IMMUNE CONTROL OF CAE LENTIVIRUS

采用表达山羊关节炎-脑炎病毒（CAEV） env基因的重组痘苗或质粒DNA载体或表达CAEV env和CAEV的质粒DNA，对远交山羊进行了疫苗接种试验。质粒DNA皮内接种诱导了对载体编码表面包膜（SU）的偏1型免疫反应，而痘苗诱导了2型免疫反应。在Freund's不完全佐剂中皮下注射纯化SU，特异性地扩大了通过质粒DNA或牛痘初始免疫建立的1型或2型记忆。将这些山羊与假接种和未接种的对照山羊一起用组织培养扩增的CAEV分子克隆进行静脉攻击。攻毒后24周的初步结果表明，病毒复制受到质粒DNA诱导的1型免疫的限制，而不受牛痘诱导的2型免疫的限制。这些数据为确定慢病毒SU在控制病毒复制和疾病进展中的定性不同免疫反应的作用提供了基础。因此，本研究的第一个目的是验证质粒DNA诱导的1型免疫限制病毒复制并阻止CAEV攻击后关节炎的发展，而重组痘苗诱导的2型免疫不能控制病毒复制并促进关节炎的发展。拟议的实验将初步研究扩展到更多的动物，以便对病毒载量和疾病进展进行重要评估。此外，挑战疫苗将是来自CAE关节炎野外病例的野生型病毒。另外用表达CAEV env的质粒DNA（含或不含CAEV env）和编码山羊干扰素γ (IFN)的质粒DNA共同免疫山羊。这些研究提供了初步证据，证明编码Tat的质粒和IFN的协同作用抑制了原代适应性B细胞对质粒编码SU的反应，而不影响SU反应的Th1淋巴细胞的激活。利用这种疫苗诱导的免疫特征显著控制山羊的CAEV复制，将支持进一步研究Tat和IFN作为疫苗成分的作用。因此，本研究的第二个目的是评估用表达CAEV env及其基因和山羊IFN的质粒DNA共同免疫山羊CAEV攻击后的病毒复制。

Vaccination trials were conducted in outbred Saanen goats using recombinant vaccinia or plasmid DNA vectors expressing the caprine arthritis-encephalitis virus (CAEV) env gene or plasmid DNA expressing CAEV env and tat. Intradermal vaccination with plasmid DNA induced biased type 1 immune responses to vector encoded surface envelope (SU), whereas vaccinia induced type 2 responses. Subcutaneous boost with purified SU in Freund's incomplete adjuvant specifically expanded type 1 or type 2 memory established by initial immunizations with plasmid DNA or vaccinia. These goats together with sham vaccinated and non-vaccinated control goats were challenged intravenously with a molecular clone of tissue culture amplified CAEV. Preliminary results through 24 weeks postchallenge indicate that virus replication is restricted by type 1 immunity induced by plasmid DNA but not by type 2 responses induced by vaccinia. These data provide a basis to determine the role of qualitatively distinct immune responses to lentiviral SU in control of virus replication and disease progression. Therefore, the first objective of this proposal is to test the hypothesis that type 1 immunity induced by plasmid DNA restricts virus replication and prevents development of arthritis following CAEV challenge, whereas type 2 immunity induced by recombinant vaccinia fails to control virus replication and promotes development of arthritis. Proposed experimants expand the preliminary studies to a larger number of animals required for significant evaluation of virus load and disease progression. In addition, the challenge inoculum will be wild type virus derived from field cases of CAE arthritis. Additional goats were co- immunized with plasmid DNA expressing CAEV env with or without tat together with a second plasmid DNA encoding caprine interferon gamma (IFN). These studies provide preliminary evidence that synergistic effects of plasmid encoded Tat and IFN inhibit primary adaptive B cell responses to plasmid encoded SU without effect on activation of SU responsive Th1 lymphocytes. Significant control of CAEV replication by goats with this vaccine induced immunologic profile will support further studies on the role of Tat and IFN as vaccine components. Therefore, the second objective of this proposal is to evaluate virus replication following CAEV challenge of goats co-immunized with plasmid DNA expressing CAEV env and tat genes and caprine IFN.