Immune responses to Mycobacterial heat shock protein 70 accompany self-reactivity to human BiP in rheumatoid arthritis

Mining Autoimmune-Disorder-Linked Molecular-Mimicry Candidates in Clostridioides difficile and Prospects of Mimic-Based Vaccine Design: An In Silico Approach

Molecular mimicry, a phenomenon in which microbial or environmental antigens resemble host antigens, has been proposed as a potential trigger for autoimmune responses. In this study, we employed a bioinformatics approach to investigate the role of molecular mimicry in Clostridioides difficile-caused infections and the induction of autoimmune disorders due to this phenomenon. Comparing proteomes of host and pathogen, we identified 23 proteins that exhibited significant sequence homology and were linked to autoimmune disorders. The disorders included rheumatoid arthritis, psoriasis, Alzheimer's disease, etc., while infections included viral and bacterial infections like HIV, HCV, and tuberculosis. The structure of the homologous proteins was superposed, and RMSD was calculated to find the maximum deviation, while accounting for rigid and flexible regions. Two sequence mimics (antigenic, non-allergenic, and immunogenic) of ≥10 amino acids from these proteins were used to design a vaccine construct to explore the possibility of eliciting an immune response. Docking analysis of the top vaccine construct C2 showed favorable interactions with HLA and TLR-4 receptor, indicating potential efficacy. The B-cell and T-helper cell activity was also simulated, showing promising results for effective immunization against C. difficile infections. This study highlights the potential of C. difficile to trigger autoimmunity through molecular mimicry and vaccine design based on sequence mimics that trigger a defensive response.

Characteristics of the (Auto)Reactive T Cells in Rheumatoid Arthritis According to the Immune Epitope Database

T cells are known to be involved in the pathogenesis of rheumatoid arthritis (RA). Accordingly, and to better understand T cells' contribution to RA, a comprehensive review based on an analysis of the Immune Epitope Database (IEDB) was conducted. An immune CD8+ T cell senescence response is reported in RA and inflammatory diseases, which is driven by active viral antigens from latent viruses and cryptic self-apoptotic peptides. RA-associated pro-inflammatory CD4+ T cells are selected by MHC class II and immunodominant peptides, which are derived from molecular chaperones, host extra-cellular and cellular peptides that could be post-translationally modified (PTM), and bacterial cross-reactive peptides. A large panel of techniques have been used to characterize (auto)reactive T cells and RA-associated peptides with regards to their interaction with the MHC and TCR, capacity to enter the docking site of the shared epitope (DRB1-SE), capacity to induce T cell proliferation, capacity to select T cell subsets (Th1/Th17, Treg), and clinical contribution. Among docking DRB1-SE peptides, those with PTM expand autoreactive and high-affinity CD4+ memory T cells in RA patients with an active disease. Considering original therapeutic options in RA, mutated, or altered peptide ligands (APL) have been developed and are tested in clinical trials.

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.

Key interactions in the trimolecular complex consisting of the rheumatoid arthritis-associated DRB1*04:01 molecule, the major glycosylated collagen II peptide and the T-cell receptor

Objectives

Rheumatoid arthritis (RA) is an autoimmune disease strongly associated with the major histocompatibility complex (MHC) class II allele DRB1*04:01, which encodes a protein that binds self-peptides for presentation to T cells. This study characterises the autoantigen-presenting function of DRB1*04:01 (HLA-DRA*01:01/HLA-DRB1*04:01) at a molecular level for prototypic T-cell determinants, focusing on a post-translationally modified collagen type II (Col2)-derived peptide.

Methods

The crystal structures of DRB1*04:01 molecules in complex with the peptides HSP70_289-306, citrullinated CILP_982-996 and galactosylated Col2_259-273 were determined on cocrystallisation. T cells specific for Col2_259-273 were investigated in peripheral blood mononuclear cells from patients with DRB1*04:01-positive RA by cytofluorometric detection of the activation marker CD154 on peptide stimulation and binding of fluorescent DRB1*0401/Col2_259-273 tetramer complexes. The cDNAs encoding the T-cell receptor (TCR) α-chains and β-chains were cloned from single-cell sorted tetramer-positive T cells and transferred via a lentiviral vector into TCR-deficient Jurkat 76 cells.

