Antibodies against cyclic citrullinated peptides in infectious diseases—a systematic review

The Extracellular Vesicle Citrullinome and Signature in a Piglet Model of Neonatal Seizures

Neonatal seizures are commonly associated with acute perinatal brain injury, while understanding regarding the downstream molecular pathways related to seizures remains unclear. Furthermore, effective treatment and reliable biomarkers are still lacking. Post-translational modifications can contribute to changes in protein function, and post-translational citrullination, which is caused by modification of arginine to citrulline via the calcium-mediated activation of the peptidylarginine deiminase (PAD) enzyme family, is being increasingly linked to neurological injury. Extracellular vesicles (EVs) are lipid-bilayer structures released from cells; they can be isolated from most body fluids and act as potential liquid biomarkers for disease conditions and response to treatment. As EVs carry a range of genetic and protein cargo that can be characteristic of pathological processes, the current study assessed modified citrullinated protein cargo in EVs isolated from plasma and CSF in a piglet neonatal seizure model, also following phenobarbitone treatment. Our findings provide novel insights into roles for PAD-mediated changes on EV signatures in neonatal seizures and highlight the potential of plasma- and CSF-EVs to monitor responses to treatment.

Putative Roles for Peptidylarginine Deiminases in COVID-19

Peptidylarginine deiminases (PADs) are a family of calcium-regulated enzymes that are phylogenetically conserved and cause post-translational deimination/citrullination, contributing to protein moonlighting in health and disease. PADs are implicated in a range of inflammatory and autoimmune conditions, in the regulation of extracellular vesicle (EV) release, and their roles in infection and immunomodulation are known to some extent, including in viral infections. In the current study we describe putative roles for PADs in COVID-19, based on in silico analysis of BioProject transcriptome data (PRJNA615032 BioProject), including lung biopsies from healthy volunteers and SARS-CoV-2-infected patients, as well as SARS-CoV-2-infected, and mock human bronchial epithelial NHBE and adenocarcinoma alveolar basal epithelial A549 cell lines. In addition, BioProject Data PRJNA631753, analysing patients tissue biopsy data (n = 5), was utilised. We report a high individual variation observed for all PADI isozymes in the patients' tissue biopsies, including lung, in response to SARS-CoV-2 infection, while PADI2 and PADI4 mRNA showed most variability in lung tissue specifically. The other tissues assessed were heart, kidney, marrow, bowel, jejunum, skin and fat, which all varied with respect to mRNA levels for the different PADI isozymes. In vitro lung epithelial and adenocarcinoma alveolar cell models revealed that PADI1, PADI2 and PADI4 mRNA levels were elevated, but PADI3 and PADI6 mRNA levels were reduced in SARS-CoV-2-infected NHBE cells. In A549 cells, PADI2 mRNA was elevated, PADI3 and PADI6 mRNA was downregulated, and no effect was observed on the PADI4 or PADI6 mRNA levels in infected cells, compared with control mock cells. Our findings indicate a link between PADI expression changes, including modulation of PADI2 and PADI4, particularly in lung tissue, in response to SARS-CoV-2 infection. PADI isozyme 1-6 expression in other organ biopsies also reveals putative links to COVID-19 symptoms, including vascular, cardiac and cutaneous responses, kidney injury and stroke. KEGG and GO pathway analysis furthermore identified links between PADs and inflammatory pathways, in particular between PAD4 and viral infections, as well as identifying links for PADs with a range of comorbidities. The analysis presented here highlights roles for PADs in-host responses to SARS-CoV-2, and their potential as therapeutic targets in COVID-19.

Post-Translational Protein Deimination Signatures in Serum and Serum-Extracellular Vesicles of Bos taurus Reveal Immune, Anti-Pathogenic, Anti-Viral, Metabolic and Cancer-Related Pathways for Deimination

