Protein Citrullination by Peptidyl Arginine Deiminase/Arginine Deiminase Homologs in Members of the Human Microbiota and Its Recognition by Anti-Citrullinated Protein Antibodies.

The human microbiome exists throughout the body, and it is essential for maintaining various physiological processes, including immunity, and dysbiotic events, which are associated with autoimmunity. Peptidylarginine deiminase (PAD) enzymes can citrullinate self-proteins related to rheumatoid arthritis (RA) that induce the production of anti-citrullinated protein antibodies (ACPAs) and lead to inflammation and joint damage. The present investigation was carried out to demonstrate the expression of homologs of PADs or arginine deiminases (ADs) and citrullinated proteins in members of the human microbiota. To achieve the objective, we used 17 microbial strains and specific polyclonal antibodies (pAbs) of the synthetic peptide derived from residues 100-200 of human PAD2 (anti-PAD2 pAb), and the recombinant fragment of amino acids 326 and 611 of human PAD4 (anti-PAD4 pAb), a human anti-citrulline pAb, and affinity ACPAs of an RA patient. Western blot (WB), enzyme-linked immunosorbent assay (ELISA), elution, and a test with Griess reagent were used. This is a cross-sectional case-control study on patients diagnosed with RA and control subjects. Inferential statistics were applied using the non-parametric Kruskal-Wallis test and Mann-Whitney U test generated in the SPSS program. Some members of phyla Firmicutes and Proteobacteria harbor homologs of PADs/ADs and citrullinated antigens that are reactive to the ACPAs of RA patients. Microbial citrullinome and homolog enzymes of PADs/ADs are extensive in the human microbiome and are involved in the production of ACPAs. Our findings suggest a molecular link between microorganisms of a dysbiotic microbiota and RA pathogenesis.

Autoantibodies against a novel citrullinated fibrinogen peptide related to smoking status, disease activity and therapeutic response to methotrexate in cuban patients with early rheumatoid arthritis.

Treatment recommendations of early rheumatoid arthritis (RA) suggest differential management of patients on the basis of prognostic factors. In this study we aimed to investigate the relationship between autoantibodies against a novel citrullinated fibrinogen peptide (anti-CFP), smoking status, clinical activity and therapeutic response in Cuban patients with early RA, receiving treatment with methotrexate in comparison to rheumatoid factor (RF), anti-cyclic citrullinated peptide of second generation (anti-CCP2) and anti-mutated citrullinated vimentin (anti-MCV). A 6-month prospective observational study was performed in 60 early RA patients at baseline and 6 months after receiving methotrexate. Baseline and outcome measures included disease activity score of 28 joints (DAS 28), simplified disease activity index (SDAI), anti-CFP antibodies, RF, anti-CCP2 and anti-MCV. Therapeutic response was determined using 20/50/70 American College of Rheumatology (ACR) response rates. DAS28 (p < 0.0001), SDAI (p < 0.0001) as well as titres of anti-CFP (p = 0.0481), anti-CCP2 (p = 0.0082), RF IgM (p = 0.0187) and RF IgA (p = 0.0252) decreased under therapy. Multivariate analyses showed association of final anti-CFP values with sex and smoking status (p = 0.0296). It is of note that anti-CFP antibodies were one of predictors for DAS 28 (p = 0.0072) SDAI (p < 0.0001) and ACR response (p = 0.0003) in multivariate models. Anti-CFP antibodies decrease in correspondence with clinical improvement after 6-month therapy and are associated with sex and smoking status. Moreover, baseline anti-CFP antibodies, using in combination with sex, smoking status and autoantibodies (anti-CCP2, anti-MCV or RF) seems to have clinical relevance for predicting clinical activity and therapeutic response.

The TNFA -857C/T Polymorphism: Association with Rheumatoid Arthritis and Anti-CCP Levels in a Mexican Population.

Rheumatoid arthritis (RA) is a chronic inflammatory disease whose association with SNPs has led to the identification of biomarkers in different populations. To determine the association of the -857C/T SNP of the TNFA gene with RA and clinical parameters, 233 RA patients and 237 healthy controls were included in this study. The -857C/T polymorphism was determined using the TaqMan® system and clinical features were also determined. We found that the -857C/T SNP was in Hardy-Weinberg equilibrium. Our results showed no association of the -857C/T SNP with RA; however, RA patients carrying the TT genotype showed lower anti-CCP levels than other groups. Therefore, the TT genotype could be a risk factor for developing anti-CCP-negative RA. Our results suggest that the T allele of the TNFA -857C/T SNP exerts an influence on anti-CCP levels and could be a candidate marker for anti-CCP-negative RA.

