Protective autoantibodies: Role in homeostasis, clinical importance, and therapeutic potential

High-throughput autoantibody screening identifies differentially abundant autoantibodies in autism spectrum disorder

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by defects in two core domains, social/communication skills and restricted/repetitive behaviors or interests. There is no approved biomarker for ASD diagnosis, and the current diagnostic method is based on clinical manifestation, which tends to vary vastly between the affected individuals due to the heterogeneous nature of ASD. There is emerging evidence that supports the implication of the immune system in ASD, specifically autoimmunity; however, the role of autoantibodies in ASD children is not yet fully understood.

Materials and methods

In this study, we screened serum samples from 93 cases with ASD and 28 healthy controls utilizing high-throughput KoRectly Expressed (KREX) i-Ome protein-array technology. Our goal was to identify autoantibodies with differential expressions in ASD and to gain insights into the biological significance of these autoantibodies in the context of ASD pathogenesis.

Result

Our autoantibody expression analysis identified 29 differential autoantibodies in ASD, 4 of which were upregulated and 25 downregulated. Subsequently, gene ontology (GO) and network analysis showed that the proteins of these autoantibodies are expressed in the brain and involved in axonal guidance, chromatin binding, and multiple metabolic pathways. Correlation analysis revealed that these autoantibodies negatively correlate with the age of ASD subjects.

Conclusion

This study explored autoantibody reactivity against self-antigens in ASD individuals' serum using a high-throughput assay. The identified autoantibodies were reactive against proteins involved in axonal guidance, synaptic function, amino acid metabolism, fatty acid metabolism, and chromatin binding.

Autoantibodies to Interferons in Infectious Diseases

Anti-cytokine autoantibodies and, in particular, anti-type I interferons are increasingly described in association with immunodeficient, autoimmune, and immune-dysregulated conditions. Their presence in otherwise healthy individuals may result in a phenotype characterized by a predisposition to infections with several agents. For instance, anti-type I interferon autoantibodies are implicated in Coronavirus Disease 19 (COVID-19) pathogenesis and found preferentially in patients with critical disease. However, autoantibodies were also described in the serum of patients with viral, bacterial, and fungal infections not associated with COVID-19. In this review, we provide an overview of anti-cytokine autoantibodies identified to date and their clinical associations; we also discuss whether they can act as enemies or friends, i.e., are capable of acting in a beneficial or harmful way, and if they may be linked to gender or immunosenescence. Understanding the mechanisms underlying the production of autoantibodies could improve the approach to treating some infections, focusing not only on pathogens, but also on the possibility of a low degree of autoimmunity in patients.

Patients with ACPA-positive and ACPA-negative rheumatoid arthritis show different serological autoantibody repertoires and autoantibody associations with disease activity

Patients with rheumatoid arthritis (RA) can test either positive or negative for circulating anti-citrullinated protein antibodies (ACPA) and are thereby categorized as ACPA-positive (ACPA+) or ACPA-negative (ACPA-), respectively. In this study, we aimed to elucidate a broader range of serological autoantibodies that could further explain immunological differences between patients with ACPA+ RA and ACPA- RA. On serum collected from adult patients with ACPA+ RA (n = 32), ACPA- RA (n = 30), and matched healthy controls (n = 30), we used a highly multiplex autoantibody profiling assay to screen for over 1600 IgG autoantibodies that target full-length, correctly folded, native human proteins. We identified differences in serum autoantibodies between patients with ACPA+ RA and ACPA- RA compared with healthy controls. Specifically, we found 22 and 19 autoantibodies with significantly higher abundances in ACPA+ RA patients and ACPA- RA patients, respectively. Among these two sets of autoantibodies, only one autoantibody (anti-GTF2A2) was common in both comparisons; this provides further evidence of immunological differences between these two RA subgroups despite sharing similar symptoms. On the other hand, we identified 30 and 25 autoantibodies with lower abundances in ACPA+ RA and ACPA- RA, respectively, of which 8 autoantibodies were common in both comparisons; we report for the first time that the depletion of certain autoantibodies may be linked to this autoimmune disease. Functional enrichment analysis of the protein antigens targeted by these autoantibodies showed an over-representation of a range of essential biological processes, including programmed cell death, metabolism, and signal transduction. Lastly, we found that autoantibodies correlate with Clinical Disease Activity Index, but associate differently depending on patients' ACPA status. In all, we present candidate autoantibody biomarker signatures associated with ACPA status and disease activity in RA, providing a promising avenue for patient stratification and diagnostics.

Omega-3 fatty acids: Current insights into mechanisms of action in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is one of the autoimmune diseases characterized by the lack of self-tolerance and the formation of immune complexes and nuclear autoantigens resulting in inflammation in multiple organs. Nowadays, the major aim of SLE therapy is the control of disease activity. However, the biological heterogeneity between patients and the absence of safe and specific targeted treatments complicate the lupus management. Therefore, the potential prophylactic effects of natural therapy considering the potential side effects of classical pharmacology, also the role of diet therapy in decreasing co-morbidities and improving quality of life in SLE patients could be a promising approach to SLE disease. Omega-3 polyunsaturated fatty acids (omega-3 PUFAs) are one of the agents that are considered for their preventive and therapeutic properties in disease activity of SLE and the related complications. The intake of omega-3 PUFAs likely has a direct relationship with improvements in inflammatory, cardiovascular, depressive, and neuromotor symptoms of the patients. The current review summarizes clinical and preclinical studies with comprehensive insights into the mechanisms of action of omega-3 fatty acids (omega-3 FAs) in Systemic Lupus Erythematosus to provide an update on the negative and positive aspects of the intake of omega-3 FAs in SLE patients.

Antibody Response to HML-2 May Be Protective in Amyotrophic Lateral Sclerosis

OBJECTIVES

Reactivation of HERV-K(HML-2) has been found in subsets of individuals with amyotrophic lateral sclerosis (ALS). This study examines the antibody response against HML-2 in ALS and analyzes its clinical relevance.

METHODS

Antibodies to HML-2 envelope (env) were analyzed using a peptide array for epitope mapping and by a peptide enzyme-linked immunosorbent assay (ELISA) in 242 healthy donors, and 243 ALS and 85 multiple sclerosis (MS) individuals. Extracellular levels of HML-2 were analyzed by digital polymerase chain reaction (PCR).

RESULTS

Antibodies in the sera of ALS individuals recognized more HML-2 env peptides compared to healthy controls (p < 0.0001). ALS individuals had higher levels of HML-2 than healthy donors (p = 0.02) and higher antibody levels against a select HML-2 env peptide compared to healthy donors or individuals with multiple sclerosis (p < 0.0001). 55.14% of ALS compared to 21.16% of healthy donors and 13.10% of MS individuals had antibodies against the HML-2 peptide (AUC = 0.769, p < 0.0001). Levels of extracellular HML-2 DNA in serum (p = 0.02) and the number of HML-2 env peptides recognized by ALS sera (p = 0.02) correlated with disease duration. Among ALS individuals, lower levels of HML-2 antibodies were associated with a definite diagnosis per EL Escorial criteria (p = 0.03), and with a lower predicted (p = 0.02) and observed survival (p = 0.03).

INTERPRETATION

There is a differential antibody response against specific epitopes of HML-2 env in ALS and controls, suggesting epitope spreading, likely due to persistent antigenic exposure following reactivation of the viral genes. Low levels of antibodies to HML-2 env in ALS are associated with poor prognosis and decreased survival probability. ANN NEUROL 2022;92:782-792.

