Evidence of chronic Chlamydia pneumoniae infection in patients with Behçet's disease

Pathogenesis of Behçet's Syndrome: Genetic, Environmental and Immunological Factors

Behçet's syndrome (BS) is a rare systemic vasculitis, characterized by a wide range of different clinical involvements and unpredictable phases of recurrence and remission. BS can be described as a multifactorial disease with an incompletely known etiopathogenesis; in fact, though presenting some peculiar features, such as its typical geographic distribution and the strong association with the well-known genetic predisposing factor HLA-B*51, the cause behind the onset and progression of the disease remains currently not fully understood. Besides genetic HLA and non-HLA predisposing associations and epigenetic influence, environmental factors also play an important role in the pathogenesis of the disease, and among these, infectious agents (both bacterial and viral) and specific microbiome alterations are considered of particular relevance in BS pathogenesis. BS has been included for decades among autoimmune diseases, in light of evidence showing T- and B-cell aberrant responses. However, because of recurrent mucocutaneous lesions and episodes of inflammation without antigen-specific T-cell or autoantibody responses, BS has also been classified among autoinflammatory disorders. Nevertheless, differently from autoinflammatory diseases, BS mildly responds to therapies targeting IL-1, its onset is not usually in childhood, and has high neutrophilic vasculitic involvement. Finally, given the association with HLA class I alleles, similar to spondyloarthropathies, the concept of BS as a major histocompatibility complex (MHC) I -opathy has been introduced. Understanding the complex etiopathogenesis of BS is essential to identify modifiable risk factors of BS occurrence or exacerbation and to develop targeted therapies. This review summarizes current evidence on the main genetic, environmental and immunological factors contributing to BS development.

Immunopathogenesis of Behcet's Disease

Behcet's disease (BD) is a chronic systemic inflammatory vasculitis of unknown etiology characterized by recurrent episodes of oral aphthous ulcers, genital ulcers, skin lesions, ocular lesions, and other manifestations. Although the pathogenesis of BD is unclear, some studies have shown that immunological aberrations play an important role in the development and progression of BD. Infection-related trigger factors, including antigens and autoantigens, are believed to mediate the development of BD in patients with a genetic predisposition and subsequently activate the innate and adaptive immune systems, resulting in the production of numerous cytokines and chemokines to combat the infection-related factors. The study of the immunological mechanism of BD paves the way for the development of innovative therapies. Recently, novel biotherapy approaches, including interferon-α (IFN-α), tumor necrosis factor-α (TNF-α) antagonists, and other agents that target interleukins and their receptors, have shown promising results in the treatment of patients with refractory BD and have improved the prognosis of BD. In this review, we provide the current concepts of BD immunopathogenesis.

Behcet’s disease: from heat shock proteins to infections

Background: Behcet’s disease (BD) is a chronic, inflammatory multisystemic condition of unknown etiology. Although the cause of BD is not clear, it is believed to be the result of an autoimmune process triggered by an infectious or environmental agent (possibly local to a geographic region) in a genetically predisposed individual.

Objective: To detail current knowledge of the role of microorganisms in the pathogenesis of BD and review the infectious etiology of this disease.

Methods: The review based on publication in SCOPUS, Science direct, and PubMed.

Results: A microbial infection has been implicated in the development of the disease to explain the strong inflammatory reactions observed, the activation of monocytes and macrophages, and the induction of proinflammatory cytokines and chemokines detected. Common factors linking some of the possible pathogenetic agents are extrinsically induced tissue stress or heat shock proteins, which react with host tissues and elicit significant T-helper type 1 cell responses.

Conclusion: Based on collected data, we conclude that the microorganisms discussed seem to participate and, at least in part, act as triggers during the course of BD. By clarifying the microbial associations of BD and finding its etiology, particularly the causative antigens leading to BD, it would be easier to suggest more effective treatment and preventive strategies for this disease.

Chlamydia pneumoniae Infection and Inflammatory Diseases

Chlamydia pneumoniae, an obligate intracellular bacterial pathogen, has long been investigated as a potential developmental or exacerbating factor in various pathologies. Its unique lifestyle and ability to disseminate throughout the host while persisting in relative safety from the immune response has placed this obligate intracellular pathogen in the crosshairs as a potentially mitigating factor in chronic inflammatory diseases. Many animal model and human correlative studies have been performed to confirm or deny a role for C. pneumoniae infection in these disorders. In some cases, antibiotic clinical trials were conducted to prove a link between bacterial infections and atherosclerosis. In this review, we detail the latest information regarding the potential role that C. pneumoniae infection may have in chronic inflammatory diseases.

