Abstract
Background
Autoantibodies are critical elements in RA pathogenesis and clinical assessment. The anti-malondialdehyde-acetaldehyde (anti-MAA) antibodies are potentially useful because of ...their claimed high sensitivity for all RA patients, including those lacking RF and anti-CCP antibodies. Therefore, we aimed to replicate these findings.
Methods
We independently attempted replication in Santiago and Barcelona using sera from 517 and 178 RA patients and 272 and 120 healthy controls, respectively. ELISA protocols for anti-MAA antibodies included five antigens (human serum albumin in three formulations, fibrinogen, and a synthetic peptide) and assays for the IgG, IgM, and IgA isotypes. We integrated our results with information found by searching the Web of Science for reports of anti-MAA antibodies in RA. The available patients (4989 in 11 sets) were included in a meta-analysis aimed at heterogeneity between studies. Factors accounting for heterogeneity were assessed with meta-regression.
Results
The sensitivity of anti-MAA antibodies in our RA patients was low, even in seropositive patients, with the percentage of positives below 23% for all ELISA conditions. Our results and bibliographic research showed IgG anti-MAA positive patients ranging from 6 to 92%. The extreme between-studies heterogeneity could be explained (up to 43%) in univariate analysis by sex, African ethnicity, the site of study, or recruitment from the military. The best model, including African ancestry and smoking, explained a high heterogeneity fraction (74%).
Conclusion
Anti-MAA antibody sensitivity is extremely variable between RA patient collections. A substantial fraction of this variability cannot be attributed to ELISA protocols. On the contrary, heterogeneity is determined by complex factors that include African ethnicity, smoking, and sex.
Objective
Recognition of a new type of rheumatoid arthritis (RA)–specific autoantibody, the anti–carbamylated protein antibodies (anti‐CarP), has provided an opportunity to improve the management and ...understanding of RA. The current study was undertaken to assess the relationship between anti‐CarP antibodies and HLA–DRB1 alleles in RA.
Methods
Serum samples were obtained from 3 different collections, comprising a total of 1,126 RA patients. Serum reactivity against in vitro carbamylated fetal calf serum proteins was determined by enzyme‐linked immunosorbent assay. HLA–DRB1 alleles were determined using either hybridization techniques or imputation from HLA‐dense genotypes. Results of these analyses were combined in a meta‐analysis with data from 3 previously reported cohorts. The carrier frequencies of the common HLA–DRB1 alleles were compared between the antibody‐positive RA subgroups and the double‐negative subgroup of RA patients stratified by anti–citrullinated protein antibody (ACPA)/anti‐CarP antibody status, and also between the 4 RA patient strata and healthy controls.
Results
Meta‐analysis was conducted with 3,709 RA patients and 2,305 healthy control subjects. Results revealed a significant increase in frequency of HLA–DRB1*03 carriers in the ACPA−/anti‐CarP+ subgroup as compared to ACPA−/anti‐CarP− RA patients and healthy controls; this was consistently found across the 6 sample collections. This association of HLA–DRB1*03 with ACPA−/anti‐CarP+ RA was independent of the presence of the shared allele (SE) and any other confounders analyzed. No other allele was specifically associated with the ACPA−/anti‐CarP+ RA patient subgroup. In contrast, frequency of the SE was significantly increased in the ACPA+/anti‐CarP− and ACPA+/anti‐CarP+ RA patient subgroups, without a significant distinction between them. Furthermore, some alleles (including HLA–DRB1*03) were associated with protection from ACPA+ RA.
Conclusion
These findings indicate a specific association of HLA–DRB1*03 with ACPA−/anti‐CarP+ RA, suggesting that preferential presentation of carbamylated peptides could be a new mechanism underlying the contribution of HLA alleles to RA susceptibility.
Biological age is not always concordant with chronological age and the departures are of interest for understanding how diseases and environmental insults affect tissue function, organismal health, ...and life expectancy. The best-known biological age biomarker is telomere length, but there are more accurate biomarkers as the recently developed based in epigenetic, transcriptomic, or biochemical changes. The most accurate are the epigenetic biomarkers based on specific changes in DNA methylation referred as DNA methylation age measures (DmAM). Here, we have developed and validated a new DmAM that addresses some limitations of the previously available. The new DmAM includes the study in whole blood (WB) of 8 CpG sites selected as the most informative on a training set of 390 healthy subjects. The 8 CpG DmAM showed better accuracy than other DmAM based in few CpG in an independent validation set of 335 subjects. Results were not significantly influenced by sex, smoking, or variation in blood cell subpopulations. In addition, the new 8 CpG DmAM was amenable to study in a single multiplex reaction done with methylation-sensitive single-nucleotide primer extension (MS-SNuPE), a methodology based on commercially available reagents and run in capillary electrophoresis sequencers. In this way, the high cost of DNA methylation microarrays or of a pyrosequencer, which are needed for alternative DmAM, was avoided. Performance of the DmAM with MS-SNuPE was assessed in a set of 557 donors, showing high call rate (>97%), low CV (<3.3%) and high accuracy (Mean Absolute Deviation = 6.07 years). Therefore, the 8 CpG DmAM is a feasible and accurate tool for assessing the epigenetic component of biological age in blood of adults.
