Impact of Rituximab Induction and Living Donation on Immunoregulation and Virus Control in Renal Transplantation - a Prospective Pilot Study

Objective. Blood group incompatible (ABOi) LD renal transplantation represents a recognized treatment modality in Germany. In this setting, ethical considerations allow for a detailed study of short- and long-term immunological and virological effects of Rtx induction therapy, including sequential protocol biopsies. In the proposed project we will perform analyses on peripheral blood, iliac lymph nodes and protocol biopsies. Protocol biopsies are routinely obtained 3 and 12 months posttransplant at the Universities of Giessen and Freiburg. In this prospective, open pilot study, immunological parameters of graft outcome and control of polyomavirus, EBV and CMV replication will be compared between RTx-treated ABOi LD renal transplant recipients (n=25-30, group 1) and blood group compatible LD renal transplant recipients without Rtx induction (n=25-30, group 2) but otherwise comparable immunosuppressive treatment (MPS and Tacr, switch to Tacr-MR (modified release) within 2 weeks posttransplant; follow-up of 5 years). The same analyses will be done in DD renal transplant recipients treated with Tacr (switch to Tacr-ME) and MPS (n=25-30, group 3). This study design allows to analyze the impact of living donation on immunoregulation and virus control (groups 2 versus 3).

Background. There is growing evidence that humoral mechanisms play a major role in chronic allograft dysfunction, which was shown to be significantly associated with de-novo formation of donor-specific antibodies against human leucocyte antigens (HLA). However, B cells appear to act not only in humoral responses against the graft but may play a significant role in T-cell mediated antidonor responses due to their role as effective antigen-presenting cells. This is further suggested by the fact that Rtx is effective in primarily T-cell mediated diseases such as rheumatoid arthritis or multiple sclerosis.

Hypothesis/specific aims. We hypothesize that Rtx induction may alter immunoregulation short- and long-term after renal transplantation with the potential to improve long-term outcome. Graft protective effects of Rtx induction may be provided by B cell depletion and the resulting effects on humoral as well as T cell responses, and also by altered responses after B cell repopulation. Possible negative effects of Rtx on polyomavirus and CMV control as well as protective effects on EBV replication, de-novo monoclonal gammopathy and regulation of lymphoma growth factors (interleukins 6 and 10 (IL-6, IL-10)) will be analyzed. Furthermore, B cell subset analysis in peripheral blood and the probably associated impact of Rtx on B cell depletion in graft draining iliac lymph nodes may enable us to establish an optimized Rtx dosage and thereby allow successful ABOi renal transplantation without the currently observed 15% drop outs.

Preliminary results. We have performed clinical studies showing the predictive power of immune parameters such as regulatory anti-Fab autoantibodies, sCD30, CD4 (cluster of differentiation 4) helper activity, and CD4 cell IL-4 (interleukin 4) and IL-10 (interleukin 10) responses on graft outcome. The long-term effect of Rtx induction therapy and of living donation on these parameters will be analyzed.

Previously, we found that patients at risk of polyomavirus nephropathy may be recognized early posttransplant by sequential reverse transcriptase polymerase chain (rt-PCR) assessment of polyomavirus replication in urine. Sequential rt-PCR testing of polyomavirus replication in urine and plasma will be used to analyze effects of Rtx induction on polyomavirus control.