IgA anti-dsDNA antibodies: A neglected serological parameter in systemic lupus erythematosus

Anti-double-stranded DNA (anti-dsDNA) autoantibodies are archetypal biomarkers found in systemic lupus erythematosus (SLE). Although they can exist in any isotype, very little is understood about the IgA isotype for which most of our knowledge is derived from observational studies. This review article summarises our knowledge of this autoantibody isotype to date. Attention will be spent on clinical associations as well as its potential links with lupus nephritis for which there is still some controversy. Further understanding of this serological parameter may facilitate diagnosis, prognosis and treatments of systemic lupus erythematosus patients.

Incorporating Gangliosides into PEGylated Cationic Liposomes that Complexed DNA Attenuates Anti-PEG Antibody Production but Not Anti-DNA Antibody Production in Mice

Gangliosides (glycosphingolipids) reduce antibody production by inhibiting B-cell receptor (BCR) signaling. We have shown that a copresentation of gangliosides and polyethylene glycol (PEG) on the same liposomes suppresses anti-PEG IgM production in mice. In addition, we recently observed that pDNA incorporated in PEGylated cationic liposomes (PCLs) induces anti-DNA IgM, which could be a hurdle to the development of efficient gene delivery systems. Therefore, the focus of this study was to determine if the copresentation of gangliosides and DNA on the same PCL would suppress antibody production against DNA. PCLs including DNA induced both anti-PEG IgM production and anti-DNA IgM production. The extent of anti-PEG and anti-DNA IgM production was likely dependent on the immunogenicity of the complexed DNA. Treatment of clodronate-containing liposomes, which causes a depletion of phagocytic cells, suppressed anti-PEG IgM production from PCLs that did not include DNA but failed to suppress anti-PEG IgM production from PCLs that complexed DNA (PCLD). Both anti-PEG IgM and anti-DNA IgM was induced in T-cell-deficient nude mice as well as in normal mice following treatment with PCLs and PCLD, respectively. These results indicate that phagocytic cells contribute to anti-PEG IgM production but not to anti-DNA IgM production, while T-cells do not contribute to any form of antibody production. The copresentation of gangliosides and DNA significantly reduced anti-PEG IgM production but unfortunately did not reduce anti-DNA IgM production. It appears that the immunosuppressive effect of gangliosides, presumably via the CD22 signaling pathway, is limited only to anti-PEG immunity.

Nucleic acids delivered by PEGylated cationic liposomes in systemic lupus erythematosus-prone mice: A possible exacerbation of lupus nephritis in the presence of pre-existing anti-nucleic acid antibodies

Nucleic acid-based therapy with plasmid DNA (pDNA) and small interfering RNA (siRNA) have received recent attention for their ability to modulate the cellular expression of genes and proteins. Polyethylene glycol-modified (PEGylated) cationic nanoparticles have been used as non-viral vectors for the in vivo delivery of these nucleic acids. We have reported that PEGylated cationic liposomes (PCL) including pDNA or siRNA induce anti-PEG antibodies upon repeated intravenous injection, leading to the formation of immune complexes and enhanced clearance from the blood of subsequent doses. However, the issue surrounding the association of nucleic acids with PCL whether induces anti-nucleic acid antibodies has not been studied. Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with the character of end-organ damage and the presence of anti-nuclear antibodies. We used a healthy mouse and an SLE mouse model to test the hypothesis that nucleic acids associated with PCL induce anti-nuclear antibodies and then induce SLE and exacerbate SLE symptoms. We report here that pDNA or siRNA associated with PCL (pDNA/PCL or siRNA/PCL) induced anti-DNA or RNA antibodies, respectively, in healthy mice. Repeated injections did not, however, cause SLE-like symptoms in the healthy mice. In addition, in SLE-prone mice with pre-existing anti-nuclear antibodies, pDNA/PCL were deposited on the kidneys and exacerbated lupus nephritis subsequent to the formation of immune complexes. These results may imply that nucleic acids associated with PCL do not contribute to the onset of SLE in healthy individuals who lack anti-nuclear antibodies, but nucleic acids may exacerbate the symptoms in SLE patients who have pre-existing anti-nuclear antibodies.

Relationship between natural and infection-induced antibodies in systemic autoimmune diseases (SAD): SLE, SSc and RA

Infection or vaccine-induced T cell-dependent immune response and the subsequent high-affinity neutralizing antibody production have been extensively studied, while the connection between natural autoantibodies (nAAbs) and disease-specific antibodies has not been thoroughly investigated. Our goal was to find the relationship between immunoglobulin (Ig)M and IgG isotype nAAbs and infection or vaccine-induced and disease-related autoantibody levels in systemic autoimmune diseases (SAD). A previously described indirect enzyme-linked immunosorbent assay (ELISA) test was used for detection of IgM/IgG nAAbs against citrate synthase (anti-CS) and F4 fragment (anti-F4) of DNA topoisomerase I in 374 SAD samples, with a special focus on systemic lupus erythematosus (SLE) (n = 92), rheumatoid arthritis (n = 73) and systemic sclerosis (n = 157) disease groups. Anti-measles IgG and anti-dsDNA IgG/IgM autoantibodies were measured using commercial and in-house indirect ELISA tests. In all SAD groups the anti-measles IgG-seropositive cases showed significantly higher anti-CS IgG titers (P = 0·011). In anti-dsDNA IgG-positive SLE patients, we detected significantly higher levels of anti-CS and anti-F4 IgG nAAbs (P = 0·001 and < 0·001, respectively). Additionally, we found increased levels of IgM isotypes of anti-CS and anti-F4 nAAbs in anti-dsDNA IgM-positive SLE patients (P = 0·002 and 0·016, respectively). The association between IgG isotypes of pathogen- or autoimmune disease-related antibodies and the IgG nAAbs may underscore the immune response-inducible nature of the diseases investigated. The relationship between protective anti-dsDNA IgM and the IgM isotype of anti-F4 and anti-CS may provide immunoserological evidence for the beneficial roles of nAAbs in SLE patients.

IgG4 Autoantibodies Attenuate Systemic Lupus Erythematosus Progression by Suppressing Complement Consumption and Inflammatory Cytokine Production

Pathogenic autoantibodies can cause inflammation and tissue injury in systemic lupus erythematosus (SLE). Although IgG4 is considered non-inflammatory owing to the unique structure of its hinge region, the role of IgG4 autoantibodies in SLE remains largely unknown. The titers of serum anti-nuclear-IgG antibodies (ANA-IgG) and anti-nuclear-IgG4 antibodies (ANA-IgG4) in newly diagnosed SLE patients were detected. The effects of IgG4 purified from SLE patients (SLE IgG4) and healthy controls on complement consumption and inflammatory cytokine production were evaluated in vitro. The therapeutic effects of mouse IgG1 (functionally resembles human IgG4) purified from lupus-prone MRL-lpr/lpr mice (lupus IgG1) and control mice on disease progression were examined in MRL-lpr/lpr mice. The results showed that SLE patients with equal titers of total serum ANA-IgG (1:3,200) were divided into group I with lower ANA-IgG4 titers (≤ 1:10) and group II with higher ANA-IgG4 titers (≥ 1:100), and disease activity, inflammatory cytokine production, complement consumption, and renal-function parameters in group I SLE patients were more severe than those in group II. Further, compared with control IgG4, SLE IgG4 inhibited complement consumption by autoantibody-autoantigen immune complexes, and also inhibited inflammatory cytokines production by SLE PBMCs in vitro. Moreover, compared with control IgG1, lupus IgG1 exhibited a therapeutic effect on lupus by attenuating disease progression in MRL-lpr/lpr mice. These findings, for the first time, suggest that IgG4 autoantibodies can attenuate SLE progression by suppressing complement consumption and inflammatory cytokine production. Hence, this study may provide novel therapeutic strategies against SLE and other autoimmune diseases.

