Tolerance to solid organ transplants through transfer of MHC class II genes

Abstract

Donor/recipient MHC class II matching permits survival of experimental allografts without permanent immunosuppression, but is not clinically applicable due to the extensive polymorphism of this locus. As an alternative, we have tested a gene therapy approach in a preclinical animal model to determine whether expression of allogeneic class II transgenes (Tg's) in recipient bone marrow cells would allow survival of subsequent Tg-matched renal allografts. Somatic matching between donor kidney class II and the recipient Tg's, in combination with a short treatment of cyclosporine A, prolonged graft survival with DR and promoted tolerance with DQ. Class II Tg expression in the lymphoid lineage and the graft itself were sequentially implicated in this tolerance induction. These results demonstrate the potential of MHC class II gene transfer to permit tolerance to solid organ allografts.

Figure 1

PCR analysis of MHC class II DRB and DQB transgenes. (a) Results from a representative long-term graft–accepting animal, no. 11585 (DRB, top), and a tolerant animal, no. 12307 (DQA+B, bottom). WBC and BM samples, taken at various time points after BMT, were analyzed for actin and retroviral DRB or DQB cDNA. Specific PCR products for actin (414 bp), DRB (358 bp), and DQB (461 bp) are shown. GS4.5-16 and STP29.20 are DRB- and DQA+B-virus producing cell clones, respectively. (b) RT-PCR and DNA-PCR analyses performed on WBC and BM samples from long-term graft–accepting pigs. Filled, gray, and open bars indicate the presence of DRB or DQB Tg DNA, DRB or DQB Tg transcription, and graft survival, respectively. KTx was performed at times indicated by arrows. Numbers over brackets show graft persistence (in days) following cessation of Tg transcription.

Figure 2

Outcome of allogeneic kidney grafts in the genetically engineered animals. Blood creatinine levels (mg/dl) of allogeneic DRB-engineered (a) and DQA+B-engineered animals (b) are displayed. Inset (c) shows results from syngeneic DRB-engineered and DQA+B-engineered control animals. Arrows indicate time of second transplantation of Tg-matched kidney grafts without CsA treatment.

Figure 3

Histology of kidney biopsies from DRB- and DQA+B-treated animals, with hematoxylin and eosin staining. Arterioles (a) and glomeruli (g) are indicated. (a) Long-term graft–accepting pig no. 11585 at POD 322. There are typical signs of chronic rejection including chronic vasculopathy with intimal hyperplasia in small arteries, CAG, focal infiltration (arrow), and diffuse interstitial fibrosis. (b) Control animal no. 11625 at POD 82. Severe ACR with acute and severe endothelialitis in small vessels, diffuse mononuclear cell infiltration, and acute allograft glomerulopathy. (c) Tolerant animal no. 12307 at POD 100. No evidence of ACR, CAG, endothelialitis, or cellular infiltration.

Figure 4

Peripheral T-cell reactivity of class II–treated animals. MLRs were performed as described in Methods. Anti-donor response is given as percent of the third-party response used as individual control in each experiment (anti-donor/third-party × 100). MLR assays were performed the day of the first KTx (day 0) and at indicated days thereafter for DQ and DR animals. The second KTx in animal no. 12426 (POD 658 after first transplant) is indicated by an arrow. T-cell proliferation of control animal no. 13286 was tested at PODs 0 and 35, four days prior to graft rejection.