Construction and characterization of E3-deleted bovine adenovirus type 3 expressing full-length and truncated form of bovine herpesvirus type 1 glycoprotein gD.

Using the homologous recombination machinery of E. coli, a 1.245-kb deletion was introduced in the E3 region of bovine adenovirus 3 (BAV3) genomic DNA cloned in a plasmid. Transfection of the restriction enzyme-excised, linear E3-deleted BAV3 genomic DNA into primary fetal bovine retina cells produced infectious virus (BAV3. E3d), suggesting that all the E3-specific open reading frames are nonessential for virus replication in vitro. Using a similar approach, we constructed replication-competent (BAV3.E3gD and BAV3. E3gDt) BAV3 recombinant expressing full-length (gD) or truncated (gDt) glycoprotein of bovine herpes virus 1. Recombinant gD and gDt proteins expressed by BAV3.E3gD and BAV3.E3gDt, respectively, were recognized by gD-specific monoclonal antibodies directed against conformational epitopes, suggesting that antigenicity of recombinant gD and gDt was similar to that of the native gD expressed in bovine herpes virus 1-infected cells. Intranasal immunization of cotton rats induced strong gD- and BAV3-specific IgA and IgG immune responses. These results suggest that replication-competent bovine adenovirus 3-based vectors have potential for the delivery of vaccine antigens to the mucosal surfaces of animals.