The bovine immune system is known for its unusual traits relating to immunoglobulin and antiviral responses. Peptidylarginine deiminases (PADs) are phylogenetically conserved enzymes that cause post-translational deimination, contributing to protein moonlighting in health and disease. PADs also regulate extracellular vesicle (EV) release, forming a critical part of cellular communication. As PAD-mediated mechanisms in bovine immunology and physiology remain to be investigated, this study profiled deimination signatures in serum and serum-EVs in Bos taurus. Bos EVs were poly-dispersed in a 70-500 nm size range and showed differences in deiminated protein cargo, compared with whole sera. Key immune, metabolic and gene regulatory proteins were identified to be post-translationally deiminated with some overlapping hits in sera and EVs (e.g., immunoglobulins), while some were unique to either serum or serum-EVs (e.g., histones). Protein-protein interaction network analysis of deiminated proteins revealed KEGG pathways common for serum and serum-EVs, including complement and coagulation cascades, viral infection (enveloped viruses), viral myocarditis, bacterial and parasitic infections, autoimmune disease, immunodeficiency intestinal IgA production, B-cell receptor signalling, natural killer cell mediated cytotoxicity, platelet activation and hematopoiesis, alongside metabolic pathways including ferroptosis, vitamin digestion and absorption, cholesterol metabolism and mineral absorption. KEGG pathways specific to EVs related to HIF-1 signalling, oestrogen signalling and biosynthesis of amino acids. KEGG pathways specific for serum only, related to Epstein-Barr virus infection, transcription mis-regulation in cancer, bladder cancer, Rap1 signalling pathway, calcium signalling pathway and ECM-receptor interaction. This indicates differences in physiological and pathological pathways for deiminated proteins in serum-EVs, compared with serum. Our findings may shed light on pathways underlying a number of pathological and anti-pathogenic (viral, bacterial, parasitic) pathways, with putative translatable value to human pathologies, zoonotic diseases and development of therapies for infections, including anti-viral therapies.

Migratory Polyarthralgias and Skin Rash: Rat Bite Fever with a Positive Anti-Cyclic Citrullinated Peptide

Rat bite fever is a rare, underdiagnosed disease caused by Streptobacillus moniliformis in the United States, and is typically characterized by leukocytosis, elevated C-reactive protein, migratory polyarthralgias, and pustular skin rash. Rat bite fever is frequently misdiagnosed as either a viral illness or a rheumatologic disease and carries a high mortality risk if untreated. We report the first case of rat bite fever associated with positive anti–cyclic citrullinated peptide. The patient initially presented with low back pain and developed a pustular rash as well as severe asymmetric polyarthralgias. Blood cultures turned positive for S. moniliformis and the patient completed a 4-week course of antibiotics for presumed septic arthritis.

Poncet’s Disease in the Preclinical Phase of Rheumatoid Arthritis

We report on a patient with seropositive polyarthritis retrospectively diagnosed as Poncet’s disease in the preclinical phase of seropositive rheumatoid arthritis. Our patient developed rheumatoid arthritis more than 2 years after being successfully treated for pulmonary tuberculosis and an initial inflammatory polyarthritis consistent with the diagnosis of Poncet’s disease. This case illustrates the importance of recognizing Poncet’s disease in a patient presenting with polyarthritis in order to avoid inappropriate long-term disease modifying antirheumatic treatment. It also illustrates the need for adequate follow-up of patients with Poncet’s disease after treatment with antituberculosis treatment so that progression to a primary inflammatory arthritis such as rheumatoid arthritis may be identified timeously. Although seropositivity for rheumatoid arthritis has been reported in Poncet’s disease as well as in tuberculosis, it is rather uncommon, and long-term follow-up of patients with Poncet’s disease is essential particularly if they have positive serological tests for rheumatoid arthritis. In this case report, we describe the first reported case of Poncet’s disease in the preclinical phase of rheumatoid arthritis and review the literature related to this rare disease presentation.

Historical observations contributing insights on etiopathogenesis of rheumatoid arthritis and role of rheumatoid factor

When studies on rheumatoid arthritis (RA) that were made many decades ago and could be considered "historical" in nature are analyzed in the context of recent observations, important insights on RA and on the function of rheumatoid factor (RF) become apparent. RF in the role of antibody to immune complexes (ICs) appears to be involved in activation of the complement system and in the production of chemotactic and inflammatory mediators, creating a condition that can be sustained and reinitiated. In the synovial cavity, a state of nonresolving inflammation is produced with the formation of citrullinated protein antigen-antibody complexes or other forms of ICs. This is followed by a second wave of IC production in the form of RF acting as antibody reactive with the initial ICs. Both of these processes are associated with complement consumption and production of inflammatory mediators. We present a model of an initiation phase of RA that might represent an example of repetitive formation of ICs and complement-mediated inflammation. Targeting therapy at this phase of RA to break the cycles of recurrent inflammation might be a novel approach to aid in further control of the disease.

