Animal Reproduction Science 109 (2008) 251–265 Development and evaluation of a novel DNA vaccine expressing inhibin  (1–32) fragment for improving the fertility in rats and sheep Li Han a , D.G. Mao b , D.K. Zhang b , A.X. Liang a , M. Fang a , Muhammad Moaeen-ud-Din a , L.G. Yang a,∗ a College of Animal Science and Technology, Huazhong Agricultural University, Wuhan 430070, China b College of Animal Science and Technology, Nanjing Agricultural University, Nanjing 210095, China Received 13 August 2007; received in revised form 11 December 2007; accepted 12 December 2007 Available online 31 December 2007 Abstract Inhibin is an important protein hormone in regulating folliculogenesis. Immunization against inhibin can improve follicle developments. The objective of present study is to investigate inhibin DNA immunization as a potential tool for improving follicle development and litter sizes of female animals. In our study, the inhibin DNA vaccine was constructed with inhibin  (1–32) fragment inserted into the C termination of HBsAg-S. Ninety rats and forty sheep were immunized with inhibin DNA vaccine. In rats, immunization against inhibin resulted in increase of positive sera ratio (P < 0.01). The treatment was accompanied by a significant increase in the total number of mature follicles of >0.8 mm in diameter on the onset of estrous cycle after twice immunization (31.0 ± 3.9 in the test groups versus 27.4 ± 5 in control groups) and after third immunization (35.2 ± 6.7 in the test groups versus 30.3 ± 5.2 in control groups). Litter sizes were significantly (P < 0.05) bigger in rats treated with inhibin DNA vaccine (12.7 ± 4.5 n = 6) than in control (9.8 ± 4.5). In sheep, twinning rate in test groups (39.2%) was significantly higher than that in control groups (10%) after immunization (P < 0.05). These results indicated that inhibin was an important factor in improvement of fertility in rats and sheep, and demonstrated that DNA immunization against inhibin could induce more mature follicles resulting in increased litter sizes. Our results revealed that inhibin DNA vaccine may be an alternative to the use of exogenous gonadotrophins for increasing ovarian follicular development and improving animal fertility. © 2007 Elsevier B.V. All rights reserved. Keywords: DNA vaccine; Inhibin; Fertility ∗ Corresponding author. Tel.: +86 27 87281813; fax: +86 27 87281813. E-mail address: yangliguo2006@yahoo.com.cn (L.G. Yang). 0378-4320/$ – see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.anireprosci.2007.12.012