CD20 Mimicry by a mAb Rituximab-Specific Linear Peptide: A Potential Tool for Active Immunotherapy of Autoimmune Diseases

Abstract

An attractive, whether alternative or complementary, approach to passive immunotherapy (IT) with the anti-CD20 mAb rituximab for the treatment of autoimmune diseases is to stimulate the host to produce an anti-CD20 immune response by using peptides that mimic CD20 (mimotopes). The only mimotope reported to target CD20 antigen is a 43-mer polypeptide corresponding to the exposed domain of the molecule (from amino acid 142 to 184). Owing to its length, however, it failed to efficiently induce a CD20-specific response. A search has now been made for a smaller mimotope by biopanning a phage-display peptide library with rituximab. A total of 10 positive phage clones expressing six distinct sequences were isolated. Their alignment produced a motif that did not match any portion of the CD20 extracellular loop, whereas the motif bearing the 12-mer linear peptide Rp10-L specifically reacted with rituximab and inhibited its binding to CD20. Furthermore, in BALB/c mice Rp10-L-induced antibodies that reacted with the CD20(+) B lymphoid cell line Raji but not with the C20(-) T lymphoid cell line CEM. This peptide is currently being investigated to determine the effectiveness of CD20-based active IT for the treatment of autoimmune diseases.

Generation of biologically active linear and cyclic peptides has revealed a unique fine specificity of rituximab and its possible cross-reactivity with acid sphingomyelinase-like phosphodiesterase 3b precursor

“…29 Altogether, these findings are not surprising, since peptides have been shown to mimic antigens with a completely different structure, namely the polysaccharide capsule of Cryptococcus neoformans, 30 the glycan shield of HIV, 31 or the pneumococcal capsular polysaccharide. 32 The specific reactivity with CD20 ϩ cells of anti-Rp5-L and -Rp15-C immune sera and their cytotoxic effects similar to those observed with rituximab paralleled our own observation with phagotope R10-L-derived Rp10-L 33 and suggest that these peptides could potentially be used to target CD20 in an active immunotherapy setting, once the immunization protocol has been optimized. Anti-CD20 antibodies were, in fact, detected in only 2 of 5 and 1 of 5 mice immunized with Rp5-L or Rp15-C, respectively.…”

Superior Activity of Fusion Protein scFvRit:sFasL over Cotreatment with Rituximab and Fas Agonists

“…PE-conjugated anti-FasL was from Alexis. Peptide Rp10-L is a 12-mer linear peptide (ITPWPHWLERSSG), previously selected from a phage-display peptide library to mimic the CD20 epitope recognized by rituximab (16). Rp10-L peptide was produced and purified by Pepscan Systems.…”

The epitope recognized by rituximab

“…The amino acid residues alanine 170 and proline 172 within the extracellular loop of CD20 are critical for rituximab binding. 12 Selection of random libraries yielded 2 distinct peptides binding rituximab 13,14 : one peptide was homologous to alanine (170)-proline(172), the otheralthough not homologous-was assumed to mimic the same epitope. 13,14 Phage display peptide libraries can be used to identify antibody epitopes.…”

“…12 Selection of random libraries yielded 2 distinct peptides binding rituximab 13,14 : one peptide was homologous to alanine (170)-proline(172), the otheralthough not homologous-was assumed to mimic the same epitope. 13,14 Phage display peptide libraries can be used to identify antibody epitopes. [15][16][17][18] We used this approach to identify the epitope of rituximab.…”