Greek rheumatoid arthritis patients have elevated levels of antibodies against antigens from Proteus mirabilis

Molecular mimicry in the pathogenesis of autoimmune rheumatic diseases

Autoimmune rheumatic diseases (ARDs) are a heterogeneous group of conditions characterized by excessive and misdirected immune responses against the body's own musculoskeletal tissues. Their exact aetiology remains unclear, with genetic, demographic, behavioural and environmental factors implicated in disease onset. One prominent hypothesis for the initial breach of immune tolerance (leading to autoimmunity) is molecular mimicry, which describes structural or sequence similarities between human and microbial proteins (mimotopes). This similarity can lead to cross-reactive antibodies and T-cell receptors, resulting in an immune response against autoantigens. Both commensal microbes in the human microbiome and pathogens can trigger molecular mimicry, thereby potentially contributing to the onset of ARDs. In this review, we focus on the role of molecular mimicry in the onset of rheumatoid arthritis and systemic lupus erythematosus. Moreover, implications of molecular mimicry are also briefly discussed for ankylosing spondylitis, systemic sclerosis and myositis.

Exploring the role of gut microbiome in autoimmune diseases: A comprehensive review

As the industrialized society advances, there has been a gradual increase in the prevalence of autoimmune disorders. A probe into the fundamental causes has disclosed several factors in modern society that have an influence on the gut microbiome. These dramatic shifts in the gut microbiome are likely to be one of the reasons for the disarray in the immune system, and the relationship between the immune system and the gut microbiome emerging as a perennial hot topic of research. This review enumerates the findings from sequencing studies of gut microbiota on seven autoimmune diseases (ADs): Rheumatoid Arthritis (RA), Systemic Lupus Erythematosus (SLE), Ankylosing Spondylitis (AS), Systemic Sclerosis (SSc), Sjögren's Syndrome (SjS), Juvenile Idiopathic Arthritis (JIA), and Behçet's Disease (BD). It aims to identify commonalities in changes in the gut microbiome within the autoimmune disease cohort and characteristics specific to each disease. The dysregulation of the gut microbiome involves a disruption of the internal balance and the balance between the external environment and the host. This dysregulation impacts the host's immune system, potentially playing a role in the development of ADs. Damage to the gut epithelial barrier allows potential pathogens to translocate to the mucosal layer, contacting epithelial cells, disrupting tight junctions, and being recognized by antigen-presenting cells, which triggers an immune response. Primed T-cells assist B-cells in producing antibodies against pathogens; if antigen mimicry occurs, an immune response is generated in extraintestinal organs during immune cell circulation, clinically manifesting as ADs. However, current research is limited; advancements in sequencing technology, large-scale cohort studies, and fecal microbiota transplantation (FMT) research are expected to propel this field to new peaks.

Association Between Soluble Cell Adhesion Molecules (sP-Selectin, sE-Selectin, and sICAM-1) and Antibodies Against the Antigens of Proteus mirabilis in Rheumatoid Arthritis Patients

Objective The purpose of this study was to examine the association between the serum concentration of soluble cell adhesion molecules (CAMs) and antibodies against antigens of Proteus mirabilis (P. mirabilis) in rheumatoid arthritis (RA) patients, taking into consideration the implication of P. mirabilis in the etiopathogenesis of RA. Methods The serum levels of soluble P-selectin (sP-selectin), soluble E-selectin (sE-selectin), and soluble intercellular adhesion molecule-1 (sICAM-1) were determined by sandwich enzyme-linked immunosorbent assay (ELISA) in 59 RA patients and 36 healthy controls. Using the same ELISA method, the serum levels of class-specific antibodies against hemolysin (HpmB), urease C (UreC), and urease F (UreF) enzymes of P. mirabilis were also measured.  Results In this study, increased levels of sP-selectin and sICAM-1 were observed in RA patients, while the levels of sE-selectin were increased in comparison with healthy controls but did not present a statistically significant difference. Moreover, increased levels of antibodies against HpmB, UreC, and UreF of P. mirabilis were found. Additionally, it was observed that the sE-selectin levels presented a significant correlation with IgG antibodies against the UreF antigen (there is no corresponding antigen in human tissue) in all the RA patients. A statistically significant correlation was observed between levels of soluble CAMs and antibodies against P. mirabilis in the different subgroups. Conclusion The observed correlation between soluble CAMs and antibodies against antigens of P. mirabilis, specifically in the subgroup of biologic therapy, indicates that P. mirabilis exists and provokes refractory in the treatment of RA.

