Background Angiogenesis is a key pathophysiological process in rheumatoid arthritis (RA). VEGF-A is considered the major player in both physiological and pathological angiogenesis. VEGF–VEGFR system blockade delays synovitis onset and ameliorates collagen-induced arthritis (CIA). We previously demonstrated the effectiveness of active anti-cytokine immunisation in RA models, with a class of therapeutics called kinoids. The kinoids (heterocomplexes consisting of a cytokine conjugated to a carrier protein, the keyhole limpet hemocyanin, KLH) induce the endogenous production of polyclonal anti-cytokine Abs. Here we tested the effectiveness in CIA of two distinct peptidic vaccines obtained by conjugation of one of two different VEGF-derived peptides to KLH.
Objectives To demonstrate the inhibitory effect on CIA of sustained VEGF blockade by vaccines based on VEGF-derived peptides linked to KLH (Vpep-K).
Materials and Methods Two peptides were chosen in the sequence of the VEGF murine isoformVEGF-A164 (90% identity and 93% homology with the human VEGF-A165): Vpep1 (16 aminoacids (aa), position 98-113) localised in the region cleaved by the plasmin between the exons 4 and 5, and Vpep2 (77 carboxy-terminal aa) which comprises the Arginine 164, essential for binding of VEGF to Neuropilin-1 (NRP1). Each peptide was linked to keyhole limpet hemocyanin (KLH) to form Vpep1-kinoid (Vpep1-K) and Vpep2-kinoid (Vpep2-K), respectively. CIA was induced in 48 DBA/1 male mice with two injections of 100µg of bovine collagen type II (day 0 and 21). Mice were divided in 4 groups to receive one of the following: Vpep1-K, Vpep2-K, KLH or PBS emulsified in Incomplete Freund Adjuvant (IFA, 5 intra muscular injections at days -36, -22, -8, 7 and 37). Sera were sampled from each mouse three times during the experiment (days -44, -2, 48).
Results Vpep1-K group showed lower arthritic scores compared to KLH and PBS groups (p<0.05). At histological analysis, inflammation and destruction scores of the paws were lower in Vpep1-K group versus KLH and PBS group (p<0.005). Vpep1-K and Vpep2-K groups showed anti-VEGF Ab production as assessed by ELISA at day -2 and sacrifice.
Conclusions Active immunotherapy with the kinoid of a single VEGF-derived peptide (Vpep1-K) induces anti-VEGF antibodies and ameliorates collagen-induced arthritis. Active anti-angiogenic immunotherapy based on peptidic vaccines might be a potential strategy to control chronic inflammation.