Factors Associated With Serological Response to SARS-CoV-2 Vaccination in Patients With Multiple Sclerosis Treated With Rituximab

Abstract

Importance: B-cell-depleting monoclonal antibodies are widely used for treatment of multiple sclerosis but are associated with an impaired response to vaccines.

Objective: To identify factors associated with a favorable vaccine response to tozinameran.

Design, setting, and participants: This prospective cohort study was conducted in a specialized multiple sclerosis clinic at a university hospital from January 21 to December 1, 2021. Of 75 patients evaluated for participation who received a diagnosis of multiple sclerosis with planned or ongoing treatment with rituximab, 69 were included in the study, and data from 67 were analyzed.

Exposures: Sex, age, number of previous rituximab infusions, accumulated dose of rituximab, previous COVID-19 infection, time since last rituximab treatment, CD19+ B-cell count before vaccination, CD4+ T-cell count, and CD8+ T-cell count were considered potential factors associated with the main outcome.

Main outcomes and measures: Serological vaccine responses were measured by quantitation of anti-spike immunoglobulin G (IgG) antibodies, anti-receptor-binding domain (RBD) IgG antibodies, and their neutralizing capacities. Cellular responses to spike protein-derived SARS-CoV-2 peptide pools were assessed by counting interferon gamma spot-forming units in a FluoroSpot assay.

Results: Among 60 patients with ongoing rituximab treatment (49 women [82%]; mean (SD) age, 43 [10] years), the median (range) disease duration was 9 (1-29) years, and the median (range) dose of rituximab was 2750 (500-10 000) mg during a median (range) time of 2.8 (0.5-8.3) years. The median (range) follow-up from the first vaccination dose was 7.3 (4.3-10.0) months. Vaccine responses were determined before vaccination with tozinameran and 6 weeks after vaccination. By using established cutoff values for anti-spike IgG (264 binding antibody units/mL) and anti-RBD IgG (506 binding antibody units/mL), the proportion of patients with a positive response increased with the number of B cells, which was the only factor associated with these outcomes. A cutoff for the B-cell count of at least 40/μL was associated with an optimal serological response. At this cutoff, 26 of 29 patients (90%) had positive test results for anti-spike IgG and 21 of 29 patients (72%) for anti-RBD IgG, and 27 of 29 patients (93%) developed antibodies with greater than 90% inhibition of angiotensin-converting enzyme 2. No factor associated with the cellular response was identified. Depending on the peptide pool, 21 of 25 patients (84%) to 22 of 25 patients (88%) developed a T-cell response with interferon gamma production at the B-cell count cutoff of at least 40/μL.

Conclusions and relevance: This cohort study found that for an optimal vaccine response from tozinameran, rituximab-treated patients with multiple sclerosis may be vaccinated as soon as possible, with rituximab treatment delayed until B-cell counts have reached at least 40/μL. An additional vaccination with tozinameran should be considered at that point.

Figure 1.. Humoral Immune Response to SARS-CoV-2 Proteins After Vaccination With Tozinameran

A, Immunoglobulin G (IgG) response to spike (S), receptor-binding domain (RBD), and nucleocapsid proteins after SARS-CoV-2 vaccination in patients with multiple sclerosis who were receiving rituximab and in anti-CD20–naive patients with multiple sclerosis. Horizontal lines represent median values; closed circles, patients with negative test results for SARS-CoV-2 using a polymerase chain reaction (PCR) test prior to vaccination; open triangles, patients with a positive test result for SARS-CoV-2 using PCR test prior to vaccination; and NS, not statistically significant. B, Correlation between peripheral CD19⁺ B-cell count before vaccination and the level of anti-S IgG antibodies (anti-S) after vaccination. C, Correlation between peripheral CD19⁺ B-cell count before vaccination and the level of anti-RBD antibodies after vaccination. Anti-N represents antinucleocapsid IgG antibodies; BAU, binding antibody units.

Figure 2.. Angiotensin-Converting Enzyme 2 (ACE-2) Neutralizing Capacity of Anti-Spike (Anti-S) and Anti-Receptor-Binding Domain (Anti-RBD) Antibodies After Vaccination with Tozinameran

A, Association of anti-S and anti-RBD antibodies with neutralization of ACE-2, measured as percent inhibition of S–ACE-2 and RBD–ACE-2 binding before and after SARS-CoV-2 vaccination in patients with multiple sclerosis receiving ongoing rituximab treatment and anti-CD20–naive patients with multiple sclerosis. Horizontal lines represent median values; closed circles, patients with negative test results for SARS-CoV-2 using a polymerase chain reaction (PCR) test prior to vaccination; and open triangles, patients with a positive test result for SARS-CoV-2 using PCR test prior to vaccination. B, Correlation between peripheral CD19⁺ B-cell count before vaccination and S–ACE-2 inhibition after vaccination. C, Correlation between peripheral CD19⁺ B-cell count before vaccination and RBD–ACE-2 inhibition after vaccination.

Figure 3.. Cellular Response to SARS-CoV-2–Derived Peptides After Vaccination With Tozinameran

Interferon gamma (IFN-γ) secretion in response to 24-hour stimulation with a positive control (anti-cluster of differentiation 3 antibodies), a commercially available peptide pool containing 100 peptides derived from the spike protein of SARS-CoV-2, or an in-house peptide pool containing 8 validated peptides from the spike protein of SARS-CoV-2. Secretion was quantitated by counting spot-forming units (SFUs) in a FluoroSpot assay. Horizontal lines represent median values; closed circles, patients with negative test results for SARS-CoV-2 using a polymerase chain reaction (PCR) test prior to vaccination; open triangles, patients with positive SARS-CoV-2 test results using PCR test prior to vaccination. NS indicates not statistically significant.