The role of microbiota on rheumatoid arthritis onset

Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes inflammation and pain, which can lead to the loss of normal joint function. Although the exact cause of the disease is not yet fully understood, both environmental factors and genetics may play a role in its development. Moreover, research suggests microbiota contributes to the onset and progression of RA. People with RA show higher quantities of bacteria such as Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Prevotella copri, Proteus mirabilis, and Lactobacillus salivarius compared to healthy individuals. Conversely, studies propose that Lactobacillus casei, a probiotic bacterium with immunomodulatory properties, has beneficial effects for RA in murine and human models. Therefore, this work reviews the potential role of the gut microbiota in the development of RA and explores the feasibility of using probiotic bacteria as a supplementary treatment for this disease.

Antibody Cross-Reactivity in Auto-Immune Diseases

Autoimmunity is defined by the presence of antibodies and/or T cells directed against self-components. Although of unknown etiology, autoimmunity commonly is associated with environmental factors such as infections, which have been reported to increase the risk of developing autoimmune diseases. Occasionally, similarities between infectious non-self and self-tissue antigens may contribute to immunological cross-reactivity in autoimmune diseases. These reactions may be interpreted as molecular mimicry, which describes cross-reactivity between foreign pathogens and self-antigens that have been reported to cause tissue damage and to contribute to the development of autoimmunity. By focusing on the nature of antibodies, cross-reactivity in general, and antibody-antigen interactions, this review aims to characterize the nature of potential cross-reactive immune reactions between infectious non-self and self-tissue antigens which may be associated with autoimmunity but may not actually be the cause of disease onset.

Molecular mimicry and autoimmunity in the time of COVID-19

Infectious diseases are commonly implicated as potential initiators of autoimmune diseases (ADs) and represent the most commonly known factor in the development of autoimmunity in susceptible individuals. Epidemiological data and animal studies on multiple ADs suggest that molecular mimicry is one of the likely mechanisms for the loss of peripheral tolerance and the development of clinical disease. Besides molecular mimicry, other mechanisms such as defects in central tolerance, nonspecific bystander activation, epitope-determinant spreading, and/or constant antigenic stimuli, may also contribute for breach of tolerance and to the development of ADs. Linear peptide homology is not the only mechanism by which molecular mimicry is established. Peptide modeling (i.e., 3D structure), molecular docking analyses, and affinity estimation for HLAs are emerging as critical strategies when studying the links of molecular mimicry in the development of autoimmunity. In the current pandemic, several reports have confirmed an influence of SARS-CoV-2 on subsequent autoimmunity. Bioinformatic and experimental evidence support the potential role of molecular mimicry. Peptide dimensional analysis requires more research and will be increasingly important for designing and distributing vaccines and better understanding the role of environmental factors related to autoimmunity.

Immune dysregulation and pathogenic pathways mediated by common infections in rheumatoid arthritis

Rheumatoid arthritis (RA) is one of the world's most prevalent inflammatory autoimmune diseases, affecting between 0.4 and 1.3% of the population. The susceptibility to RA appears to be influenced by a complex interaction between a favorable genetic background and the existence of a specific immune reaction against a wide range of environmental variables. Among the known environmental variables, infections are believed to have a significant role in promoting the formation of autoimmune disorders, which are frequently caused by specific microorganisms. Infections have been linked to RA in recent medical studies. In this study, we selected the most prevalent infections associated with RA from the literature and described the data confirming their pathogenic role in RA. Our investigation included Mycobacterium, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Proteus mirabilis, Epstein-Barr virus, parvovirus, and Prevotella copri.