Anti-complement factor H autoantibodies may be protective in lupus nephritis

BACKGROUND

This study aimed to investigate the role of anti-CFH autoantibodies in lupus nephritis based on a well-defined cohort.

METHODS

One hundred twenty patients with biopsy-proven active lupus nephritis were collected as the discovery cohort, sixty patients served as the validation cohort, thirty-four patients with SLE without renal involvement (NR-SLE) were as disease controls, and thirty healthy donors were also included. The anti-CFH autoantibodies and IgG subclasses were detected by ELISA, and epitopes were evaluated by western blot. Anti-CFH autoantibodies were purified by affinity chromatography column, and the interference on the biofunctions of CFH was further studied by the C3b binding assay and cofactor activity assay in vitro.

RESULTS

The prevalence of anti-CFH autoantibodies in lupus nephritis was significantly higher than that in healthy controls (8.3% (10/120) vs. 0% (0/30), P = 0.017), and no significant difference was found between the discovery and the validation group (8.3% (10/120) vs. 11.7% (7/60), P = 0.268) or the discovery and the NR-SLE group (8.3% (10/120) vs. 11.8% (4/34), P = 0.231). The subclass was mainly IgG2 (7/10), and major epitopes were in the middle (8/10 in SCRs 11-14) and N-terminal (7/10 in SCRs 1-4) regions of CFH. Patients with anti-CFH autoantibodies had a significantly lower prevalence of acute kidney injury (0% (0/10) vs. 40.0%(4/10), P = 0.025), lower serum creatinine levels (0.76 (0.40, 1.06) vs. 1.43 (0.46, 11.15), mg/dL, P = 0.023), and higher hemoglobin levels (113.8 ± 24.63 vs. 90.0 ± 22.53, g/L, P = 0.037) than those who were negative after further stratified analysis. A functional study showed that anti-CFH autoantibodies purified from patients with lupus nephritis could improve the binding between CFH and C3b, and also enhance the cofactor activity of CFH in vitro.

CONCLUSIONS

Anti-CFH autoantibodies were detected in patients with lupus nephritis in approximately 10% of patients with polyepitopes and IgG2 subclass predominance. Patients with anti-CFH autoantibodies presented with milder renal damage, and the purified autoantibodies could enhance the C3b binding and CFI cofactor activity of CFH in vitro, which suggested a protective role in the lupus nephritis.

Synovial Fluid Cell Proteomic Analysis Identifies Upregulation of Alpha-Taxilin Proteins in Rheumatoid Arthritis: A Potential Prognostic Marker

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease affecting the joints and surrounding tissue. Identification of novel proteins associated with the progression of a disease is a prerequisite for understanding the pathogenesis of RA. The present study was undertaken to identify the potential biomarkers from a less explored biological sample such as synovial fluid (SF) cells which is specific for RA and to analyze their functional aspects using proteomic approach. Two-dimensional gel electrophoresis (2-DE) was performed using synovial fluid cells of RA and osteoarthritis (OA) patients, and 7 differentially expressed proteins were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS/MS). Αlpha-Taxilin (α-Taxilin) has been found as one of the novel, significantly up regulated protein in RA. It has been validated in the synovium, synovial fluid (SF), SF cells, and plasma samples by Western blot, enzyme-linked immunosorbent assay (ELISA), fluorescence-activated cell sorting (FACS), immunohistochemistry (IHC), and real-time PCR. The identification of autoantibody against α-Taxilin and in silico studies has further helped us to understand its involvement in disease mechanism. The present study will therefore provide knowledge towards the etiology of RA that pave the way for suitable prognostic marker identification along with other clinical parameters.

The Repertoire of Human Antiglycan Antibodies and Its Dynamics in the First Year of Life

The repertoire of antiglycan antibodies of peripheral blood was studied using a microarray containing 487 glycan antigens: fragments of mammalian glycans (N- and O-chains of glycoproteins, as well as glycolipids) and also bacterial polysaccharides. The sera samples correspond to the third, sixth, and twelfth months of life. The infants were divided into four groups according to their nutrition type: breast milk, standard formula, and partially or extensively hydrolyzed formula. During the first year of life, the total amount of IgG decreased; presumably, the lifetime of maternal IgG in the newborns' bloodstream is much greater than is generally assumed. At the same time, the IgM content was low during the first six months and increased significantly by the twelfth month. The antiglycan IgM repertoire of one-year-old infants was still different from that of their mothers, as well as from the repertoire of unrelated donors, in particular, by the absence of antibodies against the Galβ1-3GlcNAc (Le^C) disaccharide, which is found in almost all healthy humans. It is noteworthy that the level of IgM of breast-fed infants was significantly lower than that of formula-fed by the twelfth month.

Serum anti-GAPDH autoantibody levels reflect the severity of cervical lesions: A potential serum biomarker for cervical cancer screening

Recent studies have indicated that a certain level of autoantibodies may be essential for maintaining good health as well as preventing cancer development, and that the levels of serum autoantibodies can decline during malignant progression. The aim of the present study was to identify such an autoantibody-based biomarker for screening cervical lesions. An autoantigen reactive with healthy female sera was detected in the cytosolic fraction of HeLa cells, a cervical cancer cell line, and identified. Serum immunoglobulin (Ig)-G and IgM levels against the purified autoantigen in normal, cervical intraepithelial neoplasias (CINs) I, II and III, and cervical cancer were compared using ELISAs. The autoantigen in HeLa cells was identified to be GAPDH. The serum levels of anti-HeLa-GAPDH IgG decreased with increasing severity of cervical lesions, and similar decreases in IgM levels were revealed. Notably, the anti-HeLa-GAPDH IgG level was discovered to discriminate cervical cancer from normal samples with 80.0% sensitivity and 96.6% specificity. The serum anti-HeLa-GAPDH autoantibody level, as a single parameter, is a promising serum biomarker for screening cervical lesions.

Autoantibody Biomarker Discovery in Primary Open Angle Glaucoma Using Serological Proteome Analysis (SERPA)

Glaucoma is an optic neurological disorder and the leading cause of irreversible blindness worldwide, with primary open angle glaucoma (POAG) as its most prevalent form. An early diagnosis of the disease is crucial to prevent loss of vision. Mechanisms behind glaucoma pathogenesis are not completely understood, but disease related alterations in the serological autoantibody profile indicate an immunologic component. These changes in immunoreactivity may serve as potential biomarkers for glaucoma diagnostics. We aimed to identify novel disease related autoantibodies targeting antigens in the trabecular meshwork as biomarkers to support early detection of POAG. We used serological proteome analysis (SERPA) for initial autoantibody profiling in a discovery sample set. The identified autoantibodies were validated by protein microarray analysis in a larger cohort with 60 POAG patients and 45 control subjects. In this study, we discovered CALD1, PGAM1, and VDAC2 as new biomarker candidates. With the use of artificial neural networks, the panel of these candidates and the already known markers HSPD1 and VIM was able to classify subjects into POAG patients and non-glaucomatous controls with a sensitivity of 81% and a specificity of 93%. These results suggest the benefit of these potential autoantibody biomarkers for utilization in glaucoma diagnostics.

