Prevention of AIDS

为了研究艾滋病的预防，我们产生了高效的DNA表达载体，目前被评价为SIV和HIV的疫苗。这项工作是基于我们之前的认识，即存在于HIV gag/pol和env编码区的RNA元件（称为INS）负责在没有Rev的情况下转录本的核保留和不稳定性，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表达载体在接种过疫苗的猕猴中介导保护性免疫反应的发展，无论是仅作为DNA还是作为DNA原疫苗方式。我们现在已经证明，在恒河猴/SIVmac251模型中，产生天然抗原和修饰抗原的DNA疫苗载体的组合能够诱导免疫反应，从而防止高病毒血症。我们与其他研究人员合作，研究了其他HIV和SIV基因的免疫原性，无论是作为dna还是作为病毒载体的一部分。我们已经证明这些DNA在DNA引物重组疱疹促进研究中提供了极好的引物，诱导保护性免疫反应。我们还表明SIV DNA疫苗与IL-12或IL-15作为DNA佐剂联合使用可提高免疫原性。重要的是，我们还发现，在抗逆转录病毒治疗（ART）期间接种DNA疫苗可诱导有效的免疫反应，能够在ART中断后控制病毒血症。因此，DNA疫苗接种作为一种额外的治疗方式具有很大的潜力。另一个重要的新进展是，我们已经表明，通过体内电穿孔传递DNA可以大大提高细胞免疫反应的水平，并且这些反应是持久的。因此，这些结果表明，基因传递和表达的改善显著提高了DNA疫苗的免疫原性和有效性。为了设计更好的疫苗策略，重要的是剖析保护性免疫的相关因素。因此，能够控制病毒血症的受感染猕猴可以作为研究其潜在机制的模型。“控制者”包括来自我们疫苗研究的动物以及感染SIV减毒活毒株的动物。这些“控制者”为研究导致疾病发展的细胞和病毒决定因素提供了一个重要的模型，它们也为研究导致保护性免疫的机制提供了独特的资源。在最近的一项长期随访研究中，感染活减毒SIV的动物显示出持续的体液和细胞SIV特异性免疫反应，与慢性感染一致，但缺乏致病性。多色流式细胞分析显示，减毒siv感染动物的t细胞的中央记忆亚群得以保存。这项研究证明了一种有效的、持久的猕猴减毒SIV控制方法。因此，感染SIV减毒活株的动物不仅为我们提供了一个独特的资源来解剖导致艾滋病发展的细胞和病毒决定因素，而且对研究保护性免疫的相关因素也很有用。这些研究将为具有不同致病结果的慢性逆转录病毒感染期间宿主免疫反应的建立和维持提供关键信息，并将有助于我们设计改进DNA疫苗接种研究。

To study prevention of AIDS, we have generated efficient DNA expression vectors, which are currently evaluated as vaccines against SIV and HIV. This work is based on our 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 have now shown that 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. In collaboration with other investigators we have studied immunogenicity of additional HIV and SIV genes either as DNAs or as part of viral vectors. We have shown that these DNAs provide an excellent prime in DNA prime-recombinant Herpes boost studies inducing protective immune responses. We have also shown that combinations of SIV DNA vaccine together with IL-12 or IL-15 as DNA adjuvants improve immunogenicity. Importantly, we also found that DNA vaccination during antiretroviral treatment (ART) induces potent immune responses that are able to control viremia after ART interruption. Thus, DNA vaccination has great potential to be used as an additional therapeutic modality. Another important new development is that we have shown that DNA delivery via in vivo electroporation elicits greatly improved levels of cellular immune responses and these responses are long-lasting. Thus, these results indicate that improved gene delivery and expression dramatically improves immunogenicity and effectiveness of DNA vaccination. To design better vaccine stratgeis, it is important to dissect correlates of protective immunity. Thus infected macaques, able to control viremia serve as model to study the underlying mechanisms. Among the 'controllers' are animals from our vaccine studes as well as animals infected with live-attenuated SIV strains. These 'controllers' provide an important model to study cellular and viral determinants that contribute to disease development and they also provide a unique resources to study mechanisms leading to protective immunity. In a recent long-term follow-up study of animals infected with the live-attenuated SIV show persistent humoral and cellular SIV-specific immune responses, consistent with chronic infection but lack of pathogenicity. Multicolor flow cytometric analysis demonstrated preservation of the Central Memory subset of T-cells in the attenuated SIV-infected animals. This study demonstrates a potent, long-lasting control of the live-attenuated SIV in macaques. Therefore, the animals infected with live-attenuated SIV strains provide us not only with a unique resource 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 and will aid in our design to improve DNA vaccination studies.