Pathogenicity and immunogenicity of live attenuated SIV

减毒活SIV毒株为研究促进疾病发展的细胞和病毒决定因素提供了重要的模型，也为研究导致保护性免疫的机制提供了独特的工具。我们研究了由病毒Rev蛋白介导的HIV的调控表达，目的是评估Rev在发病机制中的作用。我们发现了其他RNA输出机制(通过细胞RNA输出因子和逆转录病毒RNA输出元件CTE、RTE)，为产生取代REV/RRE调控系统的HIV和SIV变体提供了关键工具。CTE或RTE也为我们提供了有用的工具，以实现HIV和SIV结构蛋白在简单DNA载体中的高效表达，这些DNA载体被用作抗艾滋病疫苗。重要的是，我们发现我们的REV非依赖性SIV毒株对恒河猴没有致病作用，这表明REV调控在SIV致病中起着重要作用。用CTE取代REV-RRE的自然调控为降低致病慢病毒的毒力提供了一种新的方法。这些研究提供了关于在慢性逆转录病毒感染期间建立和维持宿主免疫反应的关键信息，这些病毒感染具有不同的致病结果。用减毒病毒免疫的猕猴产生持久的体液和细胞免疫反应，能够保护动物免受高致病性SIV攻击。因此，这些减毒活的SIV毒株不仅为我们提供了一个独特的工具来剖析导致艾滋病发生的细胞和病毒决定因素，而且对于研究保护性免疫的相关性也很有用。这些研究将提供关于在具有不同致病结果的慢性逆转录病毒感染期间建立和维持宿主免疫反应的关键信息。为了研究艾滋病的预防，我们与George Pavlakis(人类逆转录病毒科，疫苗分部)长期合作，我们已经产生了高效的DNA表达载体，目前被评估为针对SIV和HIV的疫苗。这项工作是基于先前的认识，即HIV的Gag/Poll和env编码区中的RNA元件(称为INS)是在没有REV的情况下导致转录本的核保留和不稳定的，并且这些元件可以通过改变RNA组成而不影响氨基酸序列来消除。这些RNA优化的Gag和env表达载体在仅作为DNA和DNA初始疫苗的情况下，介导了免疫猕猴保护性免疫反应的发展。我们还发现，在恒河猴/SIVmac251模型中，产生天然抗原和修饰抗原的DNA疫苗载体组合能够诱导免疫反应，能够预防高病毒血症。正在进行的研究集中于评估这些进一步优化的基于DNA的疫苗载体作为预防和治疗疫苗形式的有效性。

Live-attenuated SIV strains provide an important model to study cellular and viral determinants that contribute to disease development and they also provide a unique tool to study mechanisms leading to protective immunity. We study the regulated expression of HIV which is mediated via the viral Rev protein with the goal to evaluate the role of Rev in pathogenesis. Our discovery of other RNA export mechanisms (mediate via cellular RNA export factors and retroviral RNA export elements CTE, RTE) provided the key tools to generate HIV and SIV variants that have the Rev/RRE regulatory system replaced. CTE or RTE provide us also with useful tools to achieve efficient expression of HIV and SIV structural protein in simple DNA vectors used as vaccine approaches against AIDS. Importantly, we found that our Rev-independent SIV strains are not pathogenic in rhesus macaques, which demonstrates that the Rev regulation plays an important role in pathogenicity of SIV. Replacement of the natural regulatory controls of Rev-RRE by the CTE provides a novel approach to lower the virulence of a pathogenic lentivirus. These studies provide critical information about the establishment and maintenance of host immune responses during chronic retroviral infections with distinct pathogenic outcomes. Macaques immunized with attenuated viruses develop persistent humoral and cellular immune responses, able to protect the animals from highly pathogenic SIV challenge. Therefore, these live-attenuated SIV strains provide us not only with a unique tool to dissect cellular and viral determinants that contribute to AIDS development, but are also useful for studying correlates of protective immunity. These studies will provide critical information about the establishment and maintenance of host immune responses during chronic retroviral infections with distinct pathogenic outcomes.To study prevention of AIDS, we have a long-standing collaboration with George Pavlakis (Human Retrovirus Section, Vaccine Branch), and we have generated efficient DNA expression vectors, which are currently evaluated as vaccines against SIV and HIV. This work is based on the previous recognition that RNA elements (called INS) present within the gag/pol and env coding regions of HIV are responsible for nuclear retention and instability of the transcripts in the absence of Rev, and that these elements can be eliminated by changing the RNA composition without affecting the amino acid sequence. These RNA optimized gag and env expression vectors mediate the development of protective immune responses in vaccinated macaques when used as DNA only as well as DNA prime vaccine modality. We also found that a combination of DNA vaccine vectors producing native and modified antigens are able to induce immune responses able to protect from high viremia in the rhesus macaque/SIVmac251 model. On-going studies focus on evaluating the efficacy of these further optimized DNA based vaccine vectors both as preventive and therapeutic vaccine modalities.