Multiple Sclerosis (MS) is a progressive, disabling, neurological illness that
affects the brain and spinal cord. Nerve cells, which are usually surrounded by
oligodendrocyte myelin, are damaged, die and won’t be replaced when the
Central Nervous System (CNS) is inflamed. As a consequence, progressive loss of
the lipid rich myelin sheath surrounding axons result in disrupted, lower fidelity
action potentials and slow signal conduction. MS is thought to have a number of causes, however, none has been identified as the true causative agent. MS is the most common neurological disease in people below 30 and it affects more than 1 million young adults worldwide. It is five times more common in
temperate climates than in tropical areas and women are affected twice as often
as men are. Scientists suspect that MS develops because of the influence of genes
acting together. However, a common belief held by many scientists is that not
only the genetic influences, but also environmental influences, especially those of
viral infections, which trigger the disease.
This review considers the evidence in existence implicating viral responsibility in
the onset of myelination disorders.
Table of Contents
1. INTRODUCTION
1.1 MYELIN
1.2 CLINICAL ASPECTS
1.2.1 Multiple Sclerosis
1.2.2. Acute Disseminated Encephalomyelitis
2. THE PROCESS OF MYELINATION IN THE NERVOUS SYSTEM
2.1. THE FOUR STAGES OF SCHWANN CELL DEVELOPMENT
2.1.2. The mature myelinating Schwann cell
2.2. MYELINATION BY SCHWANN CELLS
2.3. FROM PRECURSOR CELL TO OLIGODENDROCYTE
2.4. MYELINATION BY OLIGODENDROCYTES
2.4.1. Definition
2.4.2. The process of myelination
3. THE ACTION POTENTIAL
3.1. THE AXON
3.2. GENERATION OF AN ACTION POTENTIAL IN HEALTH
3.3. THE ROLE OF MYELIN IN THE CONDUCTION OF THE ACTION POTENTIAL
3.4. UNMYELINATED AXONS
3.5. THE GENERATION OF ACTION POTENTIAL IN DISEASE
4. MULTIPLE SCLEROSIS: WHAT WE KNOW
4.1. A POSSIBLE MECHANISM OF THE AUTOIMMUNE REACTION
4.2. FACTORS INVOLVED IN THE DEVELOPMENT OF MS
4.2.1. Genetic factors
4.2.3. Environment
5. IS MULTIPLE SCLEROSIS LINKED TO VIRAL INFECTION?
5.1. THE VIRAL PATHWAYS
5.1.1. Viral entry into the cell
5.2.1. Viral entry into the CNS
5.2. THE MECHANISMS CAUSING DAMAGE
5.3. MS AND THE HUMAN HERPES VIRUS 6
5.4. MS AND THE EPSTEIN-BARR VIRUS
5.5. EVIDENCE FOR A VIRAL INDUCTION OF MS
6. ACUTE DISSEMINATED ENCEPHALOMYELITIS: A DISEASE OF ITS OWN OR A VARIANT OF MS?
6.1. OLIGODENDROCYTE PATHOLOGY IN MYELINATION DISORDERS
6.2. AXONAL DEATH
7. ANIMAL MODELS OF DEMYELINATING DISEASES
7.1. MOUSE HEPATITIS VIRUS
7.2. THEILER’S MURINE ENCEPHALOMYELITIS VIRUS
7.2.1. The time course of the TMEV infection
7.3. EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS
8. FUTURE RESEARCH
8.1. RESEARCH DIRECTED AT ROLE OF IMMUNE SYSTEM IN MS
8.2. ETIOLOGY OF MS
8.2.1. Immunologic
8.2.2. Environmental:
8.2.3. Infectious agents
8.2.4. Genetic:
8.3. THE FUTURE OF MYELIN REPAIR
9. SUMMARY
Objectives and Scope
The primary objective of this review is to examine the potential viral triggers of central nervous system (CNS) demyelinating disorders, with a specific focus on Multiple Sclerosis (MS) and Acute Disseminated Encephalomyelitis (ADEM). The research aims to clarify the cellular and molecular mechanisms of demyelination and evaluate current scientific evidence linking viral infections to these autoimmune-like conditions.
- Cellular and molecular basis of myelination and action potential conduction.
- Pathophysiology of MS and ADEM as inflammatory, demyelinating diseases.
- Role of environmental and genetic factors in the etiology of MS.
- Analysis of specific viral candidates (EBV and HHV6) and molecular mimicry.
- Evaluation of animal models used in demyelination research.
