The potential of a novel Adenovirus vector for vaccination

Abstract

Adenoviruses (Ads) have many attractive characteristics for use as agents of genebased vaccines and therapies. The most frequently used Ad vectors in preclinical research are based on Ad5. However, in the clinical setting Ad5 vectors have severe limitations. About 90% of the population have neutralising antibodies against Ad5 and infection requires expression of the viral receptor CAR, which is not present on important cell types. Previous data from this laboratory suggested that the species D adenovirus, Ad19a, may overcome some of these limitations. Most relevant for vaccination is its high efficiency of infection of human dendritic cells (DCs), the most important antigen presenting cells. This highly effective DC targeting was retained in Ad19aGFP vectors. To investigate the potential of Ad19a vectors for vaccination further, two transgenes, the nucleocapsid gene from pneumovirus of mice (PVM-N), and a HIV polyprotein cassette (HIVA), were inserted into replication-deficient Ad5 and Ad19a vectors using recombineering. rAd19aPVM and rAd19aHIVA expressed a significantly higher amount of transgene compared with their Ad5 homologues. Encouraging results were obtained when the ability of rAd5PVM and rAd19aPVM to protect mice from lethal PVM challenge was examined using various prime/boost vaccinations. A dose of 106 pfu of rAd19aPVM, but not rAd5PVM, provided protection. rAd5PVM did, however, protect mice at the same dose when combined with rAd19aPVM in a heterologous prime boost schedule. Vaccination-induced IgG responses to PVM-N did not correlate with protection, implicating cell-mediated immune responses in protection. Utilising rAd19aGFP, evidence is also provided that Ad19a may use CD46 and to some extent CAR as a receptor on CHO cells, expanding our knowledge of the basic biology of this virus