CIGB-814, an altered peptide ligand derived from human heat-shock protein 60, decreases anti-cyclic citrullinated peptides antibodies in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic T cell-mediated autoimmune disease. Serum autoantibodies against cyclic citrullinated peptides (anti-CCP) are significant markers for diagnosis and prognosis of this disease. Induction of immune tolerance as therapeutic approach for RA constitutes a current research focal point. In this sense, we carried out a phase I clinical trial in RA patients with a new therapeutic candidate (called CIGB-814); which induced mechanisms associated with restoration of peripheral tolerance in preclinical studies. CIGB 814 is an altered peptide ligand (APL), derived from a CD4+ T cell epitope of human heat-shock protein 60 (HSP60), an autoantigen involved in the pathogenesis of RA. Twenty patients with moderate disease activity were included in this open label trial. Sequential dose-escalation of 1, 2.5 and 5 mg of CIGB-814 was studied. Consecutive groups of six, five, and nine patients received a subcutaneous dose weekly of the peptide during the first month and one dose monthly during the next 5 months. The peptide was well tolerated and reduced disease activity. Here, we reported the quantification of anti-CCP antibodies during the treatment with this APL and in the follow-up stage. Anti-CCP antibodies were quantified in the plasma from patients by a commercial enzyme immunoassay at baseline (T0) and at weeks 28 and 48. Results showed that CIGB-814 induced a significant reduction of anti-CCP antibodies. In addition, this decrease correlated with clinical improvement in patients assessed by Disease Activity Score in 28 joints (DAS28) criteria. These findings reinforce the therapeutic potential of CIGB-814.

α-enolase is an antigenic target in primary Sjögren's syndrome.

OBJECTIVES: Although anti-cyclic citrullinated peptides antibodies are specific markers for rheumatoid arthritis (RA), they might be present in other diseases. Our aim was to assess the native or citrullinated antigens recognised by patients with primary Sjögren's syndrome (pSS) and to evaluate their association with clinical and serological features. METHODS: In an initial screening, we assessed the serum reactivity of 12 patients with pSS against native or in vitro citrullinated antigens of HEp-2 cells by immunoblotting. We identified a 47kDa band, which was preferentially recognised and corresponded to α-enolase. Thus, levels of IgA and IgG anti-native and citrullinated α-enolase antibodies were measured in 50 pSS patients, 20 RA patients and 20 healthy subjects (HS) by ELISA. RESULTS: We identified α-enolase as a predominant antigen recognised in pSS. These patients had higher levels of anti-citrullinated α-enolase IgG antibodies compared with RA or HS (p=0.003 and p<0.0001, respectively). Furthermore, there was an increase of IgG anti-citrullinated α-enolase vs IgG anti-non-citrullinated α-enolase antibodies in pSS patients (p=0.001), by contrast no difference was found in RA. The presence of IgA and IgG anti-non-citrullinated and anti-citrullinated α-enolase antibodies were not associated with any clinical manifestation whatsoever, including non-erosive arthritis among pSS, but an association of IgA anti-citrullinated α-enolase with anti-Ro/SSA antibodies was found. CONCLUSIONS: We characterised α-enolase as a dominant antigen in lysates of HEp- 2 cells in pSS. Nevertheless, their precise role in pSS remains to be elucidated.

Eficacia diagnóstica de anticuerpos antipéptidos citrulinados de segunda y tercera generaciones para la artritis reumatoide / Diagnostic effectiveness of anti-citrullinated peptides antibodies of second and third generations for rheumatoid arthritis

