Rheumatoid arthritis is an autoimmune inflammatory disease leading to joint cartilage, bone degradation and limitation of mobility. Diagnosis of RA is difficult and complex. There are also no effective methods for clear discrimination between RA patients and non-RA individuals. In this work we use IR spectroscopy to differentiate RA patients and blood donors’ sera. We found differences between investigated sera (RA and non-RA) in range of 3000–2800 and 1800–800 cm−1 (W1–W5 regions). Based on mathematical analysis we developed a K-NN model characterized by 85 % of sensitivity and 100 % of specificity. Also we found that, wavenumber 1424 cm−1, comprising in W3 region, was the most effective in human sera distinguishing. We conclude that IR spectroscopy may serve as a fast and easy method useful in RA serology.
Bacteria of the genus Proteus of the family Enterobacteriaceae are facultative human pathogens responsible mainly for urinary tract and wound infections, bacteremia and the development of rheumatoid arthritis (RA). We have analyzed and compared by ELISA the titer of antibodies in plasmas of healthy individuals and in sera of rheumatoid arthritis patients recognizing a potential host cross-reactive epitope (lysine-galacturonic acid epitopes) present in Proteus lipopolysaccharide (LPS). In our experiments LPSs isolated from two mutants of smooth Proteus mirabilis 1959 (O3), i.e. strains R110 and R45, were used. R110 (Ra type mutant) is lacking the O-specific polysaccharide, but possesses a complete core oligosaccharide, while R45 (Re type) has a reduced core oligosaccharide and contains two 3-deoxy-d-manno-oct-2-ulosonic acid residues and one of 4-amino-4-deoxy-l-arabinopyranose residues. Titer of P. mirabilis S1959 LPS-specific-antibodies increased with the age of blood donors. RA and blood donors’ sera contained antibodies against S and Ra and Re type of P. mirabilis O3 LPSs. Antibodies recognizing lysine-galacturonic acid epitopes of O3 LPS were detected by ELISA in some plasmas of healthy individuals and sera of rheumatoid arthritis patients. RA patients antibodies reacting with P. mirabilis S1959 S and R LPSs may indicate a potential role of anti-LPS antibodies in molecular mimicry in RA diseases.
Most rheumatic diseases, including rheumatoid arthritis (RA), are characterized by immune disorders that affect antibody activity. In the present study, using Dot blot and ELISA assay, we showed that patients with rheumatic disease produced significantly more antibodies against lipopolysaccharide (LPS) P. mirabilis O3 compared to healthy donors (p < 0.05), and affinity purified antibodies against LPS O3 may cross-react with collagen type I. It was demonstrated that purified of antibodies isolated from RA patients sera, reacted stronger with the collagen than healthy donors (p = 0.015), and cross-reaction was correlated with level of anti-citrullinated peptide antibodies (r = 0.7, p = 0.003). Moreover, using six different lipopolysaccharides were demonstrated the significant correlations in sera reactivity among lysine-containing lipopolysaccharides observed in patients’ sera (p < 0.05). Using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) it was shown that unique wavenumbers of sera spectra correlate with reactivity with lipopolysaccharides allowing distinguish patients from healthy blood donors. Antibodies adsorption by synthetic antigens shows that in patients’ group anti-LPS O3 antibodies can be adsorbed by both amides of galacturonic acid and lysine or threonine, which suggests less specificity of antibodies binding with non-carbohydrate LPS component. The observed correlations suggest that non-carbohydrate components of LPS may be an important epitope for less specific anti-LPS antibodies, which might lead to cross-reactions and affect disease development.
Rheumatoid arthritis (RA) is one of the most common autoimmune diseases worldwide. Due to high heterogeneity in disease manifestation, accurate and fast diagnosis of RA is difficult. This study analyzed the potential relationship between the infrared (IR) spectra obtained by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and the presence of autoantibodies and antibodies against urease in sera. Additionally, the wave number of the IR spectrum that enabled the best differentiation between patients and healthy blood donors was investigated. Using a mathematical model involving principal component analysis and discriminant analysis, it was shown that the presence of anti-citrullinated protein antibody, rheumatoid factor, anti-neutrophil cytoplasmic antibodies, and anti-nuclear antibodies correlated significantly with the wave numbers in the IR spectra of the tested sera. The most interesting findings derived from determination of the best predictors for distinguishing RA. Characteristic features included an increased reaction with urease mimicking peptides and a correspondence with particular nucleic acid bands. Taken together, the results demonstrated the potential application of ATR-FTIR in the study of RA and identified potential novel markers of the disease.
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