IgM Natural Autoantibodies in Physiology and the Treatment of Disease

Antibodies are vital components of the adaptive immune system for the recognition and response to foreign antigens. However, some antibodies recognize self-antigens in healthy individuals. These autoreactive antibodies may modulate innate immune functions. IgM natural autoantibodies (IgM-NAAs) are a class of primarily polyreactive immunoglobulins encoded by germline V-gene segments which exhibit low affinity but broad specificity to both foreign and self-antigens. Historically, these autoantibodies were closely associated with autoimmune disease. Nevertheless, not all human autoantibodies are pathogenic and compelling evidence indicates that IgM-NAAs may exert a spectrum of effects from injurious to protective depending upon cellular and molecular context. In this chapter, we review the current state of knowledge regarding the potential physiological and therapeutic roles of IgM-NAAs in different disease conditions such as atherosclerosis, cancer, and autoimmune disease. We also describe the discovery of two reparative IgM-NAAs by our laboratory and delineate their proposed mechanisms of action in central nervous system (CNS) disease.

T Helper 1 Cellular Immunity Toward Recoverin Is Enhanced in Patients With Active Autoimmune Retinopathy

Autoimmune retinopathy (AIR) causes rapidly progressive vision loss that is treatable but often is confused with other forms of retinal degeneration including retinitis pigmentosa (RP). Measurement of anti-retinal antibodies (ARA) by Western blot is a commonly used laboratory assay that supports the diagnosis yet does not reflect current disease activity. To search for better diagnostic indicators, this study was designed to compare immune biomarkers and responses toward the retinal protein, recoverin, between newly diagnosed AIR patients, slow progressing RP patients and healthy controls. All individuals had measurable anti-recoverin IgG and IgM antibodies by ELISA regardless of disease status or Western blot results. Many AIR patients had elevated anti-recoverin IgG1 levels and a strong cellular response toward recoverin dominated by IFNγ. RP patients and controls responded to recoverin with a lower IFNγ response that was balanced by IL-10 production. Both AIR and RP patients displayed lower levels of total peripheral blood mononuclear cells that were due to reductions of CD4⁺ T_H cells. A comparison of messenger RNA (mRNA) for immune-related genes in whole blood of AIR patients versus RP patients or controls indicated lower expression of ATG5 and PTPN22 and higher expression of several genes involved in T_H cell signaling/transcription and adhesion. These data indicate that an immune response toward recoverin is normal in humans, but that in AIR patients the balance shifts dramatically toward higher IFNγ production and cellular activation.

Repertoire of Abs primed by bacteria in gnotobiotic mice

Innate immunity natural Abs (NAbs) execute a number of functions, including protection and surveillance. Despite active research, the stimuli that induce the formation of NAbs are still described only hypothetically. Here, we compared repertoires of anti-glycan Abs in the peripheral blood of mice that received per os various bacteria. The repertoires of Abs of mice primed in this way were compared using a microarray that included about 350 glycans, as well as 150 bacterial polysaccharides. Sterile mice did not possess anti-glycan Abs. Oral inoculation of a single strain or combination of two to four strains of bacteria, as well as putting the animals on short-term nutrition with non-sterile food, did not contribute significantly to the formation of Abs, whereas a single gavage of digested food of non-sterile mice induced the formation of a repertoire close to the natural ones. Interestingly, the priming with polysaccharide Ags (in a composition of the bacterial cell envelope), that is, dominant Ags of bacteria, led to the induction of Abs against typical glycans of mammalian glycoproteins and glycolipids (e.g. Abs of the ABH blood group system) that do not have a structural similarity to the polysaccharides. The results support the importance of early contact with a naïve immune system with microorganisms of the environment to form a normal NAbs repertoire.

Antibody response against HERV-W env surface peptides differentiates multiple sclerosis and neuromyelitis optica spectrum disorder

Background

A specific humoral immune response against HERV-W envelope surface (env-su) glycoprotein antigens has been reported in serum of patients with multiple sclerosis (MS). However, it has not been evaluated to date in patients with neuromyelitis optica spectrum disorder (NMOSD).

Objective

The objective of this paper is to investigate whether antibody (Ab) response against HERV-W env-su antigenic peptides differs between NMOSD and MS.

Methods

Serum samples were collected from 36 patients with NMOSD, 36 patients with MS and 36 healthy control individuals (HCs). An indirect ELISA was set up to detect specific Abs against HERV-W env-su peptides.

Results

Our data showed that two antigenic peptides, particularly HERV-Wenv_93–108 and HERV-Wenv_248–262, were statistically significantly present only in serum of MS compared to NMOSD and HCs. Thus, the specific humoral immune response against HERV-W env-su glycoprotein antigens found in MS is widely missing in NMOSD.

Conclusion

Increased circulating serum levels of these HERV-W Abs may be suitable as additional biomarkers to better differentiate MS from NMOSD.

Anti-pentraxin 3 auto-antibodies might be protective in lupus nephritis: a large cohort study

Objectives: Anti-pentraxin 3 (PTX3) auto-antibodies were found to be associated with the absence of renal involvement in systemic lupus erythematosus (SLE). This study is to investigate the prevalence of anti-PTX3 auto-antibodies and their clinical significance based on a large Chinese lupus nephritis cohort.

Methods: One hundred and ninety-six active lupus nephritis patients, 150 SLE patients without clinical renal involvement, and 100 healthy controls were enrolled. Serum anti-PTX3 auto-antibodies and PTX3 levels were screened by enzyme-linked immunosorbent assay (ELISA). The associations between anti-PTX3 auto-antibodies and clinicopathological parameters in lupus nephritis were further analyzed.

Results: Anti-PTX3 auto-antibodies were less prevalent in active lupus nephritis patients compared with SLE without renal involvement (19.4% (38/196) versus 40.7% (61/150), p < .001). The serum levels of anti-PTX3 auto-antibodies were negatively correlated with proteinuria in lupus nephritis (r = −.143, p = .047). The levels of proteinuria, serum creatinine, and the prevalence of thrombotic microangiopathy were significantly higher in patients with higher PTX3 levels (≥3.207 ng/ml) and without anti-PTX3 auto-antibodies compared with patients with lower PTX3 levels (<3.207 ng/ml) and with anti-PTX3 auto-antibodies (4.79 (3.39–8.28) versus 3.95 (1.78–7.0), p = .03; 168.84 ± 153.63 versus 101.44 ± 47.36, p = .01; 34.1% (14/41) versus 0% (0/9), p = .04; respectively).

Conclusion: Anti-PTX3 auto-antibodies were less prevalent in active lupus nephritis patients compared with SLE without renal involvement and associated with less severe renal damage, especially with the combined evaluation of serum PTX3 levels.

Detection of Antibodies to dsDNA: An Overview of Laboratory Assays

This brief review is focused on different methodologies available for detection of anti-dsDNA antibodies with respect to the best adequacy between biological results of laboratory and clinical significance. A large array of assays has been developed for the measurement of anti-dsDNA. New assays continually introduced have reflected not only technical innovations to avoid difficulties of some assays, but even more with hope to correlate better with systemic lupus erythematosus (SLE), particularly with its clinical course and exacerbations. Finally, with the development of micro arrays technology new insights into the pathophysiology of autoimmune disease processes should be revealed.