Mining the capacity of human-associated microorganisms to trigger rheumatoid arthritis-A systematic immunoinformatics analysis of T cell epitopes

Autoimmune diseases, often triggered by infection, affect ~5% of the worldwide population. Rheumatoid Arthritis (RA)–a painful condition characterized by the chronic inflammation of joints—comprises up to 20% of known autoimmune pathologies, with the tendency of increasing prevalence. Molecular mimicry is recognized as the leading mechanism underlying infection-mediated autoimmunity, which assumes sequence similarity between microbial and self-peptides driving the activation of autoreactive lymphocytes. T lymphocytes are leading immune cells in the RA-development. Therefore, deeper understanding of the capacity of microorganisms (both pathogens and commensals) to trigger autoreactive T cells is needed, calling for more systematic approaches. In the present study, we address this problem through a comprehensive immunoinformatics analysis of experimentally determined RA-related T cell epitopes against the proteomes of Bacteria, Fungi, and Viruses, to identify the scope of organisms providing homologous antigenic peptide determinants. By this, initial homology screening was complemented with de novo T cell epitope prediction and another round of homology search, to enable: i) the confirmation of homologous microbial peptides as T cell epitopes based on the predicted binding affinity to RA-related HLA polymorphisms; ii) sequence similarity inference for top de novo T cell epitope predictions to the RA-related autoantigens to reveal the robustness of RA-triggering capacity for identified (micro/myco)organisms. Our study reveals a much larger repertoire of candidate RA-triggering organisms, than previously recognized, providing insights into the underestimated role of Fungi in autoimmunity and the possibility of a more direct involvement of bacterial commensals in RA-pathology. Finally, our study pinpoints Endoplasmic reticulum chaperone BiP as the most potent (most likely mimicked) RA-related autoantigen, opening an avenue for identifying the most potent autoantigens in a variety of different autoimmune pathologies, with possible implications in the design of next-generation therapeutics aiming to induce self-tolerance by affecting highly reactive autoantigens.

The Changing Face of the Family Enterobacteriaceae (Order: "Enterobacterales"): New Members, Taxonomic Issues, Geographic Expansion, and New Diseases and Disease Syndromes

The family Enterobacteriaceae has undergone significant morphogenetic changes in its more than 85-year history, particularly during the past 2 decades (2000 to 2020). The development and introduction of new and novel molecular methods coupled with innovative laboratory techniques have led to many advances. We now know that the global range of enterobacteria is much more expansive than previously recognized, as they play important roles in the environment in vegetative processes and through widespread environmental distribution through insect vectors. In humans, many new species have been described, some associated with specific disease processes. Some established species are now observed in new infectious disease settings and syndromes. The results of molecular taxonomic and phylogenetics studies suggest that the current family Enterobacteriaceae should possibly be divided into seven or more separate families. The logarithmic explosion in the number of enterobacterial species described brings into question the relevancy, need, and mechanisms to potentially identify these taxa. This review covers the progression, transformation, and morphogenesis of the family from the seminal Centers for Disease Control and Prevention publication (J. J. Farmer III, B. R. Davis, F. W. Hickman-Brenner, A. McWhorter, et al., J Clin Microbiol 21:46-76, 1985, https://doi.org/10.1128/JCM.21.1.46-76.1985) to the present.

Antibodies Isolated from Rheumatoid Arthritis Patients against Lysine-Containing Proteus mirabilis O3 (S1959) Lipopolysaccharide May React with Collagen Type I

Most rheumatic diseases, including rheumatoid arthritis (RA), are characterized by immune disorders that affect antibody activity. In the present study, using Dot blot and ELISA assay, we showed that patients with rheumatic disease produced significantly more antibodies against lipopolysaccharide (LPS) P. mirabilis O3 compared to healthy donors (p < 0.05), and affinity purified antibodies against LPS O3 may cross-react with collagen type I. It was demonstrated that purified of antibodies isolated from RA patients sera, reacted stronger with the collagen than healthy donors (p = 0.015), and cross-reaction was correlated with level of anti-citrullinated peptide antibodies (r = 0.7, p = 0.003). Moreover, using six different lipopolysaccharides were demonstrated the significant correlations in sera reactivity among lysine-containing lipopolysaccharides observed in patients’ sera (p < 0.05). Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) it was shown that unique wavenumbers of sera spectra correlate with reactivity with lipopolysaccharides allowing distinguish patients from healthy blood donors. Antibodies adsorption by synthetic antigens shows that in patients’ group anti-LPS O3 antibodies can be adsorbed by both amides of galacturonic acid and lysine or threonine, which suggests less specificity of antibodies binding with non-carbohydrate LPS component. The observed correlations suggest that non-carbohydrate components of LPS may be an important epitope for less specific anti-LPS antibodies, which might lead to cross-reactions and affect disease development.

