Analysis of targeting approaches intended to enhance the immunogenicity of adenovirally-vectored vaccine antigens.

摘要

This thesis has attempted to develop better strategies for recombinant adenovirus (rAd) vector-mediated gene delivery to dendritic cells (DC), with the final objective being improved HIV vaccines. Other groups have shown that rAd-mediated gene transfer to DC can be improved by "retargeting" the virus to alternate receptors. Some of the receptors that have been targeted are not exclusively DC-specific. We hypothesized that more DC-specific receptors, such as DC-SIGN and ChemR23, will allow a more efficient gene delivery to DC and therefore a more potent immune response to adenovirul-delivered transgene encoded antigens.; The DC targeting study was divided into two portions; one in vitro and the other in vivo. Both studies utilized a recently described, genetically modified rAd which has the unique capability of being able to bind to essentially any biotinylated ligand. The first portion was performed in cultured human DC to ascertain whether targeting rAd to the receptors DC-SIGN, ChemR23, and alphavbeta3 would enhance rAd-mediated gene delivery to DC. Our results showed that all three of the above mentioned receptors could enhance transduction of DC, enhance the maturation status of these cells, and also enhance the presentation of rAd-encoded antigens to autologous memory T cells. The second portion of the study, used the DC-SIGN targeted rAd as well as a transgenic mouse model which expresses human DC-SIGN solely on the mouse DC cell lineage, to investigate whether enhancing DC transduction in vivo would enhance the immune response to rAd encoded antigens. There is currently some debate on the utility of such an approach, with some studies showing that direct DC transduction is not required for strong immune responses to rAd-encoded antigens, and other studies suggesting that modified rAd vectors which target receptors on DC can elicit enhanced immune responses against vectored antigens. Our study revealed no correlation between the efficiency of DC transduction in vitro and the in vivo immune response to a rAd-vectored model antigen (which was not enhanced by this targeting approach). This finding suggests that, at least in some cases, enhanced transduction of DC does not result in improved immune responses to a rAd-vectored model antigen.