Regulating MHC expression for cellular therapeutics.

Abstract

BACKGROUND: In the past decade, regenerative medicine and cell-based therapies have emerged as new science and technology, with the main goal of repairing, replacing, or regenerating new tissues. A critical issue in this field is the high polymorphism of HLA, which compromises immune acceptance. The lentivirus-mediated delivery of short-hairpin RNAs (shRNAs) has proved to be an efficient method to inhibit the translation of a specific gene. STUDY DESIGN AND METHODS: A lentiviral-based vector system was used for drug-inducible expression of shRNA sequences that target either beta2-microglobulin (beta2m) or HLA heavy-chain transcripts. RESULTS: The transduction of inducible RNA interference cassettes containing the sequences for shRNAs targeting beta2m or HLA heavy chain suppressed HLA class I expression by up to 90 percent in HeLa and B-lymphocyte cell lines as well as in peripheral blood monocytes. The expression of HLA class I antigens was fully restored in these cells after the drug had been discontinued. It was demonstrated that HLA class I knockdown was effective in preventing antibody-mediated cell lysis and CD8+ T-cell response. The residual HLA expression in HLA-silenced cells may provide sufficient protection against natural killer cell-mediated lysis. CONCLUSIONS: These data demonstrate the feasibility of controlling HLA expression by genetically modifying cell-based therapeutics to overcome the limitations of immune rejection, bringing cellular therapies closer to reality.