Expression of MHC Class II DQ α/β Heterodimers from Recombinant Polycistronic Retroviral Genomes

Abstract.

Purpose: In the swine model, the transfer of the polymorphic DRβ or DQα/β cDNAs in vivo via double copy retroviruses led to a prolonged survival or tolerance of subsequent kidney grafts which were matched for DR or DQ, respectively. However, DQ-induced tolerance required the expression of the α/β heterodimers in the same target cell, a task not reproducibly achieved with double copy vectors. Therefore, the present study was designed to evaluate the ability of polycistronic proviral constructs to express class II DQ α/β heterodimers in transduced cells.

Methods: A swine class II DQ recombinant polycistronic construct (JAB) was developed to contain two internal ribosomal entry sites (IRES) for sequential translation of the DQα and DQβ chains.

Results: Although a genomic recombination occurred between the two identical IRES, flow cytometry analyses of JAB-transfected virus-packaging cells demonstrated the cell surface expression of DQα/DQβ heterodimers, indicative of a correct transcription, translation, and transport of swine class II.

Conclusion: JAB-transfected virus-packaging cells demonstrated the cell surface expression of DQα/DQβ heterodimers. We believe that our study represents an essential step in the design of efficient protocols to transfer graft-matched class II molecules in recipient bone marrow cells and thereby induce transplantation tolerance.