OBJECTIVETo explore the prophylaxis effect of pretreatment of allograft with methoxypolyethylene glycol-succinimidyl-propionic acid ester (mPEG-SPA) and anti-OX40L monoclonal antibody (McAb) on acute graft-versus-host disease (aGVHD) after allogeneic bone marrow transplantation (allo-BMT) in mice.

METHODSResponder splenocytes from C57BL/6 donor mice (H-2(b)) were co-cultured with stimulator splenocytes from BALB/c recipient mice (H-2(d)) for 7 days in the presence or absence of anti-OX40L McAb followed by mPEG-SPA chemical modification. Donor bone marrow cells plus the mixed culture of T-cells were then transplanted into lethally irradiated BALB/c mice. The BALB/c recipient mice were divided into four groups: group A (allo-BMT control group), group B(mPEG-SPA modification group), group C (anti-OX40L McAb pretreated group) and group D (mPEG-SPA and anti-OX40L McAb dual-treated group). Survival time and survival rate of the recipients were observed after allo-BMT. GVHD was assessed by clinical signs and histological changes of skin, liver and small intestines. Enzyme-linked immunosorbent assay (ELISA) was used to detect cytokines (IL-4, IL-10 and INF-gamma) production. Flow cytometry (FCM) analysis was used to detect allogeneic chimerism.

RESULTS(1) The mice in group A developed typical clinical signs of aGVHD and all mice died within 17 days after BMT with an average survival time (AST) of (12.1 +/- 5.5) days. The signs of aGVHD were less evident in mice of groups B, C and D, and their AST (36.2 +/- 24.9, 32.0 +/- 24.8 and 44.3 +/- 23.2 days, respectively) were all longer than that in group A (P < 0.05). AST of group D being the longest (P < 0.05). The survival rates at day 60 post-BMT in groups B, C and D were 50%, 41.7% and 66.7%, respectively. (2) Serum IFN-gamma level was increased after BMT in group A, and peaked in day 10 to day 15 post-BMT, while the level was decreased in groups B, C and D, reached the nadir on the day 10 post-BMT, with the lowest in group D (P < 0.01). After BMT, IL-4 and IL-10 levels were slightly decreased in group A, their levels were elevated in groups B and C (P < 0.05) and even more significantly increased in group D (P < 0.01). IL-4 and IL-10 levels peaked between day 10 and 15 post-BMT. (3) The average proportion of H-2(b) positive cells in recipient mice was 95% - 100% on day 60 post-BMT, with complete donor-type implantation.

CONCLUSIONCombination of mPEG-SPA and anti-OX40L McAb can block T-cell activated antigens and co-stimulatory pathway, regulate the T cells differentiation and induce the immune shift of Th0 cells toward Th2 cells. The immune tolerance induced by this method can significantly relieve aGVHD after allo-BMT.