Excerpt from the Book
1.1 What is Myelin?
Myelin is a high resistance specialised wrapping that insulates the axons of neurons, enabling the quick conduction and improved fidelity of electrical signals in the nervous system. Its task is the same in the CNS as in the PNS. Myelin consists mostly of lipids, such as cholesterol and phospholipids and proteins, as the Myelin Basic Protein (MBP), the myelin Proteolipid Protein (PLP) and the Peripheral Myelin Protein (PMP22). Myelin possesses its insulating properties through its lipid richness, structure, thickness and its low H2O content, which is about 40% by volume.
Depending on the type of the nerves, the extent of myelination varies, with motor and sensory nerves in the PNS being the most heavily myelinated and sympathetic nerves are unmyelinated.
Summary of Chapters
1. INTRODUCTION: Outlines the cellular and molecular changes accompanying myelin deficit disorders and defines key terms like demyelination and dysmyelination.
2. THE PROCESS OF MYELINATION IN THE NERVOUS SYSTEM: Details the developmental stages of Schwann cells and the mechanisms of myelination by oligodendrocytes.
3. THE ACTION POTENTIAL: Explains the generation of electrical signals in neurons and the critical role of myelin in saltatory conduction.
4. MULTIPLE SCLEROSIS: WHAT WE KNOW: Discusses the autoimmune nature of MS, genetic predispositions, and potential environmental influences.
5. IS MULTIPLE SCLEROSIS LINKED TO VIRAL INFECTION?: Investigates the hypothesis of viral triggers, focusing on pathways of entry and mechanisms like molecular mimicry.
6. ACUTE DISSEMINATED ENCEPHALOMYELITIS: A DISEASE OF ITS OWN OR A VARIANT OF MS?: Compares ADEM with MS and analyzes oligodendrocyte pathology and axonal death.
7. ANIMAL MODELS OF DEMYELINATING DISEASES: Evaluates the use of viruses like MHV and TMEV, and models like EAE, to study human disease.
8. FUTURE RESEARCH: Explores current research directions regarding the immune system, etiology, and the future of regenerative myelin repair therapies.
9. SUMMARY: Concludes that while viruses like EBV and HHV6 are significant candidates in MS etiology, they likely act in concert with genetic and environmental factors.
Keywords
Multiple Sclerosis, MS, Acute Disseminated Encephalomyelitis, ADEM, Myelin, Oligodendrocytes, Schwann Cells, Viral Infection, Epstein-Barr Virus, EBV, Human Herpes Virus 6, HHV6, Molecular Mimicry, Autoimmunity, EAE.
Frequently Asked Questions
What is the core focus of this scientific report?
This report examines the potential link between viral infections and severe demyelinating disorders of the central nervous system, particularly focusing on how Multiple Sclerosis and ADEM develop.
Which neurological diseases are primarily discussed?
The work focuses on Multiple Sclerosis (MS) and Acute Disseminated Encephalomyelitis (ADEM), providing detailed comparisons of their clinical and pathological characteristics.
What is the primary hypothesis regarding viral involvement?
The report investigates the hypothesis that viral infections may trigger these demyelinating diseases, possibly through the mechanism of molecular mimicry or by inducing an unregulated autoimmune response.
What methodology is used to arrive at these conclusions?
The research relies on a comprehensive review of existing clinical data, studies on environmental and genetic factors, and an evaluation of various animal models of demyelination.
How is the myelin process structured in the report?
It provides an in-depth breakdown of myelination in the peripheral nervous system (via Schwann cells) and the central nervous system (via oligodendrocytes), establishing a baseline for understanding how these processes fail.
Which keywords best capture the scope of this research?
Key terms include Multiple Sclerosis, Myelin, Viral Infection, Molecular Mimicry, Autoimmunity, Oligodendrocytes, and EAE.
Does the report conclude that a specific virus causes MS?
No, the report concludes that while agents like EBV and HHV6 are heavily implicated through molecular mimicry, it remains unclear if they are sole causative agents or if they function as triggers in genetically susceptible hosts.
What role do animal models play in the research presented?
Animal models such as the Mouse Hepatitis Virus and Experimental Autoimmune Encephalomyelitis are used to simulate human disease processes, allowing researchers to study demyelination and potential therapies in vivo.
- Arbeit zitieren
- Jihane Minh-Châu Belkoura (Autor:in), 2004, Do viral infections trigger severe demyelinating disorders of the Central Nervous System? An assessment with a special focus on Multiple Sclerosis and Acute Disseminated encephalomyelitis, München, GRIN Verlag, https://www.hausarbeiten.de/document/27494
