Vaccination by Two DerG LEAPS Conjugates Incorporating Distinct Proteoglycan (PG, Aggrecan) Epitopes Provides Therapy by Different Immune Mechanisms in a Mouse Model of Rheumatoid Arthritis

Abstract

Rheumatoid arthritis (RA) can be initiated and driven by immune responses to multiple antigenic epitopes including those in cartilage proteoglycan (PG, aggrecan) and type II collagen. RA is driven by T helper 1 (Th1) or Th17 pro-inflammatory T cell responses. LEAPS (Ligand Epitope Antigen Presentation System) DerG peptide conjugate vaccines were prepared using epitopes from PG that elicit immune responses in RA patients: epitope PG70 (DerG-PG70, also designated CEL-4000) and the citrullinated form of another epitope (PG275Cit). The LEAPS peptides were administered alone or together in Seppic ISA51vg adjuvant to mice with PG G1 domain-induced arthritis (GIA), a mouse model of RA. Each of these LEAPS peptides and the combination modulated the inflammatory response and stopped the progression of arthritis in the GIA mouse model. Despite having a therapeutic effect, the DerG-PG275Cit vaccine did not elicit significant antibody responses, whereas DerG-PG70 (alone or with DerG-PG275Cit) induced both therapy and antibodies. Spleen T cells from GIA mice, vaccinated with the DerG LEAPS peptides, preferentially produced anti-inflammatory (IL-4 and IL-10) rather than pro-inflammatory (IFN-γ or IL-17) cytokines in culture. Similarly, cytokines secreted by CD4+ cells of unvaccinated GIA mice, differentiated in vitro to Th2 cells and treated with either or both DerG vaccine peptides, exhibited an anti-inflammatory (IL-4, IL-10) profile. These results suggest that the two peptides elicit different therapeutic immune responses by the immunomodulation of disease-promoting pro-inflammatory responses and that the combination of the two LEAPS conjugates may provide broader epitope coverage and, in some cases, greater efficacy than either conjugate alone.

Vaccine Immunomodulation of Disease: Targeting the Treatment of Autoimmune Diseases

“…The derG LEAPS peptide vaccines activate humoral (Th2) and regulatory responses by interacting with CD4 T cells. 94,95 The derG ICBL consists of the DGQEEKAGVVSTGLI peptide from the beta chain of the MHC II molecule. Immunomodulatory vaccines developed for RA include CEL-4000, which incorporates the ATEGRVRVNSAYQDK (PG70) proteoglycan peptide, and a related LEAPS vaccine, which incorporates the citrullinated PG275 proteoglycan peptide, MDMCSAGWLAD{Cit}SVR.…”

Restoring the Balance between Pro-Inflammatory and Anti-Inflammatory Cytokines in the Treatment of Rheumatoid Arthritis: New Insights from Animal Models

“…The CIA (Th17 with IL-17) and PGIA/GIA (Th1 with IFN-γ) mouse models of arthritis were used to explore the potential therapeutic effects of CEL-2000 (J-C-II 254 ) and CEL-4000 (DerG-PG 70 ) Ligand Epitope Antigen Presentation System (LEAPS) vaccines, respectively [ 3 , 27 , 29 , 30 , 31 ]. CEL-2000 [ 27 ] attaches a peptide from human collagen to the J-immune cell-binding ligand (ICBL) (J-C-II 254 ) and CEL-4000 attaches a peptide from proteoglycan to the DerG-ICBL (DerG-PG 70 ) [ 29 , 30 ].…”

“…As shown in Figure 3 A, the application of LEAPS immunotherapy to disease-bearing mice in the animal models of RA promotes a return to a balanced immune response by promoting an increase in anti-inflammatory cytokines and a decrease in pro-inflammatory cytokines [ 3 , 29 , 30 ].…”

“…Unlike the ablative therapy alluded to above, the LEAPS peptide therapeutic vaccines have an immunomodulatory effect on the T cells driving the disease, as illustrated in Figure 3 A,B. In so doing, the LEAPS peptides affect the entire cytokine conversation, increasing the expression of some and decreasing other cytokines to return immunobalance, rather than acting on a single cytokine [ 3 , 27 , 29 , 30 , 31 ].…”

“…LEAPS therapeutics incorporating the DerG peptide act directly on CD4 T cells to promote Th2 cytokine responses. CEL-4000 and a related LEAPS therapeutic, which attach the DerG LEAPS ICBL to peptides from proteoglycan [ 3 , 29 , 30 ], elicited antigen-specific responses to stop the progression of disease by acting on memory T cells, including those in the spleen, to increase the expression of anti-inflammatory IL-4, IL-10, and TGF-β cytokines and Treg numbers while decreasing the expression of pro-inflammatory IFN-γ and IL-17 in the PGIA/GIA models [ 29 , 30 ].…”