IgA1 and IgA2 subclass antibodies against Klebsiella pneumoniae in the sera of patients with peripheral and axial types of ankylosing spondylitis

Antibodies of the immunoglobulin a isotype to novel antigens in early axial spondyloarthritis

Introduction

There is an unmet need for biomarkers to identify patients with axial spondyloarthritis (axSpA). Increasing evidence suggest the presence of autoantibodies in a subset of axSpA patients. The aim of this study was to identify novel IgA antibodies in early axSpA patients and to determine their diagnostic potential in combination with previously determined IgG antibodies against UH (Hasselt University)-axSpA-IgG antigens.

Methods

An axSpA cDNA phage display library constructed from axSpA hip synovium, was used to screen for novel IgA antibodies in plasma from early axSpA patients. The presence of these antibodies against novel UH-axSpA-IgA antigens was determined in two independent axSpA cohorts, in healthy controls and in patients with chronic low back pain.

Results

We identified antibodies to 7 novel UH-axSpA-IgA antigens, of which 6 correspond to non-physiological peptides and 1 to the human histone deacetylase 3 (HDAC3) protein. IgA antibodies against 2 of these 7 novel UH-axSpA-IgA antigens and IgG antibodies against 2 of the previously identified antigens were significantly more present in early axSpA patients from the UH cohort (18/70, 25.7%) and the (Bio)SPAR cohort (26/164, 15.9%), compared to controls with chronic low back pain (2/66, 3%). Antibodies to this panel of 4 antigens were present in 21.1% (30/142) of patients with early axSpA from the UH and (Bio)SPAR cohorts. The positive likelihood ratio for confirming early axSpA using antibodies to these 4 UH-axSpA antigens was 7.0. So far, no clinical correlation between the novel identified IgA antibodies and inflammatory bowel disease could be identified.

Discussion

In conclusion, screening an axSpA cDNA phage display library for IgA reactivity resulted in the identification of 7 novel UH-axSpA-IgA antigens, of which 2 show promising biomarker potential for the diagnosis of a subset of axSpA patients, in combination with previously identified UH-axSpA-IgG antigens.

B Cell Involvement in the Pathogenesis of Ankylosing Spondylitis

Extensive research into ankylosing spondylitis (AS) has suggested the major role of genetics, immune reactions, and the joint-gut axis in its etiology, although an ultimate consensus does not yet exist. The available evidence indicates that both autoinflammation and T-cell-mediated autoimmune processes are actively involved in the disease process of AS. So far, B cells have received relatively little attention in AS pathogenesis; this is largely due to a lack of conventional disease-defining autoantibodies. However, against prevailing dogma, there is a growing body of evidence suggestive of B cell involvement. This is illustrated by disturbances in circulating B cell populations and the formation of auto-reactive and non-autoreactive antibodies, along with B cell infiltrates within the axial skeleton of AS patients. Furthermore, the depletion of B cells, using rituximab, displayed beneficial results in a subgroup of patients with AS. This review provides an overview of our current knowledge of B cells in AS, and discusses their potential role in its pathogenesis. An overarching picture portrays increased B cell activation in AS, although it is unclear whether B cells directly affect pathogenesis, or are merely bystanders in the disease process.

The Gut Microbiome in Inflammatory Bowel Disease: Lessons Learned From Other Immune-Mediated Inflammatory Diseases

There is a growing appreciation for the role of the gut microbiome in human health and disease. Aided by advances in sequencing technologies and analytical methods, recent research has shown the healthy gut microbiome to possess considerable diversity and functional capacity. Dysbiosis of the gut microbiota is believed to be involved in the pathogenesis of not only diseases that primarily affect the gastrointestinal tract but also other less obvious diseases, including neurologic, rheumatologic, metabolic, hepatic, and other illnesses. Chronic immune-mediated inflammatory diseases (IMIDs) represent a group of diseases that share many underlying etiological factors including genetics, aberrant immunological responses, and environmental factors. Gut dysbiosis has been reported to be common to IMIDs as a whole, and much effort is currently being directed toward elucidating microbiome-mediated disease mechanisms and their implications for causality. In this review, we discuss gut microbiome studies in several IMIDs and show how these studies can inform our understanding of the role of the gut microbiome in inflammatory bowel disease.

Detection of novel diagnostic antibodies in ankylosing spondylitis: An overview

Ankylosing spondylitis (AS) is a debilitating, chronic, rheumatic disease characterized by inflammation and new bone formation resulting in fusion of the spine and sacroiliac joints. Since early treatment is impeded by a delayed diagnosis, it is highly important to find new biomarkers that improve early diagnosis and may also contribute to a better assessment of disease activity, prognosis and therapy response in AS. Because of the absence of rheumatoid factor, AS was long assumed to have a seronegative character and antibodies are thus not considered a hallmark of the disease. However, emerging evidence suggests plasma cells and autoantibodies to be involved in the disease course. In this review, the role of B cells and antibodies in AS is discussed. Furthermore, an overview is provided of antibodies identified in AS up till now, and their diagnostic potential. Many of these antibody responses were based on small study populations and further validation is lacking. Moreover, most were identified by a hypothesis-driven approach and thus limited to antibodies against targets that are already known to be involved in AS pathogenesis. Hence, we propose an unbiased approach to identify novel diagnostic antibodies. The already successfully applied techniques cDNA phage display and serological antigen selection will be used to identify antibodies against both known and new antigen targets in AS plasma. These newly identified antibodies will enhance early diagnosis of AS and provide more insight into the underlying disease pathology, resulting in a more effective treatment strategy and eventually an improved disease outcome.

