The potential therapeutic use of adenoviral vector platforms for vaccine applications is considerable. An adenoviral-based vaccine platform offers several advantages over other vaccine platforms, but a few important limitations currently hamper its optimal implementation as a pharmacological agent. The most relevant limitation is host pre- existing immunity against the vector, which, when present, mitigates the immunogenicity of Ad5 vector-based vaccines. Even in hosts in which such responses are initially absent, anti-vector immunity is developed soon after vector application, thereby limiting the efficiency of homologous boost immunizations or heterologous vaccine products based on this same platform. Several strategies have been attempted to overcome such neutralizing immunity. Here, we propose to use adenovirus-specific antibodies in order to overcome pre-existing immunity. Recently, we have chemically coupled mouse and human polyclonal adenovirus-specific antibodies with poly-arginine, which serves as a protein transduction domain (PTD), to generate complex adenovirus-antibody particles that we have named adenobodies. When the antibody-PTD conjugated reacts with adenoviral particles, they engage the epitopes targeted by neutralizing antibodies and redirect the entry of adenoviral particles thru the heparan sulfate proteoglycans receptors expressed by several cell types, including antigen presenting cells (APCs). Our preliminary studies show that replication-incompetent adenovirus serotype 5-complex adenobodies are able, in this format, to overcome neutralizing immunity and infect lung carcinoma cell line A549 and human dendritic cells in vitro. In light of these observations, we hypothesize that adenoviral vectors carrying antigen, when coupled with PTD-modified anti-adenovirus antibodies, will be able to overcome pre-existing neutralizing immunity in vivo and stimulate specific humoral and cellular immunity directed against the vaccine-incorporated antigen(s). To address this hypothesis, we will use influenza hemagglutinin (HA) as a model antigen to test the ability of adenobodies to efficiently vaccinate mice that exhibit existing neutralizing reactivity against adenovirus and to study specific immunity, as well as, mechanisms that underline immune responsiveness to vaccination.
The potential contribution of an effective vaccine platform applicable to several infectious disease targets is invaluable to public health. We propose to develop a vaccine platform that is capable of inducing a prolonged and specific immune response to an H5N1avian influenza infection. This study will be performed in an animal model system;however, if successful, the results may be a prelude to Phase I clinical testing in humans.
