Capsid-Incorporated Antigen for Novel Adenovirus Vaccine

DESCRIPTION (provided by applicant): The recognition that most cancers possess tumor-specific antigens or over-express antigens present in normal tissue, which can be immunogenic, provides the rational for using immunotherapy approaches as treatments for c ancer patients. One such approach is delivery of the tumor-associated antigen (TAA) to the main antigen presentation cells of the immune system, dendritic cells (DCs), as these are able to generate a potent and long lasting immune response. Preclincal stud ies and initial clinical trials employing these cells for tumor antigen presentation have produced some encouraging results, but gene transfer technology for DCs has not yet been optimized. Among the delivery systems considered for this vaccination approac h is the adenovirus (Ad) vector, which is an attractive vehicle for the delivery of TAA genes due to its high efficiency, ability to rapidly evoke an immune response, ease of genetic manipulation, and low risk for insertional mutagenesis. However DCs are r elatively resistant to Ad5 infections due to the low level of expression of the primary Ad5 receptor on the cell surface. In addition, ex vivo manipulation of DCs for cancer immunotherapy is not suitable for widespread applications. To address these limita tions, we propose to use a tropism-modified Ad-vector optimized for antigen delivery to DC in vivo. An Ad vector modified at the C-terminus of the fiber knob domain to contain seven lysines (pK7) will be utilized, as this modification significantly enhance s Ad5 transduction and will permit subcutaneous delivery of the vector. We will expand on novel strategies that demonstrate genetic inclusion of small immunogenic epitopes in the adenovirus capsid at the hexon proteins and fiber knob can confer epitope-spe cific immunity. We have identified the pIX adenovirus capsid protein as a suitable genetic fusion site for large complex proteins. We propose to incorporate a full size TAA into the capsid to provide more immunogenic epitopes and promote efficient cross-pr esentation with the goal of circumventing tumor associated suppressive conditions and generating potent cellular as well as humoral immune responses. In the first specific aim we will construct an Ad vector using well-defined TAA, carcinoembryonic antigen (CEA) as a transgene and as a fusion to pIX, and validate vector integrity and transduction of cells. In specific aim 2 we will utilize a transgenic CEA mouse model to assess the ability of the Ad vector to break immunological tolerance and elicit specific humoral and cellular immune. Validation of these principles, in vitro and in vivo in this Phase I study, will rationalize the full development of this system for a commercially relevant Ad vector-based vaccine. PUBLIC HEALTH RELEVANCE:Colorectal cancer is the third most commonly diagnosed cancer and the second most common cause of cancer death in the United States with approximately 150,000 new cases and 52,000 deaths estimated in 2007 according to the American Cancer Society. The development of the propos ed capsid incorporated CEA adenovirus vector will provide an efficient and single component vaccine for an immunotherapy approach for the treatment of colorectal cancers. Furthermore this approach will be applicable for an array of other cancer types.