The possible role of HSPs on Behçet's disease: a bioinformatic approach

Current evidence lends increasing support to immunoinflammatory mechanisms as one of the prime pathogenic processes involved in the development and progression of Behçet's disease (BD). It has been observed that most human beings have cellular and humoral reactions against microbial heat shock proteins (HSPs). The observation that eukaryotic and prokaryotic HSPs have high sequence similarity promoted the hypothesis that HSPs might be potential candidates for molecular mimicry and could act as potentially dangerous autoantigens. In this study, using bioinformatics tools, we examined the hypothesis that HSPs (evolutionarily conserved proteins), which are present in pathogenic and commensal organisms and their hosts, provide the stimulus that initiates BD in susceptible individuals. In this regards, the nucleotide and amino acid sequences of the human HSP 60 kDa and bacterial HSP 60 kDa deposited in the NCBI and PDB databases were subjected to analysis using bioinformatics tools, including The CLC Sequence Viewer and MEGA softwares. These data showed that the sequence homology between bacterial and self HSPs (leading to cross-reactivity and molecular mimicry phenomenon) may be associated with the development of the disease; and suggesting that microbial HSPs, which cross-react with host tissues and elicit significant immune responses are possible pathogenetic agents involved in the development and progression of BD.

Etiopathogenesis of Behçet's disease with emphasis on the role of immunological aberrations

Behçet's disease (BD) is a chronic multisystemic inflammatory disorder of unknown origin consisting of oral aphthous ulcers, ocular symptoms, skin lesions, and genital ulcerations. It has many features in common with systemic vasculitides and is more prevalent in countries along the ancient Silk route. Immune-mediated mechanisms play a major role in the pathogenesis of the disease, and inflammatory mediators are also involved. BD is not considered to be an autoimmune disorder, and the character of the disease needs to be clarified. Immunological aberrations in BD have been extensively studied by many investigators; genetic factors have been related to disease susceptibility, but their exact role in the development of disease is uncertain. Environmental factors such as infectious agents have also been implicated in the etiology of BD. However, the etiopathogenesis of the disease remains to be elucidated. Factors involved in the immunopathogenesis of BD with emphasis on the role of immunological aberrations are analyzed in this review.

Vasculitis and systemic infections

PURPOSE OF REVIEW

In recent years, many investigators have focused on potential associations between infections and vascular inflammation. We review the principal pathogenic mechanisms that have been implicated for possible roles in the vascular inflammation initiated by infectious agents. We also summarize the most important literature related to this topic.

RECENT FINDINGS

A novel theory known as autoantigen complementarity suggests that an infectious agent could trigger antineutrophil cytoplasmic antibody-associated vasculitis. Several recent studies investigating the presence of parvovirus B19 and herpesviruses in temporal arteries with giant cell arteritis have yielded contradictory results. A recent study has identified higher frequency of a novel human virus, the 'New Haven coronavirus', in respiratory secretions of children with Kawasaki disease. Many case reports have suggested potential relationships between human pathogens and vasculitis.

SUMMARY

There remains considerable interest in the possibilities of primary vasculitic syndromes caused in some fashion by infection. With the exception of a few well sustained associations - for example hepatitis B or C with known vasculitic syndromes - most of the purported links between microbial agents and primary vasculitides remain speculative.

Response to vaccination against hepatitis B in patients with Behcet's disease

BACKGROUND AND AIM

Hepatitis B virus infection is an important public health problem in Turkey. Although hepatitis B vaccination is regarded as safe and effective for the general population, recommendations for hepatitis B immunization in patients with Behcet's disease are not clear. The aim of the present study was to elucidate the response of patients with Behcet's disease to hepatitis B vaccination and to determine whether hepatitis B vaccination has any adverse effects on the course of the disease.

METHODS

Thirteen patients with Behcet's disease and 15 healthy individuals were enrolled into a prospective study. All subjects received the 3-dose series of routine hepatitis B vaccine. Anti-hepatitis B surface response was evaluated 1-3 months after the third dose of vaccine.

RESULTS

The responder rates for patient and control groups were 12/13 (92.8%) and 14/15 (93.8%), respectively. Statistical analysis showed no significant difference between the two groups in terms of both the responder rates and mean antibody titers.

CONCLUSIONS

These preliminary findings might suggest that the majority of patients with Behcet's disease develop protective antibody response after hepatitis B vaccination and that the immune response against hepatitis B surface antigen is adequate, efficient and intact.