[172-POS]

Abstract

Objectives Proper regulation of human leukocyte antigen-C (HLA-C) expression on trophoblast cells is essential for the immunological privilege of these cells. Endoplasmic reticulum aminopeptidase 2 (ERAP2) is known to trim antigenic peptide precursors for loading onto HLA. Altered expression of the ERAP2 could play a critical role in shaping HLA-C expression and antigen presentation, but their relationships have not been defined. Methods We examined the genotype and expression levels of ERAP2 and HLA-C in several choriocarcinoma cell lines (BeWo, JAr, and JEG-3) by allelic discrimination qPCR, Western blotting and immunocytochemistry. Additionally, expression profiling of untreated versus gamma-interferon (IFN- γ , 20 ng/ml)-treated cells was performed. Lastly, to determine if there is a relationship between ERAP2 and HLA-C expression levels, transfection of major and minor allele ERAP2 variants was performed. Results JAr cells were homozygous for the rs2248374 minor A allele, and express ERAP2 protein. BeWo and JEG-3 cells are homozygous for ERAP2 genetic variant (major G allele of SNP rs2248374) that causes non-sense mediated RNA decay, and thus lack ERAP2 protein expression. Interestingly, BeWo and JEG-3 cells express HLA-C, whereas, JAr cells do not. IFN- γ treatment of BeWo and JEG-3 cells increased HLA-C expression by 2-fold ( p  = 0.0037) and 3-fold ( p  = 0.0446) above control levels, respectively, but ERAP2 remained undetectable. In contrast, JAr cells treated with IFN- γ had increased ERAP2 protein expression by 2-fold ( p  = 0.003), but had no effect on HLA-C expression. Transfection of JEG-3 cells (ERAP2 null) with ERAP2 plasmids with the SNP rs2549782, encoding an amino acid substitution (N392K) that alters substrate specificities and antigen presentation, revealed that the different ERAP2 isoforms do not affect the expression level of HLA-C. Conclusions Our observations suggest that the expression patterns of ERAP2 and HLA-C allow choriocarcinoma cells to escape immune surveillance. Disclosures E.D. Lee: None. S. Brockett: None. D. Hilliard: None. M.E. Teves: None. R. Ramus: None. J.F. Strauss: None.