SPRi-based strategy to identify specific biomarkers in systemic lupus erythematosus, rheumatoid arthritis and autoimmune hepatitis.

BACKGROUND

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 is a target for antinuclear autoantibodies in systemic Lupus erythematosus (SLE), rheumatoid arthritis (RA), and autoimmune hepatitis (AIH).

AIM

To monitor molecular interactions between peptides spanning the entire sequence of hnRNP A2/B1 and sera from patients and healthy controls.

METHODS

Sera from 8 patients from each pathology and controls were passed across a surface plasmon resonance Imagery (SPRi) surface containing 39 overlapping peptides of 17 mers covering the human hnRNP B1. Interactions involving the immobilised peptides were followed in real time and dissociation rate constants k(off) for each interaction were calculated.

RESULTS

Several significant interactions were observed: i) high stability (lower k(off) values) between P₅₅₋₇₀ and the AIH sera compared to controls (p= 0.003); ii) lower stability (higher k(off) values) between P₁₁₈₋₁₃₃ and P₂₆₂₋₂₇₇ and SLE sera, P₁₄₅₋₁₆₀ and RA sera compared to controls (p=0.006, p=0.002, p=0.007). The binding curves and k(off) values observed after the formation of complexes with anti-IgM and anti-IgG antibodies and after nuclease treatment of the serum indicate that i) IgM isotypes are prevalent and ii) nucleic acids participate in the interaction between anti-hnRNAP B1 and P₅₅₋₇₀ and also between controls and the peptides studied.

CONCLUSIONS

These results indicate that P₅₅₋₇₀ of hnRNP B1 is a potential biomarker for AIH in immunological tests and suggest the role of circulating nucleic acids, (eg miRNA), present or absent according to the autoimmune disorders and involved in antigen-antibody stability.