Introducción: La artritis reumatoide es una enfermedad autoinmune caracterizada por la presencia de anticuerpos contra péptidos citrulinados, que constituyen indicadores para el diagnóstico de la enfermedad. Es necesario determinar la utilidad de diferentes métodos de determinación de estos anticuerpos para el diagnóstico de pacientes cubanos con artritis reumatoide. Objetivo: Determinar la eficacia de los ensayos de determinación de anticuerpos anti-CCP2 y anti-CCP3 para el diagnóstico de pacientes cubanos con artritis reumatoide. Material y método: Participaron 101 pacientes con artritis reumatoide, 58 pacientes con otras enfermedades reumáticas e inflamatorias y 43 individuos sanos. Se determinó la eficacia diagnóstica de los anticuerpos factor reumatoideo (FR), anti-CCP2 y anti-CCP3 medidos mediante ELISA, con el cálculo de la sensibilidad, especificidad, valores predictivos positivos y negativos. Resultados: El ensayo anti-CCP2 mostró un mejor balance sensibilidad (48,5 por ciento) y especificidad (98,0 por ciento). Cuando se fijó la especificidad a 98 por ciento, se observó la menor sensibilidad para el FR (40,3 por ciento). Utilizar los ensayos anti-CCP2 y FR aumentó la especificidad a 100 por ciento. Todos los autoanticuerpos mostraron asociación con la proteína C reactiva y correlación con la velocidad de sedimentación globular. Solamente los anticuerpos anti-CCP2 no mostraron correlación con el indicador clínico de actividad DAS 28. Conclusiones: Los anticuerpos anti-CCP2 son los de mayor eficacia para el diagnóstico de pacientes cubanos con artritis reumatoide. La determinación de FR permite identificar pacientes con artritis reumatoide seronegativos de anticuerpos anti-CCP2, por lo que la combinación de ambos inmunoensayos produce una mejoría en la eficacia diagnóstica(AU)

Introduction: Rheumatoid arthritis is an autoimmune disease characterized by the presence of antibodies against citrullinated peptides, which are one of the indicators for the diagnosis of a disease. The usefulness of different methods for the determination of these antibodies in the diagnosis of Cuban patients with rheumatoid arthritis is necessary to be established. Objective: To establish the diagnostic effectiveness of the second (anti-CCP2) and third (anti-CCP3) generation assays for the determination these antibodies against citrullinated peptides in Cuban patients with rheumatoid arthritis. Material and method: 101 patients with rheumatoid arthritis, 58 patients with other rheumatic and inflammatory diseases, and 43 healthy persons participated in the study. The diagnostic efficiency of rheumatoid factor (RF), anti-CCP2 and anti-CCP3 antibodies were determined using ELISA test, by calculating sensitivity, specificity, and positive and negative predictive values. Results: The anti-CCP2 assay showed a better balance of sensitivity (48.5 percent) and specificity (98.0 percent). The lower sensibility was observed for RF (40.3 percent) when the specificity was set at 98 percent. Specificity increased to 100 percent when anti-CCP2 and RF assays were used. All autoantibodies showed association with C-reactive protein and correlation with erythrocyte sedimentation rate. Only anti-CCP2 antibodies showed no correlation with the DAS28 clinical indicator. Conclusions: Anti-CCP2 antibodies are the ones of greater effectiveness in the diagnosis of Cuban patients with rheumatoid arthritis. RF identification allows to identify seronegative anti-CCP2 patients; therefore, the combination of both immunoassays leads to an improvement in the diagnostic effectiveness(AU)

Association between levels of synovial anti-citrullinated peptide antibodies and neutrophil response in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is characterized by the presence of anti-citrullinated peptide antibodies (ACPAs) and neutrophils infiltrating the synovial fluid (SF) of the affected joints. The aim of this work was to analyze whether the presence of ACPAs in SF is associated with neutrophil infiltration and with their phenotype in the inflamed joints of RA patients. We found that in the presence of ACPAs, the number of synovial neutrophils correlated with severe disease activity. The SF were divided according to synovial ACPA levels in negative- (<25 U/mL), low- (25-200 U/mL) and high level (˃200 U/mL; ACPAhigh ). We observed that IL-6, IL-17, and IL-8 were significantly elevated in ACPAhigh SF and that IL-8 levels correlated positively with neutrophil counts and with worse clinical manifestations. Additionally, in vitro incubation of neutrophils with ACPAhigh SF resulted in an increased ROS production and extracellular DNA release compared to neutrophils incubated with ACPA-negative SF. These exacerbated effector functions were associated with a fraction of ICAM-1-positive neutrophils, which were induced by ACPAhigh SF. Likewise, in in vivo, we could also detect this subset among neutrophils present in ACPAhigh SF. In conclusion, the data presented here shed light on the role of SF-ACPAs as inductors of a proinflammatory profile in neutrophils.