARS-CoV-2 at the individual scale, to potentially adapt the vaccination scheme in non-responder patients.

Evaluation of Infliximab and Anti-infliximab LISA-TRACKER Immunoassays for the Therapeutic Drug Monitoring of SB2 Infliximab Biosimilar.

BACKGROUND: SB2, an infliximab (IFX) biosimilar to the reference infliximab (R.I.) product (Remicade), received approval in the European Union for all IFX indications. Many decision algorithms based on the measurement of IFX trough levels and antibodies to infliximab are being increasingly used to optimize IFX treatment. The aim of our study was to evaluate whether the biosimilar SB2 could be efficiently monitored using the LISA-TRACKER IFX and anti-IFX assays developed by Theradiag (Croissy Beaubourg, France). METHODS: Standard curves of R.I. and SB2 were compared, and then accuracy of the LISA-TRACKER IFX assay in detecting the spiked concentration of SB2 was measured. Levels of IFX from SB2 spiked samples and R.I. clinical samples were calculated. Intra-run and inter-run imprecision were also measured with SB2 spiked samples. The ability of polyclonal antibodies directed against R.I. to block the detection of SB2 using the LISA-TRACKER IFX assay and the capacity of SB2 to block the detection of anti-R.I. antibodies using the LISA-TRACKER anti-IFX assay were tested. RESULTS: Twelve patients treated with SB2 including 2 patients with SB2-specific antibodies were measured with the LISA-TRACKER anti-IFX assay. We demonstrated that the LISA-TRACKER assay is suitable for the quantification of SB2 in human serum samples. The percentage of recovery was between 82% and 113%. High intra-run and inter-run imprecisions were obtained with the LISA-TRACKER infliximab assay for the quantification of SB2 (SD ranged from 3.3% to 17.9%). The SB2-blocking capacity of R.I. polyclonal antibodies in spiked samples was demonstrated with inhibition between 80% and 97%. SB2 trough levels and anti-SB2 antibodies have also been confirmed in SB2-treated patients. CONCLUSIONS: LISA-TRACKER IFX and anti-IFX assays are suitable for the monitoring of patients treated with SB2.