Results

The crystal structures identified peptide binding to DRB1*04:01 and potential side chain exposure to T cells. The main TCR recognition sites in Col2_259-273 were lysine residues that can be galactosylated. RA T-cell responses to DRB1*04:01-presented Col2_259-273 were dependent on peptide galactosylation at lysine 264. Dynamic molecular modelling of a functionally characterised Col2_259-273-specific TCR complexed with DRB1*04:01/Col2_259-273 provided evidence for differential allosteric T-cell recognition of glycosylated lysine 264.

Conclusions

The MHC-peptide-TCR interactions elucidated in our study provide new molecular insights into recognition of a post-translationally modified RA T-cell determinant with a known dominant role in arthritogenic and tolerogenic responses in murine Col2-induced arthritis.

Role of Infections in the Pathogenesis of Rheumatoid Arthritis: Focus on Mycobacteria

Rheumatoid arthritis (RA) is a systemic inflammatory autoimmune disease characterized by chronic erosive polyarthritis. A complex interaction between a favorable genetic background, and the presence of a specific immune response against a broad-spectrum of environmental factors seems to play a role in determining susceptibility to RA. Among different pathogens, mycobacteria (including Mycobacterium avium subspecies paratuberculosis, MAP), and Epstein–Barr virus (EBV), have extensively been proposed to promote specific cellular and humoral response in susceptible individuals, by activating pathways linked to RA development. In this review, we discuss the available experimental and clinical evidence on the interplay between mycobacterial and EBV infections, and the development of the immune dysregulation in RA.

The role of commensal microflora-induced T cell responses in glaucoma neurodegeneration

Over the last decade, new evidence has become increasingly more compelling that commensal microflora profoundly influences the maturation and function of resident immune cells in host physiology. The concept of gut-retina axis is actively being explored. Studies have revealed a critical role of commensal microbes linked with neuronal stress, immune responses, and neurodegeneration in the retina. Microbial dysbiosis changes the blood-retina barrier permeability and modulates T cell-mediated autoimmunity to contribute to the pathogenesis of retinal diseases, such as glaucoma. Heat shock proteins (HSPs), which are evolutionarily conserved, are thought to function both as neuroprotectant and pathogenic antigens of T cells contributing to cell protection and tissue damage, respectively. Activated microglia recruit and interact with T cells during this process. Glaucoma, characterized by the progressive loss of retinal ganglion cells, is the leading cause of irreversible blindness. With nearly 70 million people suffering glaucoma worldwide, which doubles the number of patients with Alzheimer's disease, it represents the most frequent neurodegenerative disease of the central nervous system (CNS). Thus, understanding the mechanism of neurodegeneration in glaucoma and its association with the function of commensal microflora may help unveil the secrets of many neurodegenerative disorders in the CNS and develop novel therapeutic interventions.

Sensitized heat shock protein 27 induces retinal ganglion cells apoptosis in rat glaucoma model

AIM

To investigate the relationships between the changes of heat shock protein 27 antibody (anti-HSP27) in serum/cerebrospinal fluid (CSF), intraocular pressure (IOP), retinal ganglion cell (RGC) apoptosis in a rat glaucoma model and disclose the underlying pathogenesis of glaucoma.

METHODS

A total of 115 Wistar rats were randomly divided into 4 groups. Group 1 was the ocular hypertension group by condensing 3 episcleral & limbal veins or episcleral area of right eye (HP group, n=25) and sham operation group with conjunctiva incision without coagulation (n=25). Group 2: HSP27 or dose-matched PBS was injected into the vitreous (V-HSP27 group, n=15; V-PBS group, n=15). Group 3: HSP27 and complete Freund's adjuvant or dose-matched PBS was injected subcutaneously into the hind limb accompanied intraperitoneal injection of pertussis toxin [sensitized group (I-HSP27 group), n=15; I-PBS group, n=15)]. Group 4 was normal group without any treatment (n=5). IOPs of the rats were measured before, day 3, weeks 1, 2, 4, 6, and 8 after treatment. Paraffin-embedded sections were prepared for HE staining and RGCs apoptosis were detected by TUNEL. Anti-HSP27 level in serum and CSF were examined by ELISA.