Autoimmune aspects in glaucoma

The pathogenesis of glaucoma, a common neurodegenerative disease, involves an immunologic component. Studies demonstrate changes of autoantibody concentrations against retinal and optic nerve head antigens in glaucoma patients. Furthermore we found antibody deposits in human glaucomatous retinae in a pro-inflammatory environment. Clinical studies showed up regulated, but also significantly down-regulated autoantibody levels. These antibodies belong to the natural autoimmunity. The upregulation of autoantibodies can be associated with fatal conditions, but several studies demonstrate that natural autoantibodies entail also neuroprotective characteristics and influence the protein expression of neuroretinal cells. A misbalance in the physiological equilibrium may shift from regulatory immunity into a neuroinflammatory degenerative process, what may lead to a predisposition to glaucoma. However, the protective nature of autoantibodies and the molecular mechanisms underlying the very sensitive equilibrium of natural autoimmunity between autoaggression and neuroprotection offer promising target sites for new therapeutic approaches. Finally, the changes in antibody profiles represent a new opportunity as highly sensitive and specific biomarkers for diagnostics purposes.

Autoantibody profile of patients infected with knowlesi malaria

BACKGROUND

Autoantibodies or antibodies against self-antigens are produced either during physiological processes to maintain homeostasis or pathological process such as trauma and infection. Infection with parasites including Plasmodium has been shown to generally induce elevated self-antibody (autoantibody) levels. Plasmodium knowlesi is increasingly recognized as one of the most important emerging human malaria in Southeast Asia that can cause severe infection leading to mortality. Autoimmune-like phenomena have been hypothesized to play a role in the protective immune responses in malaria infection.

METHODS

We studied the autoantibody profile from serum of eleven patients diagnosed with P. knowlesi. Autoantigen arrays were used to elucidate the autoantibody repertoire of P. knowlesi infected patients. The patented OGT Discovery Array with 1636 correctly folded antigen was employed.

RESULTS

Analysis of the patient versus control sera gave us 24 antigens with high reactivity with serum antibodies.

CONCLUSIONS

Understanding the autoantibody profile of malarious patients infected with P. knowlesi would help to further understand the host-parasite interaction, host immune response and disease pathogenesis. These reactive antigens may serve as potential biomarkers for cases of asymptomatic malaria and mild malaria or predictive markers for severe malaria.

Immunosuppressants increase the levels of natural autoantibodies reactive with glycosaminoglycans in myasthenia gravis

Increasing number of evidences support the role of glycosylation in the evolution of autoimmunity. We examined carbohydrate-reactive natural autoantibodies systematically for the first time in patients with autoimmune myasthenia gravis. Antibodies reactive to glycosaminoglycans were measured with CovaLink ELISA in the sera of 59 myasthenia patients as well as in 54 healthy controls. We used the GlycoChip carbohydrate array to characterize individual carbohydrate recognition patterns. Chondroitin-sulphate C and anti-α-mannose-specific IgG levels were significantly elevated in myasthenia patients. Unexpectedly, we found that immunosuppressants increased the levels of the protective IgM glycosaminoglycan-reactive natural antibodies demonstrating a new role for these agents in immunoregulation.

The spectrum of anti-chromatin/nucleosome autoantibodies: independent and interdependent biomarkers of disease

Autoantibodies directed to chromatin components date back to the discovery of the LE cell and the LE cell phenomenon circa 1950, and subsequent evidence that major components of that reaction were chromatin components and histones in particular. Over time, immunoassays ranging from ELISA and line immunoassays to more modern bead-based assays incorporated histone and DNA mixtures, purified histones, and purified nucleosomes leading to a more thorough understanding of the genesis and pathogenetic relationships of antibodies to chromatin components in systemic lupus erythematosus and other autoimmune conditions. More recently, interest has focussed on other components of chromatin such as high mobility group (HMG) proteins both as targets of B cell responses and pro-inflammatory mediators. This review will focus on immunoassays that utilize chromatin components, their clinical relationships, and newer evidence implicating HMG proteins and DNA neutrophil extracellular traps (NETs) as important players in systemic autoimmune rheumatic diseases.

Serology of Lupus Erythematosus: Correlation between Immunopathological Features and Clinical Aspects

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the aberrant production of a broad and heterogenous group of autoantibodies. Even though the presence of autoantibodies in SLE has been known, for more than 60 years, still nowadays a great effort is being made to understand the pathogenetic, diagnostic, and prognostic meaning of such autoantibodies. Antibodies to ds-DNA are useful for the diagnosis of SLE, to monitor the disease activity, and correlate with renal and central nervous involvements. Anti-Sm antibodies are highly specific for SLE. Anti-nucleosome antibodies are an excellent marker for SLE and good predictors of flares in quiescent lupus. Anti-histone antibodies characterize drug-induced lupus, while anti-SSA/Ro and anti-SSB/La antibodies are associated with neonatal lupus erythematosus and photosensitivity. Anti-ribosomal P antibodies play a role in neuropsychiatric lupus, but their association with clinical manifestations is still unclear. Anti-phospholipid antibodies are associated with the anti-phospholipid syndrome, cerebral vascular disease, and neuropsychiatric lupus. Anti-C1q antibodies amplify glomerular injury, and the elevation of their titers may predict renal flares. Anti-RNP antibodies are a marker of Sharp's syndrome but can be found in SLE as well. Anti-PCNA antibodies are present in 5–10% of SLE patients especially those with arthritis and hypocomplementemia.

Tracing environmental markers of autoimmunity: introducing the infectome

We recently introduced the concept of the infectome as a means of studying all infectious factors which contribute to the development of autoimmune disease. It forms the infectious part of the exposome, which collates all environmental factors contributing to the development of disease and studies the sum total of burden which leads to the loss of adaptive mechanisms in the body. These studies complement genome-wide association studies, which establish the genetic predisposition to disease. The infectome is a component which spans the whole life and may begin at the earliest stages right up to the time when the first symptoms manifest, and may thus contribute to the understanding of the pathogenesis of autoimmunity at the prodromal/asymptomatic stages. We provide practical examples and research tools as to how we can investigate disease-specific infectomes, using laboratory approaches employed from projects studying the “immunome” and “microbiome”. It is envisioned that an understanding of the infectome and the environmental factors that affect it will allow for earlier patient-specific intervention by clinicians, through the possible treatment of infectious agents as well as other compounding factors, and hence slowing or preventing disease development.

Reflections on Lupus 2013: butterflies, wolves and prophecies

The recently concluded Tenth International Congress on Systemic Lupus Erythematosus (SLE) held in Buenos Aires was a resounding success. This overview summarizes some of the origins of the First International Congress held in Calgary, Canada in 1986, predictions offered by past Congress Presidents, and a perspective on the trends in autoantibody testing, which remains one of the key approaches to the early and accurate diagnosis of SLE. The last few decades have witnessed a remarkable proliferation of new diagnostic technologies including addressable laser bead immunoassays and, more recently, chemiluminescence and lateral flow technologies that could find a clinical niche in point-of-care diagnostics. Against the backdrop of these constantly emerging technologies, indirect immunofluorescence has remained the platform of choice for many laboratories and diagnosticians. The notion that autoantibodies are pathogenic has been challenged by evidence that some autoantibodies are protective, some may have catalytic capacity while others may be neutral or have no function at all. The latter notion of functionless or "junk" autoantibodies needs to be taken under some advisement, because there was a time when a great proportion of the human genome was considered to include "junk DNA". The butterfly as a symbol of hope and progress in SLE research over the past 27 years since the First International Congress on SLE is almost certainly to be even more appropriate when future Congresses are held in Geneva (2015), Melbourne (2017) and eventually one in 2050.

