Capsid-incorporation of HIV antigens as a novel adenovirus HIV vaccine approach

描述（由申请人提供）：尽管Ad载体在疫苗应用方面有许多潜在的优势，但目前Ad疫苗的充分利用可能受到宿主抗载体免疫反应的限制。具体而言，抗Ad体液免疫取消了后续Ad载体施用的有效性，混淆了编码转基因的表达，从而实际上限制了可能通过增强效应积累的收益。为了利用Ad载体固有的抗原性，我们开发了一种基于将免疫抗原表位直接纳入Ad衣壳的疫苗接种方法。这种新模式是基于Ad将抗原作为衣壳的组成部分而不是编码的转基因。将免疫原性肽结合到Ad衣壳中提供了潜在的优势。最值得注意的是，通过外源性途径对衣壳结合抗原的加工应导致类似于天然Ad衣壳蛋白引起的强烈体液反应。此外，由于抗Ad衣壳反应可通过反复给药而增强，因此针对Ad衣壳部分抗原表位的免疫反应也应通过反复给药而增强，从而允许增强。这些考虑表明，这种新的衣壳结合抗原方法可能提供令人兴奋的潜力，以实现基于Ad的疫苗策略，绕过Ad载体相关的主要限制。

DESCRIPTION (provided by applicant): Despite the many potential advantages of Ad vectors for vaccine application, full utility of current Ad vaccines may be limited by the host anti-vector immune response. Specifically, the anti-Ad humoral immunity abrogates the effectiveness of subsequent administrations of the Ad vector, confounding expression of the encoded transgene, and thus practically restricting the gains that might be accrued via booster effect. In order to exploit the inherent antigenicity of the Ad vector we have developed a vaccination approach based on incorporation of the immunizing antigen epitope directly into the Ad capsid. This novel paradigm is based upon Ad presenting the antigen as a component of the capsid rather than an encoded transgene. Incorporation of immunogenic peptides into the Ad capsid offers potential advantages. Most noteworthy, the processing of the capsid incorporated antigen via the exogenous pathway should result in a strong humoral response akin to the response provoked by native Ad capsid proteins. In addition, since anti-Ad capsid responses are augmented by repeated vector administration, immune responses against antigenic epitopes that are part of the Ad capsid should be augmented by repeated administration as well, thus allowing boosting. These considerations suggest that this novel capsid-incorporated antigen approach may offer exciting potentials to realize Ad-based vaccine strategies that circumvent the major limitations associated with Ad vectors. Critical to the realization of this approach is to define the optimal configuration of antigen in the adenoviral capsid context. To this end, we have established several key technologies that will enable us to reach our goal. In particular, we have developed the means to incorporate heterologous peptide epitopes within the surface-exposed domains of the major Ad capsid protein hexon. We have begun to determine the size and structural factors that predicate functional utility of these domains in the hexon. In addition, we have developed the means to apply cryoelectron microscopy (cryoEM) single particle reconstruction methods to allow us to explore the capsid-incorporated peptide localization with unprecedented, subnanometer resolution. Based on these technologies, we will be able to establish the critical correlates between antigen locale/accessibility within the capsid context and vaccine efficacy. On the basis of these established feasibilities, we hypothesize that Ad vectors can be created with novel capsid-incorporated antigens that can serve as vaccine agents against HIV in animal models. CryoEM-guided capsid design will be applied to develop an optimized vector with optimal anti-HIV immunization. We envision that our proposed structural studies will provide complementary information to in vitro assays and biological readouts and thereby will enable us to understand the functional determinants of incorporated HIV epitopes. This project will design new and innovative methodologies to create HIV vaccines, in hopes of preventing the spread of HIV disease.