RESULTS

IOPs were elevated significantly in HP and V-HSP27, V-PBS groups (P<0.01) and positively related to anti-HSP27 levels in serum and CSFs. Anti-HSP27 levels in serum and CSF were elevated significantly in I-HSP27 group compared to other groups (P<0.05). However, the IOPs did not show any relationship with the high-level anti-HSP27 in serum and CSFs. RGC apoptosis were all elevated significantly in the HP, V-HSP27, V-PBS and I-HSP27 groups and also positively relative with anti-HSP27 level in serum and CSFs except that high-level of anti-HSP27 in the serum of I-HSP group.

CONCLUSION

The increases of anti-HSP27 levels in serum and CSFs both promote IOP escalation and the increase of RGC apoptosis in retina when anti-HSP27 is at low level. The case of high-level anti-HSP27 is opposite and shows protective function in preventing IOP increase and RGC apoptosis.

Modulation of autoimmune arthritis by environmental 'hygiene' and commensal microbiota

Observations in patients with autoimmune diseases and studies in animal models of autoimmunity have revealed that external environmental factors including exposure to microbes and the state of the host gut microbiota can influence susceptibility to autoimmunity and subsequent disease development. Mechanisms underlying these outcomes continue to be elucidated. These include deviation of the cytokine response and imbalance between pathogenic versus regulatory T cell subsets. Furthermore, specific commensal organisms are associated with enhanced severity of arthritis in susceptible individuals, while exposure to certain microbes or helminths can afford protection against this disease. In addition, the role of metabolites (e.g., short-chain fatty acids, tryptophan catabolites), produced either by the microbes themselves or from their action on dietary products, in modulation of arthritis is increasingly being realized. In this context, re-setting of the microbial dysbiosis in RA using prebiotics, probiotics, or fecal microbial transplant is emerging as a promising approach for the prevention and treatment of arthritis. It is hoped that advances in defining the interplay between gut microbiota, dietary products, and bioactive metabolites would help in the development of therapeutic regimen customized for the needs of individual patients in the near future.

Autoantibodies in the Pathogenesis, Diagnosis, and Prognosis of Juvenile Idiopathic Arthritis

Autoantibody production occurs in juvenile idiopathic arthritis (JIA) and numerous other autoimmune diseases. In some conditions, the autoantibodies are clearly pathogenic, whereas in others the roles are less defined. Here we review various autoantibodies associated with JIA, with a particular focus on antinuclear antibodies and antibodies recognizing citrullinated self-antigens. We explore potential mechanisms that lead to the development of autoantibodies and the use of autoantibody testing in diagnosis and prognosis. Finally, we compare and contrast JIA-associated autoantibodies with those found in adults with rheumatoid arthritis (RA).

Recent Advances in Research Regarding Autoantibodies in Connective Tissue Diseases and Related Disorders

Connective tissue diseases (CTDs), also known as systemic autoimmune diseases, involve a variety of autoantibodies against cellular components. An important factor regarding these autoantibodies is that each antibody is exclusively related to a certain clinical feature of the disease type, which may prove useful in clinical practice. Thus far, more than 100 types of autoantibodies have been found in CTDs, and most of their target antigens have been identified. Many of these autoantigens are enzymes or regulators involved in important cellular functions, such as gene replication, transcription, repair/recombination, RNA processing, and protein synthesis, as well as proteins that form complexes with RNA and DNA. This article reviews the autoantibodies for each CTD, along with an assessment of their clinical significance, and provides suggestions regarding their utilization for clinical practice.

