Humoral Response to Microbial Biomarkers in Rheumatoid Arthritis Patients

Abstract

Background/objective: Chronic humoral immune response against multiple microbial antigens may play a crucial role in the etiopathogenesis of rheumatoid arthritis (RA). We aimed to assess the prevalence and magnitude of antibody response against various bacterial and viral immunogen peptides in the sera of RA patients compared with the general population.

Methods: Polyclonal IgG antibodies (Abs) specific for peptides derived from Porphyromonas gingivalis (RgpA, Kpg), Aggregatibacter actinomycetemcomitans (LtxA1, LtxA2), Mycobacterium avium subsp. paratuberculosis (MAP4027), Epstein-Barr virus (EBNA1, EBVBOLF), and human endogenous retrovirus (HERV-W env-su) were detected by ELISA in serum samples from 148 consecutive RA patients and 148 sex and age-matched healthy controls (HCs). In addition, the presence of a relationship between the positivity and the titer of antibodies and RA descriptors was explored by bivariate correlation analysis.

Results: RA patients exhibit a higher prevalence of humoral immune response against all tested peptides compared to HCs with a statically significant difference for MAP4027 (30.4% vs. 10.1%), BOLF (25.7% vs. 8.1%), RgpA (24.3% vs. 9.4%), HERV W-env (20.3% vs. 9.4%), and EBNA1 (18.9% vs. 9.4%) peptides. Fifty-three (35.8%) out of 148 RA serum and 93 (62.8%) out of 148 HCs were negative for all pathogen-derived peptides. There was a significant correlation between OD values obtained by ELISA test against all peptides (p < 0.0001). We also found an increased titer and prevalence of Abs against LtxA1 and LtxA2 in seropositive vs. seronegative RF (p = 0.019, p = 0.018).

Conclusion: This study demonstrates a significantly increased humoral response against multiple pathogens in patients with RA and implies that they could be an important factor in the pathogenesis of the disease. Therefore, the role of each individual pathogen in RA needs to be further investigated.

Keywords: A. actinomycetemcomitans; Epstein–Barr virus; M. avium subspecies paratuberculosis; P. gingivalis; human endogenous retroviruses; immune response; rheumatoid arthritis.

Figure 1

ELISA-based analysis of Abs reactivity against pathogenic microorganism-derived peptides in RA patients and HCs. Sera samples were tested against plate-coated (A) MAP4027, (B) RgpA, (C) Kpg, (D) LtxA1, (E) LtxA2, (F) EBNA1, (G) EBVBOLF, and (H) HERV-W env peptides. Dashed lines represent thresholds used to assess the samples’ positivity (cut-off value based on the ROC curve with ≥90% specificity and 95% confidence interval).

Figure 2

Number of sera positive to MAP4027, BOLF1, RgpA, HERV-W, and EBNA1 peptides in RA and HCs (Fisher’s exact test: p < 0.05).

Figure 3

Abs response against LtxA1 (A) and LtxA2 (B) in RF-positive RA patients vs. RF-negative RA patients. The black bars represent the average ±S, dashed lines represent thresholds used to assess the samples’ positivity.

Figure 4

Heatmap displaying the r values obtained from Spearman correlation analysis performed among derived peptides.