Anti-dsDNA antibody isotypes in systemic lupus erythematosus: IgA in addition to IgG anti-dsDNA help to identify glomerulonephritis and active disease

OBJECTIVES

To evaluate the role of serum IgG, IgM and IgA anti-dsDNA antibody isotypes in the diagnosis of systemic lupus erythematosus (SLE), and their association with clinical features and disease activity, in a large cohort of SLE patients.

METHODS

Sera of 200 SLE patients (mean age 34±10.3 years; 26 male and 174 female; median duration of disease 115 months, range 7-378), and of 206 controls, including 19 Sjögren's syndrome, 27 rheumatoid arthritis, 26 psoriatic arthritis, 15 idiopathic inflammatory myopathies (IIM), 13 systemic sclerosis, 49 infectious diseases and 57 healthy subjects, were tested for anti-dsDNA IgG, IgM and IgA isotypes.

RESULTS

Selecting a cutoff corresponding to 95% specificity, the sensitivity of IgG, IgM and IgA anti-dsDNA antibodies in SLE was 55%, 30% and 49%, respectively; 12.5%, 1% and 7.5% of SLE patients had positive IgG, IgM or IgA isotype alone, respectively. SLE patients with glomerulonephritis showed higher levels of IgA anti-dsDNA (p = 0.0002), anti-dsDNA IgG/IgM (p = 0.001) and IgA/IgM (p<0.0001) ratios than patients without renal disease. No significant associations have been found between anti-dsDNA isotypes and other clinical features. IgA anti-dsDNA (p = 0.01) (but not IgG or IgM) and IgG/IgM ratio (p = 0.005) were significantly higher in patients with more active disease (ECLAM score >4).

CONCLUSIONS

The detection of IgA anti-dsDNA autoantibodies seems to improve our ability to diagnose SLE and to define lupus nephritis phenotype and active disease. By contrast, IgM anti-dsDNA antibodies might be protective for renal involvement. These data support the hypothesis that anti-dsDNA antibody class clustering may help to refine SLE diagnosis and prognosis.

An apoptosis-associated mammary protein deficiency leads to enhanced production of IgM antibodies against multiple damage-associated molecules

Milk fat globule epidermal growth factor 8 (MFG-E8) is a protein that binds to apoptotic cells by recognizing phosphatidylserine and enhances the engulfment of apoptotic cells by macrophages. Many apoptotic cells are left unengulfed in the germinal centers of the spleen in the MFG-E8-deficient (MFG-E8^−/−) mice, and these mice develop an autoimmune disease resembling human systemic lupus erythematosus. We found that the MFG-E8 deficiency was accompanied by the increased production of immunoglobulins. Further Western blot and ELISA analyses validated the increase in the IgM levels in the MFG-E8^−/− mice. It was also revealed that the sera from the MFG-E8^−/− mice cross-reacted with oxidation-specific epitopes generated upon incubation of serum albumin with the peroxidized lipids. Among the modified proteins with several unsaturated aldehydes of chain lengths varying from three to nine carbons, the MFG-E8^−/− mice sera exclusively cross-reacted with the protein-bound 4-oxo-2-nonenal (ONE), a highly reactive aldehyde originating from the peroxidation of ω6 polyunsaturated fatty acids. In addition, the IgM monoclonal antibodies (mAbs) that selectively cross-reacted with the ONE-modified proteins were generated from the MFG-E8^−/− mice. A subset of the ONE-specific IgM mAbs significantly recognized the late apoptotic and necrotic cells and enhanced the phagocytosis by macrophages. These data demonstrate that the impairment of the phagocytic clearance of apoptotic cells through MFG-E8 can lead to the generation of natural antibodies, which may play a critical role in removing multiple damage-associated molecules, including oxidation-specific epitopes and late apoptotic/necrotic cells.

Decline in titers of anti-idiotypic antibodies specific to autoantibodies to GAD65 (GAD65Ab) precedes development of GAD65Ab and type 1 diabetes

The humoral Idiotypic Network consisting of antibodies and their anti-idiotypic antibodies (anti-Id) can be temporarily upset by antigen exposure. In the healthy immune response the original equilibrium is eventually restored through counter-regulatory mechanisms. In certain autoimmune diseases however, autoantibody levels exceed those of their respective anti-Id, indicating a permanent disturbance in the respective humoral Idiotypic Network. We investigated anti-Id directed to a major Type 1 diabetes (T1D)-associated autoantibody (GAD65Ab) in two independent cohorts during progression to disease. Samples taken from participants of the Natural History Study showed significantly lower anti-Id levels in individuals that later progressed to T1D compared to non-progressors (anti-Id antibody index of 0.06 vs. 0.08, respectively, p = 0.02). We also observed a significant inverse correlation between anti-Id levels and age at sampling, but only in progressors (p = 0.014). Finally, anti-Id levels in progressors showed a significant decline during progression as compared to longitudinal anti-Id levels in non-progressors (median rate of change: -0.0004 vs. +0.0004, respectively, p = 0.003), suggesting a loss of anti-Id during progression. Our analysis of the Diabetes Prediction in Skåne cohort showed that early in life (age 2) individuals at risk have anti-Id levels indistinguishable from those in healthy controls, indicating that low anti-Id levels are not an innate characteristic of the immune response in individuals at risk. Notably, anti-Id levels declined significantly in individuals that later developed GAD65Ab suggesting that the decline in anti-Id levels precedes the emergence of GAD65Ab (median rate of change: -0.005) compared to matched controls (median rate of change: +0.001) (p = 0.0016). We conclude that while anti-Id are present early in life, their levels decrease prior to the appearance of GAD65Ab and to the development of T1D.

Multispecificity of immunoglobulin M antibodies raised against advanced glycation end products: involvement of electronegative potential of antigens

BACKGROUND

Advanced glycation end products (AGEs) can act as neoantigens to trigger immune responses.

RESULTS

Natural IgM antibodies against AGEs recognize multiple molecules, including DNA and chemically modified proteins.

CONCLUSION

There is a close relationship between the formation of AGEs and innate immune responses.

SIGNIFICANCE

Our findings highlight AGEs and related modified proteins as a source of multispecific natural antibodies Advanced glycation end products (AGEs) are a heterogeneous and complex group of compounds that are formed when reducing sugars, such as dehydroascorbic acid, react in a nonenzymatic way with amino acids in proteins and other macromolecules. AGEs are prevalent in the diabetic vasculature and contribute to the development of atherosclerosis. The presence and accumulation of AGEs in many different cell types affect the extracellular and intracellular structure and function. In the present study, we studied the immune response to the dehydroascorbic acid-derived AGEs and provide multiple lines of evidence suggesting that the AGEs could be an endogenous source of innate epitopes recognized by natural IgM antibodies. Prominent IgM titers to the AGEs were detected in the sera of normal mice and were significantly accelerated by the immunization with the AGEs. Patients with systemic lupus erythematosus (SLE), a potentially fatal systemic autoimmune disease characterized by the increased production of autoantibodies, showed significantly higher serum levels of the IgM titer against the AGEs than healthy individuals. A progressive increase in the IgM response against the AGEs was also observed in the SLE-prone mice. Strikingly, a subset of monoclonal antibodies, showing a specificity toward the AGEs, prepared from normal mice immunized with the AGEs and from the SLE mice cross-reacted with the double-stranded DNA. Moreover, they also cross-reacted with several other modified proteins, including the acetylated proteins, suggesting that the multiple specificity of the antibodies might be ascribed, at least in part, to the increased electronegative potential of the proteins. These findings suggest that the protein modification by the endogenous carbonyl compounds, generating electronegative proteins, could be a source of multispecific natural antibodies.

