IMMUNE CONTROL OF CAE LENTIVIRUS

用表达山羊关节炎脑炎病毒(CAEV)env基因的重组痘苗或表达CAEV env和Tat的质粒DNA对杂交萨能山羊进行了免疫试验。真皮内接种质粒DNA可诱导对载体编码的表面膜(SU)的偏向1型免疫应答，而痘苗疫苗可诱导2型免疫应答。在弗氏不完全佐剂中用纯化的SU进行皮下增强，特别是通过用质粒DNA或牛痘疫苗初始免疫建立的1型或2型记忆。用组织培养扩增的CAEV分子克隆与假免疫和未免疫对照山羊一起进行静脉攻击。攻毒后24周的初步结果表明，病毒复制受质粒DNA诱导的1型免疫的限制，而不受牛痘疫苗诱导的2型免疫的限制。这些数据为确定针对慢病毒SU的定性不同免疫反应在控制病毒复制和疾病进展中的作用提供了基础。因此，本研究的第一个目的是验证一种假说，即重组痘苗疫苗诱导的2型免疫不能控制病毒复制，而促进关节炎的发生。拟议的实验人员将初步研究扩大到更多的动物，这些动物需要对病毒载量和疾病进展进行重大评估。此外，挑战疫苗将是来自CAE关节炎现场病例的野生型病毒。用含或不含TAT的CAEV env表达载体DNA与编码山羊干扰素-γ(IFN)的第二个载体DNA共同免疫山羊。这些研究提供了初步证据，表明TAT和干扰素的协同作用抑制了SU编码的原代适应性B细胞对SU的应答，而不影响SU应答的Th1淋巴细胞的激活。用该疫苗诱导的免疫学特征显著控制山羊的CAEV复制将支持进一步研究TAT和干扰素作为疫苗成分的作用。因此，本研究的第二个目的是评估表达CAEV env和Tat基因的质粒DNA与山羊干扰素联合免疫的山羊在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.