Travel- and immigration-related problems in rheumatology

Health problems are self-reported by up to 64% of travellers to the developing world. Traditionally, rheumatic symptoms are accorded little significance, but many travellers do return home with musculoskeletal complaints. The assessment of these patients is often hindered by the Western clinician's lack of familiarity with the types of infections that the patient may have encountered while travelling. Standard serological tests for autoimmune diseases can be unreliable in the setting of concomitant tropical infection, and these infections themselves can have musculoskeletal manifestations. Even in the absence of tropical infection, laboratory investigation of musculoskeletal symptoms in individuals of different ethnicities is challenging due to genetic and physiological variation. This review focusses on addressing the impact global migration has had on rheumatological clinical practice.

Arthritis and benznidazole: more closely related than we thought

Chagas disease is a parasitic infection that leads to a significant public health problem in countries where the disease is endemic and where it is nonendemic. Benznidazole is the most commonly used drug for the etiological treatment of Chagas disease. Patients treated with benznidazole suffer frequent adverse drug reactions. Although arthralgia is common, arthritis has been reported as a very rare side effect. The objective of this study was to describe arthritis in a cohort of Trypanosoma cruzi-infected patients treated with benznidazole.

The antibodies cyclic citrullinated peptides (anti-CCP) positivity could be a promising marker in brucellosis patients presented with peripheric arthritis

INTRODUCTION

The anti-cyclic citrullinated peptide (anti-CCP) enzyme-linked immunosorbent assay has a high sensitivity and specificity for rheumatoid arthritis (RA). It has been used in especially early diagnosis of RA, and used to discriminate from other forms of arthritis. Anti-CCP positivity is unknown in brucellosis presented with peripheric arthritis (BPA), like other rheumatic diseases. The objective of this study was to investigate the positivity of anti-CCP in patients with BPA in contrast to the patients with RA and healthy controls. Additionally, we have aimed to monitor changes of anti-CCP levels following the brucellosis treatment.

METHODS

The study group consisted of 137 subjects. 62 brucellosis patients presented with peripheric arthritis. Additionally, 33 RA patients and 42 healthy subjects selected as control groups. The anti-CCP, rheumatoid factor and anti-nuclear antibody levels of the subjects were measured.

RESULTS

Concerning the 62 BPA, 20 % (13 patients) of them had elevated anti-CCP levels. On the other side, of the 33 RA patients, 78.78 % (26 patients) of them had increased anti-CCP levels. Only one healthy subject's anti-CCP level was positive. There was statistically significant difference among the groups. After brucellosis treatment, monitorisation of the 13 patients with BPA who have the positive anti-CCP levels, were challengingly interesting because none of the patients had positive anti-CCP levels.

CONCLUSIONS

Anti-CCP may be positive marker in the diagnosis of BPA but clinicians need to be careful during the follow up period because it may turn into normal ranges. Additionally, patients presented with peripheric arthritis and anti-CCP positivity need to be evaluated also for the differential diagnosis of BPA.

Leprosy and rheumatoid arthritis: consequence or association?

Leprosy or Hansen's disease is a chronic granulomatous infectious disease caused by Mycobacterium leprae with a high prevalence in some developing countries however, it is rarely seen in non-endemic regions. Arthritis has been described in all types of Hansen's disease. Chronic arthritis is known to exist even in paucibacillary forms, resolved or treated disease and in patients without reaction, suggesting a perpetuated inflammatory process. In these cases leprosy can mimic some autoimmune diseases such as rheumatoid arthritis. When a patient with a history of leprosy presents with a symmetric, distal, polyarthritis the diagnosis may not be linear. Possibly it is a rheumatoid-like leprous arthritis with M leprae acting as the trigger element for the chronic process or it is an overlap condition, with a concomitant rheumatoid arthritis? A case report of a patient with a chronic inflammatory arthritis with 10 years of evolution is presented. The differential diagnosis between leprous and rheumatoid arthritis is discussed.

Frequency and clinical significance of a variety of autoantibodies in patients with definite infective endocarditis

BACKGROUND

Patients with infective endocarditis (IE) may present rheumatic manifestations concurrent with autoantibodies with low specificity, thus increasing misdiagnosis. Frequency of autoantibodies with high specificity remains unknown.

