Chlamydia pneumoniae and its proposed link to multiple sclerosis: to be or not to be?

An Overview of Peptide-Based Molecules as Potential Drug Candidates for Multiple Sclerosis

Multiple sclerosis (MS) belongs to demyelinating diseases, which are progressive and highly debilitating pathologies that imply a high burden both on individual patients and on society. Currently, several treatment strategies differ in the route of administration, adverse events, and possible risks. Side effects associated with multiple sclerosis medications range from mild symptoms, such as flu-like or irritation at the injection site, to serious ones, such as progressive multifocal leukoencephalopathy and other life-threatening events. Moreover, the agents so far available have proved incapable of fully preventing disease progression, mostly during the phases that consist of continuous, accumulating disability. Thus, new treatment strategies, able to halt or even reverse disease progression and specific for targeting solely the pathways that contribute to the disease pathogenesis, are highly desirable. Here, we provide an overview of the recent literature about peptide-based systems tested on experimental autoimmune encephalitis (EAE) models. Since peptides are considered a unique therapeutic niche and important elements in the pharmaceutical landscape, they could open up new therapeutic opportunities for the treatment of MS.

Identifying the culprits in neurological autoimmune diseases

The target organ of neurological autoimmune diseases (NADs) is the central or peripheral nervous system. Multiple sclerosis (MS) is the most common NAD, whereas Guillain-Barré syndrome (GBS), myasthenia gravis (MG), and neuromyelitis optica (NMO) are less common NADs, but the incidence of these diseases has increased exponentially in the last few years. The identification of a specific culprit in NADs is challenging since a myriad of triggering factors interplay with each other to cause an autoimmune response. Among the factors that have been associated with NADs are genetic susceptibility, epigenetic mechanisms, and environmental factors such as infection, microbiota, vitamins, etc. This review focuses on the most studied culprits as well as the mechanisms used by these to trigger NADs.

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Neurological autoimmune diseases are caused by a complex interaction between genes, environmental factors, and epigenetic deregulation.

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Infectious agents can cause an autoimmune reaction to myelin epitopes through molecular mimicry and/or bystander activation.

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Gut microbiota dysbiosis contributes to neurological autoimmune diseases.

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Smoking increases the risk of NADs through inflammatory signaling pathways, oxidative stress, and Th17 differentiation.

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Deficiency in vitamin D favors NAD development through direct damage to the central and peripheral nervous system.

Role of pathogens in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating autoimmune disease of the central nervous system (CNS). Although the etiology of MS is unknown, genetic and environmental factors play a role. Infectious pathogens are the likely environmental factors involved in the development of MS. Pathogens associated with the development or exacerbation of MS include bacteria, such as Mycoplasma pneumoniae and Chlamydia pneumoniae, the Staphylococcus aureus-produced enterotoxins that function as superantigens, viruses of the herpes virus (Epstein-Barr virus and human herpesvirus 6) and human endogenous retrovirus (HERV) families and the protozoa Acanthamoeba castellanii. Evidence, from studies with humans and animal models, supporting the association of these various pathogens with the development and/or exacerbation of MS will be discussed along with the potential mechanisms including molecular mimicry, epitope spreading and bystander activation. In contrast, infection with certain parasites such as helminthes (Schistosoma mansoni, Fasciola hepatica, Hymenolepis nana, Trichuris trichiura, Ascaris lumbricoides, Strongyloides stercolaris, Enterobius vermicularis) appears to protect against the development or exacerbation of MS. Evidence supporting the ability of parasitic infections to protect against disease will be discussed along with a brief summary of a recent Phase I clinical trial testing the ability of Trichuris suis ova treatment to improve the clinical course of MS. A complex interaction between the CNS (including the blood-brain barrier), multiple infections with various infectious agents (occurring in the periphery or within the CNS), and the immune response to those various infections may have to be deciphered before the etiology of MS can be fully understood.

