Wu Changxin, Barbezange Cyril, McConnell Ian, Blacklaws Barbara A
Department of Veterinary Medicine, University of Cambridge, Cambridge, UK.
J Gen Virol. 2008 Oct;89(Pt 10):2586-2596. doi: 10.1099/vir.0.2008/002634-0.
CD8(+) cytotoxic T-lymphocyte (CTL) responses have been shown to be important in the control of human and simian immunodeficiency virus infections. Infection of sheep with visna/maedi virus (VISNA), a related lentivirus, induces specific CD8(+) CTL in vivo, but the specific viral proteins recognized are not known. To determine which VISNA antigens were recognized by sheep CTL, we used recombinant vaccinia viruses expressing the different genes of VISNA: in six sheep (Finnish LandracexDorset crosses, Friesland and Lleyn breeds) all VISNA proteins were recognized except TAT. Two sheep, shown to share major histocompatibility complex (MHC) class I alleles, recognized POL and were used to map the epitope. The pol gene is 3267 bp long encoding 1088 aa. By using recombinant vaccinia viruses a central portion (nt 1609-2176, aa 537-725) was found to contain the CTL epitope and this was mapped with synthetic peptides to a 25 aa region (aa 612-636). When smaller peptides were used, a cluster of epitopes was detected: at least three epitopes were present, at positions 612-623: DSRYAFEFMIRN; 620-631: MIRNWDEEVIKN; and 625-635: EEVIKNPIQAR. A DNA-prime-modified vaccinia virus Ankara (MVA)-boost strategy was employed to immunize four sheep shown to share MHC class I allele(s) with the sheep above. Specific CTL activity developed in all the immunized sheep within 3 weeks of the final MVA boost although half the sheep showed evidence of specific reactivity after the DNA-prime immunizations. This is the first report, to our knowledge, of induction of CTL by a DNA-prime-boost method in VISNA infection.
CD8(+)细胞毒性T淋巴细胞（CTL）反应已被证明在控制人类和猿猴免疫缺陷病毒感染中很重要。用相关慢病毒维斯纳/梅迪病毒（VISNA）感染绵羊可在体内诱导特异性CD8(+) CTL，但所识别的特异性病毒蛋白尚不清楚。为了确定绵羊CTL识别哪些VISNA抗原，我们使用了表达VISNA不同基因的重组痘苗病毒：在6只绵羊（芬兰长白×多塞特杂交羊、弗里斯兰羊和莱因羊品种）中，除了TAT外，所有VISNA蛋白都能被识别。有2只绵羊显示共享主要组织相容性复合体（MHC）I类等位基因，它们识别POL并被用于绘制表位图谱。pol基因长3267 bp，编码1088个氨基酸。通过使用重组痘苗病毒，发现中央部分（核苷酸1609 - 2176，氨基酸537 - 725）包含CTL表位，并用合成肽将其定位到一个25个氨基酸的区域（氨基酸612 - 636）。当使用更小的肽时，检测到一组表位：至少存在三个表位，分别位于612 - 623位：DSRYAFEFMIRN；620 - 631位：MIRNWDEEVIKN；以及625 - 635位：EEVIKNPIQAR。采用DNA初免 - 改良痘苗病毒安卡拉（MVA）加强策略免疫4只显示与上述绵羊共享MHC I类等位基因的绵羊。在最后一次MVA加强免疫后的3周内，所有免疫的绵羊都产生了特异性CTL活性，尽管一半的绵羊在DNA初免后就显示出特异性反应的迹象。据我们所知，这是关于在VISNA感染中通过DNA初免 - 加强方法诱导CTL的首次报告。
