Identification and characterization of the antigen recognized by the germ cell mAb TRA98 using a human comprehensive wet protein array

Proteome-Wide Analysis of Autoantibodies in Open-Angle Glaucoma in Japanese Population: A Pilot Study

Objectives: The objective of this study was to identify novel autoantibodies specific for open-angle glaucoma (OAG), including normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG), using proteome-wide autoantibody screening and to determine their utility for diagnosis. Methods: We conducted proteome-wide autoantibody screening by wet protein arrays. Autoantibody reactivity in the plasma of OAG patients (50 NTG and 69 POAG patients) was quantitatively analyzed and compared to that of controls (35 cataract patients). The area under the curve (AUC) of the receiver operating characteristic (ROC) and multivariate analyses were used to determine diagnostic potential in patients with OAG. Results: Based on differences in autoantibody titers and positivity rates, four autoantibodies against ETNK1, VMAC, NEXN, and SUN1 were selected as potential biomarkers to discriminate OAG and cataract. In discrimination between POAG and cataract, the AUCs of ETNK1 and VMAC were calculated to be 0.820 (95%CI: 0.733-0.907) and 0.889 (95%CI: 0.818-0.959), respectively. Furthermore, the combination of these four antibodies demonstrated diagnostic potential for OAG with an AUC of 0.828 (95%CI: 0.757-0.898) by multivariate analysis. Conclusions: Four new glaucoma-associated autoantibodies were identified in this study. The differences in autoantibody patterns in the plasma between glaucoma and cataract patients support their potential utility as biomarkers for glaucoma screening.

Anti-interferon gamma-inducible protein 16 antibodies: Identification of a novel autoantigen in idiopathic interstitial pneumonia and its clinical characteristics based on a multicenter cohort study

Autoantibodies are detected in idiopathic interstitial pneumonias (IIPs) without a clear connective tissue disease diagnosis, and their clinical significance is unclear. This study aimed to identify a novel autoantibody in IIPs. We screened 295 IIP patients using a 35S-methionine labeled protein immunoprecipitation assay. Candidate autoantigens were identified via protein array and confirmed by immunoprecipitation. Six sera from 295 IIP patients immunoprecipitated common tetrameric proteins (100 kDa). The protein array identified interferon gamma-inducible protein 16 (IFI16) as the candidate autoantigen. Patients with anti-IFI16 antibodies received immunosuppressants less frequently. Five-year survival rates were 50 %, 69 %, and 63 % (P = 0.60), and acute exacerbation-free rates were 50 %, 96 %, and 84 % (P = 0.15) for patients with anti-IFI16, anti-aminoacyl tRNA antibodies, and others. Anti-IFI16 is a novel autoantibody in IIPs. Patients with this antibody often receive less immunosuppressive therapy and could have a poor prognosis. Further research is needed to refine patient stratification and management.

Autoantibodies to nuclear valosin-containing protein-like protein: systemic sclerosis-specific antibodies revealed by in vitro human proteome

OBJECTIVES

To identify and characterize undescribed systemic sclerosis (SSc)-specific autoantibodies targeting nucleolar antigens and to assess their clinical significance.

METHODS

We conducted proteome-wide autoantibody screening (PWAS) against serum samples from SSc patients with nucleolar patterned anti-nuclear antibodies (NUC-ANAs) of specific antibodies (Abs) unknown, utilizing wet protein arrays fabricated from in vitro human proteome. Controls included SSc patients with already-known SSc-specific autoantibodies, patients with other connective tissue diseases and healthy subjects. The selection of nucleolar antigens was performed by database search in the Human Protein Atlas. The presence of autoantibodies was certified by immunoblots and immunoprecipitations. Indirect immunofluorescence assays on HEp-2 cells were also conducted. Clinical assessment was conducted by retrospective review of electronic medical records.