The link between ankylosing spondylitis, Crohn's disease, Klebsiella, and starch consumption

Both ankylosing spondylitis (AS) and Crohn's disease (CD) are chronic and potentially disabling interrelated conditions, which have been included under the group of spondyloarthropathies. The results of a large number of studies support the idea that an enteropathic pathogen, Klebsiella pneumoniae, is the most likely triggering factor involved in the initiation and development of these diseases. Increased starch consumptions by genetically susceptible individuals such as those possessing HLA-B27 allelotypes could trigger the disease in both AS and CD by enhancing the growth and perpetuation of the Klebsiella microbes in the bowel. Exposure to increased levels of these microbes will lead to the production of elevated levels of anti-Klebsiella antibodies as well as autoantibodies against cross-reactive self-antigens with resultant pathological lesions in the bowel and joints. Hence, a decrease of starch-containing products in the daily dietary intake could have a beneficial therapeutic effect on the disease especially when used in conjunction with the currently available medical therapies in the treatment of patients with AS and CD.

Recognition of B cells epitopes of the Klebsiella pneumoniae GroEL-like protein by HLA-B27 positive subjects

The presence of antibodies against antigens of K. pneumoniae in HLA-B27 positive patients with ankylosing spondylitis (AS), has been well documented. We have previously reported that sera from HLA-B27 positive subjects react with the K. pneumoniae GroEL-like protein (HSP60Kp) and have higher titers than HLA-B27 negative individuals. We cloned the gene that codes for this protein, determined hydrophilic regions by computer analysis of the predicted amino acid sequence and found that residues 389-397, 360-368 and 282-290, were possible B cell epitopes. To test this prediction, and to determine if the HLA-B27 positive and negative AS patients recognize the same or different epitopes, we truncated the hsp60Kp gene, from the 3; terminal nucleotide, to obtain fragments having or not the predicted epitopes. Four polypeptides of 40, 37, 30 and 18 kDa were obtained and analysed, by ELISA and inhibition of ELISA, for their reactivity with IgG antibodies from three high responders HLA-B27 positive AS patients and three HLA-B27 negative subjects who recognized the rHSP60Kp. Sera from both HLA-B27 positive and negative subjects reacted equally well with rHSP60Kp or with the 40 and 37 kDa peptides, which do not have residues 389-397 and 360-368, respectively, but reactivity was lost with the 30 kDa peptide, which also lacks residues 282-290. Contrary to what we expected, antibodies from HLA-B27 negative and positive individuals recognized the same epitope of the HSP60Kp. Our results indicate that the important epitope for B cells could be the 282-290 region and that the contribution of the two other predicted regions is minimal. We also conclude that the differences in response to the HSP60Kp in HLA-B27 positive AS patients and HLA-B27 negative individuals is not qualitative, but only quantitative.

Pathogenesis of human leukocyte antigen B27-positive arthritis. Information from clinical materials

In the spondyloarthropathies human leukocyte antigen (HLA) B27 confers a strong genetic predisposition to the development and to the chronicity of disease after extra-articular infection with certain gram-negative bacteria. The close relationships between infection, HLA-B27, other genetic factors, and the host immune system, however, still are unexplained. HLA-B27-positive arthritis continues to be an area of intensive investigation in basic and clinical research. New animal models with HLA-B27 transgenic mice and rats, as well as recent developments in understanding the processes involved in signal transduction, cytokine production, and human T-lymphocyte activation, contribute to the development of new pathogenic models of the spondyloarthropathies. This article summarizes the current concepts of the cause and pathogenesis of the spondyloarthropathies resulting from studies of clinical materials. The host-microbial interplay in human disease, namely in bacteria-induced reactive arthritis, may eludicate principle disease mechanisms in acute disease and in the development of chronic autoimmune arthritis or ankylosing spondylitis.

Enhanced jejunal production of antibodies to Klebsiella and other Enterobacteria in patients with ankylosing spondylitis and rheumatoid arthritis

OBJECTIVE

To measure gut immunity directly in jejunal fluid in patients with ankylosing spondylitis (AS) and rheumatoid arthritis (RA).

METHODS

Antibodies against three different Enterobacterias were measured in jejunal perfusion fluids (collected by a double balloon perfusion device) of 19 patients with AS, 14 patients with RA, and 22 healthy controls using enzyme linked immunosorbent assay.

RESULTS

The AS patients had significantly increased jejunal fluid concentrations of IgM, IgG, and IgA class antibodies against Klebsiella pneumoniae, and IgM and IgA class antibodies against Escherichia coli and Proteus mirabilis compared with healthy controls. When compared with the patients with RA, the AS patients had higher concentrations of IgA and IgG class antibodies only against K pneumoniae. The RA patients had higher IgM class antibody concentrations against all three studied Enterobacterias, when compared with the healthy controls, suggesting an enhanced mucosal immune response in these patients. A three month treatment with sulphasalazine did not decrease enterobacterial antibody concentrations in the 10 patients with AS.

CONCLUSION

There is strong direct evidence for an abnormal mucosal humoral immune response particularly to K pneumoniae in patients with AS.