Early and Short-Term Interventions in the Gut Microbiota Affects Lupus Severity, Progression, and Treatment in MRL/lpr Mice

There have been attempts to reveal the possible associations between systemic lupus erythematosus (SLE) and gut microbiota. Using MRL/lpr mice, this study was performed to reveal whether early and short-term interventions in gut microbiota affect lupus. MRL/lpr mice were treated with antibiotics or fecal microbiota transplantation (FMT) before onset. Then, prednisone was used to treat the lupus mice with initially different gut microbiota compositions. The compositions of gut microbiota were assessed by the V3-V4 region of 16S rRNA gene sequence. Early and short-term antibiotics exposure aggravated lupus severity by depleting beneficial gut microbiota for lupus, such as Lactobacillus and Bifidobacterium, and enriching harmful gut microbiota for lupus, such as Klebsiella and Proteus. FMT alleviated lupus severity by renovating the antibiotic-induced dysbiosis of gut microbiota in the following 1 week after antibiotics exposure. Besides, short-term antibiotics exposure before onset imposed no significant effects on lupus progression, but the following one week of FMT suppressed lupus progression. Moreover, the short-term antibiotics or FMT before onset inhibited the therapeutic efficiency of prednisone on lupus from 9 to 13 weeks old of MRL/lpr mice. These data demonstrate that the gut microbiota before onset is important for lupus severity, progression and treatment.

Germinal centers and autoantibodies

Preventing self-reactive lymphocytes from participating in effector responses is fundamental to maintaining immunological self-tolerance and circumventing autoimmunity. A range of complementary mechanisms are known to act upon the primary B- and T-cell repertoires to this effect, eliminating or silencing lymphocytes expressing self-reactive antigen receptors generated through V(D)J recombination in early lymphoid precursors. In the case of B cells, secondary diversification of antigen receptor repertoire by somatic hypermutation (SHM) provides an additional challenge, especially because this occurs in germinal center (GC) B cells that are actively responding to antigen and primed for differentiation into antibody-producing plasma cells. While it is clear that self-tolerance mechanisms do act to prevent antibody production by self-reactive GC B cells, it is also apparent that most pathogenic autoantibodies carry somatic mutations and so have derived from a GC response. Recent advances in the analysis of autoantibody-producing cells associated with human autoimmune diseases together with insights gained from animal models have increased our understanding of the relationships between GCs, SHM and autoantibody production. Here we discuss these developments and focus in particular on how they have illuminated the genesis and pathogenesis of one archetypal autoantibody, rheumatoid factor.

Comparative analysis of high CRP-levels in human blood using point-of-care and laboratory-based methods

Objectives

The use of point-of-care (POC) methods and the measurements of C-reactive protein (CRP) as a diagnostic marker have both increased over the past years. This has led to an increase in POC-methods analysing CRP. High CRP levels are often seen as an indication for the subscription of antibiotics. The quality of POC-systems compared to routine diagnostic measurements for the analysis of CRP is thereby of main importance, since many small practises will use POC-methods. This study compared high-level CRP concentrations (above 100 mg/L) using an i-CHROMA^TM with 2 routinely used laboratory-based systems (Architect and ABX).

Design

and Methods: A total of 199 patient samples with a CRP concentration above 100 mg/L were analysed with the i-CHROMA^TM POC system and the turbidimetric routine methods using the Architect and ABX equipment.