Does autoimmunity play a part in the pathogenesis of glaucoma?

Glaucoma is a chronic neurodegenerative disease and one of the leading causes of blindness. Several risk factors have been described, e.g. an elevated intraocular pressure (IOP), oxidative stress or mitochondrial dysfunction. Additionally, alterations in serum antibody profiles of glaucoma patients, upregulation (e.g. anti-HSP60, anti-MBP) and downregulation (e.g. anti-14-3-3), have been described, but it still remains elusive if the autoantibodies seen in glaucoma are an epiphenomenon or causative. However, it is known that elicited autoimmunity causes retinal ganglion cell loss resulting in glaucomatous-like damage and according to the autoaggressive nature of some autoantibodies we found antibody deposits in human glaucomatous retinae in a pro-inflammatory environment. Furthermore, glaucomatous serum has the potential to influence neuroretinal cell regulatory processes. Importantly, we demonstrate that some autoantibodies hold neuroprotective potential for neuroretinal cells. The protective nature of autoantibodies and the molecular mechanisms underlying the very sensitive equilibrium between autoaggression and protection remain subject of future examinations and offer promising target sites for new therapeutic approaches. Additionally, the changes in antibody profiles could be used as highly sensitive and specific marker for diagnostics purposes. Early diagnosis and intervention in risk patients would offer the chance of early treatment and to slow down the progression of glaucoma and delay the resulting blindness.

Microbead-based technologies in diagnostic autoantibody detection

BACKGROUND

There is a rapid proliferation of new technologies to identify a spectrum of autoantibodies in medical conditions that range from organ-specific autoimmune diseases to systemic rheumatic diseases. Although many laboratories have adopted high-throughput diagnostic platforms such as enzyme linked immunoassays (ELISA), other technologies such as microbead-based assays are emerging as an alternative diagnostic platform.

OBJECTIVE

To understand the performance and importance of bead based immunoassays in clinical diagnostics and therapeutics.

METHOD

Current literature was reviewed using the PubMed search engine combining keywords of immunoassay and Luminex, as well as a personal literature database. Included in the evaluation and commentary are bead-based assays such as addressable laser bead immunoassays and related magnetic bead assays.

CONCLUSIONS

Comparison with other conventional technologies has indicated that laser microbead immunoassays are reliable, accurate, cost-effective, highly sensitive and have rapid turn around time for results. While there are advantages to this diagnostic platform, there are challenges that must be addressed before wider acceptance or long-term use of this technology platform in the routine clinical diagnostic laboratory.

Clinical phenotypes of patients with anti-DFS70/LEDGF antibodies in a routine ANA referral cohort

OBJECTIVE

To analyze the clinical value of anti-DFS70 antibodies in a cohort of patients undergoing routine antinuclear antibodies (ANAs) testing.

METHODS

Sera with a dense fine speckled (DFS) indirect immunofluorescence (IIF) pattern from 100 consecutive patients and 100 patients with other IIF patterns were tested for anti-DFS70 antibodies by a novel chemiluminescence immunoassay (CIA) and for ANA by ANA Screen ELISA (both INOVA).

RESULTS

Among the 100 patients with a DFS IIF pattern, 91% were anti-DFS70 positive by CIA compared to 3% in the comparator group (P < 0.0001). The CIA and IIF titers of anti-DFS antibodies were highly correlated (rho = 0.89). ANA by ELISA was positive in 35% of patients with the DFS IIF pattern as compared to 67% of patients with other patterns (P < 0.0001). Only 12.0% of patients with DFS pattern and 13.4% with DFS pattern and anti-DFS70 antibodies detected by CIA had systemic autoimmune rheumatic disease (SARD). Only 5/91 (5.5%) patients with anti-DFS70 antibodies had SARD and their sera were negative on the ANA Screen ELISA.

CONCLUSION

Although anti-DFS70 antibodies cannot exclude the presence of SARD, the likelihood is significantly lower than in patients with other IIF patterns and should be included in test algorithms for ANA testing.

Natural autoantibodies in the physiology and pathophysiology of the immune system

Natural autoantibodies (autoNAb) recognize self antigens and are an important component of the immune system, as species ranging from invertebrates to vertebrates have polyreactive IgM NAbs. In higher vertebrates, different polyreactive autoNAbs isotypes are also frequently encountered and autopolyreactive IgG NAbs are largely predominant compared to low-titer monoreactive IgG NAbs specific for either self or non-self antigens. Autopolyreactive NAbs manifest the capacity to recognize three-dimensional structures and thus represent a fundamental feature of the immune system that has long been preserved during evolution. NAbs are produced in a continuum of functional and phenotypic tiers of B cells and are likely to derive from proteins initially selected to build the organism that were adapted through evolution to recognize environmental constituents, while preserving their capacity to recognize self antigens. The clonal selection is considered the predominant mechanism of the regulation of the immune system complexity but growing evidence suggests that autoNAbs are also actively implicated. In all species NAbs reacting with either self or non-self antigens constitute a vast network of infinite interactions providing high complexity, stability and plasticity. This evolutionary process was intended to allow the effective recognition of environmental antigens, immune memory, immunoregulatory phenomena, as well as tissue homeostasis. The present article is intended to illustrate the history and the current and future developments in our understanding of self and non-self recognizing NAbs to ultimately enlighten the complexity of the immune system regulation.

Infectome: a platform to trace infectious triggers of autoimmunity

The "exposome" is a term recently used to describe all environmental factors, both exogenous and endogenous, which we are exposed to in a lifetime. It represents an important tool in the study of autoimmunity, complementing classical immunological research tools and cutting-edge genome wide association studies (GWAS). Recently, environmental wide association studies (EWAS) investigated the effect of environment in the development of diseases. Environmental triggers are largely subdivided into infectious and non-infectious agents. In this review, we introduce the concept of the "infectome", which is the part of the exposome referring to the collection of an individual's exposures to infectious agents. The infectome directly relates to geoepidemiological, serological and molecular evidence of the co-occurrence of several infectious agents associated with autoimmune diseases that may provide hints for the triggering factors responsible for the pathogenesis of autoimmunity. We discuss the implications that the investigation of the infectome may have for the understanding of microbial/host interactions in autoimmune diseases with long, pre-clinical phases. It may also contribute to the concept of the human body as a superorganism where the microbiome is part of the whole organism, as can be seen with mitochondria which existed as microbes prior to becoming organelles in eukaryotic cells of multicellular organisms over time. A similar argument can now be made in regard to normal intestinal flora, living in symbiosis within the host. We also provide practical examples as to how we can characterise and measure the totality of a disease-specific infectome, based on the experimental approaches employed from the "immunome" and "microbiome" projects.