METHODS

Nineteen patients with definite IE were studied for low specificity (rheumatoid factor [RF], antinuclear antibodies, anti-Ro/SSA, anti-La/SSB, anti-ribonucleoproteins (anti-RNP) anticardiolipin [aCL], and anti-β2 glycoprotein 1) and high specificity (anti-cyclic citrullinated peptides [anti-CCPs], anti-double-stranded DNA, anti-Sm, anti-Scl70, and anticentromere) antibodies.

RESULTS

Frequency of RF was 68%; antinuclear antibodies, 47%; aCL/IgG, 58%; aCL/IgM, 47%; anti-β2 glycoprotein 1/IgG, 5%; and anti-Ro/SSA, 5%. Three patients had antiphospholipid syndrome-related antibodies in high titers, one of them also having pulmonary embolism. Except for anti-CCP (1 patient), other highly specific antibodies were absent.Rheumatoid factor of 100 UI/mL or greater and multifocal endocarditis were independently associated with in-hospital mortality.

CONCLUSIONS

Clinicians should need to be aware about the common presence of a variety of antibodies with low specificity but also the exceptional occurrence of anti-CCP antibodies in IE. Special attention to multifocal endocarditis and high RF is also suggested.

Arthritis after infection with Chikungunya virus

Chikungunya virus (CHIKV) is an emerging alphavirus responsible for several infectious outbreaks in the world. After an acute stage of illness characterised by a fever-arthralgia syndrome and rash, joint disorders due to CHIKV infection can sometimes persist for several months or years. Chronic arthritis after this emerging disease is well documented, and similarities to rheumatoid arthritis have been described. Knowledge of the geographical epidemiology of CHIKV infection is crucial for better control of the disease. Thus, recent outbreaks have led to several studies, which have highlighted the need for a better understanding of the clinical features of Chikungunya (CHIK) and beginning knowledge of the pathophysiogenesis, which can lead to further research.

Autoimmunity in Rheumatic Diseases Is Induced by Microbial Infections via Crossreactivity or Molecular Mimicry

A general consensus supports fundamental roles for both genetic and environmental, mainly microbial, factors in the development of autoimmune diseases. One form of autoimmune rheumatic diseases is confined to a group of nonpyogenic conditions which are usually preceded by or associated with either explicit or occult infections. A previous history of clinical pharyngitis, gastroenteritis/urethritis, or tick-borne skin manifestation can be obtained from patients with rheumatic fever, reactive arthritis, or Lyme disease, respectively, whilst, other rheumatic diseases like rheumatoid arthritis (RA), ankylosing spondylitis (AS), and Crohn's disease (CD) are usually lacking such an association with a noticeable microbial infection. A great amount of data supports the notion that RA is most likely caused by Proteus asymptomatic urinary tract infections, whilst AS and CD are caused by subclinical bowel infections with Klebsiella microbes. Molecular mimicry is the main pathogenetic mechanism that can explain these forms of microbe-disease associations, where the causative microbes can initiate the disease with consequent productions of antibacterial and crossreactive autoantibodies which have a great impact in the propagation and the development of these diseases.

Mutated citrullinated vimentin antibodies in rheumatoid arthritis

Rheumatoid arthritis (RA) is the most common inflammatory systemic autoimmune disease, primarily affecting the peripheral joints. The past decade has been marked with revolutionary changes both in the therapeutic and diagnostic perspectives of RA. The discovery of an RA-specific citrullination-driven immune reaction gave a substantial contribution in the diagnostic approach to RA. Efforts directed towards the identification of the antigenic target specifically recognized by these autoantibodies resulted in the identification of vimentin in citrullinated form as the potential native antigen, among other proteins. Furthermore, it was found that the mutation of vimentin represents an independent trigger of antigenic properties, in addition to citrullination. As a result of this discovery, a commercial ELISA using mutated citrullinated vimentin (MCV) was developed. Increasingly, data now support the use of anti-MCV in RA diagnosis and prognosis for errosion. This review summarizes the research to date on the use of anti-MCV in RA diagnosis and prognosis and its potential use as a therapeutic marker. The pathologic role of these antibodies in RA disease is also discussed.