The characteristics and pivotal roles of triggering receptor expressed on myeloid cells-1 in autoimmune diseases

Triggering receptor expressed on myeloid cells-1 (TREM-1) engagement can directly trigger inflammation or amplify an inflammatory response by synergizing with TLRs or NLRs. Autoimmune diseases are a family of chronic systemic inflammatory disorders. The pivotal role of TREM-1 in inflammation makes it important to explore its immunological effects in autoimmune diseases. In this review, we summarize the structural and functional characteristics of TREM-1. Particularly, we discuss recent findings on TREM-1 pathway regulation in various autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD), type 1 diabetes (T1D), and psoriasis. This receptor may potentially be manipulated to alter the inflammatory response to chronic inflammation and possible therapies are explored in this review.

Ts-Hsp70 induces protective immunity against Trichinella spiralis infection in mouse by activating dendritic cells through TLR2 and TLR4

Background

Trichinellosis is a serious food-borne parasitic zoonosis worldwide. In the effort to develop vaccine against Trichinella infection, we have identified Trichinella spiralis Heat shock protein 70 (Ts-Hsp70) elicits partial protective immunity against T. spiralis infection via activating dendritic cells (DCs) in our previous study. This study aims to investigate whether DCs were activated by Ts-Hsp70 through TLR2 and/or TLR4 pathways.

Methods and findings

After blocking with anti-TLR2 and TLR4 antibodies, the binding of Ts-Hsp70 to DCs was significantly reduced. The reduced binding effects were also found in TLR2 and TLR4 knockout (TLR2^-/- and TLR4^-/-) DCs. The expression of TLR2 and TLR4 on DCs was upregulated after treatment with Ts-Hsp70 in vitro. These results suggest that Ts-Hsp70 is able to directly bind to TLR2 and TLR4 on the surface of mouse bone morrow-derived DCs. In addition, the expression of the co-stimulatory molecules (CD80, CD83) on Ts-Hsp70-induced DCs was reduced in TLR2^-/- and TLR4^-/- mice. More evidence showed that Ts-Hsp70 reduced its activation on TLR2/4 knockout DCs to subsequently activate the naïve T-cells. Furthermore, Ts-Hsp70 elicited protective immunity against T. spiralis infection was reduced in TLR2^-/- and TLR4^-/- mice correlating with the reduced humoral and cellular immune responses.

Conclusion

This study demonstrates that Ts-Hsp70 activates DCs through TLR2 and TLR4, and TLR2 and TLR4 play important roles in Ts-Hsp70-induced DCs activation and immune responses.

Trichinellosis is a serious food-borne parasitic zoonosis caused by tissue-dwelling nematode Trichinella spiralis. Vaccine development is needed as an alternative approach to control the infection in domestic livestock or in humans. Ts-Hsp70 has been identified to elicit partial protective immunity against Trichinella spiralis infection via activating dendritic cells (DCs) in our previous study. This study aims to investigate the pathway(s) through which the Ts-Hsp70 activates DCs. Our results identified that Ts-Hsp70 could bind to DCs which was inhibited by blocking TLR2 and TLR4 with antibodies or TLR2 and TLR4 knockout. Ts-Hsp70 stimulated the expression of TLR2 and TLR4 and the co-stimulatory CD80, CD83 and CD86 on the surface of DCs which was reduced in TLR2 or TLR4 knockout mice. With TLR2 or TLR4 knockout, DCs were less stimulated by Ts-Hsp70 and subsequently reduce the activation of naïve T-cells. The protective immunity induced by Ts-Hsp70 against T. spiralis infection was also reduced in TLR2 or TLR4 knockout mice. The results conclude that Ts-Hsp70 activates DCs through activating TLR2 and TLR4 and TLR2 and TLR4 play important roles in Ts-Hsp70-induced protective immunity against Trichinella infection.

A mode of error: Immunoglobulin binding protein (a subset of anti-citrullinated proteins) can cause false positive tuberculosis test results in rheumatoid arthritis