Immunoproteomic analysis of potential serum biomarker candidates in human glaucoma

PURPOSE

Evidence supporting the immune system involvement in glaucoma includes increased titers of serum antibodies to retina and optic nerve proteins, although their pathogenic importance remains unclear. This study using an antibody-based proteomics approach aimed to identify disease-related antigens as candidate biomarkers of glaucoma.

METHODS

Serum samples were collected from 111 patients with primary open-angle glaucoma and an age-matched control group of 49 healthy subjects without glaucoma. For high-throughput characterization of antigens, serum IgG was eluted from five randomly selected glaucomatous samples and analyzed by linear ion trap mass spectrometry (LC-MS/MS). Serum titers of selected biomarker candidates were then measured by specific ELISAs in the whole sample pool (including an additional control group of diabetic retinopathy).

RESULTS

LC-MS/MS analysis of IgG elutes revealed a complex panel of proteins, including those detectable only in glaucomatous samples. Interestingly, many of these antigens corresponded to upregulated retinal proteins previously identified in glaucomatous donors (or that exhibited increased methionine oxidation). Moreover, additional analysis detected a greater immunoreactivity of the patient sera to glaucomatous retinal proteins (or to oxidatively stressed cell culture proteins), thereby suggesting the importance of disease-related protein modifications in autoantibody production/reactivity. As a narrowing-down strategy for selection of initial biomarker candidates, we determined the serum proteins overlapping with the retinal proteins known to be up-regulated in glaucoma. Four of the selected 10 candidates (AIF, cyclic AMP-responsive element binding protein, ephrin type-A receptor, and huntingtin) exhibited higher ELISA titers in the glaucomatous sera.

CONCLUSIONS

A number of serum proteins identified by this immunoproteomic study of human glaucoma may represent diseased tissue-related antigens and serve as candidate biomarkers of glaucoma.

Immune regulation toward immunomodulation for neuroprotection in glaucoma

Although the immune system functions to preserve and restore tissue homeostasis, accumulating risk factors, prolonged glial activation, and sustained release of pro-inflammatory mediators in glaucoma may lead to a failure in the regulation of stress-induced immune response, and innate immune cells, autoreactive T cells, autoantibodies, and excess complement attack may exhibit potent stimuli that harm retinal ganglion cell somas, axons, and synapses. Identification of the cellular and molecular components of immune response pathways can provide immunomodulatory treatment strategies to attenuate neuroinflammation, protect neural tissue from collateral injury, and enhance endogenous recovery processes. This review highlights the current knowledge of molecular mechanisms regulating neuroinflammation in glaucoma.

Nephritogenic-antinephritogenic antibody network in lupus glomerulonephritis

Lupus glomerulonephritis (LGN) is one of the most threatening manifestations of systemic lupus erythematosus (SLE) and a major predictor of poor prognosis. The mechanisms leading to kidney inflammation are not completely clear; however, autoantibodies seem to play a pivotal role. Apoptosis dysregulation in SLE is likely to trigger generation of autoantibodies, the released nucleosomes being the driving autoantigen for further epitope amplification and selection of DNA or nucleosome-specific B cells. Growing evidence supports a multistep path to LGN involving initial autoantibody binding to chromatin fragments in the mesangial matrix, where they can induce mesangial inflammation leading to a shut-down of the renal DNase gene, generation and deposition of secondary necrotic chromatin on the glomerular basement membrane favouring antibody binding, complement activation and development of membrano-proliferative glomerular lesions. Anti-DNA IgG antibodies display the major pathogenetic potential in LGN initiation; however, other isotypes (IgA or IgE) as well as autoantibodies targeting other molecules (e.g. anti-C1q, anti-C reactive protein) can perpetuate renal injury. Conversely, protective autoantibodies are also likely in SLE which can contain renal damage targeting either DNA (i.e. IgM anti-DNA) or other molecules (e.g. pentraxin 3). Thus, lupus nephritogenic-antinephritogenic antibodies orchestrate the balance between harm and defence of renal tissue.

Anti-DFS70/LEDGF antibodies are more prevalent in healthy individuals compared to patients with systemic autoimmune rheumatic diseases

OBJECTIVE

Antinuclear antibodies (ANA) are a serological hallmark of systemic autoimmune rheumatic diseases (SARD) such as systemic lupus erythematosus (SLE). While a number of ANA patterns detected by indirect immunofluorescence (IIF) have diagnostic significance, autoantibodies producing the dense fine speckled (DFS) pattern have been reported to be more prevalent in healthy individuals than in SARD.

METHODS

Sequential samples submitted for ANA testing were screened for anti-DFS antibodies by IIF (n = 3263). Samples with the DFS pattern were tested for anti-DFS70/lens epithelium-derived growth factor (LEDGF) antibodies by ELISA and by a novel chemiluminescence assay (CIA, Quanta Flash DFS70). Sera from patients with various diseases and healthy individuals were tested for anti-DFS70/LEDGF antibodies by CIA. A cohort of 251 patients with SLE was used to analyze serological and clinical associations of anti-DFS70 antibodies.

RESULTS

The frequency of anti-DFS antibodies by IIF was 1.62%. The prevalence of anti-DFS70/LEDGF antibodies as detected by CIA in the different cohorts was 8.9% in healthy individuals, 2.8% in SLE, 2.6% in rheumatoid arthritis, 4.0% in asthma, 5.0% in interstitial cystitis, 1.7% in Graves' disease, and 6.0% in Hashimoto's thyroiditis. Of note, the prevalence of anti-DFS70/LEDGF antibodies was significantly higher in healthy individuals compared to patients with SARD (p = 0.00085). In SLE results, anti-DFS70/LEDGF antibodies were not significantly associated with clinical features or other autoantibodies typically found in SLE. Only 1/7 SLE sera showed anti-DFS70/LEDGF, but no other autoantibody reactivity.

CONCLUSION

"Monospecific" anti-DFS70/LEDGF antibodies may represent a biomarker for differentiating SARD from non-SARD individuals, but there is a need for a reliable assay to ensure reactivity to DFS70.

Toward a new autoantibody diagnostic orthodoxy: understanding the bad, good and indifferent

Rapid advances in diagnostic technologies used to detect autoantibodies have made it difficult for even the most modern laboratory to keep abreast of the changing approaches and platforms, not to mention the clinicians who are hard pressed to keep abreast of evolving diagnostic paradigms attended by these newer techniques. While autoantibody testing is traditionally considered to be primarily serving the realm of diagnostic medicine, there is little doubt that autoantibodies are also being recognized as an approach to providing prognostic and therapeutic information. Accordingly, along with related proteomics, genomics and metabolomics, it is taking on increasing importance in the realm of personalized medicine. In today's world of autoantibody diagnostics, overarching concerns about false-negative and false-positive autoantibodies tests cannot be summarily dismissed by citing pros or cons of any one technology or diagnostic platform, but often point to persisting gaps in our knowledge about, and understanding of, the origin and roles of autoantibodies. Before we can hope to completely understand the enigmas that attend the results of autoantibody diagnostic tests, perhaps it is time to step back and re-examine long-accepted paradigms and beliefs. This review will address some of the issues that impact on autoantibody detection technologies and some of the considerations and issues that will attend a new orthodoxy of autoantibody diagnostics. These issues will be addressed in the context of "bad" (pathogenic), "good" (protective) or "indifferent" (no apparent role in disease) autoantibodies.