Peptide mimetics of anti-dsDNA idiotypes as a tool for lupus-specific IVIG preparation: specificity and efficacy in the treatment of experimental systemic lupus erythematosus

Background

Since the idiotypic network is an important mechanism for controlling the immune repertoire, we tested anti-idiotypic modulation employing concentrated specific natural polyclonal anti-dsDNA anti-idiotypic antibodies obtained from a commercial IVIG in the treatment of experimental systemic lupus erythematosus (SLE).

Aim

To address the specificity and efficacy of affinity purified IVIG, affinity purified on peptide mimetics of anti-dsDNA idiotypes, in vitro and in vivo, as treatment for experimental lupus.

Materials and methods

Specific natural polyclonal anti-dsDNA anti-idiotypic antibodies were affinity purified from IVIG (OMRIX Biopharmaceuticls Inc., Nes-Ziona, Israel) on an anti-dsDNA-Sepharose column constructed with anti-dsDNA idiotypes affinity purified from 55 patients with SLE. This compound improved the clinical manifestations of NZBXWXF1 mice in 200 times lower concentration than IVIG. This lupus-specific IVIG was introduced to a peptide phage display library (C-7mer-C). The identified synthetic peptides (idiotype mimetics) were synthesized and used to replace the human anti-dsDNA idiotypes column. IVIG affinity purified on the synthetic peptides columns were determined as peptide-specific IVIG (psIVIG). The psIVIG compound was tested for specificity by ELISA and competition assays.

Results

Each psIVIG inhibited the binding of anti-dsDNA antibodies from 12 lupus patients, to dsDNA, differentially by 15% up to 46% or as a mix up to 87–94%. Naïve mice immunized with a branched peptide composed of the synthetic mimetics of anti-dsDNA idiotypes induced the generation of elevated titers of anti-dsDNA. The anti-dsDNA generation was inhibited in the branced peptide immunized mice, following treatment with psIVIG. A cocktail of psIVIG was introduced to NZBxWxF1. The following clinical parameters were improved in the NZBxWxF1 psIVIG subjected mice: circulating anti-dsDNA antibodies, leukopenia, proteinuria and immunoglobulin deposits in the kidneys.

Conclusion

We introduce herein an IVIG subfraction, specific for anti-dsDNA treatment for lupus patients, and discuss its efficacy and beneficial effect in suppression of humoral and clinical signs of SLE versus regular IVIG.