T-cell-specific response in people with multiple sclerosis on disease-modifying therapies by flow cytometry: focus on latent infections and vaccinations

Multiple sclerosis (MS) is an immune-mediated disease of the central nervous system (CNS), with a heterogeneous clinical course of the disease. Disease-modifying therapies (DMTs) have been approved for the treatment of MS, with beneficial effects on the prognosis, annual relapse rates, and quality of life in people with MS (pwMS). However, DMTs act at various levels of the immune system, increasing the risk of herpesvirus reactivations, such as Epstein-Barr virus (EBV), cytomegalovirus (CMV) and varicella-zoster virus (VZV), as well as affecting the development of humoral and cellular responses to vaccination. In this context, the aim of this study was to perform an in vitro characterization of humoral and T-cell-specific responses to EBV, CMV and VZV in pwMS under DMTs. Moreover, the immunogenicity of both anti-SARS-CoV-2 and recombinant VZV vaccines was investigated. At the Neuroinfectious Unit of the Policlinico Umberto I, Sapienza University of Rome, pwMS were enrolled as part of the infectious risk assessment routinely performed before and during DMTs. Healthy donors (HD) were enrolled as a control group. An evaluation of the humoral response was performed assessing anti-EBV viral capsid antigen (VCA), anti-EBV Epstein-Barr nuclear antigen (EBNA), anti-CMV, anti-VZV and anti-Spike antibody titers. Moreover, the T-cell-specific responses to EBV, CMV, VZV and SARS-CoV-2 were conducted upon overnight stimulation with specific peptides. Intracellular cytokine production of IFNγ, IL2 and TNFα by CD4+ and CD8+ T-cell was evaluated, and T-cells were identified as responding T-cell, those secreting at least one cytokine of interest, and triple-positive T-cells, those secreting all three cytokines simultaneously. A total of 87 pwMS were enrolled in the study. In examining the latent herpesviruses, no differences were identified in either the humoral or T-cell-specific 3 responses between pwMS and HD, as well as among pwMS subgroups. However, the polyfunctional T-cell profile exhibited variability among pathogens, with a more polyfunctional T-cell response observed in response to CMV and EBV. Additionally, given the capacity of CMV to modulate the immune response and to its propensity to influence EBV infection, an evaluation of herpesviruses’ humoral and specific T-cell responses was conducted, stratifying pwMS according to CMV seropositivity. The VZV-specific response appeared to be uninfluenced by CMV co-infection, whereas the EBV-specific response resulted in quantitative inferiority but qualitative superiority in individuals who were negative for CMV. Furthermore, due to their influence on lymphocyte distribution, DMTs may alter immune response to vaccinations. The evaluation of both the humoral and the T-cell-specific response to the anti-SARS-CoV-2 and recombinant VZV vaccination was performed. Despite the robust humoral response observed, DMTs have been demonstrated to affect the T-cell response in pwMS, resulting in a qualitative decline and lower response in those patients on B-cell and T-cell depleting and sequestering drugs. In conclusion, due to the immunosuppressive and/or immunomodulating nature of DMTs, there is an increased risk of viral reactivation in pwMS. Moreover, they may impact on the development of both the humoral and the T-cell-specific responses to vaccination. Although these premises, pwMS appear to exhibit robust T-cell responses to CMV and EBV. However, the EBV-specific response seems to be influenced by CMV co-infection. Finally, a robust humoral response to both vaccinations was observed. However, DMTs may affect the T-cell response in pwMS, resulting in a qualitative inferior and lower response in those patients under B-cell and T-cell depleting and sequestering drugs.