Immune modulating peptides for the treatment and suppression of multiple sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease in which the immune system recognizes proteins of the myelin sheath as antigenic, thus initiating an inflammatory reaction in the central nervous system. This leads to demyelination of the axons, breakdown of the blood-brain barrier, and lesion formation. Current therapies for the treatment of MS are generally non-specific and weaken the global immune system, thus making the individual susceptible to opportunistic infections. Antigenic peptides and their derivatives are becoming more prevalent for investigation as therapeutic agents for MS because they possess immune-specific characteristics. In addition, other peptides that target vital components of the inflammatory immune response have also been developed. Therefore, the objectives of this review are to (a) summarize the immunological basis for the development of MS, (b) discuss specific and non-specific peptides tested in EAE and in humans, and (c) briefly address some problems and potential solutions with these novel therapies.

Systemic infections in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). It has been suggested that viral and bacterial infections contribute to the pathogenesis of MS. This review will give an overview about the influence of viral and bacterial infections on MS and experimental autoimmune encephalomyelitis (EAE). It will focus on bacterial infections and will also emphasise therapeutic consequences such as the impact of antibiotic treatment on the course of EAE. In summary, a growing body of evidence suggests that systemic infections are a risk factor for the initiation of autoimmune processes including the induction of acute events in MS. Experimental and clinical data strongly suggest early treatment of bacterial infections in MS patients to avoid aggravation and relapse.

Sudden psychotic episode probably due to meningoencephalitis and Chlamydia pneumoniae acute infection

Background

Since 9% to 20% of all cases of acute psychosis presenting to an Emergency Department (ED) are due to a general medical condition, cautious medical workup should be mandatory in such patients. Differential diagnosis must consider conditions as diverse as renal failure or CNS infection.

Acute Chlamydia pneumoniae infection usually causes a self-limited respiratory syndrome. Rarely, acute neurological complications occur, with acute meningoencephalitis most frequently reported. Diagnosis requires a high level of suspicion and is difficult to confirm.

Case report

We describe a 22 year-old female Caucasian who, three days after a mild pharingitis, developed an acute psychosis with exuberant symptoms interspersed with periods of lucidity, in a background of normal consciousness and orientation.

Initial medical and imagiological workup were inconclusive. After 20 days of unsuccessful treatment with antipsychotics she developed a high fever and was re-evaluated medically. Lumbar puncture revealed an inflammatory cerebrospinal fluid. MRI showed irregular thickening and nodularity of the lateral ventricles' lining. An anti-Chlamydia pneumoniae IgM antibody titter of 85 IU/ml was detected. All symptoms cleared after treatment with antibiotics and corticosteroids.

Conclusion

This is, to our knowledge, the first reported case of acute CP-associated meningoencephalitis manifesting as an acute psychotic episode. It illustrates the principle that non-organic psychiatric syndromes must remain a diagnosis of exclusion in first-time acute psychosis.

Infection with Chlamydia pneumoniae and risk of multiple sclerosis

BACKGROUND

Chlamydia pneumoniae (Cpn) has been proposed as a possible etiologic agent for multiple sclerosis (MS), but results of previous studies are conflicting.

METHODS

Using a nested case-control design, we examined the association between Cpn infection and MS in the Nurses' Health Study (NHS) and Nurses' Health Study II (NHS II) cohorts. Among 32,826 women in the NHS and 29,722 women in the NHS II with blood samples, 141 incident cases of definite or probable MS were documented. Each case was matched to two healthy controls on year of birth and NHS cohort. Serum samples were tested for the presence of Cpn-specific immunoglobin G antibodies using microimmunofluorescence.

RESULTS

Cpn immunoglobin G seropositivity was positively associated with risk of MS (odds ratio [OR] = 1.7; 95% confidence interval [CI] = 1.1-2.7). This association did not change after adjusting for age at blood collection, ancestry, latitude of residence at birth, and smoking (OR = 1.9; CI = 1.1-3.1). Seropositivity for Cpn was only moderately associated with risk of relapsing-remitting MS (OR = 1.7; CI = 0.9-3.2), but it was strongly associated with risk of progressive MS (OR = 7.3; CI = 1.4-37.2). Geometric mean titers of Cpn-specific immunoglobin G antibody were similar in women with relapsing-remitting MS as compared with matched controls (44 vs 39), but they were elevated in women with progressive MS (99 vs 40).

CONCLUSIONS

These results support a positive association between Cpn infection and progressive MS.