DNA Vaccines

该项目的一个方面仍然是产生最有效的表达载体的特定抗原。我们已经产生了一组优化的表达载体的HIV和SIV。HIV载体被开发用于最终的人类临床试验。与此同时，SIV表达载体在最可靠的人类AIDS模型系统中被开发和研究，即，SIV感染恒河猴，SIV是一种与HIV密切相关的病毒，其引起的病理与人类AIDS非常相似。我们的结果表明，在没有任何其他形式的疫苗加强的情况下，优化的DNA表达载体能够保护恒河猴在高致病性SIVmac 251攻击后免受高病毒血症。我们已经开发了表达大多数HIV或SIV抗原的质粒组。这些质粒已通过我们的CRADA合作者进入人体临床试验。它们还被用于几项合作疫苗研究，并被证明在DNA-初免-病毒加强疫苗接种中提供出色的初免。我们还建议使用DNA疫苗定期增强免疫反应。这是因为人们认识到，DNA疫苗接种在每次应用中都能增强现有的免疫应答，并且不存在病毒载体的问题，病毒载体的问题是将免疫应答集中在疫苗载体上。为了进一步提高疫苗效率，我们研究了不同候选抗原的内在特性。我们已经证明，调节DNA产生的抗原的形式、稳定性和细胞命运对其免疫原性和产生的反应类型具有深远的影响。我们进行比较研究，以开发几种抗原的最佳形式。除了抗原修饰外，我们还研究了分子佐剂如细胞因子、趋化因子和共刺激分子在DNA疫苗改进中的作用。我们已经显示了IL-12和IL-15的优化细胞因子载体的表达和功能的极大增加。IL-12作为DNA疫苗佐剂，可显著增强猕猴对SIV的细胞和体液免疫应答。我们目前测试优化使用IL-15是否也可以改善免疫应答的寿命和质量。这些强大的细胞因子的最佳使用在癌症免疫治疗领域也引起了极大的兴趣。我们已经将我们优化的DNA载体用于慢性感染SIVmac 251的猕猴的治疗性疫苗接种。我们发现，与未接种疫苗的对照组相比，感染猕猴接种DNA疫苗后免疫应答增加，病毒载量大幅下降。这些结果支持DNA疫苗的发展，用于感染者的治疗性免疫。我们的实验已经强调了成功接种疫苗的充分抗原表达的必要性。我们已经开发了合理的方法来量化表达并将抗原水平和免疫原性相关联，以进一步优化疫苗结果。我们已经表明，在体内电穿孔大大诱导DNA疫苗接种后的细胞和体液免疫反应。我们在灵长类动物中优化了这种新的递送方法，以最终用于人类。

One aspect of this project continues to be the generation of maximally efficient expression vectors for the specific antigens. We have generated a set of optimized expression vectors for HIV and SIV. HIV vectors are developed for eventual human clinical trials. In parallel, SIV expression vectors are developed and studied in the most faithful model system for human AIDS, ie., infection of Rhesus macaques by SIV, a virus closely related to HIV, which causes very similar pathology to human AIDS. Our results show that optimized DNA expression vectors in the absence of any other form of vaccine boosting are able to protect rhesus macaque from high viremia after challenge with a highly pathogenic SIVmac251 challenge. We have developed sets of plasmids expressing the majority of HIV or SIV antigens. These plasmids have entered human clinical trials through our CRADA collaborators. They have also been used in several collaborative vaccine studies and were shown to provide excellent priming in DNA-prime-virus boost vaccinations. We have also proposed to use DNA vaccination for periodically boosting the immune response. This comes from the realization that DNA vaccination boosts existing immune responses with every application and does not have the problem of viral vectors, which focus immune response to the vaccine vector. To further improve vaccine efficiency we study the intrinsic properties of the different candidate antigens. We have shown that modulating the form, stability and cellular fate of the DNA produced antigens has profound effects on their immunogenicity and the type of response generated. We perform comparative studies to develop optimal forms of several antigens. In addition to antigen modification, we study the role of molecular adjuvants such as cytokines, chemokines and costimulatory molecules for the improvement of DNA vaccines. We have shown great increases in expression and function of optimized cytokine vectors for IL-12 and IL-15. IL-12 used as a DNA vaccine adjuvant increased dramatically the cellular and humoral immune response of macaques to SIV. We presently test whether optimized use of IL-15 may also improve the longevity and quality of immune response. The optimal use of these powerful cytokines is of great interest also in the cancer immunotherapy field. We have used our optimized DNA vectors in therapeutic vaccination of macaques chronically infected with SIVmac251. We showed an increased immune response after DNA vaccination of infected macaques and a strong decrease of viral load compared to unvaccinated controls. These results support the development of DNA vaccination for therapeutic immunization of infected persons. Our experiments have highlighted the necessity for adequate antigen expression for a successful vaccination. We have developed rational methods to quantify expression and to correlate antigen levels and immunogenicity in an effort to further optimize vaccine outcome. We have shown that in vivo electroporation greatly induces cellular and humoral immune responses after DNA vaccination. We optimize this new delivery method in primates for eventual human use.