RESULTS

PWAS identified three candidate autoantibodies, including anti-nuclear valosin-containing protein-like (NVL) Ab. Additional measurements in disease controls revealed that only anti-NVL Abs are exclusively detected in SSc. Detection of anti-NVL Abs was reproduced by conventional assays such as immunoblotting and immunoprecipitation. Indirect immunofluorescence assays demonstrated homogeneous nucleolar patterns. Anti-NVL Ab-positive cases were characterized by significantly low prevalence of diffuse skin sclerosis and interstitial lung disease, compared with SSc cases with NUC-ANAs other than anti-NVL Abs, such as anti-U3-RNP and anti-Th/To Abs.

CONCLUSION

Anti-NVL Ab is an SSc-specific autoantibody associated with a unique combination of clinical features, including limited skin sclerosis and lack of lung involvement.

Coexistence of systemic sclerosis and cryopyrin-associated periodic syndrome

Systemic sclerosis (SSc) and cryopyrin-associated periodic syndrome (CAPS) are distinct clinical entities belonging to the autoimmune and autoinflammatory diseases, respectively. The coexistence of the two entities has rarely been reported and is poorly characterized. Here, we described a case of a 38-year-old Japanese woman diagnosed with anti-centromere antibody-positive SSc and CAPS carrying the pathogenic mutation in the NLRP3 gene, with a detailed autoantibody profile by a high-throughput comprehensive protein array covering approximately 90% of the human transcriptome. The clinical manifestations of the patient were typical of both SSc and CAPS. Comprehensive autoantibody profiling identified 65 autoantibodies in the patient's serum and 78 autoantibodies in the serum of her daughter with CAPS, who carried the same NLRP3 mutation as the patient. SSc-associated autoantibodies (anti-DBT, anti- CENP-B, and anti-CENP-A) and anti-CD320 antibody were detected at high levels only in the patient's serum, while autoantibodies to the following four proteins were detected in the sera of both the patient and her daughter: TRIM21, LIMS1, CLIP4, and KAT2A. The TRRUST enrichment analysis identified NF-κB1 and RelA as overlapping key transcription factors that regulate the genes encoding proteins to which autoantibodies were detected in the patient and her daughter, therefore the autoantibody profile of the patient cannot be solely attributed to SSc, but may also be influenced by CAPS. Although autoimmune and autoinflammatory diseases are considered to be at opposite ends of the immunological spectrum, detailed autoantibody profiling may reveal a unique immunological landscape in an overlapping case of the two entities.

Reliability, validity, and sensitivity of the Japanese version of the University of California Los Angeles scleroderma clinical trial consortium gastrointestinal tract instrument: Application to efficacy assessment of intravenous immunoglobulin administration

This study aimed to develop and assess the reliability, validity, and sensitivity of the Japanese version of the University of California Los Angeles Scleroderma Clinical Trial Consortium gastrointestinal tract (GIT) Instrument 2.0 (the GIT score), as an evaluation tool for GIT symptoms in systemic sclerosis (SSc). The Japanese version of the GIT score was constructed using the forward-backward method. The reliability and validity of this instrument were evaluated in a cohort of 38 SSc patients. Correlation analysis was conducted to assess the relationship between the GIT score and existing patient-reported outcome measures. Additionally, the sensitivity of the GIT score was examined by comparing GIT scores before and after intravenous immunoglobulin (IVIG) administration in 10 SSc-myositis overlap patients, as IVIG has recently demonstrated effectiveness in alleviating GIT symptoms of SSc. As a result, the Japanese version of the GIT score exhibited internal consistency and a significant association with the Frequency Scale for the Symptoms of Gastroesophageal Reflux Disease. Furthermore, the total GIT score, as well as the reflux and distention/bloating subscales, displayed moderate correlations with the EuroQol 5 dimensions (EQ-5D) pain/discomfort subscale and the Short Form-36 body pain subscale. Notably, following IVIG treatment, there was a statistically significant reduction in the total GIT score and multiple subscales. We first validated the Japanese version of the GIT score in Japanese SSc patients in real-world clinical settings. This instrument holds promise for application in future clinical trials involving this patient population.

