Oral Vaccination for AIDS Prevention in Rhesus Macaques

说明（由申请人提供）：发展中国家艾滋病流行的严重程度，加上其中一些国家可用于保健的资源有限，使得对艾滋病疫苗的需求日益迫切。当在恒河猴中进行测试时，迄今为止开发的候选疫苗主要通过肌肉注射途径进行评估，不能防止慢性感染，但可以降低病毒血症设定点并延迟向艾滋病的进展。病毒血症的控制和无病感染的持续时间取决于在非人灵长类动物中用于疫苗评估的感染模式。由于除了淋巴器官外，大量病毒复制也发生在胃肠道，因此预防HIV感染和艾滋病可能需要疫苗在粘膜和全身区室诱导免疫的能力。我们已经建立了免疫接种方案，用SIV DNA疫苗刺激粘膜反应，该疫苗由携带SIV前病毒基因组的单个质粒组成，产生非传染性颗粒，无论疫苗是通过直肠还是鼻腔途径接种。我们有适当的工具来测量粘膜分泌物中siv特异性IgA水平，粘膜细胞介导的反应和siv特异性全身反应。因此，我们相信我们在确定口服DNA疫苗的有效性以及刺激病毒特异性粘膜反应如何影响HIV/SIV疫苗的有效性方面处于独特的地位。探索通过口服途径进行的疫苗接种方案可能对建立能够提供实质性控制病毒在胃肠道复制的方案很重要。为实现这一目标，我们提出以下建议：目的评价不同剂量的表达丙型肝炎病毒70kd E2包膜蛋白的DNA质粒与PLG微颗粒联合给药是否能刺激恒河猴全身和粘膜产生显著的抗丙型肝炎病毒70kd E2免疫应答。2. 评估DNA-MVA SIV疫苗的脂质体或微颗粒制剂在口服后是否能刺激更广泛的粘膜和全身反应。3. 评估上述两种方案中哪一种能最好地保护阴道免受SIV的攻击。4. 评估是否可以通过同时给予类似配方的DNA-MVA皮内免疫，进一步改善上述两种方案中较好的方案在防止进展为艾滋病方面的保护作用。项目说明：艾滋病疫苗可能需要产生比其他疫苗更大程度和更广泛的免疫。重要的是探索可能提高免疫反应质量而不仅仅是数量的方法，因为有效的疫苗必须在免疫反应高峰期以外的时间提供保护。同时存在的粘膜和全身免疫可能是重要的，以防止建立慢性艾滋病毒/SIV感染和控制疾病进展，如果感染发生。口服疫苗接种可能最适合于提供存在于胃肠道的病毒特异性反应，在胃肠道感染期间发生大量HIV和SIV复制。为了实现这一目标，我们打算研究能够最大限度地提高SIV DNA疫苗在免疫系统所有区室中产生免疫反应的质量和数量的策略。本文提出的研究目的是评估DNA/MVA疫苗的两种不同配方中，哪一种在口服时提供最多样化的免疫反应，以及在病毒攻击后对疾病进展的最显著保护。生殖道中的抗病毒免疫不仅至关重要，因为这些反应在性接触艾滋病毒时可以发挥作用，而且还因为这些反应可能在防止垂直传播方面发挥作用。这些研究的结果对于艾滋病疫苗的开发应该是非常有价值的。

DESCRIPTION (provided by applicant): The severity of the AIDS epidemic in the developing world combined with the limited resources that some of these countries have available for health care render the need of an AIDS vaccine more urgent every day. When tested in Rhesus macaques, the candidate vaccines developed thus far, evaluated predominantly via the intramuscular route, do not protect from chronic infection but provide a reduction in the viremia set point and a delay of progression to AIDS. The control of viremia and the length of disease-free infection depend on the model of infection used for the vaccine evaluation in non-human primates. As substantial virus replication occurs in the gastrointestinal tract in addition to the lymphoid organs, the ability of vaccines to induce immunity both in mucosal and systemic compartments may be required for prevention of HIV infection and AIDS. We have established vaccination regimens that stimulate mucosal responses with an SIV DNA vaccine, which consists of a single plasmid carrying an SIV proviral genome that produces noninfectious particles, whether the vaccination occurs via the rectal or nasal route. We have the appropriate tools to measure SIV-specific IgA levels in mucosal secretions, mucosal cell-mediated responses, and SIV-specific systemic responses. As a consequence, we believe that we are uniquely placed to determine the effectiveness of oral DNA vaccination and how stimulation of virus-specific mucosal responses can affect the efficacy of a HIV/SIV vaccine. Exploring vaccination regimens administered via the oral route may be important to establish regimens capable of providing substantial control of viral replication in the gastrointestinal tract. Towards this goal we propose 1. To evaluate whether different doses of a DNA plasmid expressing the Hepatitis C Virus 70 kD E2 Envelope protein and combined with PLG micro particles stimulate significant anti- Hepatitis C Virus 70 kD E2 immune responses systemically and mucosally when administered orally to Rhesus macaques. 2. To evaluate whether a liposome or a micro particle formulation of a DNA-MVA SIV vaccine stimulates broader mucosal and systemic responses after oral administration. 3. To evaluate which of the two above regimens provides the best protection from vaginal SIV challenge. 4. To evaluate whether the better of the two above regimens can be further improved in its protection from progression to AIDS by the simultaneous administration of a similarly formulated DNA-MVA intradermal immunization. Project Narrative: AIDS vaccines may need to engender a substantially greater level and breadth of immunity than other vaccines. It is important to explore approaches that may enhance the quality and not simply the quantity of the immune response because an efficacious vaccine will have to provide protection at times other than the peak of the immune response. The simultaneous presence of both mucosal and systemic immunity may be important in preventing the establishment of a chronic HIV/SIV infection and in controlling disease progression if infection occurs. Oral vaccination may be best suited at providing virus-specific responses that reside in the gastrointestinal tract where a significant amount of HIV and SIV replication occurs during the infection. Toward this goal we intend to investigate strategies that should maximize the quality and quantity of immune responses produced by our SIV DNA vaccine in all the compartments of the immune system. The objective of the studies proposed here is to evaluate which of two different formulations of the DNA/MVA vaccine provides the most diverse immune responses when administered orally and the most significant protection from disease progression after viral challenge. Antiviral immunity in the genital tract is not only critical because of the role that these responses can play at the time of sexual exposure to HIV but also because of the role that these responses may play in preventing vertical transmission. The results of such studies should be highly valuable for AIDS vaccine development.