Results

The results of the i-CHROMA^TM device showed a significant decrease in the CRP levels compared to those obtained with the Architect and the ABX (i-CHROMA^TM vs. Architect: y ​= ​0.6792x + 94.701; R² = 0.4980, i-CHROMA^TM vs. ABX: y ​= ​0.3674x + 118.05; R² ​= ​0.3964, Architect vs. ABX: y ​= ​0.7657x + 36.337; R² = 0.9311). Furthermore, data analysis showed a partition of the i-CHROMA^TM measurements in two defined clouds, which could not be explained with any of the available sample information.

Conclusions

This analysis showed the limitations of the i-CHROMA^TM CRP analyser. In addition, it illustrates the need for strict regulations on the information and output provided by companies regarding the boundaries of novel and existing diagnostic methods.

A single bacterium restores the microbiome dysbiosis to protect bones from destruction in a rat model of rheumatoid arthritis

Background

Early treatment is key for optimizing the therapeutic success of drugs, and the current initiating treatment that blocks the progression of bone destruction during the pre-arthritic stages remains unsatisfactory. The microbial disorder in rheumatoid arthritis (RA) patients is significantly reversed with effective treatment. Modulating aberrant gut microbiomes into a healthy state is a potential therapeutic approach for preventing bone damage.

Results

By using metagenomic shotgun sequencing and a metagenome-wide association study, we assessed the effect of Lactobacillus casei (L. casei) on the induction of arthritis as well as on the associated gut microbiota and immune disorders in adjuvant-induced arthritis (AIA) rats. Treatment of AIA rats with L. casei inhibited joint swelling, lowered arthritis scores, and prevented bone destruction. Along with the relief of arthritis symptoms, dysbiosis in the microbiome of arthritic rats was significantly reduced after L. casei intervention. The relative abundance of AIA-decreased Lactobacillus strains, including Lactobacillus hominis, Lactobacillus reuteri, and Lactobacillus vaginalis, were restored to normal and Lactobacillus acidophilus was upregulated by the administration of L. casei to the AIA rats. Moreover, L. casei downregulated the expression of pro-inflammatory cytokines, which are closely linked to the effect of the L. casei treatment-associated microbes. Functionally, the maintenance of the redox balance of oxidative stress was involved in the improvement in the L. casei-treated AIA rats.

Conclusion

A single bacterium, L. casei (ATCC334), was able to significantly suppress the induction of AIA and protect bones from destruction in AIA rats by restoring the microbiome dysbiosis in the gut, indicating that using probiotics may be a promising strategy for treating RA, especially in the early stage of the disease.

Electronic supplementary material

The online version of this article (10.1186/s40168-019-0719-1) contains supplementary material, which is available to authorized users.

Detection of human antibodies binding with smooth and rough LPSs from Proteus mirabilis O3 strains S1959, R110, R45

Bacteria of the genus Proteus of the family Enterobacteriaceae are facultative human pathogens responsible mainly for urinary tract and wound infections, bacteremia and the development of rheumatoid arthritis (RA). We have analyzed and compared by ELISA the titer of antibodies in plasmas of healthy individuals and in sera of rheumatoid arthritis patients recognizing a potential host cross-reactive epitope (lysine-galacturonic acid epitopes) present in Proteus lipopolysaccharide (LPS). In our experiments LPSs isolated from two mutants of smooth Proteus mirabilis 1959 (O3), i.e. strains R110 and R45, were used. R110 (Ra type mutant) is lacking the O-specific polysaccharide, but possesses a complete core oligosaccharide, while R45 (Re type) has a reduced core oligosaccharide and contains two 3-deoxy-D-manno-oct-2-ulosonic acid residues and one of 4-amino-4-deoxy-L-arabinopyranose residues. Titer of P. mirabilis S1959 LPS-specific-antibodies increased with the age of blood donors. RA and blood donors' sera contained antibodies against S and Ra and Re type of P. mirabilis O3 LPSs. Antibodies recognizing lysine-galacturonic acid epitopes of O3 LPS were detected by ELISA in some plasmas of healthy individuals and sera of rheumatoid arthritis patients. RA patients antibodies reacting with P. mirabilis S1959 S and R LPSs may indicate a potential role of anti-LPS antibodies in molecular mimicry in RA diseases.