Involvement of transporter associated with antigen processing 2 (TAP2) gene polymorphisms in hepatitis C virus infection

Background & Aims: Transporter associated with antigen processing (TAP) has essential roles in the antigen-presenting systems, translocating antigenic peptides from the cytosol into the endoplasmic reticulum. The aim of this study was to clarify whether TAP polymorphisms are involved in hepatitis C virus (HCV) infection. Methods: The 145 HCV-infected Japanese patients exam ined in this study were categorized into two groups: 36 carriers with persi stently normal alanine transaminase (ALT) values and 109 patients with chro nic liver disease (CLD), TAP2 gene phenotypes were determined by means of p olymerase chain reaction-restriction fragment length polymorphism, and thei r frequencies were compared between the two groups. Results: Frequencies of TAP2*0101, *0102, and *0201 were not different between the two groups. How ever, TAP2*0103 frequency in carriers with normal ALT levels was significan tly higher than that in patients with CLD (44% vs. 16%; P = 0.00064, P-c < 0.005), Although the TAP2*0103 allele was tightly linked with class II DRB1 *1302-DQB1*0604 haplotype in this study, the TAP2*0103 frequency in the nor mal ALT group was also significantly higher than that in the CLD group even in DRB1*1302-DQB1*0604-negative patients (31% vs. 10%; P = 0.0076, P-c < 0 .05). Conclusions: These findings suggest that TAP2*0103 may be closely ass ociated with low serum ALT activity in HCV-infected Japanese patients.