BLOCKADE OF VERY LATE ANTIGEN-4 INTEGRIN BINDING TO FIBRONECTIN IN ALLOGRAFT RECIPIENTS - II - TREATMENT WITH CONNECTING SEGMENT-1 PEPTIDESPREVENTS CHRONIC REJECTION BY ATTENUATING ARTERIOSCLEROTIC DEVELOPMENT AND SUPPRESSING INTRAGRAFT T-CELL AND MACROPHAGE ACTIVATION

Background, Chronic rejection remains the leading obstacle to long-ter m allograft survival. We have shown that treatment of sensitized rats with rapamycin (RPM) does not prevent progressive chronic-type cardiac allograft failure, Having documented the role of fibronectin (FN) in the allograft rejection cascade, we hypothesized that treatment with s ynthetic peptides that specifically block adhesive interactions betwee n the connecting segment-1 (CS1)-binding domain of FN and alpha 4 beta 1 integrin on circulating cells may prevent the development of chroni c rejection in transplant recipients, Methods and Results, Lewis rats were sensitized with Brown Norway skin grafts (day -7), followed by tr ansplantation of LBNF1 hearts (day 0), Experimental animals were treat ed with RPM (day -7 to -1; 0.25 mg/kg/day i.p.), or RPM + CS1 peptides (day +7 to +13; 4 mg/kg/day i.v.), and euthanized at day 60. Unlike c ardiac allografts in rats undergoing RPM monotherapy, those after adju nctive CS1 peptides had well preserved myocardial architecture and wer e free of arteriosclerotic lesions. Moreover, reverse transcription-po lymerase chain reaction-based intragraft expression of transcripts for CD3, interferon-gamma, interleukin-12, monocyte chemoattractant prote in-1, and transforming growth factor-beta were diminished in the CS1 g roup when compared with levels in the RPM group. The corresponding exp ression of cytokine proteins, as determined by immunoperoxidase labeli ng, was also depressed and correlated with decreased infiltration by T cells and macrophages. Conclusion, CS1 peptide-facilitated blockage o f alpha 4 beta 1-FN interactions prevents the development of chronic r ejection and depresses the expression of key T cell-and macrophage-ass ociated cytokines/chemoattractants, Hence, local synthesis of FN is an ongoing feature of, and adhesive FN-alpha 4 beta 1 associations are c ritical for, the development of chronic transplant rejection.