Citrullinated Immunoglobulin Binding Protein (BiP) is a newly described autoimmune target in rheumatoid arthritis (RA), one of many cyclic citrullinated peptides(CCP or ACPA). BiP is over-expressed in RA patients causing T cell expansion and increased interferon levels during incubation for the QuantiFERON-Gold tuberculosis test (QFT-G TB). The QFT-G TB has never been validated where interferon is increased by underlying disease, as for example RA. Of ACPA-positive RA patients (n = 126), we found a 13% false-positive TB test rate by QFT-G TB. Despite subsequent biologic therapy for 3 years of all 126 RA patients, none showed evidence of TB without INH. Most of the false-positive RA patients after treatment with biologic therapy reverted to a negative QFT-G test. False TB tests correlated with ACPA level (p < 0.02). Three healthy women without arthritis or TB exposure had negative QFT-G TB. In vitro, all three tested positive every time for TB correlating to the dose of BiP or anti-BiP added, at 2 ug/ml, 5 ug/ml, 10 ug/ml, and 20 ug/ml. BiP naturally found in the majority of ACPA-positive RA patients can result in a false positive QFT-G TB. Subsequent undertreatment of RA, if biologic therapy is withheld, and overtreatment of presumed latent TB may harm patients.

Immune responses against Helicobacter pylori-specific antigens differentiate relapsing remitting from secondary progressive multiple sclerosis

To assess whether Helicobacter pylori (Hp) antibody (ab) reactivity against individual Hp antigens is pathogenetically relevant to multiple sclerosis (MS), we systematically investigated prevalence and clinical significance of abs against 14 immunodominant and subdominant Hp antigens by ELISA and immunoblotting in 139 consecutive MS patients with relapsing-remitting (RRMS, n = 102) or secondary progressive (SPMS, n = 37). Sera from 39 patients with Parkinson’s disease (PD), 21 with Alzheimer’s disease (ALZ) and 68 healthy controls (HCs), were also tested. Anti-flagellin (18.3%) and anti-p41 (25.0%) abs in MS were less frequent than in HCs (39.4%, 48.5%, respectively). Abs against 5 of the 14 antigens were less frequent in RRMS than HCs, including p41, p54-flagellin, p29-UreA, p67-FSH, and p120-CagA. Anti-VacA abs were more frequent in SPMS than in HCs (42.1 vs 12.1%, p = 0.019). Anti-p54, anti-p29-UreA and anti-p26 correlated with extended disability status scale (EDSS) (p = 0.017, p = 0.005, p = 0.002, respectively). Anti-p26 and anti-p17 correlated with the number of relapses (p = 0.037 and p = 0.047, respectively). This is the first comprehensive analysis of ab reactivities against most Hp antigens in MS patients. Ab responses differ between MS and HCs and between RRMS and SPMS, being more prevalent in SPMS than RRMS, thus suggesting an association between anti-Hp and the former type of MS.

Association between a history of mycobacterial infection and the risk of newly diagnosed Sjögren's syndrome: A nationwide, population-based case-control study

OBJECTIVE

To address the association between a history of tuberculosis (TB) or nontuberculous mycobacterial (NTM) infection and the risk of newly diagnosed Sjögren's syndrome (SS).

METHODS

Using a nationwide, population-based, claims dataset, and after excluding those who had rheumatoid arthritis or systemic lupus erythematosus, we identified 5,751 newly diagnosed SS cases during 2007-2012, and compared them to 86,265 non-SS controls matched (1:15) for age, sex, and the year of first SS diagnosis date. The association between the risk of incident SS and a history of mycobacterial infection, including TB and NTM, was quantified by calculating odds ratios (ORs) with 95% confidence intervals (CIs) using conditional logistic regression analysis after adjustment for Charlson comorbidity index (CCI) and bronchiectasis.

RESULTS

The mean age was 55±14 years, and the proportion of female gender was 87.8% in both newly diagnosed SS cases andnon-SS controls. An association was observed between NTM infection (OR, 11.24; 95% CI, 2.37-53.24) and incident SS, but not between TB infection and incident SS (OR, 1.29; 95% CI, 0.97-1.71) after adjustment for CCI and bronchiectasis. The association between NTM and SS risk was remarkably strong among those aged between 45 and 65 years (OR, 39.24; 95% CI, 3.97-387.75) and those without bronchiectasis (OR, 39.98; 95% CI, 3.83-376.92).

CONCLUSION

The study reveals a significant association of newly diagnosed SS with a history NTM infection, especially among individuals aged 40-65 years or those without bronchiectasis.