Evidence of immune response to BNT162b2 COVID-19 vaccine in systemic lupus erythematosus patients treated with Belimumab

Objectives: To evaluate humoral and cell-mediated response after three doses of BNT162b2 SARS-CoV-2 vaccine in patients with systemic lupus erythematosus (SLE) treated with Belimumab (BLM). Methods: SLE patients were vaccinated with three doses of BNT162b2-mRNA vaccine (two-dose primary vaccination, third booster dose after 6 months). The humoral immune response was assessed one and 6 months after the second dose (T1, T2), and 6 months after the booster dose (T3). Serological assay was performed (The Liaison® SARS-CoV-2 TrimericS IgG chemiluminescent). Spike-specific T-cell response was monitored 6 months after the second vaccine dose and the percentage of cytokines producing T cells was assessed by flow cytometry. Results: Twelve patients [12F; median age 46 years (IQR 8.25); median disease duration 156 months (IQR 188)] were enrolled. At T1, all patients showed seroconversion (median anti-Spike IgG levels 1610 BAU/mL, IQR 1390). At T2--day of the third dose--a significant reduction of median anti-Spike IgG antibodies levels was observed [214 BAU/mL (IQR 94); p = 0.0009]. Anti-Spike IgG were significantly increased at T3, reaching a median value of 1440 BAU/mL (IQR 1316; p = 0.005). Despite declining humoral immunity, almost 60% of patients mounted a virus-specific CD4 + T-cell response 6 months after primary vaccination. Conclusions: BLM does not impair humoral response to primary BNT162b2 SARS-CoV-2 vaccination. During the follow-up, a decline in antibody levels is evident and the third dose is crucial to increase the specific immune response. Finally, we observed a recall T-cell response to the Spike antigen 6 months after the first vaccination cycle.