193 HUMAN CYTOMEGALOVIRUS PROTEIN US11 DOWN-REGULATES THE EXPRESSION OF SWINE LEUKOCYTE ANTIGEN-I IN MINIPIG CELLS

Abstract

The CD8+ cytotoxic T lymphocyte (CTL)-mediated immune response is important in porcine xenotransplantation, and pigs could be used as a good model for organ donor if these immunological barriers are overcome. Human cytomegalovirus (HCMV) encodes unique short (US) 11 gene, which interferes with cellular immune responses by inducing rapid degradation of newly synthesized heavy chains of major histocompatibility (MHC) class I. The destruction of heavy chains by US11 helps the virus to hide from recognition by cytotoxic T lymphocytes at early stage. In this study we demonstrated the inhibitory effect of US11 on the cytotoxicity of CTL cells by down-regulation of swine leukocyte antigen (SLA)-I expression. We established five US11 clonal cell lines by transfection into minipig fetal fibroblasts and confirmed the integration of US11 gene by PCR and Southern blot assay. The reduction of SLA-I, which was expressed on the cell surface, was also detected by flow cytometry assay. The level (14.6% to 21.2%) of SLA-1 expression in US11 clonal cell lines was decreased relative to that in the control. In the CTL assay, the rate of CD8+ T cell-mediated cytotoxicity was significantly reduced to 31.9 � 11.3%, compared to that of the control (81.4 � 5.3%; P < 0.01; n = 4). These results indicate that HCMV viral protein US11 can effectively suppress the presentation of SLA-I in pig fetal fibroblast cells. This work was supported by a grant (Code # 20070101034005) from the BioGreen 21 Program, Rural Development Administration, Republic of Korea.