The major environmental risk factor for rheumatoid arthritis (RA) is smoking, which according to a widely accepted model induces protein citrullination in the lungs, triggering the production of ...anti-citrullinated protein antibodies (ACPA) and RA development. Nevertheless, some research findings do not fit this model. Therefore, we obtained six independent cohorts with 2253 RA patients for a detailed analysis of the association between smoking and RA autoantibodies. Our results showed a predominant association of smoking with the concurrent presence of the three antibodies: rheumatoid factor (RF), ACPA and anti-carbamylated protein antibodies (ACarPA) (3 Ab vs. 0 Ab: OR = 1.99, p = 2.5 × 10
). Meta-analysis with previous data (4491 patients) confirmed the predominant association with the concurrent presence of the three antibodies (3 Ab vs. 0 Ab: OR = 2.00, p = 4.4 ×10
) and revealed that smoking was exclusively associated with the presence of RF in patients with one or two antibodies (RF
vs. RF
: OR = 1.32, p = 0.0002). In contrast, no specific association with ACPA or ACarPA was found. Therefore, these results showed the need to understand how smoking favors the concordance of RA specific antibodies and RF triggering, perhaps involving smoking-induced epitope spreading and other hypothesized mechanisms.
Osteoarthritis (OA) is a disease affecting multiple tissues of the joints in the elderly, but most notably articular cartilage. Premature biological aging has been described in this tissue and in ...blood cells, suggesting a systemic component of premature aging in the pathogenesis of OA. Here, we have explored epigenetic aging in OA at the local (cartilage and bone) and systemic (blood) levels. Two DNA methylation age-measures (DmAM) were used: the multi-tissue age estimator for cartilage and bone; and a blood-specific biomarker for blood. Differences in DmAM between OA patients and controls showed an accelerated aging of 3.7 years in articular cartilage (95% CI = 1.1 to 6.3,
= 0.008) of OA patients. By contrast, no difference in epigenetic aging was observed in bone (0.04 years; 95% CI = -1.8 to 1.9,
= 0.3) and in blood (-0.6 years; 95% CI = -1.5 to 0.3,
= 0.2) between OA patients and controls. Therefore, premature epigenetic aging according to DNA methylation changes was specific of OA cartilage, adding further evidence and insight on premature aging of cartilage as a component of OA pathogenesis that reflects damage and vulnerability.
Objective
Recognition of a new type of rheumatoid arthritis (
RA
)–specific autoantibody, the anti–carbamylated protein antibodies (anti‐CarP), has provided an opportunity to improve the management ...and understanding of
RA
. The current study was undertaken to assess the relationship between anti‐CarP antibodies and
HLA
–
DRB
1
alleles in
RA
.
Methods
Serum samples were obtained from 3 different collections, comprising a total of 1,126
RA
patients. Serum reactivity against in vitro carbamylated fetal calf serum proteins was determined by enzyme‐linked immunosorbent assay.
HLA
–
DRB
1
alleles were determined using either hybridization techniques or imputation from
HLA
‐dense genotypes. Results of these analyses were combined in a meta‐analysis with data from 3 previously reported cohorts. The carrier frequencies of the common
HLA
–
DRB
1
alleles were compared between the antibody‐positive
RA
subgroups and the double‐negative subgroup of
RA
patients stratified by anti–citrullinated protein antibody (
ACPA
)/anti‐CarP antibody status, and also between the 4
RA
patient strata and healthy controls.
Results
Meta‐analysis was conducted with 3,709
RA
patients and 2,305 healthy control subjects. Results revealed a significant increase in frequency of
HLA
–
DRB
1*03
carriers in the
ACPA
−/anti‐CarP+ subgroup as compared to
ACPA
−/anti‐CarP−
RA
patients and healthy controls; this was consistently found across the 6 sample collections. This association of
HLA
–
DRB
1*03
with
ACPA
−/anti‐CarP+
RA
was independent of the presence of the shared allele (
SE
) and any other confounders analyzed. No other allele was specifically associated with the
ACPA
−/anti‐CarP+
RA
patient subgroup. In contrast, frequency of the
SE
was significantly increased in the
ACPA
+/anti‐CarP− and
ACPA
+/anti‐CarP+
RA
patient subgroups, without a significant distinction between them. Furthermore, some alleles (including
HLA
–
DRB
1*03
) were associated with protection from
ACPA
+
RA
.
Conclusion
These findings indicate a specific association of
HLA
–
DRB
1*03
with
ACPA
−/anti‐CarP+
RA
, suggesting that preferential presentation of carbamylated peptides could be a new mechanism underlying the contribution of
HLA
alleles to
RA
susceptibility.
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