424: Anti-CD20 prevents alloantibody production and attenuates cardiac allograft vasculopathy in monkeys treated with anti-CD154

Purpose: Blockade of CD40-154 prolongs cardiac allograft survival in cynomolgus macaques, but cardiac allograft vasculopathy (CAV) causes graft failure, and is closely associated with appearance of anti-donor antibody (Ab). We hypothesized that depletion of CD20 B-cells might interfere with formation of anti-donor plasma cells and alloantibodies, and thus prevent CAV. Methods and Materials: Thirty MLR-mismatched heterotopic cardiac cynomolgus allograft recipients were treated with anti-CD154 high intensity monotherapy ( CD154; n 17, 6 with ATG) or CD154 with additional CD20 (20mg/kg q wk for 4 weeks: CD154 CD20; n 13, 11 with ATG). Some animals received an additional donor thymus graft or bone marrow infusion. Acute rejection was usually treated with steroids; graft survival was censored at 90 days. Results: 10 animals died with beating grafts, mainly with ATG-associated lung pathology, and are excluded from the survival analysis. Graft survival with CD154 CD20 (median 90d) and proportion of grafts surviving to 90 days (5/5) was significantly increased relative to CD154 (median 43d, IQR(25-75) 35-82d, p 0.007; 3/15 90d). With CD154, 15/15 (100%) developed anti-donor IgM and 14/15 (93%) IgG, usually weeks before graft failure, whereas no IgG was detected in samples analyzed to date from the CD154 CD20 group, and weak IgM was transiently detected in only one animal. All CD154 grafts had severe CAV (score 3 on 0-4 scale), in many instances with fibrosis and unscorable vessels due to infarction. In stark contrast, CD154 CD20 was associated with CAV 1 in 4 of 5 grafts, and CAV 2 in the 5, and preserved myocardial architecture. Conclusions: Using CD20 with CD154 is associated with decreased elaboration of alloAb, prolonged graft survival to 90 days, and significant attenuation of CAV. Concomitant thymus transplant or ATG induction did not appear to be necessary to this effect; ATG is associated with significant morbidity. These findings suggest that CD20 may reduce the incidence of CAV, perhaps by inhibiting alloAb.