Objective: To assess the immunogenic properties of the glycosaminoglycan peptide complex Rumalon, an aqueous extract of bovine cartilage and bone marrow frequently used in patients with osteoarthritis (OA).
Methods: Sera from 31 patients with OA who had received several series of Rumalon injections (Group 1, n = 17: before therapy and after one injection series; Group 2, n = 6: after 2-3 injection series; Group 3, n = 4: after 4-8 injection series; Group 4, n = 4: after 9-18 injection series) were tested by ELISA for antibodies against Rumalon and its components as well as by a double sandwich ELISA for type 1 [interferon-gamma, interleukin 2 (IL-2)] and type 2 cytokines (IL-4, IL-5, IL-10, IL-13).
Results: After the first injection series antibodies to Rumalon were induced in 7 of the 17 patients that were all negative before therapy. The antibodies were preferentially of the IgG4 type. IgG4 levels were increased during therapy (ELISA optical density x 1000 in Group 1: 73.9 +/- 209.5; Group 4: 1354.5 +/- 307.6), and in Group 4 all patients had developed these antibodies. Upon analysis of cytokine levels, there was a significant increase in IL-5 (Group 1 before therapy 407.4 +/- 257.1 pg/ml, Groups 3 and 4: 1409.4 +/- 963.1 pg/ml; p < 0.001) and to a lesser extent of IL-10 during therapy (Group 1 before therapy 950.2 +/- 867.8 pg/ml, Groups 3 and 4: 2817.8 +/- 3127.3 pg/ml; p < 0.05), while type 1 cytokines were not affected.
Conclusion: Rumalon appears to have immunomodulatory properties and preferentially stimulates IgG4 antibodies via the activation of type 2 cytokines in vivo. Whether these phenomena can be correlated with the postulated therapeutic effect of Rumalon in patients with OA remains to be seen, but pain relief via release of endorphins by Th2 cells could be one explanation.