Liver- Directed MHC gene transfer: Towards transplantation tolerance induction across a full MHC mismatch

Abstract

organ transplantation has been used successfully to treat end stage organ failure. The success of this treatment has led to high demand for organs and the requirement for long-term maintenance immunosuppression can cause serious complications, such as malignancies and infections. Optimizing a treatment to promote immunological tolerance using gene transfer technologies is a feasible option. In previous studies, AAV-mediated gene transfer of a single mismatched donor MHC class I molecule (K«sup»d «/sup»or K«sup»b«/sup») to C57BL/6 or B10.BR recipient liver respectively induced tolerance to skin grafts expressing the same mismatched MHCI molecule. Moreover, regulatory tolerance to allogeneic cardiac grafts after donor MHC II gene transfer to recipient bone marrow is reported. «strong»Aim«/strong»: to determine whether gene transfer of either single or multiple donor MHC class I and II genes to recipient liver, using recombinant adeno-associated viral vectors, could result in long-term survival and tolerance induction to allogeneic heart grafts. «strong»Method«/strong»: we created a liver-specific rAAV2/8 vector encoding MHC genes H2-IA«sup»d«/sup» , H2-IE«sup»d«/sup» ,and H2-D«sup»d«/sup», L«sup»d«/sup» and K«sup»d«/sup» (DaLeK). C57BL/6 (H2-b) mice were transduced with these vectors, alone or in combination. Transgene expression, co-stimulatory/inhibitory molecules, chaperones and inflammatory infiltrate were assessed. Fully allogeneic hearts from DBA/2 (H-2d) or semi-allogeneic hearts from B6D2F1 were transplanted into C57BL/6 (H-2b) at either d7 or d14 post-inoculation. «strong»Results«/strong»: Administration of AAV-IA«sup»d«/sup» or AVV-IE«sup»d«/sup» or AVV-DaLeK to C57BL/6 mice yielded strong gene expression on hepatocytes. DaLeK expression was enhanced by co-transduction with a vector encoding β2 microglobulin, and expression of IA«sup»d«/sup» or IE«sup»d«/sup» conjoined with transduction of Class II transactivator (CIITA), ALT levels remained normal and no inflammatory infiltrates were detected in all subjects. Survival of DBA/2 hearts transplanted into AAV-DaLeK treated mice was prolonged from a MST of 7 days to 23 days. DBA/2 cardiac graft survival is not extended in AAV-IA«sup»d«/sup» or AVV-IE«sup»d«/sup» inoculated mice, wheres survival of B6D2F1 hearts was prolonged in mice receiving IE«sup»d«/sup» and CIITA vectors in combination. «strong»Conclusion«/strong»: administration of AAV-DaLeK significantly prolongs survival of fully-allogeneic heart transplants. Expression of CIITA and a single mismatched MHC II in hepatocytes was not sufficient to confer tolerance to fully allogeneic heart grafts. Tolerance induction may require expression of all mismatched MHC molecules (3 class I and 2 class II).