Ha SJ, Chang J, Song MK, Suh YS, Jin HT, Lee CH, Nam GH, Choi G, Choi KY, Lee SH, Kim WB, Sung YC.

1. National Research Laboratory of DNA Medicine, Department of Life Science, Pohang University of Science & Technology, San 31, Hyoja-Dong, Nam-Ku, Pohang, Kyungbuk, 790-784, Korea.
2. ProGen Co. Ltd., 47-5, Sanggal-Ri, Kiheung-Up, Youngin, Kyunggi, 449-905, Korea.
3. These authors contributed equally to this work.
Correspondence should be addressed to Y C Sung.

Interleukin-12 (IL-12), consisting of p40 and p35 subunits, produces both p70 heterodimer and free p40. p70 is essential for the induction of T-helper 1 (Th1) and cytotoxic T-cell (CTL) immunity, whereas p40 inhibits p70-mediated function. Here, we found that mutations introduced into N-glycosylation sites (N220 of murine p40 and N222 of human p40) reduced secretion of p40 but not p70. Co-immunization of N220 mutant mIL-12 gene with hepatitis C virus (HCV) E2 DNA significantly enhanced long-term E2-specific CD8+ T-cell response and protection against tumor challenge compared with that of wild type. Our results indicate that the ratio of p70 to p40 is important for generating sustained long-term cell-mediated immunity. Thus, the mutant IL-12 could be utilized for the development of DNA vaccines as an adjuvant for the generation of long-term memory T-cell responses.