Comprehensive autoantibody profiling in systemic autoimmunity by a highly-sensitive multiplex protein array

Comprehensive autoantibody evaluation is essential for the management of autoimmune disorders. However, conventional methods suffer from poor sensitivity, low throughput, or limited availability. Here, using a proteome-wide human cDNA library, we developed a novel multiplex protein assay (autoantibody array assay; A-Cube) covering 65 antigens of 43 autoantibodies that are associated with systemic sclerosis (SSc) and polymyositis/dermatomyositis (PM/DM). The performance of A-Cube was validated against immunoprecipitation and established enzyme-linked immunosorbent assay. Further, through an evaluation of serum samples from 357 SSc and 172 PM/DM patients, A-Cube meticulously illustrated a diverse autoantibody landscape in these diseases. The wide coverage and high sensitivity of A-Cube also allowed the overlap and correlation analysis between multiple autoantibodies. Lastly, reviewing the cases with distinct autoantibody profiles by A-Cube underscored the importance of thorough autoantibody detection. Together, these data highlighted the utility of A-Cube as well as the clinical relevance of autoantibody profiles in SSc and PM/DM.

Significance of anti-transcobalamin receptor antibodies in cutaneous arteritis revealed by proteome-wide autoantibody screening

Cutaneous arteritis (CA) is a single-organ vasculitis that exclusively affects the small to medium-sized arteries of the skin. Diagnosis depends on a histological investigation with skin biopsy, which could be burdensome for both patients and clinicians. Moreover, the pathogenesis of CA remains unstudied, and treatment has not yet been established. Herein, we applied our proteome-wide autoantibody screening method to explore autoantibodies in the serum of CA patients. As a result, anti-transcobalamin receptor (TCblR) antibodies (Abs) were specifically detected in 24% of CA patients. Patients with positive anti-TCblR Abs were spared from peripheral neuropathy compared to those with negative anti-TCblR Abs, showing characteristics as CA confined to the skin. In addition, we revealed that anti-TCblR Abs trigger the autocrine loop of interleukin-6 mediated by tripartite motif-containing protein 21 in human endothelial cells and induce periarterial inflammation in murine skin. Furthermore, we demonstrated that methylcobalamin, a ligand of TCblR, ameliorates inflammation caused by anti-TCblR Abs both in vitro and in vivo. Collectively, our investigation unveils the pathologic significance of anti-TCblR Abs in CA and their potential as a diagnostic marker and a pathophysiology-oriented therapeutic target.

Analysis of Ser/Thr Kinase HASPIN-Interacting Proteins in the Spermatids

HASPIN is predominantly expressed in spermatids, and plays an important role in cell division in somatic and meiotic cells through histone H3 phosphorylation. The literature published to date has suggested that HASPIN may play multiple roles in cells. Here, 10 gene products from the mouse testis cDNA library that interact with HASPIN were isolated using the two-hybrid system. Among them, CENPJ/CPAP, KPNA6/importin alpha 6, and C1QBP/HABP1 were analyzed in detail for their interactions with HASPIN, with HASPIN phosphorylated C1QBP as the substrate. The results indicated that HASPIN is involved in spermatogenesis through the phosphorylation of C1QBP in spermatids, and also may be involved in the formation of centrosomes.

Autoantibody Landscape Revealed by Wet Protein Array: Sum of Autoantibody Levels Reflects Disease Status

Autoantibodies are found in various pathological conditions such as autoimmune diseases, infectious diseases, and malignant tumors. However their clinical implications have not yet been fully elucidated. Herein, we conducted proteome-wide autoantibody screening and quantification with wet protein arrays consisting of proteins synthesized from proteome-wide human cDNA library (HuPEX) maintaining their three-dimensional structure. A total of 565 autoantibodies were identified from the sera of three representative inflammatory disorders (systemic sclerosis, psoriasis, and cutaneous arteritis). Each autoantibody level either positively or negatively correlated with serum levels of C-reactive protein, the best-recognized indicator of inflammation. In particular, we discovered total levels of a subset of autoantibodies correlates with the severity of clinical symptoms. From the sera of malignant melanoma, 488 autoantibodies were detected. Notably, patients with metastases had increased overall autoantibody production compared to those with tumors limiting to the primary site. Collectively, proteome-wide screening of autoantibodies using the in vitro proteome can reveal the "autoantibody landscape" of human subjects and may provide novel clinical biomarkers.