Humoral and Cellular Response to Spike of Delta SARS-CoV-2 Variant in Vaccinated Patients With Multiple Sclerosis

Objectives: We assessed vaccination-induced antibody and cellular response against spike from the ancestral strain and from the Delta Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2) variant in patients with Multiple Sclerosis (MS) treated with disease modifying treatments. Methods: We enrolled 47 patients with MS and nine controls (“no MS”) having completed the vaccination schedule within 4–6 months from the first dose. The Interferon (IFN)-γ-response to spike peptides derived from the ancestral and the Delta SARS-CoV-2 was measured by enzyme-linked immunoassay (ELISA). Anti-Receptor Binding Domain (RBD) IgG were also evaluated. Results: No significant differences were found comparing the IFN-γ-specific immune response between MS and “no MS” subjects to the ancestral (P = 0.62) or Delta peptide pools (P = 0.68). Nevertheless, a reduced IFN-γ-specific response to the ancestral or to the Delta pools was observed in subjects taking fingolimod or cladribine compared to subjects treated with ocrelizumab or IFN-β. The antibody response was significantly reduced in patients with MS compared to “no MS” subjects (P = 0.0452) mainly in patients taking ocrelizumab or fingolimod. Conclusions: Cellular responses to Delta SARS-CoV-2 variant remain largely intact in patients with MS. However, the magnitude of these responses depends on the specific therapy.