Optimization of bovine coronavirus hemagglutinin-estrase glycoprotein expression in E3 deleted bovine adenovirus-3

Adenoviral vectors expressing foreign genes have many desirable properties in applications such as vaccination. Recently, we have generated replicatio n-competent (E3 deleted) bovine adenovirus-3 (BAV-3) recombinants expressin g significant amounts of glycoprotein D (gD) of bovine herpesvirus-l (a DNA virus). However, attempts to express the RNA virus genes using the same st rategy were not successful. In an effort to optimize the expression, we hav e constructed several BAV-3 recombinants carrying the hemagglutinin esteras e (HE) gene of bovine coronavirus (BCV) in the E3 region with or without ex ogenous transcription control elements. The expression studies suggest that the introduction of a 137 bp chimeric intron upstream of the HE cDNA is ab le to increase the level of HE gene expression. The introduction of a SV40 early promoter or human cytomegalovirus (HCMV) immediate early (IE) promote r into the expression cassette changed the kinetics of the HE expression. H owever, the recombinant BAV-3 containing HE under the HCMV IE promoter repl icated less efficiently than the wild-type BAV-3. These studies should prov e useful in expression of other RNA viral genes in the E3 region of BAV-3 e xpression system. (C) 2000 Elsevier Science B.V. All rights reserved.