Immunological pathways dysregulated in COVID-19 largely overlap with multiple sclerosis (MS) pathogenetic mechanisms. In COVID-19 brains, choroid barrier cells and glia limitans release chemokines toward brain parenchyma and promote complement activation, fueling neuroinflammation and neural damage. A similar mechanism is described in MS, where an activated choroid epithelium in response to peripheral inflammation activates pathogenic B and T lymphocytes.
In a study, it has been reported that 20% of COVID-19 patients had myelitis in the context of an Acute Disseminated Encephalomyelitis (ADEM), which involved mostly women. Another study reported in 70% of COVID-19-associated myelitis cases, longitudinally extensive lesions involving >3 spinal cord segments appeared typical. The majority of MS patients developing COVID-19 reported clinical worsening of pre-existing neurological symptoms, and 20–35% developed new MS symptoms.
On the other hand, a “protective” effect of COVID-19 on relapse rate was reported in a retrospective study on 125 relapsing-remitting people with MS. Only 7.14% of MS patients in the COVID-19 group experienced a clinical relapse when compared to 26.09% of the non-COVID-19 group. Thus COVID-19-associated lymphopenia could have a role in containing the proliferative rate of CNS-targeting T clones. There are three pivotal crossroads of MS and COVID-19 immunological substrates. They are the type-1 IFN (IFN-I) response, the TH-17 axis, and the inflammasome pathway.
Furthermore, MS-associated viruses, such as the Epstein-Barr Virus (EBV) and Human Endogenous Retroviruses (HERVs), enhance SARS-CoV-2 virus infectivity and also lead to the relapse and progression of MS. Thus, in conclusion, SARS-CoV-2 infection can trigger both pseudo-relapses and true relapses of MS. Anti-COVID-19 mRNA-based vaccines showed satisfactory levels of safety in MS individuals. Administration of live-attenuated vaccines (such as VZV) should be programmed before starting disease-modifying therapies (DMTs) and avoided during immunosuppression owing to the risk of a productive infection. Conversely, some MS DMTs could be repurposed to manage COVID-19-associated immune dysregulation.
Ref Link: Frontiers
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