Alterations of Gut Microbiota and the Brain-Immune-Intestine Axis in Patients With Relapsing-Remitting Multiple Sclerosis After Treatment With Oral Cladribine: Protocol for a Prospective Observational Study

The gut-brain-axis one year after treatment with cladribine tablets in patients with relapsing remitting multiple sclerosis: a pilot study

Introduction

Cladribine tablets are an effective treatment for relapsing remitting multiple sclerosis (RRMS). However, almost half of the treated patients are not free of disease activity after two years. The aim of this study was to describe the changes that cladribine tablets effectuate in the gut and oral microbiota and the peripheral immunological profile between responders and non-responders.

Methods

In this pilot study of the multicenter, prospective, observational BIA (Brain-Immune-Intestine Axis) study, we included patients aged 18 to 55 years with RRMS who were scheduled to start treatment with cladribine tablets. We assessed the clinical status and the immunological and microbiological profile prior to the start of the treatment and after three and twelve months. At twelve months, we assessed the response status, based on clinical relapses, radiological activity and disability progression on the Expanded Disability Status Scale.

Results

The first twenty-five patients of the BIA study were included in this analysis. Ten patients (40%) were responders twelve months after treatment. Three months after treatment we found a significant decline of naïve and transitional B cells and memory B cells, and of CD57+ CD56dim NK cells. After twelve months the values recovered to baseline levels, except for the memory B cells. We did not find significant changes of the microbiological profile over time, except for a decline of the phylum Bacteroidetes in the oral samples twelve months after treatment. Baseline values and changes over time did not significantly differ between responders and non-responders. However, several phyla, genera or species (Bacteroidetes, Prevotella, Faecalibacterium prausnitzii) showed a higher relative abundance, and several phyla, genera or species (Proteobacteria, Escherichia coli) had a lower relative abundance in responders compared to non-responders.

Discussion

After treatment with cladribine tablets, we found significant changes in the immunological landscape. Also, the microbiological profile showed several differences in microbes with known anti- or pro-inflammatory properties between responders and non-responders. Overall, we showed that we can measure a treatment effect from cladribine tablets with our analyses. Future research on data from the BIA study, with a larger sample size and extended follow-up, can possibly confirm the reliability of our findings.

Impact of Disease-Modifying Therapies on Gut-Brain Axis in Multiple Sclerosis

Multiple sclerosis is a chronic, autoimmune-mediated, demyelinating disease whose pathogenesis remains to be defined. In past years, in consideration of a constantly growing number of patients diagnosed with multiple sclerosis, the impacts of different environmental factors in the pathogenesis of the disease have been largely studied. Alterations in gut microbiome composition and intestinal barrier permeability have been suggested to play an essential role in the regulation of autoimmunity. Thus, increased efforts are being conducted to demonstrate the complex interplay between gut homeostasis and disease pathogenesis. Numerous results confirm that disease-modifying therapies (DMTs) used for the treatment of MS, in addition to their immunomodulatory effect, could exert an impact on the intestinal microbiota, contributing to the modulation of the immune response itself. However, to date, the direct influence of these treatments on the microbiota is still unclear. This review intends to underline the impact of DMTs on the complex system of the microbiota-gut-brain axis in patients with multiple sclerosis.

Multiple Sclerosis and Microbiome

The composition of microbiota and the gut-brain axis is increasingly considered a factor in the development of various pathological conditions. The etiology of multiple sclerosis (MS), a chronic autoimmune disease affecting the CNS, is complex and interactions within the gut-brain axis may be relevant in the development and the course of MS. In this article, we focus on the relationship between gut microbiota and the pathophysiology of MS. We review the contribution of germ-free mouse studies to our understanding of MS pathology and its implications for treatment strategies to modulate the microbiome in MS. This summary highlights the need for a better understanding of the role of the microbiota in patients’ responses to disease-modifying drugs in MS and disease activity overall.

Immune-microbiome interplay and its implications in neurodegenerative disorders

The neurodegeneration and its related CNS pathologies need an urgent toolbox to minimize the global mental health burden. The neuroimmune system critically regulates the brain maturation and survival of neurons across the nervous system. The chronic manipulated immunological drive can accelerate the neuronal pathology hence promoting the burden of neurodegenerative disorders. The gut is home for trillions of microorganisms having a mutual relationship with the host system. The gut-brain axis is a unique biochemical pathway through which the gut residing microbes connects with the brain cells and regulates various physiological and pathological cascades. The gut microbiota and CNS communicate using a common language that synchronizes the tuning of immune cells. The intestinal gut microbial community has a profound role in the maturation of the immune system as well as the development of the nervous system. We have critically summarised the clinical and preclinical reports from the past a decade emphasising that the significant changes in gut microbiota can enhance the host susceptibility towards neurodegenerative disorders. In this review, we have discussed how the gut microbiota-mediated immune response inclines the host physiology towards neurodegeneration and indicated the gut microbiota as a potential future candidate for the management of neurodegenerative disorders.